Sec 3 Chemistry Kinetic Particle Theory topical questions

State the three states of matter and, for each, one property that follows from its particle arrangement.

Name the change of state described in each case.

1. (a)Solid carbon dioxide turns straight into gas at room conditions.[1]
2. (b)Water droplets form on the outside of a cold glass.[1]
3. (c)Molten wax turns back to solid on cooling.[1]

Explain, using the kinetic particle theory, why a solid expands slightly when heated.

A sealed flask holds a few drops of perfume in a vacuum and an identical flask holds the same drops in air. In which flask does the scent spread faster, and why?

A student heats a beaker of crushed ice steadily and records the temperature.

1. (a)Sketch-in-words the shape of the temperature–time graph from −10 °C to above 100 °C.[2]
2. (b)State what is happening to the water particles and the energy during the flat section at 0 °C.[2]

Explain why evaporation lowers the temperature of the liquid left behind.

Gas X has a relative molecular mass of 28; gas Y has 44. Equal amounts of each are released at one end of a long sealed tube at 25 °C.

1. (a)State which gas reaches the far end first and explain why.[2]
2. (b)State one change to the conditions that would make both gases diffuse faster.[2]

A tube has cotton wool soaked in concentrated hydrochloric acid at one end and in ammonia solution at the other. A white ring appears 36 cm from the ammonia end and 24 cm from the acid end (tube length 60 cm).

1. (a)Identify the white substance formed.[1]
2. (b)Explain why the ring is not halfway along the tube.[3]
3. (c)Write the equation for the reaction forming the ring.[1]

A cooling curve for a hot liquid in a beaker shows a smooth fall from 85 °C to 40 °C with no plateau, then a flat step at 40 °C for several minutes before falling again.

1. (a)State what happens during the flat step.[1]
2. (b)Explain why the temperature stays constant during it, even though the beaker keeps losing heat.[3]

Two identical dishes, one with water and one with a deep layer of the same water covered by a film of oil, are left on a balance for a week.

1. (a)State which dish loses more mass and explain the process responsible.[2]
2. (b)Explain, using the particle model, why the oil film slows the loss.[3]

A student compares two identical scented balloons, one in a 30 °C room and one in a 5 °C fridge, by timing how long the smell takes to reach a fixed point in each space.

1. (a)Predict which reaches first and explain in particle terms.[3]
2. (b)State one variable that must be kept the same for a fair comparison.[2]

A hard-ball sweet is dropped into still water and an identical crushed sweet into a second identical beaker. The crushed one dissolves noticeably faster.

1. (a)Explain why crushing speeds dissolving, using particle ideas.[3]
2. (b)Explain how the dissolved sweet spreads through the still water without stirring, naming the process.[3]