Sec 3 Physics Kinetic Particle Model topical questions

Complete the table using the words: far apart, touching, vibrate about fixed positions, move fast in random straight lines, slide past one another.

State two physical properties that distinguish a gas from a solid.

A metal rod is heated and its temperature rises. Describe what happens to its particles.

A student views smoke in an illuminated cell through a microscope and records that the specks "dance" in random, jerky hops.

1. (a)Name the effect.[1]
2. (b)Explain the cause of the specks’ motion in detail.[4]
3. (c)State what the observation is evidence for.[1]

A rigid metal container holds a fixed mass of gas at room temperature. The container is placed in a refrigerator and cools.

1. (a)Explain, using the kinetic model, why the gas pressure falls.[4]
2. (b)State one everyday observation that supports your explanation.[2]

Explain each observation using the kinetic particle model.

1. (a)A smell of perfume spreads across a room even without any breeze.[2]
2. (b)A car tyre feels harder after a long motorway drive in summer.[2]
3. (c)A diver at 10 m feels pressure on all sides of her body, including from below.[2]

A syringe of volume 50 cm³ contains air. The nozzle is sealed and the plunger is pushed to 25 cm³. The temperature stays constant.

1. (a)Explain why the pressure of the trapped air rises.[3]
2. (b)State what happens to the average speed of the molecules.[1]
3. (c)State one reason the plunger becomes harder to push as the volume shrinks.[1]

A student claims: "Brownian motion proves that smoke particles are alive." Write the correct physics explanation of the observation, and identify the claim’s error.

1. (a)Give the full kinetic-model explanation of Brownian motion.[4]
2. (b)State the error in the claim.[2]

A weather balloon partially filled with helium at ground level is released. As it rises, the outside air pressure falls. Explain what happens to the balloon and to its gas, using the kinetic model.

1. (a)Explain why the balloon expands as it rises.[3]
2. (b)State what happens to the helium molecules’ average kinetic energy if the balloon’s gas cools during the ascent, and how this modifies the expansion.[3]

Two identical rigid containers hold the same number of molecules of the same gas. Container A is at 20 °C; container B is at 60 °C.

1. (a)Compare the average kinetic energy and average speed of the molecules in the two containers.[2]
2. (b)Explain which container shows the higher pressure, in terms of collisions.[3]
3. (c)Container B is cooled to 20 °C. State and explain the final pressure compared with A.[2]

A strong glass jar contains a small amount of water sealed by a tight lid. The jar is left on a sunny windowsill and the water slowly evaporates until the space above the water is full of vapour.

1. (a)Explain, using particles, why some water molecules escape from the surface.[3]
2. (b)Explain why a vapour pressure builds up and eventually stops net evaporation.[4]

A dentist’s ultrasonic cleaner shakes a beaker of water thousands of times per second, and small air bubbles in the water are seen to shrink and vanish.

1. (a)Explain why a small air bubble in water experiences a net inward pressure, using the kinetic model for both the bubble gas and the surrounding water.[4]
2. (b)The bubble shrinks. Describe what happens to the gas molecules inside as the bubble shrinks, and to the pressure they exert.[4]