Course: Combined and Separate | Find each scene on YouTube, watch it, then answer the questions. Write your answers on paper first, then tap Show answer.
Equations and data: ρ = m ÷ V · ΔE = mcΔθ · E = mL · pV = constant (Separate only)
Specific heat capacity of water = 4200 J/kg °C · Specific latent heat of fusion of ice = 334 000 J/kg · Density of water = 1000 kg/m³ · Density of ice = 920 kg/m³
1. Frozen – Olaf starts to melt
🎬 The scene: Olaf lights a fire to keep Anna warm and starts to melt – “Some people are worth melting for.”
Q1 (F) Olaf sits by the fire and starts melting. Describe what happens to the particles as snow melts.
Show answer
The particles gain energy and break out of their fixed positions. They are still close together but can now move past each other – a liquid.
Q2 (F/H) While Olaf is melting, his temperature stays at 0 °C even though he is being heated. Explain why.
Show answer
The energy is used to break the bonds between particles (changing state), not to make them move faster. His internal energy increases but his temperature doesn’t.
Q3 (H) Olaf is made of 10 kg of snow at 0 °C. Calculate the energy needed to melt him completely.
Show answer
E = mL = 10 × 334 000 = 3 340 000 J
2. Despicable Me – Gru’s freeze ray
🎬 The scene: Gru uses his freeze ray on the queue in a coffee shop to get served first.
Q1 (F) To freeze something, does energy need to go into it or out of it?
Show answer
Out of it. Its internal energy must decrease – there’s no such thing as adding “cold”.
Q2 (F/H) A cup holds 0.3 kg of coffee (treat it as water) at 60 °C. How much energy must be removed to cool it to 0 °C?
Show answer
ΔE = mcΔθ = 0.3 × 4200 × 60 = 75 600 J
Q3 (H) Real or fake? How much more energy must be removed to freeze it at 0 °C? Could a ray do all this in a split second?
Show answer
E = mL = 0.3 × 334 000 = 100 200 J. Total about 176 000 J. Removing that in a fraction of a second would need an enormous rate of energy transfer – fake!
3. Willy Wonka – Fizzy Lifting Drinks
🎬 The scene: Charlie and Grandpa Joe sneak a taste of Fizzy Lifting Drinks and float up towards the ceiling fan (1971 film).
Q1 (F) Is the gas in the fizzy drink more or less dense than the liquid? How do you know?
Show answer
Less dense – the bubbles rise to the top. Gas particles are far apart, so a gas has a much lower density.
Q2 (F/H) Charlie has a mass of 50 kg and a volume of 0.05 m³. Calculate his density.
Show answer
ρ = m ÷ V = 50 ÷ 0.05 = 1000 kg/m³ – about the same as water.
Q3 (H) Real or fake? Air has a density of about 1.2 kg/m³. Explain why drinking a fizzy drink could never make you float.
Show answer
To float in air, your overall density would have to be less than 1.2 kg/m³. Charlie is about 1000 kg/m³ – over 800 times too dense. A little gas in your stomach makes almost no difference. Fake!
4. The Wizard of Oz – the hot-air balloon leaves
🎬 The scene: The Wizard’s hot-air balloon floats away from the Emerald City – leaving Dorothy behind.
Q1 (F) What happens to the air particles inside a balloon when the air is heated?
Show answer
They gain kinetic energy, move faster and spread further apart.
Q2 (F/H) Explain why a hot-air balloon rises.
Show answer
The hot air’s particles are further apart, so it is less dense than the cooler air around it. The less dense hot air rises, carrying the balloon up.
Q3 (H) The balloon holds 2000 m³. Cool air has a density of 1.2 kg/m³; the hot air inside is 0.95 kg/m³. How much lighter is the hot air than the same volume of cool air?
Show answer
Cool air: 1.2 × 2000 = 2400 kg. Hot air: 0.95 × 2000 = 1900 kg. Difference = 500 kg – roughly how much the balloon, basket and passengers can weigh.
5. Moana – Te Kā and the lava
🎬 The scene: Moana faces Te Kā, the lava monster – watch the lava hissing into steam where it meets the sea.
Q1 (F) When lava hits the sea, clouds of steam appear. Name the two changes of state happening.
Show answer
The water boils/evaporates (liquid → gas). The lava freezes/solidifies into rock (liquid → solid).
Q2 (F/H) Is lava turning into rock a physical or a chemical change? Explain.
Show answer
Physical – it is a change of state. No new substance is made, and the rock could be melted back into lava. Mass is conserved.
Q3 (H) 1000 kg of rock cools from 1200 °C to 200 °C. Its specific heat capacity is 840 J/kg °C. Calculate the energy it transfers to the sea.
Show answer
ΔE = mcΔθ = 1000 × 840 × 1000 = 840 000 000 J
6. The Polar Express – on the frozen lake
🎬 The scene: The train skids across a frozen lake as the ice starts to crack beneath it.
Q1 (F) Why does ice form on top of a lake rather than at the bottom?
Show answer
Ice is less dense than water, so it floats.
Q2 (F/H) A block of ice has a volume of 2 m³ and a mass of 1840 kg. Calculate its density.
Show answer
ρ = 1840 ÷ 2 = 920 kg/m³
Q3 (H) Water is unusual: most substances are denser as solids. Suggest why it matters to fish that ice floats.
Show answer
The floating ice layer insulates the water underneath, so the lake doesn’t freeze solid and fish can survive in the liquid water below.
7. Ice Age – Scrat cracks the glacier
🎬 The scene: The opening of Ice Age – Scrat tries to bury his acorn in the ice and sets off a huge crack in the glacier.
Q1 (F) In real life, water seeps into cracks in rock and freezes. Does the water get bigger or smaller when it freezes?
Show answer
Bigger – water expands when it freezes. This can split rocks apart.
Q2 (F/H) 1 kg of water has a volume of 0.001 m³. Use the density of ice to calculate the volume of 1 kg of ice.
Show answer
V = m ÷ ρ = 1 ÷ 920 = 0.00109 m³ (to 3 s.f.) – about 9% bigger.
Q3 (H) The water froze but its mass did not change. Explain why its density changed.
Show answer
Density = mass ÷ volume. The mass stayed the same but the volume increased, so the density decreased. The particles in ice are arranged slightly further apart than in liquid water.
8. Frozen 2 – Elsa freezes the Dark Sea
🎬 The scene: Elsa tries to cross the stormy Dark Sea, freezing the crashing waves as she goes.
Q1 (F) Elsa freezes the waves into ice. Describe the particle arrangement before and after.
Show answer
Before (liquid): close together, random arrangement, moving past each other. After (solid): close together in a regular pattern, vibrating about fixed positions.
Q2 (F/H) Is mass conserved when the wave freezes? Explain.
Show answer
Yes. It is a physical change – the same particles are there, just arranged differently.
Q3 (H) A wave contains 2000 kg of water already at its freezing point. Calculate the energy Elsa must remove to freeze it.
Show answer
E = mL = 2000 × 334 000 = 668 000 000 J
9. Ratatouille – Remy makes the soup
🎬 The scene: Remy secretly rescues Linguini’s ruined soup, heating and seasoning it into a masterpiece.
Q1 (F) What is meant by the specific heat capacity of the soup?
Show answer
The energy needed to raise the temperature of 1 kg of the soup by 1 °C.
Q2 (F/H) 2 kg of soup is heated from 20 °C to 90 °C. Its specific heat capacity is 4000 J/kg °C. Calculate the energy needed.
Show answer
ΔE = mcΔθ = 2 × 4000 × 70 = 560 000 J
Q3 (H) The hob supplies 2000 W and all the energy goes into the soup. How long does it take to heat? Why would it really take longer?
Show answer
t = E ÷ P = 560 000 ÷ 2000 = 280 s (about 4.7 minutes). Really it takes longer because energy is also wasted heating the pan and the surroundings.
10. Up – landing in South America
🎬 The scene: Carl’s balloon-powered house comes down through the clouds and lands in South America.
Q1 (F) What causes the pressure of the helium inside a balloon?
Show answer
The helium particles collide with the inside walls of the balloon, exerting a force on them.
Q2 (F/H) If the helium in a balloon is heated, what happens to its pressure? Explain using particles.
Show answer
The pressure increases. The particles move faster, so they hit the walls more often and with more force.
Q3 (H, Separate) A balloon has a volume of 0.01 m³ at 100 000 Pa. It drifts up to where the pressure is 50 000 Pa. Assuming constant temperature, calculate its new volume.
Show answer
pV = constant: 100 000 × 0.01 = 50 000 × V, so V = 0.02 m³. The balloon doubles in size – which is why balloons that rise very high eventually burst.
Teachers: the buttons open a YouTube search, so you can pick whichever upload is currently available. Please watch the clip through before showing it to a class.
