## Archive for the ‘Classroom Activities’ Category:

### Modeling Atoms : Mini Rutherford

Description: With the Mini Rutherford Activity, students deduce shapes and sizes of unseen objects by tracking the movements of objects they can see, in relation to the unseen object. By extension, this device is a useful analogy to Rutherford’s alpha scattering experiments and to atomic particle detection utilizing accelerators. (Since the particles are too small to be seen, it was necessary to deduce their sizes by other means in both of these instances.) This experiment is best used by students working in pairs.

5-12

Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8

Time for Teacher Preparation
40-60 minutes – To make the Rutherford boards
40-60 minutes – To prepare for the classroom

Activity Time:
40-60 minutes (1 Class Period)

Materials

• 5-10 blocks of various shapes 20 cm (8” x 10″ x 3/4″)
• 5-10 30.5 x 30.5 cm (12” x 12” x 1/8”) masonite boards
• Pkg./30-1.9 cm (3/4”) or (5/8”) marbles
• Paper
• Pen, marker, or pencil
• Ruler
• Student Data Collection Sheets

Safety

• Students should use care when handling marbles
• Students should not throw marbles
• Students should avoid stepping on marbles

Science and Engineering Practices (NGSS)

• Define Problems
• Use Models
• Plan and Carry out investigation
• Analyze and interpret Data
• Construct Explanations
• Communicate Information

Cross Cutting Concepts (NGSS)

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models

Objective
Students will try to determine the shape of an unknown object by using the scientific thought process of creating a hypothesis, then testing it through inference. It is based upon the Rutherford Gold Foil Experiment where scientists discovered that the structure of the atom includes the nucleus in the center surrounded by electrons in empty space. It is a great introduction to the scientific process of deducing, forming scientific theories, and communicating with peers. It is also useful in the mathematics classroom by plotting the angles of incidence and reflection

Background
From 1911 to 1913, British physicists Geiger and Marsden, working in the laboratory of Ernest Rutherford, conducted experiments with beams of positively charged, alpha particles to penetrate gold, silver, and copper atoms. They observed that most of the alpha particles went directly through the foil. However, some particles were deflected and others recoiled back toward the source. Rutherford systematically investigated the results Geiger and Marsden obtained with alpha particles; Rutherford concluded
that most of the mass of an atom is concentrated in a small region in its center, now called the nucleus.

Fundamental Particles Detection
Light has a wavelength of 10-7 m. Light microscopes enable us to view parts of a cell as small as 10-6 m. Electron microscopes enable us to see an image with a wavelength as small as 10-9 m. With the help of scanning electron microscopes, we can see fuzzy images of atoms. To detect a smaller image, such as a fundamental particle, we need to produce particles with greater energy, and thus, a shorter wavelength. The smallest fundamental particle is less than 10-18 m in diameter! Although scientists have not yet been able to actually see fundamental particles, they can infer the presence of these particles by observing events and applying conservation laws of energy, momentum, electric charges, etc. One way to do this is with a particle accelerator. Essentially, a
particle accelerator works by shooting particles at high speed toward a target. When these bullet particles hit a target, a detector records the information about the resulting event.

Necessary Components for Particle Detection
1. Bullet Particles. These can be either electrons, positrons (the anti-particle of an electron), or protons. The particles
are collected as follows:

• Electrons are collected the same way a TV picture tube collects them; a metal plate is heated and electrons are emitted.
• To obtain positrons, a beam of electrons collides with a target, resulting in a photon. From the photon, electrons and positrons may be formed and are separated by their charges in a magnetic field.
• Protons are obtained by ionizing hydrogen gas. Ionization requires collisions at energy great enough to strip electrons from hydrogen, leaving protons.

2. An accelerator increases the speed of bullet particles to greater energy levels. The particles are accelerated with an electric field by riding on traveling electromagnetic (EM) waves. The EM waves are created in devices called klystrons, which are large microwave generators.

3. The steering device directs the bullet particles to their target. Magnets are used to steer the particles around a circular accelerator and to focus the particles so they will hit the target. The same magnets make positive and negative particles traveling in the same direction bend in opposite directions.

4. A target can be any solid, liquid, or gas, or another beam of particles.

5. A detector interprets the paths of the resulting particles once the bullet particles have collided with their target. Modern detectors have several layers, to detect the many particles produced in a collision event. A detector can be up to three stories tall. An advanced computer system is used to reconstruct the many paths of the particles detected in the layers associated with a collision. By viewing particle paths through each layer of the detector, scientists can determine the results of an event. Charged particles leave a track in the inner (tracking) layer of the detector. The positive or negative charge of the resulting particle can be determined by the direction it curves in a magnetic field. A particle with great momentum (speed x mass) will have a less curved path compared to one with less momentum. After a collision, electrons and protons will leave showers of particles in certain detector layers. Photons and neutrons travel a little further through the layers before their collisions create a shower of particles. Muons (one type of a fundamental particle), however, can be detected in the outer layer of a detector. They travel right through the inner layers with little or no interaction.

### Teacher Lesson Plan:

To make Rutherford boards:
Velcro, glue, or nail block shapes underneath the masonite boards. Note: Some hardware stores will cut shapes for you free of charge.

Potential Block Shapes:

Triangle, Square,Rhombus, Isosceles Trapezoid, Hexagon

Place the Rutherford boards on a large table or on the floor, obstructing the shapes from your students’ view. Place a piece
of paper on top of each Rutherford board. Beware: your students may be tempted to peek. The student activity, described in the accompanying worksheet, should take about five minutes to complete. The activity can be repeated several times during a class period, using different shapes and/or marbles each time. Some shapes are more difficult to detect than others.

NGSS Inquiry
Explain Rutherford’s experiment. Tell students that they will design their own experiment, using rolling marbles as alpha particles to discover the shape of a hidden geometric shape, which simulates the nucleus. You might suggest that the students experiment with rolling a marble at different angles at a straight surface and seeing the different ways the marble deflects.

### Student Procedure

Using the Rutherford boards:
Middle School
Part 1

1. Working in small groups, roll one of the marbles at the hidden object underneath the Rutherford board while one student draws the marble’s path in, and the deflected path out, on the piece of paper placed on the Rutherford board. Map the paths of the marbles that do not deflect or deflect slightly, as well. Make sure you roll the marble fast enough so that it makes a clean shot in and out.
2. Repeat Step 1 as many times as needed to define the outline of the hidden shape, using the same size marble each time. Make sure you roll the marble from many points on each side of the board.
3. Once you are satisfied that you know the shape of the object under the Rutherford board, draw the shape onto the piece of paper. (You might want to trace the shape from the paper with the outline formed by the collision paths).
4. Before looking at the actual block shape, show your instructor the shape you have drawn. Then look at the block underneath the Rutherford board, and discuss any parts of the shape you have drawn that are ill-determined.
5. Part 2: Have the instructor place a different block back under the Rutherford board (or switch boards if they are permanently attached). Place a clean sheet of paper on the top of the Rutherford board and repeat the procedure (Steps 1-4).

High School
Repeat steps 1-5 as per the Middle School procedure. Place the Rutherford board on a large piece of butcher paper, and then have the students record the shapes on the large paper. Do not put the paper on the board so that students must infer the shape from the surrounding angles of incidence/reflection.

Description: What happens to seeds that are exposed to very high levels of radiation? Will they grow normally?

5-12

Disciplinary Core Ideas (DCI, NGSS)

5-PS1-3, 5-ESS3-1, 3-5 ETS1-1, MS-ETS1-2, MS-ETS1-3, HS-PS4-4, HS-ESS2-3

Time for Teacher Preparation

To gather materials and set-up

Activity Time:

1-2 Weeks Minimum. Passive observations as beans grow.

Materials

• Pen, Marker, or Pencil
• Student Data Collection Sheets
• Mung bean seed
• Potting soil
• Pots (2″ to 3″ pots)
• Small metric rulers

Safety

• Students should not put bean seeds, soil, pots, or metric rulers in their mouths due to choking hazard.
• Students should not try eating bean seeds or irradiated bean seeds.

Science and Engineering Practices (NGSS)

• Ask questions and define problems
• Plan and carry out investigation
• Analyze and interpret data
• Use mathematics and computational thinking
• Construct explanations
• Argue from Evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Energy and Matter: Flows, Cycles, and Conservation
• Structure and Function
• Stability and Change of Systems

Objectives

The students develop a procedure to study the effects of radiation on mung bean seeds and other irradiated seeds. Students will observe and record data on the germination and development of the plants. Student data, results, and conclusions will be presented, supported, and defended by the students to the class.

• To determine how irradiation affects the growth of bean seeds
• To determine how much radiation dose comes from nature and how much comes from the uses of radiation in society.
• To compare data

Background

Irradiation is becoming increasingly more popular in the treatment of foods to kill bacteria, diseases and pests. A fear of radiation causes some people to believe that food that is irradiated becomes radioactive. The irradiated bean seeds in this experiment have been exposed to various levels of gamma radiation, but are not radioactive and are completely safe to handle.

You cannot tell how much radiation the seeds were given by looking at them. These seeds were harvested and irradiated after the plants were mature. However, you will be able to observe differences in the plants growing from these seeds. Each seed contains an embryo plant. When the gamma radiation passed through these seeds, it damaged some of the cells in the embryo. The greater the radiation, the more cells were damaged. Therefore, the resulting plants grown from seeds with greater exposures will show more abnormalities than those with lower exposures.

### Teacher Lesson Plan:

Split students into groups of four and give each group four sets of bean seeds (control; 50,000; 100,000; 150,000 rad). Have each group plant their seeds in separate pots and set up a table to chart and graph the growth of the seeds over the next couple of weeks. Students should record height and observations of their beans at least twice a week. Remind students to water their beans as frequently as needed in order to take care of their plants.

Students may also grow the seeds in test tubes of water and plant them once they have germinated.

NGSS Guided Inquiry

Have students design an experiment to discover about how much radiation each of their seeds was exposed to.

Student Procedure

1. Plant seeds into separate pots and water until the soil is moist. Alternatively, grow the seeds submerged in water inside of test tubes until they germinate and then pot them.
2. Set up a data table to record height and observations of the bean seedlings. Observations should be made at least twice per week.
3. Take care of your plants by watering them as frequently as needed.
5. Add a step to include listing the variables which must be controlled in this experiment.
• Examples of this include:
• exposure to sun or artificial light
• temperature of the surroundings
• whether seed is grown in soil or in water
• the amount of water added to the soil (students should measure the added water in milliliters).

Data Collection

Student Data Collection Sheets

Post Discussion/Effective Teaching Strategies

Questions provided on the Student Data Collection Sheets

Questions

1. What happened? Why do you think the things you observed occurred? Were your observations and conclusions different from other students? Why? Who’s “right?”
2. 100,000 rads or 150,000 rads is enough to kill a human. Did it kill all the plants? What do you think are some possible explanations?

Assessment Ideas

• Test the student’s observations against the actual irradiated exposure of each plant.

Differentiated Learning/Enrichment

• Have students make slides of each of the beans for viewing under a microscope.
• Try getting a couple more generations from the plants to observe successive generations.

Enrichment Questions

1. If radiation increases on earth, what effects do you think it will that have on plant growth? On other organisms? On humans?
2. What do you think happened to the cells of the irradiated Mung bean plants?
3. Why do we use irradiation to prevent food from spoiling?

Further Resources

From Harvest to Home

Los Alamos National Laboratory (1992). Detecting the Invisible: The SWOOPE Radiation and Radon Discovery Unit

### Making Atoms Visible : Cloud Chamber

Description: Allow students to visualize and understand ionizing radiation.

5-12

Disciplinary Core Ideas (DCI, NGSS):
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8, HS-PS4-2, HS-PS4-5

Time for Teacher Preparation:
30-60 minutes – To gather materials and set-up

Activity Time:
30-60 Minutes (1 Class Period)

Materials:

• Pen, Marker, or Pencil
• Plastic cloud chamber kit, 3 1/4″ diameter: (Petrie dish with band of black construction paper around the sides and bottom painted black or lined with black construction paper)
• 3 each- Cloud Chambers
• 3 Radioactive Sources: radioisotope disks, Coleman Lantern Mantle pieces (thoriated), Uranium ore, or orange Fiestaware piece.
• Dry ice
• Rubbing alcohol – 95% ethyl
• Flashlights
• Styrofoam plates
• Gloves
• Magnet (Optional)
• Student Data Collection Sheets

Safety:

• Students should use care when handling rubbing alcohol
• Students should not touch dry ice with their bare hands
• Students should not touch radioactive materials

Science and Engineering Practices (NGSS):

• Ask questions and define problems
• Use models
• Plan and carry out investigation
• Analyze and interpret data
• Using mathematics, information and computers
• Argue from Evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts (NGSS):

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation
• Structure and Function
• Stability and Change of Systems

Objectives:

• To visually demonstrate the concepts of ionizing radiation

Background:
Radioactive elements continually undergo a process of radioactive decay during which their nuclei emit high-speed particles and rays.  These are much too small to be seen under a microscope.  The Cloud Chamber was invented by an English physicist, C. T. R. Wilson, in 1911. It is an instrument designed for the study of the trails of radioactive emissions.  The investigation is accomplished in the following way.  First, the air must be saturated with water or alcohol vapor.  When the high-energy particles flow through the air, electrons are knocked loose from some of the atoms and form ions.  Ions act as excellent centers for condensation.  This condensation, however, must be stimulated by cooling the air.  The water vapor or alcohol condenses on the ions, leaving a vapor tail which clearly reveals the path of the ray.

Cloud chambers detect the paths taken by ionizing radiation. Much like the vapor trail of a jet airplane, the tracks in a cloud chamber mark where ionizing radiation has been traveling. The radiation itself is not visible. Radioactive materials are one source of ionizing radiation. Three types of rays are given off by a radioactive element.  They are alpha particles (positive nuclei of helium atoms traveling at high speed), beta particles (high-speed, negative electrons), and gamma rays (electromagnetic waves similar to X-rays). Most of the tracks will be about one-half inch long and quite sharp. These are made by alpha radiation. Occasionally you will see some twisting, circling tracks that are so faint that they are difficult to see. These are caused by beta radiation.

### Teacher Lesson Plan:

Cloud Chambers:

1. Prepare three cloud chambers in accordance with the Cloud Chambers instructions:
1. Open the lid of the cloud chamber and saturate the felt strip inside with alcohol.
2. Put the radiation source inside the cloud chamber and replace the lid tightly.
3. Place the palm of your hand firmly on top of the cloud chamber for about 5 minutes to evaporate the alcohol.
4. Place the cloud chamber on a piece of FLAT dry ice that is at least a little larger than the chamber.
5. Turn off the lights in the room and shine the flashlight through the cloud chamber to make the ion trails easier to see.  Trails should begin a few minutes after placement on the dry ice.

Note: You can use radioisotope disks in each chamber  in lieu of Coleman lantern mantle pieces.  By providing  Alpha, Beta, and Gamma sources , students will find that only the Alpha and Beta sources will produce tracks.  This is because Gamma radiation is electromagnetic radiation not particles, and it’s the particles moving through the alcohol cloud that makes the tracks.

NGSS Guided Inquiry
Give the students radioactive samples and ask them to reduce/block the radiation to normal background levels with things they find in the classroom.

Explain about the different types of radiation and radioactivity. Tell students to design their own experiment, to detect different types of radiation, and then share their results with the class.

Student Procedure
Observe the vapor trails produced within the cloud chamber and answer the questions provided by your teacher.

High School

1. Prepare three cloud chambers in accordance with the Cloud Chambers instructions:
1. Open the lid of the cloud chamber and saturate the felt strip inside with alcohol.
2. Put the radiation source inside the cloud chamber and replace the lid tightly.
3. Place the palm of your hand firmly on top of the cloud chamber for about 5 minutes to evaporate the alcohol.
4. Place the cloud chamber on a piece of FLAT dry ice that is at least a little larger than the chamber.
5. Turn off the lights in the room and shine the flashlight through the cloud chamber to make the ion trails easier to see.  Trails should begin a few minutes after placement on the dry ice.

Note: You can radioisotope disks in each chamber  in lieu of Coleman lantern mantle pieces.  By providing  Alpha, Beta, and Gamma sources , students will find that only the Alpha and Beta sources will produce tracks.  This is because Gamma radiation is electromagnetic radiation not particles, and it’s the particles moving through the alcohol cloud that makes the tracks.

Post Discussion/Effective Teaching Strategies

Questions:

1. What is creating the vapor trails?
2. How is it creating them?
3. How far did each type of radiation travel away from the source? List your answers from furthest traveling to shortest traveling distance.
4. Are any tracks visible when no source of radiation is near the chamber? What kinds of radiation can be found in our environment?

Assessment Ideas

• Have students draw a diagram of what is happening at the atomic level when a vapor trail is created.
• Hold the north end of a strong magnet next to the chamber. How does magnetism affect the radiation tracks?
• If you have access to a Geiger counter, count the number of tracks that you can see in ten seconds and then compare that number to the number of clicks produced by the Geiger counter in the same amount of time. Which is more accurate?
• If you shield the source, which types of radiation are still visible?
• Materials to experiment with shielding include: aluminum foil, plastic, cloth. Which types of radiation are shielding by each type of material?

Differentiated Learning/ Enrichment

Enrichment Question

1. How do you think shielding is useful to the nuclear industry? Give three examples.

Further Resources

### Making Atoms Visible : Autoradiographs

Description: With the Autoradiograph activity, students gain a better understanding of the different types of radiation, alpha, beta, and gamma. This is a way that students can detect invisible emissions.

This experiment is best used by students working in groups.

1-5 (sun paper)
6-8 (demonstration)
9-12 (activity)

Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8, HS-PS4-2, HSPS4-5

Time for Teacher Preparation
30-60 minutes – To gather materials and set-up
1 Week to develop the autoradiograph

Activity Time:
30-60 minutes (1 Class Period) for set-up
30-60 minutes (1 Class Period) to develop the autoradiograph

Materials

• Pen, Marker, or Pencil
• 1 box-Polaroid Type 57 instant (3000 speed) 4×5 packet film
• 1 Coleman Lantern Mantle
• Fiesta®ware plate
• Smoke-detector part (Americium)
• Uranium ore (sealed in a plastic ziplock to prevent dust contamination)
• Rubber or plexiglass photo developing roller, rolling pin, or sturdy wooden or plastic ruler
• Sheet of aluminum foil, paper (optional)
• Student Data Collection Sheets

Safety

• Students should use care when handling aluminum foil
• Students should not touch chemicals on polaroid film on their bare hands
• Students should use care when touching radioactive materials.
• Students should wash hands after handling radioactive materials.

Science and Engineering Practices (NGSS)

• Ask questions and define problems
• Use Models
• Plan and Carry out investigation
• Analyze and interpret data
• Using mathematics, information and computers
• Argue from Evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts (NGSS)

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation
• Structure and Function
• Stability and Change of Systems

Objectives

• To visually demonstrate the concepts of ionizing radiation.

Background

Often used to detect radiation by imaging its emissions, an autoradiograph is a representation of where radioactive substances are located. The image can be projected onto a medium such as an x-ray film, nuclear emulsion, or even photographic film. Autoradiography, which can also be digital, is used in many cases for biological and medical applications. In contrast to other methods of detecting radiation, they can show the locations of radioactive materials in a sample. The images can therefore be used with biological specimens labeled with such materials, to track cellular activity for example.

In its basic form, an autoradiograph can require film to be exposed overnight. Radioactivity is detected through bands on an image, which are produced as particles hit crystals of silver halide. The images on the film typically depend on the activation of the crystals and the effects of particles on a gel. If each crystal is insulated by a gelatin capsule, then a permanently developed image can accurately show the sample and where it is radioactive.

An autoradiograph is often taken after biological tissue is exposed to a radioactive substance, left for a certain period of time, and examined under a microscope. Sections can be cut and a photographic image can be developed as a radioisotope decays. Samples are often stained to enhance the detail and to see the grains of silver that react with the substance. The resulting autoradiograph can be recorded and kept on file as part of an experiment or test.

While a solid film was typically used in the past, a liquid emulsion is often used in the 21st century to make an autoradiograph. This technique can take less time to complete. Liquid can flow and make the thickness of the sample uneven, but following the basic steps for coating slides and developing the film can dry the sample appropriately. A phosphor-imager screen can help detect radioactivity in gel quicker than x-ray film. It is typically used with electronic instruments and a computer system that can digitally image the sample.

Autoradiographs can show radioactive particles attached to enzymes or integrated into nucleic acid. Metabolic processes can be tracked in cells when images of radioactive particles are compared. Researchers can track proteins, photosynthesis, and the division and movement of cells. Sequences of deoxyribonucleic acid (DNA) can be tracked. Autoradiography DNA is often used to monitor cell cycles and track the progress of viruses to analyze their behavior.

### Teacher Lesson Plan:

Paper

1. Place a key, coin, or other metal object onto the face of the film sheet. Place a Coleman lantern mantle, Fiesta®ware plate, or a radium-dial clock completely over the object. Let it sit for at least one week.
2. Remove the mantle and object from the film sheet. Lay the sheet on a flat table with the side marked “This side toward lens” up. Locate the bulge in the sheet that contains the developer chemicals. Place a ruler, flashlight, or other stiff, heavy object (a roller works best) behind the bulge and, while applying moderate pressure, slowly and evenly drag the object across the film sheet to spread the chemicals. Even distribution of the chemicals is critical for good development. It takes lots of practice to make a good picture.
3. Wait 30 seconds for the film to develop then open the packet.
4. Students will find a dark shadow of the metal object surrounded by a white “fog”. The white is due to the radiation given off by the Coleman mantle exposing the film. The dark shadow is because the metal object shielded the radiation from the film.

NOTE: You can use the three radiation sources on one film sheet in lieu of the key and Coleman lantern mantle, Fiesta®ware plate, or a radium-dial clock. Students will find that only the beta and gamma sources will expose the film. This is because the paper surrounding the film shields alpha radiation.
NOTE: Elementary school students could try to perform this experiment using SunSensitive paper rather than Polaroid film. The SunSensitive paper reacts to UV sunlight and would be a good substitution for Polaroid film for this experiment.

NGSS Guided Inquiry

1. Break students up into groups of three
2. Give each group:
• A sheet of film
• A sheet of paper and some aluminum foil
• An alpha, beta, and gamma source
1. Have groups design an experiment to discover what kind of radiation each source is emitting.

### Student Procedure

1. Place a key, coin, or other metal object onto the face of the film sheet. Place a Coleman lantern mantle, Fiesta®ware
plate, or a radium-dial clock completely over the object
2. Allow the photos to develop for a week
3. Develop the film according to your teacher’s instructions
4. Observe the resulting image that is developed

Data Collection
Student Data Collection Sheets
Students should label sources and type of radiation on film

Post Discussion/Effective Teaching Strategies
Questions provided on the Student Data Collection Sheets

Questions

1. What caused the image to develop on the sheet of film?
2. How did you use shielding principles to identify what kind of radiation each source emits?
3. For sun paper activity, how does placing an object on the sun paper and putting sun screen on skin compare to protecting an area from the sun’s radiation?

Assessment Ideas
Have students identify an unknown source by experimenting with shielding, different sources, and different types of film.

Differentiated Learning/Enrichment

• Explore how autoradiography is used in DNA sequencing.
• Have students place various objects between the film and the source (coin, leaf, paperclips, etc.)

Enrichment Question

1. How did scientists use this concept in medicine?
• Compare the early usage of 1900’s Medicine to today’s application.

### Making Atoms Visible : Electroscope

Description: Easily create an electroscope to detect static electricity and radiation.

5-12

Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8, HS-PS4-2, HS-PS4-5

Time for Teacher Preparation
30-60 minutes – To gather materials and set-up

Activity Time:
30-60 minutes (1 Class Period)

Materials

• Pen, Marker, or Pencil
• Balloon
• Foam plate
• Foam cup
• Drinking straw
• Glue
• Aluminum pie pan
• Aluminum foil
• Wool fabric
• Comb
• Plastic ruler
• Student Data Collection Sheet

Safety

• Students should use care when handling aluminum foil
• Students should use care when handling glue

Science and Engineering Practices (NGSS)

• Ask questions and define problems
•  Use models
• Plan and carry out investigation
• Analyze and interpret data
• Using mathematics, information and computers
• Argue from evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts (NGSS)

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation
• Structure and Function
• Stability and Change of Systems

Objective
Make a simple instrument to detect static electricity and radiation.

Background
An electroscope is a very simple instrument that is used to detect the presence and magnitude of electric charge on a body such as static electricity. The type of electroscope detailed in this experiment is called a pith-ball electroscope. It was invented in 1754 by John Canton. The ball was originally made out of a spongy plant material called pith. Any lightweight nonconductive material, such as aluminum foil, can work as a pith ball. The pith ball is charged by touching it to a charged object. Since the ball is nonconductive and the electrons are not free to leave the atoms and move around the ball, when the charged ball is near a  positively charged body, or source, the negatively charged electrons are attracted to it and the ball moves towards the source. Conversely, a negatively charged source will repel the electrons, and therefore the ball. Electroscopes can also be used to detect ionizing radiation. In this case, the radiation ionizes the air to be more positively or negatively charged depending on the type of radiation, and the ball will either be attracted or repelled by the source. This is how electroscopes can be used for detecting x-rays, cosmic rays, and radiation from radioactive material.

### Teacher Lesson Plan:

1. Lecture students on background
2. Provide them with materials and procedure
3. Provide balloons and radiation sources to test the electroscopes with

NGSS Guided Inquiry

1. After students construct electroscopes, have them experiment with charged and neutral sources to experiment.
2. Have students analyze radioactive sources with electroscopes.

### Student Procedure

1. Make two holes near the bottom of a foam cup on opposite sides.
2. Push a plastic straw through the holes in the cup.
3. Turn the cup upside down and glue it onto the bottom of an aluminum pie pan. Make sure that the cup is right at the edge so that the straw sticks out over it. If you don’t want to wait for the glue to dry, tape the cup to the pan.
4. Cut a piece of thread about 8 inches long and tie a few knots in one end of the thread.
5. Cut a one-inch square of aluminum foil. Use it to make a ball around the knots in the thread. The ball should be about the size of a marble. It should be just tight enough so it doesn’t fall off the thread.
6. Tape the end of the thread to the straw so that the ball of foil hangs straight down from the straw, right next to the edge of the pan.
7. Tape the straw to the cup so it doesn’t move around when you use the electroscope.
8. To test the electroscope, create some static electricity. An easy way to create static is by rubbing a balloon on a foam plate. When you do this, you “charge” the plate, which means you cause a buildup of electrons on one side. Even though the plate is charged, the electrons don’t move because foam doesn’t conduct electrons.
9. Once you’ve created some static electricity, place the electroscope on top of the foam plate. Be sure to hold the electroscope by the foam cup and not the aluminum pan, otherwise it won’t work. Electrons move easily through metal, so when you put the pie pan onto the foam plate, the electrons travel into the pan and the foil ball. When the electroscope detects static electricity, the foil ball pushes out from the pan.
10. Try charging different objects, like a comb or ruler, with static electricity. Test them on the electroscope and record your results on the data sheet.

Data Collection
Students should record which objects hold a charge and which do not

Post Discussion/Effective Teaching Strategies

Questions

1. Which objects hold an electric charge? Which don’t?
2. Why is the ball attracted or repelled by different objects?
3. How is using an electroscope similar to testing the charge of a balloon with your hair?
4. How is the electroscope able to detect radioactivity?

Assessment Ideas
Have students use electroscopes to discern between radioactive sources and nonradioactive sources.

Differentiated Learning/Enrichment
Have students compare radioactivity of different sources.

Enrichment Question

1. Why did John Canton invent the first electroscope and what did he use it for?

Further Resources
Electroscope: http://science.howstuffworks.com/electroscopeinfo.htm

Materials:

• Table salt (NaCl) that has been irradiated with at least 180,000 RADs of gamma radiation. (Keep in DARK container or protected from light until ready to perform demonstration.)
• A frying pan or other flat-surfaced item on a hot plate
• A dark room (the darker the better).

Background:

When the salt is irradiated, gamma rays pass through the crystals and the energy deposited there excites electrons and causes them to move to a higher energy state. Due to the nature of salt crystals, the electrons become trapped in that higher energy state. After being irradiated, the salt appears as a cinnamon color rather than white; that is because the repositioned electrons affect the way that light is reflected by the crystal.

Procedure:

Preheat a dry frying on a hot plate set at its highest temperature. OR, put the pan above a lab burner. Continue heating the pan. In a completely darkened room, sprinkle or pour some of the irradiated salt into the hot frying pan. Carefully observe what happens! Then, observe the salt which remains in the bottom of the frying pan after your experiment.

Explanation/Analysis:

You should see tiny flashes of light as the irradiated salt comes into contact with the frying pan surface. (You must be fairly close; the flashes are not bright.)

Heating the salt causes increased motion (vibration) in the salt crystal. This allows the electrons to return to their normal (somewhat lower) energy state. As the electrons move to lower energy states, the previously stored energy is released in the form photons of visible light. After the electrons return to normal energy states, the salt crystals reflect light as normally and appear white.

Optional:

Concepts you can teach:

• Irradiation may change a material physically, but it does not make it radioactive.
• Applying energy (gamma radiation) to a substance may move electrons to different energy states.
• People who work in environments with radiation often wear a Thermoluminescent Dosimeter. Such dosimeters contain substances (often LiF crystals) that are sensitive to ionizing radiation. Filters are used in the badge to discriminate between alpha, beta, and gamma radiation. Periodically, the dosimeter is tested to determine how much radiation exposure the worker has received. (The flashes of light observed in our activity are a very crude representation of such a test.)

If the irradiated salt is exposed to sunlight or artificial light, it will gradually lose its coloration and turn back to white. The light exposure causes some changes in the lattice, the electrons gradually return to their original energy states and the salt returns to its original white color. Be sure to keep it protected in a dark or opaque container.

Penn State University, Breazeale Reactor, phone 814-865-6351

Other scientific supply companies may offer irradiated salt; check with your normal supply sources.

Frequently Asked Question: Is the irradiated salt safe to eat? The dose of radiation given to the salt was higher than FDA allows for this type of food; the laboratory where it was irradiated does not meet USDA/FDA standards for food handling. However, the salt is not radioactive – either before or after heating in the demo. The salt never releases ionizing radiation, only visible light.

### Half-Life : Paper, M&M’s, Pennies, or Puzzle Pieces

Description: With the Half-Life Laboratory, students gain a better understanding of radioactive dating and half-lives. Students are able to visualize and model what is meant by the half-life of a reaction. By extension, this experiment is a useful analogy to radioactive decay and carbon dating. Students use M&M’s (or pennies and puzzle pieces) to demonstrate the idea of radioactive decay. This experiment is best used by student working in pairs.

Disciplinary Core Ideas (DCI)
3-5ETS1-2, MS-ESS1-4, HS-ESS1-6

Time for Teacher Preparation
40-60 minutes – To gather materials

Activity Time:
40-60 minutes (1 Class Period)

Materials:

• Bag of: M&M’s ®, pennies or, puzzle pieces
• Paper – 8.5˝ x 11˝
• Graph Paper
• Zip-Lock Bags
• Pen, Marker, or Pencil
• Student Data Collection Sheets

Safety

• Students should not eat M&M’s®, Pennies, or Puzzle Pieces

Science and Engineering Practices

• Ask questions and define problems
• Use models
• Analyze and interpret data
• Use mathematics and computational thinking
• Construct explanations
• Argue from evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation

Objectives
Students try to model radioactive decay by using the scientific thought process of creating a hypothesis, then testing it through inference. It is a great introduction to the scientific process of deducing, forming scientific theories, and communicating with
peers. It is also useful in the mathematics classroom by the process of graphing the data.

Students should begin to see the pattern that each time they “take a half-life,” about half of the surrogate radioactive material becomes stable. Students then should be able to see the connection between the M&M’s and Puzzle Pieces and radioactive elements in archaeological samples. Seeing this connection will help students to understand how scientists can determine the age of a sample by looking at the amount of radioactive material in the sample.

• To define the terms half-life and radioactive decay
• To model the rate of radioactive decay
• To create line graphs from collected data
• To compare data
• To understand how radioactive decay is used to date archaeological artifacts

Background
Half-Life
If two nuclei have different masses, but the same atomic number, those nuclei are considered to be isotopes. Isotopes have the same chemical properties, but different physical properties. An example of isotopes is carbon, which has three main isotopes, carbon-12, carbon-13 and carbon-14. All three isotopes have the same atomic number of 6, but have different numbers of neutrons. Carbon-14 has 2 more neutrons than carbon-12 and 1 more than carbon-13, both of which are stable. Carbon-14 is radioactive and undergoes radioactive decay.

Radioactive materials contain some nuclei that are stable and other nuclei that are unstable. Not all of the atoms of a radioactive isotope (radioisotope) decay at the same time. Rather, the atoms decay at a rate that is characteristic to the isotope. The rate of decay is a fixed rate called a half-life.

The half-life of a radioactive isotope refers to the amount of time required for half of a quantity of a radioactive isotope to decay. Carbon-14 has a half-life of 5730 years, which means that if you take one gram of carbon-14, half of it will decay in 5730 years. Different isotopes have different half-lives.

The ratio of the amounts of carbon-12 to carbon-14 in a human is the same as in every other living thing. After death, the carbon-14 decays and is not replaced. The carbon-14 decays, with its half-life of 5,730 years, while the amount of carbon-12 remains constant in the sample. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing. Radiocarbon dates do not tell archaeologists exactly how old an artifact is, but they can date the sample within a few hundred years of the age.

### Teacher Lesson Plan:

M&M’s® (or Pennies or Puzzle Pieces)

1. Give each student 10 M&M’s® candies of any color and a zip lock bag. All of M&M’s® candies are considered radioactive.
2. Have the student put the M&M’s® into the zip lock bag and shake the bag. Have the students spill out the candies onto a flat surface.
3. Instruct the students to pick up ONLY the candies with the “m” showing – these are still radioactive. The students should count the “m” candies as they return them to the bag.
4. Have the students record the number of candies they returned to the bag under the next Trial.
5. The students should move the candies that are blank on the top to the side – these have now decayed to a stable state.
6. The students should repeat steps 2 through 5 until all the candies have decayed or until they have completed Trial 7.
7. Set up a place on the board where all students or groups can record their data.
8. The students will record the results for 9 other groups in their data tables and total all the Trials for the 100 candies

NGSS Guided Inquiry
Explain about radiation and half-lives of isotopes. Tell students to design their own experiment, using paper, M&M’s®, Pennies, other 2 sided material or Licorice as a radioactive material undergoing decay to discover the nature of the half-life of that material.

You might suggest that the students experiment with their graphing results to see if trends begin to form.

### Student Procedure

M&M’s® (or pennies or puzzle pieces)

1. Put 10 M&M’s® candies of any color into a zip lock bag. Each group is starting with 10 M&M’s® candies, which is recorded as Trial 0 in the data table. All of the M&M’s® candies are considered to be radioactive at the beginning.
2. Shake the bag and spill out the candies onto a flat surface.
3. Pick up ONLY the candies with the “m” showing – these are still radioactive. Count the “m” candies as you return them to the bag.
4. Record the number of candies you returned to the bag under the next Trial.
5. Move the candies that are blank on the top to the side – these have now decayed to a stable state.
6. Repeat steps 2 through 5 until all the candies have decayed or until you have completed Trial 7.
7. Record the results for 9 other groups and total all the Trials for the 100 candies.

Data Collection
Student Data Collection Sheets

Post Discussion/Effective Teaching Strategies
Questions provided on the Student Data Collection Sheets

Questions

M&M’s® (or Pennies or Puzzle Pieces)

1. Define the term half-life.
2. What does it mean when we say an atom has “decayed”?
3. Do the number of atoms you start with affect the outcome? Explain.
4. Did each group get the same results?
5. Did any group still have candies remaining after Trial 7?
6. Why do the totals for the 10 groups better show what happens during half-life rather than any other group’s results?
7. What happens to the total number of candies with each trial (half-life)?
8. Plot the total results on a graph with number of candies on the vertical axis and trial number on the horizontal axis. Is the result a straight or a curved line? What does the line indicate about the nature of decay of radionuclides?
9. How do scientists use radioactive decay to date fossils and artifacts?

Assessment Ideas

• Question the student about how this experiment is similar to Carbon Dating.

Differentiated Learning/Enrichment

• Have the students calculate the age of objects when given the half-life, original amount, and current amount of that material.

Enrichment Question

1. The population of the earth is doubling every 40 years. If the population of the earth is now 7 billion people, how many people will be here when you are 95 years old?

### Half-Life : Licorice

Description: With the Half-Life Laboratory, students gain a better understanding of radioactive dating and half-lives. Students are able to visualize and model what is meant by the half-life of a reaction. By extension, this experiment is a useful analogy to  radioactive decay and carbon dating. Students use licorice to demonstrate the idea of radioactive decay. This experiment is best used by students working in pairs.

5-12

Disciplinary Core Ideas (DCI)
3-5ETS1-2, MS-ESS1-4, HS-ESS1-6

Time for Teacher Preparation
40-60 minutes – To gather materials

Activity Time:
40-60 minutes (1 Class Period)

Materials

Safety

• Students should not eat licorice

Science and Engineering Practices

• Ask questions and define problems
• Use models
• Analyze and interpret data
• Use mathematics and computational thinking
• Construct explanations
• Argue from evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation

Objectives
Students try to model radioactive decay by using the scientific thought process of creating a hypothesis, then testing it through inference. It is a great introduction to the scientific process of deducing, forming scientific theories, and communicating with
peers. It is also useful in the mathematics classroom by the process of graphing the data.

Students should begin to see the pattern that each time they “take a half-life,” about half of the surrogate radioactive material becomes stable. Students then should be able to see the connection between the M&M’s and Puzzle Pieces and radioactive elements in archaeological samples. Seeing this connection will help students to understand how scientists can determine the age of a sample by looking at the amount of radioactive material in the sample.

• To define the terms half-life and radioactive decay
• To model the rate of radioactive decay
• To create line graphs from collected data
• To compare data
• To understand how radioactive decay is used to date archaeological artifacts

Background
Half-Life
If two nuclei have different masses, but the same atomic number, those nuclei are considered to be isotopes. Isotopes have the same chemical properties, but different physical properties. An example of isotopes is carbon, which has three main isotopes, carbon-12, carbon-13 and carbon-14. All three isotopes have the same atomic number of 6, but have different numbers of neutrons. Carbon-14 has 2 more neutrons than carbon-12 and 1 more than carbon-13, both of which are stable. Carbon-14 is radioactive and undergoes radioactive decay.

Radioactive materials contain some nuclei that are stable and other nuclei that are unstable. Not all of the atoms of a radioactive isotope (radioisotope) decay at the same time. Rather, the atoms decay at a rate that is characteristic to the isotope. The rate of decay is a fixed rate called a half-life.

The half-life of a radioactive isotope refers to the amount of time required for half of a quantity of a radioactive isotope to decay. Carbon-14 has a half-life of 5730 years, which means that if you take one gram of carbon-14, half of it will decay in 5730 years. Different isotopes have different half-lives.

The ratio of the amounts of carbon-12 to carbon-14 in a human is the same as in every other living thing. After death, the carbon-14 decays and is not replaced. The carbon-14 decays, with its half-life of 5,730 years, while the amount of carbon-12 remains constant in the sample. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing. Radiocarbon dates do not tell archaeologists exactly how old an artifact is, but they can date the sample within a few hundred years of the age.

### Teacher Lesson Plan

Licorice

1. Instruct the students to label the horizontal axis of the graph paper “Time (seconds)” and the vertical axis “Radioactive Licorice (%)”. Show them how to calibrate the horizontal axes so that one block equals 5 seconds and two blocks equal 10 seconds. Instruct them to mark the horizontal axis at 10-second intervals.
2. Give each student one piece of licorice to place onto the graph paper. Tell them to stretch the full length of the licorice vertically over the time “zero” mark and to make a mark on the paper at the top of the licorice. This mark represents 100% of the  radioactive material at time zero.
3. Call out “GO” or “HALF-LIFE” at 10-second intervals for up to 90 seconds. When you say “GO” or “HALF-LIFE,” the students will have ten seconds to remove one-half of their licorice and set it aside. They place the remaining piece of licorice on the 10 seconds line and mark its current height. At 20 seconds, they should again remove half of the licorice and set it aside, then mark the height of the remaining portion on their graphs at the 20 second line. Repeat this process until 90 seconds have gone by.
4. Now, the students should connect all the height marks with a “best fit” line, completing a graph of the “Half-Life of Licorice.”

NOTE: The original strip of licorice represents radioactive material; the portion which is “set aside” during the activity represents the material that has “decayed” and is no longer radioactive.

NGSS Guided Inquiry
Explain about radiation and half-lives of isotopes. Tell students to design their own experiment, using paper, M&M’s®, Pennies, other 2 sided material or licorice as a radioactive material undergoing decay to discover the nature of the half-life of that material.
You might suggest that the students experiment with their graphing results to see if trends begin to form.

### Student Procedure

Licorice

1. Label the horizontal axis of the graph paper “Time (seconds)” and the vertical axis “Radioactive Licorice (%)”. Calibrate the horizontal axes so that one block equals 5 seconds and two blocks equal 10 seconds. Mark the axis at 10-second intervals.
2. Start with one piece of licorice to place onto the graph paper. Stretch the full length of the licorice vertically over the time “zero” mark, which is the same as the vertical axis. Make a mark on the graph paper at the top of the licorice. This mark represents 100% of the radioactive material at time zero.
3. Your teacher will call out “GO” or “HALF-LIFE” at 10-second intervals up to 90 seconds. When your teacher says “GO” or “HALF-LIFE” you will have ten seconds to remove one-half of your licorice and set it aside. Place the remaining piece of licorice on the 10 seconds line and mark its current height. At 20 seconds, you should again remove half of the licorice and set it aside, then mark the height of the remaining portion on your graph at the 20-second line. Repeat this process until 90 seconds have gone by.
4. Now, connect all the height marks with a “best fit” line, completing a graph of the “Half-Life of Licorice.”

NOTE: The original strip of licorice represents radioactive material. The portion which is “set aside” during the activity represents the material that has “decayed” and is no longer radioactive.

Data Collection
Student Data Collection Sheets

Post Discussion/Effective Teaching Strategies
Questions provided on the Student Data Collection Sheets

### Measuring and Units : Is it Radioactive?

With the Measuring Laboratory, students gain a better understanding of radioactivity and radiation. Students are able to visualize what is meant by radiation and background radiation.

5-12

Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, 3-5ETS1-2, MS-PS1-1, MS-PS1-4, MS-PS3-2, MS-ETS1-1, MS-ETS1-3, HS-PS1-8, HS-PS3-2, HS-PS4-1, HS-PS4-4, HS-ESS1-2, HS-ESS2-3, HS-ESS3-6

Time for Teacher Preparation
30-60 minutes – Clear the room of any unnatural radioactive sources. Create identifiable “locations” within the room – to correspond to the number of lab groups you will have. Code each of these locations in some way for easy reference.

Activity Time:
30-60 minutes (1 Class Period)

Materials
Use as many Geiger counters as you have available. We will assume for this experiment that you are using Geiger counters which are not calibrated (they may not provide the same readings under the same circumstances). So, you may want to label each Geiger counter with a code number or letter; then, each group can record the code of the Geiger counter being used and use it for future activities.

• Geiger counters NOTE: digital read-out Geiger Counters give easier readouts for classroom use and more accurate measurements
• An assortment of objects with varying radioactivity, including some in each of three categories:
• Just barely radioactive (“Vaseline glass”, thoriated welding rods, “depression green” glass, some fossils)
• Unambiguously radioactive (orange/red Fiestaware, certain lantern mantles, some uranium ore and minerals)
• Student Data Collection Sheets

Number each sample and record which category they fall into in a spreadsheet.

The students love testing the “hotter” items, but having the three categories of objects assures that everyone tests at least two each of clearly radioactive, marginally radioactive (would really need more counting time than available during lab to be sure), and essentially non-radioactive. The point is to have the students struggle with and face the uncertainty concerning whether or not items are radioactive.

Safety

• Students should use care when dealing with radioactive materials
• Students should wash their hands after this experiment

Science and Engineering Practices (NGSS)

• Ask questions and define problems
• Plan and Carry out investigation
• Analyze and interpret Data
• Use mathematics and computational thinking
• Construct Explanations
• Argue from Evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts (NGSS)

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Energy and Matter: Flows, Cycles, and Conservation
• Structure and Function
• Stability and Change of Systems

Objectives

• Familiarize students with the concept of background radiation.
• Determine the amount of background radiation present at a specific location.
• To define the terms radiation
• To become familiar with the different types of radiation
• To become familiar with operating a Geiger-Mueller counter

The key ideas for students to understand upon completing this lab are:

• There is background radiation wherever they are.
• Levels of background radiation vary somewhat from one location to another and from one moment to the next.
• Background radiation must be taken into account when measuring the radiation from an object.
• Uncalibrated Geiger counters may give slightly different counts in identical situations; however, they are useful for:
• determining that radiation is present.
• comparing radiation levels for locations or objects.

Background
Introductory Information
We live in a radioactive world, as did our earliest ancestors. The radiation in our world comes from many sources – cosmic radiation (outer space), terrestrial sources (the earth), radon in the air, etc. In addition, we live and work in buildings made from materials (stone, adobe, brick, concrete) which contain elements that are naturally radioactive. The amount of naturally occurring background radiation we experience varies, depending upon location.

Geiger counters will register the presence of some radiation even if you have not placed them near a known radiation source. This is a measure of the background radiation that is always present at a given location. In order to make meaningful measurements of the radioactive nature of specific objects or materials, we will need to know how much radiation is naturally present in the  environment.

The difference between background radiation and the radiation measured near a specific object will give us the level of radiation due to the object. Although background radiation is quite steady on average, you would never conclude that by listening to or watching a Geiger counter. The amount of radiation will appear to vary, depending upon the specific time at which you take a measurement.

The covert theme of this lab is dealing with ambiguity. Because there is background radiation always giving a background signal, and a non-constant signal at that, measuring a sample for a minute or two (with ordinary Geiger counters) just cannot determine with certainty if the sample is weakly radioactive or not.

### Teacher Lesson Plan

Before beginning, make sure students have some familiarity with the Geiger counter and how it will be used. Predetermine whether measurements are to be made with the “window” on the Geiger tube open or closed. Give students an overview of how and where to set the sensitivity level, etc.

1. Have the students measure background counts for one minute.
• This is done by counting the number of “clicks” from the Geiger counter. It is not practical to make this measurement by reading the counts/min scale on the Geiger counter.
1. Have each lab group enter the results of all the groups into the proper space on the table you provide.
• Ask students to examine the results. Do the results vary? If so, what is the lowest value and the highest value? What is the “range” of results? What are some possible reasons why the results might be different? Results will vary. Possible reasons include: inaccurate counting, inaccurate timing, slight variations in background radiation from location to location within the room, and/or differences between Geiger counters. There may be other suggestions from students — which you must evaluate.
• Ask students how they could try to eliminate some sources of error. They may suggest repeating the measurements to rule out inaccurate timing and counting. They may suggest removing any jewelry, etc.
1. Have students run a second and third trial and enter only the data for their own group into the table.
• Ask the class: Do the results for your lab group vary from one trial to another? If so, why? What is the range for your own measurements? At this stage, students may have discovered that the results for their own group vary slightly in each trial.
Discuss this variation. Consider the possibility that errors were made during every measurement and discuss whether this is likely. Also, discuss the idea that the amount of background radiation present may actually be slightly different from one moment to the next — even though it has an “average” value. Refer to the water sprinkler analogy mentioned in the introduction. Have each group enter the “range” for their own measurements in the bottom row of the table.
• Regarding the counts they took, ask “Were the clicks always evenly spaced? OR, did the clicks sometimes cluster together with pauses between them?” Clicks are usually NOT evenly spaced. There are usually some “clusters” of clicks and some pauses. Discuss the possibility that this variation or “clustering” of clicks may have some impact on how long a time
period we use for measuring radioactivity levels. For example, using a really short time period might make measurements more prone to error than a longer time, especially if you did the “short period” measurement during a “pause” or during a “cluster” of clicks. 1. To illustrate, draw a clock face and let it represent a 60 second measurement. Then, make marks around the perimeter to represent when clicks are heard. This will give you clusters of marks and some empty spaces.
If someone takes a measurement in a specific period of 5 seconds, it can easily affect the count they get.
1. Then, have the students enter the data for all of the groups into the table.
• Ask the students: Are there variations from group to group? If so, what are some possible reasons?
• Discuss possibilities: variations in Geiger counters, variations due to “location” in the room, etc.
• How could we determine if these differences are due to our Geiger counters being different or to differences within the room? You should realize when you begin this activity that these “uncalibrated” instruments are likely to give slightly different results under identical conditions and at the same time. However, it IS possible for there to be slight variations within the room. Proximity to a particular building material or exposure to some other radiation source, for example, may produce higher “background” readings in a specific location.
• There are several experimental approaches you and your students could use in resolving this issue.You could have each group make measurements at the same location and compare them. OR, each group could move to each of the identified locations and make readings for comparison purposes. Students may come up with other suggested solutions. Depending upon the time you want to allow and the sophistication level of your students, you can structure another set of measurements to provide an answer to the question above.

NOTE: If you are doing this activity in a one-period time slot, it is difficult to include measurement of background. Thus, most teachers use an average value for background, measured on a previous day. (Background varies little over time.)

Geiger Counter Resources:

How to attach speakers or head phones to a  CD V-700

CD V-700 Instruction and Maintenance Manual

### Fission Demonstration

Description:With the Fission Demonstration, students gain a better understanding of nuclear fission and fusion. Students are able to visualize and model what is meant by nuclear fission. By extension, this experiment is a useful analogy to the generation of electricity via nuclear reactors. This experiment is best performed by students working in groups.

5-10

Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, 5-PS1-3, 5-ESS3-1, 3-5 ETS1-1, MS-PS1-4, MSPS1-5, MS-PS3-1, MS-PS3-2, MS-PS3-4, MS-PS3-5, HSPS1-1, HS-PS1-8

Time for Teacher Preparation
30-60 minutes – To gather materials and set-up

Activity Time:
30-60 minutes (1 Class Period)

Materials

Safety

• Student should use care when handling scissors

Science and Engineering Practices (NGSS)

• Ask questions and define problems
• Use models
• Plan and carry out investigation
• Analyze and interpret data
• Construct explanations
• Argue from Evidence
• Obtain, evaluate and communicate information

Cross Cutting Concepts (NGSS)

• Patterns
• Cause and Effect
• Scale, Proportion, and Quantity
• Systems and System Models
• Energy and Matter: Flows, Cycles, and Conservation
• Stability and Change of Systems

Objective
Learn the concepts of nuclear fission and fusion and investigate how these reactions are used to generate energy.

Background
Fission is the release of energy by splitting heavy nuclei such as uranium-235 and plutonium-239. Each fission releases 2 or 3 neutrons. These neutrons are slowed down with a moderator, so they can initiate more fission events. Control rods absorb neutrons to keep the chain reaction in check. These fast-moving fission fragments are knocked into a water molecule, which causes the water molecules to move a little bit faster. This increased amount of motion is measured as an increase in temperature. The energy from the reaction drives a steam cycle to produce electricity. Nuclear power produces no greenhouse gas emissions; each year U.S. nuclear plants prevent atmospheric emissions totaling:

• 5.1 million tons of sulfur dioxide
• 2.4 million tons of nitrogen oxide
• 164 million tons of carbon

Fusion is the opposite of fission. Fusion is the release of energy by combining two light nuclei such as deuterium and tritium.
The goal of fusion research is to confine fusion ions at high enough temperatures and pressures, and for a long enough time,
to fuse. There are two main confinement approaches:

• Magnetic confinement uses strong magnetic fields to confine the plasma.
• Inertial confinement uses powerful lasers or ion beams to compress a pellet of fusion fuel to the right temperatures and pressures.

### Teacher Lesson Plan:

This experiment can be performed as either a demonstration or by the students themselves. Regardless, the procedure remains
the same. Explain that the balloon is like a heavy nucleus, such as uranium-235 or plutonium-239. Once they have twisted the
balloon into two sections, cut the twisted section to cause the “nuclei” to undergo fission. When the two smaller balloons are released, explain that the balloons flying off represent the energy given off by the reaction and how these fragments knock
water molecules, speeding them up, and thus increasing their temperature. Afterwards, collect the balloon fragments to throw
away and explain that nuclear waste needs to be disposed of properly and not dumped into the environment (just as you would
not leave pieces of balloons lying around the classroom).

NGSS Guided Inquiry
Split students into small groups and give each group a balloon. Have students design an experiment to model nuclear fission
with the balloon acting as a heavy nucleus, such as uranium-235 or plutonium-239. Have each group discuss ways to dispose of
the waste products.

### Student Procedure

The students should draw the results that they observe onto the Student Data Collection Sheet that are provided.

1. Blow up the twisting balloon and tie off the end.
2. Twist the balloon in the center, creating two separate, but equal sections.
3. While holding both ends of each inflated section, have a partner cut the twisted portion of the balloon in the middle.
4. Hold onto the ends of both of the resulting smaller balloons.
5. Release the balloons allowing them to fly off.
6. Collect the balloon fragments to throw away.

Data Collection
Student Data Collection Sheets
Post Discussion/Effective Teaching Strategies

Questions

2. What would need to happen to model nuclear fusion?
3. Why is it important to dispose of radioactive waste properly?

Assessment Ideas

• Question the student as to the similarities and differences of nuclear fission and fusion.

Differentiated Learning/Enrichment

• Have students model fusion
• Have students research contamination by waste products of fission.

Enrichment Questions

• How could fission be used to generate electricity in a nuclear power plant?
• Instead of scissors, what is actually used to make an atom undergo fission?

Further Resources

Nuclear Fission Animation

Citations for Reference
Adapted from Easy to Perform Classroom Experiments in Nuclear Science. (1992), BROMM, B, American Nuclear Society.