Hot Stuff – Lesson 2 – Introducing photons and phonons
Students learn about Einstein’s discovery of photons and phonons through the reading play Hot Light if they have not done so already. Following the play, students join Albert to sing Einstein’s Photons and Phonons song. The lesson finishes by introducing the Nerf Gun analogy for photons and the Slinky Spring analogy to introduce phonons and then referring back to the lesson one role play to show how photons turn into phonons.
Introduction: Review what students learnt about atoms and molecules from the Lesson 1 and the Atom Frenzy module earlier in the year. Introduce the learning intentions using Lesson 2 of the Hot Stuff PowerPoint.
Acting like Einstein – Einstein’s early discoveries: If this was not performed prior to Lesson 1, Students perform a short reading play Hot Light in which Albert Einstein tells students his story of the discovery of photons and phonons and sings the Photons and Phonons song (lyrics). Remind students that in science we use models to explain things that we cannot see.
Activity – Nerf gun photon analogy: Following this, the teacher leads a discussion explaining how we use Nerf guns and Nerf gun bullets to model a light source and photons (the bullets).
Activity – Slinky spring phonon analogy: Invite two students to hold each end of a ‘slinky spring’ and stretch it a small amount on a smooth floor or desk. Then have another student fire Nerf gun bullets at the centre of the spring. As each bullet collides with the ‘slinky spring’, ask the students holding the end of the spring whether they saw or felt anything. The photons change into phonons which then move rapidly and chaotically through the solid as heat.
Revisit the class activity from lesson 1 – Being solid, liquid or gas: Revisit the kinaesthetic activity but this time have the teacher fire Nerf gun bullets or gently pass soft balls to students. When a ‘photon’ hits one student, that student starts jiggling around to produce phonons. As more students are hit, they also start jiggling. The more photons there are, the more phonons are produced and the more the random, chaotic movement of the water molecules there is, resulting in one student evaporating to show how the liquid state changes into gas.
Review and introduce the next lesson: Review all new words, write them on the class Word Wall and set up a simple evaporation activity for the next lesson by filling two identical glass jars to the same level (about ¾ full), marking the water lever and leaving one with a lid and one without until the next lesson.
Students will:
- understand the contribution Albert Einstein made to our modern understanding of light and heat and the effect these have on matter
- explain that photons change into phonons which warms up things on Earth
- Access to a clear area where students can perform the Hot Light reading play
- Review Lesson 2 of the Hot Stuff PowerPoint
- Model H2O and CO2 molecules: plasticine in different colours (alternative: Tatoms and/or Snatoms atoms, balloons and double-sided tape, or polystyrene balls and Bluetac)
- Ice cubes and water in separate containers for display
- Props for the reading play:
- Large cardboard box that a student can easily fit into
- Old walking stick
- Einstein costume and hair
- Nerf gun and foam bullets
- Tennis, ping-pong or other soft balls (optional)
- Slinky spring
- 2 identical glass jars with wide mouths, one with a tight-fitting lid
- Permanent marker or tape, preferably coloured
This is the second lesson of the Hot stuff topic. Students will start by learning about photons and phonons from Albert Einstein! Maybe not Albert himself, but a class member dressed up as Albert.
Before starting the play, remind students about atoms and molecules and the activity from last week. Present students with two model molecules (water and carbon dioxide).
- Who can tell me what they are? Water or H2O and carbon dioxide or CO2
- Who can remember what water molecules are made of? Two hydrogen atoms and an oxygen atom joined together.
- What holds atoms together? Electrical forces – electrostatic/electric and magnetic forces.
- I have some ice cubes in this clear container. Who can describe how water molecules in solid ice are arranged and how they move in ice? They vibrate backwards and forwards in a fixed position – they make up solid ice.
- In this container I have liquid water. Who can describe how the water molecules are arranged and how they move in the glass of liquid water? The molecules are still very close together, but because they have more energy they can ‘mingle’ amongst one another – this is why water can be poured from one glass to another and fill the bottom of the container it is in.
- Describe the shape of the water molecule. It is bent. / It looks like Mickey Mouse.
Introduce the Learning Intentions for Lesson 2 from the Hot Stuff PowerPoint.
If you have not already performed the Hot Light reading play, do so now.
Students are going to take part in a short reading play Hot Light to find out about two amazing things Albert Einstein discovered. Albert will tell the class about his discoveries about heat and light, and then they will join him with a song about the discoveries.
The purpose of the reading play is to introduce the human story of the discovery of photons and phonons and to familiarise students with the language.
Teachers should decide whether they should use the Standard Australian English version of the play, or whether they think their class might appreciate the exaggerated German accent. Some may not wish to present false stereotypes to their class.
Have the preferred version of the printed script with spoken words in large bold font to help with the reading if necessary.
If the cast members have not been identified previously, do this now. Cast members are: Albert Einstein (needs good reading, strong voice, and voice projection); Noisy kid, Helpful kid, Cautious kid, Question kid, Class teacher, Smartypants kid. There is one line for each supporting cast member.
The only props are a large cardboard box, walking stick and Einstein wig and costume.
The remainder of the class could be the audience.
At the conclusion to the Play, all join Albert as he sings his Photons and Phonons song
On the right you will find a demonstration video for this activity. We recommend viewing this video before proceeding with the text description below.
Now use a toy model to help students imagine what photons might be like.
- Who has a Nerf gun at home? How does it work? The toy gun fires foam bullets.
- We use our model to explain that photons are tiny bundles of energy that move very quickly. In our model, what represents photons? The Nerf gun bullets.
- What is the Nerf gun like? A light bulb, the sun or even a laser pointer. (This is shown in the Hot stuff PowerPoint diagram.)
- In what ways are our Nerf gun bullets like photons? They move very quickly, they bump into things that get in their path, they normally travel in straight lines.
- In what ways is our model not accurate? Photons travel at the speed of light and this is the fastest anything can travel in the Universe. Individual photons only have a tiny amount of energy, but yet they can still damage things they strike.
- We can use our model to say that a beam of light is photons which have ‘bulletiness’. Although photons don’t have much energy, they can cause damage. Who can think of an example where we can see that sunlight causes damage, just like bullets do? When we experience sunburn from photons in the burning part of sunshine!
On the right you will find a demonstration video for this activity. We recommend viewing this video before proceeding with the text description below.
Now students will use their Nerf gun to show how photons can turn into phonons. Invite two students to hold each end of a ‘slinky spring’ and stretch it a small amount on a smooth floor or desk.
Then ask a third student to fire Nerf gun bullets at the centre of the spring and observe what happens when the Nerf gun bullet hits the slinky spring.
Discuss the models with the class:
- What does the Nerf gun bullet represent? A photon.
- What do we observe when each Nerf gun bullet (photon) collides with the slinky spring? Ask the students holding the end of the spring whether they saw or felt anything? Give them time to describe their observations. Students feel a vibration or tiny bundle of vibrational energy.
- What does this ‘bundle of energy’ represent? A phonon.
- Then ask the class why this happens. Allow a number of students to respond. The photon turned into a phonon – vibrational bundle of heat energy.
- How did the phonons move through the spring? The photons changed into phonons which then move rapidly and chaotically through the solid as heat.
We will briefly revisit our role play of being a solid, liquid and gas.
Form up into the 5X5 or 5X6 grid (adjust for number of students).
Ask students to start moving to model being an ice block (a fixed position on the grid and ‘vibrating’ backwards and forwards).
Warning: remind students to be careful not to tread on other people’s toes!
We will now model what happens if we shine light into the ice block.
The teacher could fire Nerf gun bullets (photons) into the bodies of a few students (water molecules), or alternatively you could gently pass tennis balls, ping-pong balls, or other soft balls to the students to represent photon impacts. It is advised that you provide each student with safety goggles if you choose to use the Nerf guns for this activity. It may be advisable not to use Nerf guns if there are concerns around the use of toy guns, or if any students are likely to be affected by the use of toy guns.
When a photon hits a student, that student starts jiggling around to produce phonons.
As more Nerf gun bullets or balls are thrown into the group (ice block), more students are hit and they also start jiggling more.
Eventually, everyone is jiggling much more vigorously because the photons have turned into phonons and the ice block turns from a solid (ice) into a liquid (water). The more photons there are, the more phonons are produced and the more the random, chaotic movement of the water molecules there is.
The water droplet (students) gets hotter and hotter and jiggling around more rapidly and then one student evaporates to show how the liquid state changes into gas.
Explain that this activity will help us understand what we will see in Lesson 3.
Review all new words and write them on the class Word Wall.
Explain that in Lessons 3 to 8 we will continue to explore photons and phonons, how heat is transferred in solids and how it causes objects to get hotter. We will do a very simple activity next week to show how photons and phonons do magical things.
In preparation for the next lesson set up two identical clear glass containers of water as follow:
- place a mark about ¾ the way up the outside of the container with a fine permanent marker or piece of tape. The volume in each container must be the same.
- fill both containers to the mark with tap water.
- place a lid firmly on one and leave the other open.
- place both near a window so they receive direct sunlight.
We will look to see what, if anything, has happened next week and use our knowledge of photons and phonons to explain why.
Collision: When two or more moving objects run into one another and energy may be transferred from one object to the other.
Vibration: Repeating back and forward movement, often about a fixed position.
Photons: Individual ‘packets’ or ‘bundles’ of light or other electromagnetic radiation that carry energy and can travel through a vacuum.
Phonons: Bundles or packets of vibrational energy.