IGCSE Physics Thermal physics topical questions

Name each change of state described.

1. (a)Water vapour in a cold window turns to droplets.[1]
2. (b)Molten wax hardens into a solid shape.[1]
3. (c)A puddle disappears on a sunny day without bubbling.[1]

Complete the particle descriptions.

1. (a)State the separation of gas particles compared with solid particles.[1]
2. (b)Describe the motion of liquid particles.[1]
3. (c)State what happens to the speed of gas particles as the temperature rises.[1]

Convert these temperatures.

1. (a)0 °C into kelvin[1]
2. (b)300 K into °C[1]
3. (c)State the temperature of absolute zero in °C.[1]

A metal paperweight stands on a chilly windowsill and is then brought into a warm room, where it slowly warms up.

1. (a)State what happens to the average kinetic energy of its particles.[1]
2. (b)State what happens to the internal energy of the paperweight.[1]
3. (c)Describe the arrangement and motion of the particles in the solid metal.[2]

A balloon is filled with air at a pressure of 101 kPa and a volume of 2.4 litres. The balloon is squeezed at constant temperature until its volume is 1.6 litres.

1. (a)State the equation linking pressure and volume for a fixed mass of gas at constant temperature.[1]
2. (b)Calculate the new pressure.[3]
3. (c)Explain the pressure rise in terms of particle collisions.[1]

An electric immersion heater warms 0.80 kg of water in an insulated container from 18 °C to 50 °C in 5.0 minutes. The specific heat capacity of water is 4200 J/(kg °C).

1. (a)Calculate the energy supplied to the water.[2]
2. (b)Calculate the average power delivered to the water.[2]
3. (c)Explain why the electrical energy supplied by the heater is actually slightly larger than your answer to (a).[2]

A pan of soup is heated on a hob, and a spoon left in the pan becomes too hot to hold. Meanwhile the whole kitchen slowly warms.

1. (a)Name the transfer that heats the spoon through the metal, and explain how it happens in a metal.[3]
2. (b)Name the transfer that warms the whole kitchen air, and explain how it happens.[3]

A heater delivers 13 500 J of energy to a 0.50 kg block of aluminium (c = 900 J/(kg °C)). A second experiment delivers the same 13 500 J to 0.50 kg of water (c = 4200 J/(kg °C)).

1. (a)Calculate the temperature rise of the aluminium block.[2]
2. (b)Calculate the temperature rise of the water, to 2 significant figures.[2]
3. (c)Explain why the two rises are so different.[1]

A wet towel hangs on a washing line. It dries much faster on a warm, windy day than on a still, cold one.

1. (a)Describe evaporation in terms of particles.[2]
2. (b)State and explain the effect of wind on the rate of evaporation.[2]
3. (c)The drying towel cools as it dries. State what this tells you about the particles that escape.[1]

Two identical metal cubes sit side by side in sunlight. One is painted matt black, the other shiny silver. An infrared thermometer reads their surface temperatures after an hour.

1. (a)State and explain which cube is hotter.[2]
2. (b)Both cubes are now moved into a dark, cool room. State and explain which cube cools faster.[2]
3. (c)State what condition must hold for an object’s temperature to stay constant, and apply it to the silver cube in the room.[2]

A fixed mass of gas is trapped in a cylinder by a piston. The cylinder walls can be heated. Initially the gas is at 300 K, occupying 400 cm³ at a pressure of 90 kPa.

1. (a)The gas is heated to 360 K with the piston locked. Explain, in terms of particles, what happens to the pressure.[3]
2. (b)The gas cools back to 300 K, and is then squeezed at constant temperature from 400 cm³ to 250 cm³. Calculate the new pressure, and explain in terms of particles why the pressure rises.[4]

An air bubble is released by a diver at a depth where the pressure is 300 kPa. The bubble has a volume of 8.0 cm³ there. As it rises, the water pressure on it falls to 100 kPa at the surface. The bubble’s temperature stays constant and no air enters or leaves.

1. (a)Write the equation linking pressure and volume for the bubble’s journey.[1]
2. (b)Calculate the bubble’s volume at the surface.[2]
3. (c)Explain, in terms of particles, why the volume increases.[2]
4. (d)State the assumption made in the calculation.[1]