Wave and Particle Models of Energy: a full term of science

Ten ready-to-teach lessons for Year 9 Physical sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards or tickets.
3. Gather the few items under “You need” on the plan. Most come from the science prep room or the supermarket.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 9 science teacher

The pack suits a physics specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: energy can travel without matter travelling with it, and scientists picture this with two models. The wave model describes a pattern of disturbance moving through a medium, or, for light, through empty space. The particle model describes particles knocking their neighbours and passing energy on. Each model explains some things well and others poorly, so part of the work is choosing the more useful one.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lessons 1, 2 and 8 need slinkies, Lesson 3 needs an open space at least 170 m long, and Lesson 5 needs a conduction rod set from the prep room.

Safety and care in one look

Hot water is poured by the teacher, and the Lesson 9 cups hold warm tap water, not boiling water. The clap in Lesson 3 is made with two wooden blocks held at arm’s length, never near anyone’s ears. Slinkies are stretched along the floor, not flicked at people. In Lesson 6 nobody looks at the Sun, even through a CD.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lessons 1 to 3 build the wave model: a wave carries energy and not matter, it has a wavelength, a frequency and a speed, and the speed of sound can be measured. Lessons 4 and 5 bring in the particle model, for sound in different mediums and for conduction. Lesson 6 meets light, a wave that needs no medium at all, and Lesson 7 weighs the two models against each other. Lessons 8 and 9 use both models on earthquakes and on keeping heat in, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S9U04 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 9 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: the thunderstorm task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons, and most of it is already in the science prep room. Three things are worth doing ahead: book slinkies for Lessons 1, 2 and 8, find an open space at least 170 m long for Lesson 3, and check the conduction rod set for Lesson 5.

The one-trip list

• From the prep room: slinkies, a conduction rod set, a heatproof container, thermometers, timers, a trundle wheel and eye protection.
• From the supermarket or home: paper cups, string, zip bags, butter, aluminium foil, cotton wool, bubble wrap and newspaper.
• From a cupboard: old CDs or DVDs, torches and two flat wooden blocks.
• For Lesson 3: an open space such as an oval, at least 170 m long.

Safety and care in one look

• The teacher pours hot water; the Lesson 9 cups hold warm tap water, not boiling water.
• Wooden blocks are clapped at arm’s length, never near ears.
• Slinkies stay on the floor and are never flicked at people.
• Nobody looks at the Sun, even through a CD.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the task, in which students explain six moments of a thunderstorm with the wave and particle models, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: wave, medium, transverse wave and longitudinal wave in Lesson 1; crest, trough, amplitude, wavelength, frequency, compression and rarefaction in Lesson 2; particle model in Lesson 4; conduction and insulator in Lesson 5; electromagnetic wave and vacuum in Lesson 6; P wave and S wave in Lesson 8.

Dear families

This term in science, Year 9 studies how energy travels: as waves through water, air, the ground and even empty space, and as particles passing energy on to their neighbours. Students use two models, the wave model and the particle model, and learn to judge which one explains a happening more usefully.

Along the way your student will send pulses along a slinky, measure the speed of sound on the school oval, build a string telephone, time heat travelling along metal rods, split light into colours with an old CD, work out how far away an earthquake was, and test which wrapping keeps a cup of water warm.

Try this at home

• In a storm, count the seconds between the lightning and the thunder. Every 3 seconds is about a kilometre.
• Put an ear to a table while someone taps the far end gently. Is it louder through the table or through the air?
• Tilt an old CD under a torch. Where do the colours come from?
• Wrap one hot drink in a tea towel and leave another bare. Which stays hot longer, and why?

What to ask your scientist

• If a wave carries energy, does the water in an ocean wave travel to the beach?
• Why does sound travel faster through steel than through air?
• How can light reach us from the Sun when space is empty?
• When is the wave model more useful, and when is the particle model?

A small note on care: hot water is poured by the teacher, the claps in the sound test are made at arm’s length, and nobody looks at the Sun.

Warm regards,

The Year 9 science team

Printed from the free seegongsik Wave and Particle Models of Energy teaching pack · seegongsik.com/au/y9/physical/AC9S9U04/pack

Waves carry energy, not matter

A wave is a disturbance that carries energy from one place to another, and the material it travels through, the medium, stays where it is. A surfer feels the energy of a wave that may have started hundreds of kilometres away, yet the water itself has only risen and fallen. In a transverse wave the medium moves at right angles to the direction the wave travels, like a flick along a rope. In a longitudinal wave the medium moves back and forth along the direction of travel, like a push along a slinky, and like sound. Students send both kinds of pulse along a slinky, watch a taped coil, and time a pulse to find its speed.

We are learning to

• describe a wave as energy moving through a medium while the medium stays where it is,
• tell transverse and longitudinal waves apart by the way the medium moves,
• measure the speed of a pulse with repeated timings.

Success criteria

• I can make both kinds of pulse on a slinky and describe how the taped coil moves in each.
• I can work out the speed of a pulse from its distance and the mean time.

You need

• for each group: a slinky, a small piece of coloured tape, a metre ruler and a timer; a clear stretch of floor,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Care: keep the slinkies on the floor, stretch them gently, and never let one go while it is stretched: walk the ends together.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the pulses in Session A, and Parts B and C in Session B.

Watch for these ideas

• “The water in a wave travels to the beach.” The water mostly rises and falls; the energy travels.
• “A bigger flick makes a faster pulse.” It makes a taller pulse; the speed depends on the slinky and how tightly it is stretched.
• “Sound is a transverse wave.” Sound is longitudinal: the air moves back and forth along the way the sound travels.

Make it easier, make it bigger

• Easier: time the pulse three times instead of five, and use the example times for the speed.
• Bigger: stretch the slinky further and time the pulse again. Predict, then test: does the speed change?

Answers and look-fors

• Part A: transverse, the taped coil moves sideways and back; longitudinal, it moves forward and back along the slinky. Either way it ends where it started.
• Part B, example: mean time 1.2 s; speed = 3 m ÷ 1.2 s = 2.5 m/s.
• Part C: 1. Energy: the coils pass the disturbance on and stay in place. 2. Transverse: the medium moves at right angles to the wave; longitudinal: back and forth along it. 3. Single timings vary with reaction time, so the mean of five is more reliable. 4. Sound.
• Bigger: a more tightly stretched slinky usually carries the pulse faster; a fair test keeps the same slinky and the same kind of flick.
• Exit tickets: 1. Energy. 2. It moves up and down (at right angles) and stays in place. 3. Longitudinal.

Waves carry energy, not matter

A. Two kinds of pulse

Draw the slinky as each pulse passes. Add an arrow for the way the pulse travels and one for the way the taped coil moves.

B. How fast is a pulse?

The slinky is stretched to 3 m. Time a pulse from one end to the other.

Speed = distance ÷ time, in m/s.

C. Questions

Exit tickets

Cut out one ticket for each student.

Describing a wave

The wave model gives every wave a few measurements. The amplitude is how far the medium moves from its rest position: a bigger amplitude carries more energy. The wavelength is the distance from one crest to the next, or from one compression to the next. The frequency is how many waves pass a point each second, measured in hertz (Hz). Multiply them and you get the speed of the wave: wave speed = frequency × wavelength. Students label two waves, then use the rule for six real waves, from a slinky to an FM radio signal.

We are learning to

• name and measure the parts of transverse and longitudinal waves,
• use wave speed = frequency × wavelength, rearranged when needed,
• compare waves that differ hugely in size and speed.

Success criteria

• I can label the crest, trough, amplitude, wavelength, compression and rarefaction.
• I can find the missing value for each of the six waves, with units.

You need

• a slinky and a long skipping rope to show,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the rope, the board and the labels in Session A, and the six waves and Part C in Session B.

Watch for these ideas

• “The wavelength is the height of the wave.” The height from rest to crest is the amplitude; the wavelength is along the wave.
• “A higher frequency makes a faster wave.” In one medium the speed stays the same; a higher frequency means a shorter wavelength.
• “Longitudinal waves have no wavelength.” Their wavelength is from one compression to the next.

Make it easier, make it bigger

• Easier: give the rule in all three forms on the board: v = f × λ, f = v ÷ λ, λ = v ÷ f.
• Bigger: a person can hear from about 20 Hz to 20 kHz. Work out the longest and shortest wavelengths of sound we can hear in air.

Answers and look-fors

• Part A: 1 crest, 2 trough, 3 wavelength, 4 amplitude, 5 compression, 6 rarefaction, 7 wavelength.
• Part B: a wave on a slinky: speed 2.4 m/s; a note of 440 Hz in air: wavelength 0.78 m; ripples in a tray of water: frequency 4 Hz; a low note in water: wavelength 7.4 m; an ocean swell: speed 15.6 m/s; an FM radio signal: frequency 100,000,000 Hz.
• Part C: 1. The wavelength halves: in one medium the speed stays the same, so twice the frequency means half the wavelength. 2. Radio waves are electromagnetic, like light, so they travel far faster than sound or water waves. 3. A bigger amplitude, which carries more energy.
• Bigger: 343 ÷ 20 = about 17 m; 343 ÷ 20,000 = about 0.017 m, or 1.7 cm.
• Exit tickets: 1. The distance from one crest to the next. 2. 10 Hz. 3. 5 × 2 = 10 m/s.

Describing a wave

A. Label the waves

Write the part at each number. Use the word bank; one word is used twice.

B. Wave speed = frequency × wavelength

C. Questions

Exit tickets

Cut out one ticket for each student.

The speed of sound

Light travels so fast that, across a school oval, it arrives almost at once; sound in air travels at about 343 m/s, so it arrives noticeably later. That gap is how a storm’s distance is judged from the lightning and the thunder, and it lets a class measure the speed of sound with a clap and a stopwatch. A timer stands 170 m from a clapper, starts the stopwatch on seeing the blocks meet and stops it on hearing the clap. The times are short, so reaction time matters a great deal, and judging the method is as much the point as the answer.

We are learning to

• measure the speed of sound with a simple outdoor method,
• use repeated trials and a mean, and calculate a speed,
• identify sources of error and suggest a better method.

Success criteria

• I can work out the speed of sound from our distance and mean time.
• I can name the biggest source of error and how to make it smaller.

You need

• two flat wooden blocks, three or four stopwatches (or phone timers), and a trundle wheel or long tape measure; an open space at least 170 m long,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Care: the clapper holds the blocks at arm’s length, high above the head, and never near anyone’s ears. Stay together as a class on the oval.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the plan and the claps in Session A, and Parts B and C in Session B.

Watch for these ideas

• “We hear things the moment they happen.” Sound takes about 3 seconds to travel a kilometre through air.
• “Light also takes a moment to arrive.” Across 170 m light takes less than a millionth of a second, so it counts as instant here.
• “Our answer is wrong because it is not 343.” Every measurement has some error; the question is how big, and why.

Make it easier, make it bigger

• Easier: use the example times for the mean and the speed.
• Bigger: an echo method stands 85 m from a tall wall and claps in time with the echo. Explain why this could give a better answer.

Answers and look-fors

• Part A: the clapper, timers 170 m away who can see the clapper, a start on seeing and a stop on hearing.
• Part B, example: mean time 0.5 s; speed = 170 ÷ 0.5 = 340 m/s, within 0.9% of 343 m/s.
• Part C: 1. The times spread by 0.2 s, which is a large part of a time this short. 2. Reaction time: starting and stopping a stopwatch takes about 0.2 s each, nearly half of the time being measured. 3. Use a longer distance, more timers and more claps; or use an echo, or a phone that records both the flash and the sound. 4. Wind blowing towards or away from the timers, and the distance being measured roughly.
• Bigger: clapping in time with the echo turns many trips into one long time, so reaction time becomes a small part of it.
• Exit tickets: 1. About 343 m/s. 2. Light travels much faster than sound. 3. Reaction time.

The speed of sound

A. Our plan

B. Times over 170 m (s)

C. How good was the method?

Exit tickets

Cut out one ticket for each student.

Sound needs particles

Sound is a longitudinal wave, so it needs particles to pass the vibration on; in the empty space between the stars there is nothing to carry it. Here the particle model earns its place, because it also explains why sound travels at different speeds. In a solid the particles are close together and tightly linked, so a vibration is handed on fastest; in a liquid they touch but slide past one another; in a gas they are far apart and pass the vibration on slowest. Students build string telephones, listen through a bench and a bag of water, and work out how long sound takes to cross a kilometre of air, water and steel.

We are learning to

• explain why sound needs a medium and cannot cross empty space,
• compare the speed of sound in solids, liquids and gases,
• use the particle model to explain the differences.

Success criteria

• I can work out how long sound takes to travel a kilometre in air, water and steel.
• I can explain the order with the spacing and linking of the particles.

You need

• for each pair: two paper cups and 5 m of string for a string telephone; a sealed zip bag of water; a bench,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the stations in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Sound travels fastest in air because air is light.” Air particles are far apart, so they pass the vibration on slowly.
• “Sound gets used up as it travels.” It spreads out, so its energy is shared over more space and it sounds quieter.
• “Your voice travels along the string as air.” The string itself vibrates: the sound travels through a solid.

Make it easier, make it bigger

• Easier: visit the string telephone station only, and work out the times for air and steel.
• Bigger: whales call to each other across the ocean. How long would a call take to cross 100 km of water?

Answers and look-fors

• Part A: the telephone is clearest with the string tight; slack or pinched, it fails. The scratch is louder through the bench, and the tap is clear through the water.
• Part B: air 2.92 s, water 0.68 s, steel 0.17 s. Sound is about 17.2 times as fast in steel as in air.
• Part C: 1. There are no particles in space to pass the vibration on. 2. In a solid the particles are close and tightly linked, so each one hands the vibration to the next quickly; in a gas they are far apart. 3. The vibrating string carries the sound; pinching it stops the string vibrating.
• Bigger: 100,000 ÷ 1,480 = about 68 s, just over a minute.
• Exit tickets: 1. There are no particles to carry it. 2. Steel (a solid). 3. Its particles are close together and tightly linked.

Sound needs particles

A. Listening stations

B. One kilometre of sound

C. Questions

Exit tickets

Cut out one ticket for each student.

Passing heat along

Conduction is the transfer of energy through a material from particle to particle. At the hot end of a rod the particles vibrate faster; they knock their neighbours, which knock theirs, and the energy is handed along while every particle stays in place. Metals conduct well, partly because they also contain electrons that are free to move and carry energy quickly. Glass, plastic and wood conduct poorly: they are insulators. Students put a dab of butter at the end of five rods, stand the other ends in hot water, and time how long each takes to melt the butter.

We are learning to

• describe conduction with the particle model,
• compare how well materials conduct, keeping the test fair,
• present results in a bar chart and explain them.

Success criteria

• I can rank the five rods from the best conductor to the worst, with evidence.
• I can explain conduction as particles passing energy to their neighbours.

You need

• a conduction rod set (copper, aluminium, brass, steel and glass, all the same size), butter, a heatproof container, hot water from a kettle, a timer and eye protection,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: the teacher pours the hot water; eye protection on; the rods get hot, so nobody touches them until they have cooled for five minutes.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the rods in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Heat flows like a liquid through the rod.” Nothing flows: particles stay put and hand their energy on.
• “Metals feel cold because they give out cold.” They feel cold because they carry heat away from your hand quickly.
• “Insulators stop heat completely.” They slow it down; given long enough, the glass end would warm too.

Make it easier, make it bigger

• Easier: test three rods (copper, steel and glass), and use the example times for the rest.
• Bigger: saucepans are often metal with a plastic or wooden handle. Explain both choices with the particle model.

Answers and look-fors

• Part A, example: copper 35 s, aluminium 42 s, brass 115 s, steel 290 s; glass, not melted in 10 minutes.
• Part B: the bars rise from copper to steel; glass needs an arrow or a note, as it did not melt the butter at all.
• Part C: 1. Copper, Aluminium, Brass, Steel, then glass. 2. The same size of rod, the same dab of butter, the same depth and temperature of water, and the same start. 3. The particles at the hot end vibrate faster and knock their neighbours, passing energy along. 4. Copper melted the butter about 8 times as fast as steel.
• Bigger: the metal pan conducts heat quickly to the food; the handle is an insulator, so it passes heat to the hand slowly.
• Exit tickets: 1. Conduction. 2. An insulator. 3. They knock their neighbours and pass energy on.

Passing heat along

A. Time for the butter to melt (s)

B. Bar chart

Draw a bar for each rod. For a rod that never melted the butter, draw the bar to the top and write “more than 600 s”.

C. Questions

Exit tickets

Cut out one ticket for each student.

Light: a wave with no medium

Light crosses about 150,000,000 km of nearly empty space to reach us from the Sun. There are no particles out there to knock one another, so the particle-collision picture cannot explain it. The wave model can: light is an electromagnetic wave, which needs no medium, and it travels at about 300,000 km/s. Light is one small part of a family, the electromagnetic spectrum, from radio waves longer than a building to X-rays smaller than an atom. White light is a mix of wavelengths, and the fine tracks of a CD spread them apart into colours. Students make a CD spectrum, time light on three trips, and put the spectrum in order.

We are learning to

• explain why light can cross empty space and sound cannot,
• use the speed of light to work out travel times,
• order the electromagnetic spectrum by wavelength.

Success criteria

• I can work out how long light takes to reach Earth from the Sun.
• I can put six kinds of electromagnetic wave in order of wavelength.

You need

• old CDs or DVDs and torches; a darkened room,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: nobody looks at the Sun, even through a CD or sunglasses; torches are not shone into eyes.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the CDs in Session A, and Parts B to D in Session B.

Watch for these ideas

• “Light arrives instantly.” It is very fast but takes time: about 8 minutes from the Sun.
• “Radio waves are sound.” Radio waves are electromagnetic, like light; a radio turns them into sound.
• “White light is one colour.” It is a mix of every colour, which the CD spreads apart.

Make it easier, make it bigger

• Easier: work out the Sun and Moon times together, and give the spectrum with the first and last kinds already placed.
• Bigger: scientists also picture light as tiny packets of energy, which explains how a solar panel works. Why might science keep two models for one thing?

Answers and look-fors

• Part A: bands of colour in rainbow order, red at one end and violet at the other: white light is a mix of colours, spread out by the CD.
• Part B: Sun to Earth 500 s, Moon to Earth 1.28 s, Perth to Sydney 0.011 s; the Sun’s light is about 8 minutes 20 seconds old.
• Part C, longest to shortest: radio waves, microwaves, infrared, visible light, ultraviolet, x-rays. In the printed order: visible light 4, x-rays 6, microwaves 2, ultraviolet 5, radio waves 1, infrared 3.
• Part D: 1. Light is an electromagnetic wave and needs no medium; sound needs particles to pass it on. 2. The wave model: light is a wave, and each colour is a different wavelength. 3. Radio waves, microwaves and visible light are all electromagnetic waves: they all travel at the speed of light and need no medium.
• Bigger: each model explains some things well; using both gives a fuller picture than either alone.
• Exit tickets: 1. It needs no medium: it is an electromagnetic wave. 2. About 8 minutes. 3. Radio waves.

Light: a wave with no medium

A. A CD spectrum

Draw the colours you see, in the order they appear.

B. How long does light take?

Light travels at about 300,000 km/s. Time = distance ÷ speed.

C. The electromagnetic spectrum

Number the kinds of wave from 1 (the longest wavelength) to 6 (the shortest).

D. Questions

Exit tickets

Cut out one ticket for each student.

Which model works?

A scientific model is a simplified picture that helps explain and predict. No model is the whole truth, so scientists judge a model by how useful it is for the job. The wave model is most useful when the pattern matters: wavelength, frequency, colour, pitch, and energy crossing empty space. The particle model is most useful when what the particles do matters: conduction, a gas pressing on a wall, a smell spreading, a solid expanding when heated. Some things need both: a sound wave is a pattern, but it is made of particles jostling. Students sort twelve phenomena and explain each choice.

We are learning to

• choose the more useful model for a phenomenon and give a reason,
• describe what each model explains well and what it leaves out,
• recognise phenomena that need both models.

Success criteria

• I can sort the twelve phenomena and explain one card from each pile.
• I can name something each model cannot explain.

You need

• the model cards (third sheet), one set per pair, with scissors,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the sort in Session A, and Parts B to D in Session B.

Watch for these ideas

• “One model is right and the other is wrong.” Both are useful pictures; each fits some phenomena better.
• “Waves are made of particles, so the particle model is always enough.” It cannot explain light crossing empty space.
• “A model is the same as the real thing.” A model leaves things out on purpose so that the important part is clear.

Make it easier, make it bigger

• Easier: sort into two piles first, wave and particle, and then pull out the cards that seem to fit both.
• Bigger: write two new cards of your own, one for each model, and swap them with another pair.

Answers and look-fors

• Part A: wave model A, D, F, G, L; particle model B, E, I, K; both C, H, J.
• Part B, the reason for each card: A there are no particles in space to pass energy on; light is a wave that needs no medium; B vibrating particles knock their neighbours; C the wave model describes the compressions; the particle model describes what each particle does; D energy spreads out from the source while the water stays where it is; E particles of the smell move and mix through the air; F each colour is a different wavelength, bent by a different amount; G pitch is the frequency of the wave; H tightly linked particles pass the wave on faster; I moving particles collide with the walls; J a sound wave needs particles to carry it; K its particles vibrate more and take up more room; L radio waves are electromagnetic waves, like light.
• Part C: the wave model explains wavelength, frequency, pitch, colour and light crossing space, but not why heat moves along a spoon; the particle model explains conduction, gas pressure, smells spreading and expansion, but not light in a vacuum.
• Part D: 1. A model is judged by how well it explains and predicts what we see. 2. The particle model cannot explain how light crosses empty space. 3. Sound is a wave pattern made by particles vibrating, so the full explanation uses both.

Which model works?

A. Our sort

B. Three cards, three reasons

C. Strengths and limits

D. Questions

Wave model, particle model, or both?

Cut out the cards. Lay down the three grey heading cards, then sort the phenomena under them.

Teacher note: the piles are not the same size. The answer letters and the reasons are in the plan.

Waves through the Earth

An earthquake sends energy through the Earth as waves. The fastest, P waves, are longitudinal: the rock is squeezed and stretched along the way the wave travels, and they pass through solids and liquids. The slower S waves are transverse: the rock shakes from side to side, and they pass only through solids. Because S waves from a large quake never reach the far side of the planet, scientists concluded that part of the Earth’s core is liquid. At a seismometer the S wave arrives some seconds after the P wave, and the longer the lag, the further away the quake was. Students act out both waves on a slinky, then turn lags at three stations into distances.

We are learning to

• describe P waves as longitudinal and S waves as transverse,
• use wave speeds to turn a time lag into a distance,
• explain how earthquake waves show that part of the core is liquid.

Success criteria

• I can find the distance of a quake from each of three stations.
• I can explain why S waves do not pass through a liquid, using the particle model.

You need

• a slinky to show the two kinds of wave,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the slinky in Session A, and Parts A to C in Session B.

Watch for these ideas

• “Earthquake waves carry the rock along.” The rock moves back and forth or side to side; the energy travels.
• “All the waves from a quake arrive together.” P waves are faster, so they arrive first.
• “We know the core is liquid because someone has drilled there.” The deepest holes reach only about 12 km; the evidence comes from the waves.

Make it easier, make it bigger

• Easier: give the rule “each second of lag is about 8.4 km” and work out station A together.
• Bigger: on a map, draw a circle around each station with its distance as the radius. Where do the circles meet, and why are three stations needed?

Answers and look-fors

• Part A: P wave 100 ÷ 6 = 16.7 s; S wave 100 ÷ 3.5 = 28.6 s; lag 11.9 s. So each second of lag is about 100 ÷ 11.9 = 8.4 km.
• Part B: Station A 10 s, about 84 km; Station B 25 s, about 210 km; Station C 40 s, about 336 km.
• Part C: 1. P waves are longitudinal, S waves are transverse. 2. In a liquid the particles slide past one another, so a sideways shake is not passed on; S waves stop at the liquid outer core and never reach the far side. 3. Station A: it has the shortest lag.
• Bigger: the quake is where all three circles meet; two circles cross at two points, so a third station decides between them.
• Exit tickets: 1. The P wave. 2. Transverse. 3. The further away the quake.

Waves through the Earth

A. A race over 100 km

In the Earth’s crust, P waves travel at about 6 km/s and S waves at about 3.5 km/s.

B. Three stations

C. Questions

Exit tickets

Cut out one ticket for each student.

Keeping heat in

A warm cup loses energy to its surroundings in more than one way, and the two models explain different parts of it. The particle model explains conduction: energy passes from particle to particle, and a gas, whose particles are far apart, passes it on slowly, so a material that traps still air is a good insulator. The wave model explains radiation: a warm object gives off infrared waves, and a shiny surface reflects much of it back. Students wrap four cups of warm water in different materials, leave one bare, and compare the temperature drops after 20 minutes.

We are learning to

• compare insulating materials with a fair test,
• explain insulation with the particle model and the wave model,
• use results to design a better insulator.

Success criteria

• I can work out each drop in temperature and rank the wraps.
• I can explain why trapped air insulates, and what the foil does.

You need

• for each group: five cups, warm tap water (about 50 °C), thermometers, a measuring jug, a timer, newspaper, aluminium foil, bubble wrap, cotton wool and rubber bands,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: warm tap water only, never boiling; the teacher fills the jugs; carry cups with two hands and wipe up spills.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the plan and the cups in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Insulators make heat.” They only slow down how fast energy leaves, or arrives.
• “Foil is the best insulator because it is used for cooking.” Foil reflects radiation but conducts well; on its own it traps little air.
• “Cold gets in.” Energy flows from warmer to cooler: into a cold drink, out of a hot one.

Make it easier, make it bigger

• Easier: test the bare cup and two wraps, and use the example results for the others.
• Bigger: design the best wrap you can from these materials, combining the ideas from both models, and explain each layer.

Answers and look-fors

• Part A: change the wrap; measure the temperature drop after 20 minutes; keep the same cups, volume, starting temperature, lids and time.
• Part B, example drops: nothing 14 °C, newspaper 10 °C, aluminium foil 11 °C, bubble wrap 7 °C, cotton wool 6 °C. Best to worst: cotton wool, bubble wrap, newspaper, aluminium foil, nothing.
• Part C: 1. The bare cup is the control: it shows how fast the water cools with no wrap. 2. Cotton wool and bubble wrap trap still air; air is a gas, its particles are far apart, so it passes energy on slowly. 3. Foil reflects infrared radiation back towards the cup, which helps, but it is thin and conducts well. 4. For example: bubble wrap or cotton wool inside, for trapped air, with shiny foil on the outside, to reflect radiation.
• Exit tickets: 1. Trapped air, a gas whose particles are far apart, passes energy on slowly. 2. The wave model (infrared radiation). 3. From the warmer thing to the cooler thing.

Keeping heat in

A. Our fair test

B. After 20 minutes (started at 50 °C)

C. Questions

Exit tickets

Cut out one ticket for each student.

Show what we know

The term comes together. In the task, students explain six moments of a thunderstorm: for each, they choose the model that explains it best, say what carries the energy and through what, and work out how far away the lightning struck. Then they sit the eight-question final check, and the class plays the unit quiz as a game on the board.

We are learning to

• apply the wave and particle models to everyday events,
• use the speeds of light and sound to work out distances and times,
• justify the choice of model for each event.

Success criteria

• I can explain each storm moment with the more useful model and a reason.
• I can answer the final check on my own.

You need

• the task (next sheet) and the final check (third sheet), one each per student,
• the interactive unit open on the board for the quiz; mini whiteboards if you have them.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the models and the storm task in Session A, and the final check and the quiz in Session B.

Watch for these ideas

• Students who say the thunder is late because it is made later: the flash and the sound happen together; the sound is slower.
• Students who name the medium for the radio crackle as air: radio waves need no medium.
• Students who think the gate is colder than the wood: both are at the same temperature; the metal conducts energy away faster.

Make it easier, make it bigger

• Easier: give the three choices (the wave model, the particle model, both) to circle for each moment.
• Bigger: the gap between flash and thunder grows by 3 seconds every few minutes. Which way is the storm moving, and how fast?

Answers and look-fors

• Task table: 1. the wave model: light, an electromagnetic wave, needs no medium and arrives almost at once; 2. both: sound is a longitudinal wave passed on by air particles, which is slow compared with light; 3. the particle model: vibrating air particles push on the glass and pass energy to it; 4. the wave model: lightning gives off radio waves, which are electromagnetic like light; 5. the wave model: the waves carry energy while the water mostly rises and falls in place; 6. the particle model: the metal conducts energy away from the hand faster. Accept a well-argued “both” for the rattling window.
• Task questions: 1. 343 × 6 = 2058 m, about 2.1 km. 2. About 0.0000069 s: far too short to notice. 3. About 0.00013 s. 4. Light and radio waves are electromagnetic and travel at the same speed; sound is far slower.
• Final check: 1. At right angles to the wave. 2. 4 × 3 = 12 m/s. 3. Steel. 4. There are no particles in space to pass the vibration on. 5. The particle model. 6. Light is an electromagnetic wave and needs no medium. 7. A longitudinal wave. 8. For example: the wave model explains colour and pitch; the particle model explains conduction.
• Bigger: the storm is moving away, by about 1 km for every 3 seconds added.

A thunderstorm, two ways

For each moment, write the model that explains it best (the wave model, the particle model, or both) and say what carries the energy, and through what.

Show what we know