Thermal properties of matter

Which statement about evaporation is correct?

• Evaporation causes the temperature of the remaining liquid to decrease.

• Evaporation does not occur from a cold liquid near its freezing point.

• Evaporation does not occur from a dense liquid, such as mercury

• Evaporation occurs from all parts of a liquid.

A substance loses thermal energy (heat) to the surroundings at a steady rate. The graph shows how the temperature of the substance changes with time. What could the portion PQ of the graph represent?

• gas condensing

• gas cooling

• liquid cooling

• liquid solidifying

What causes the random, zig-zag movement (Brownian motion) of smoke particles suspended in air?

• air molecules colliding with smoke particles

• convection currents as the hot smoke rises

• smoke particles colliding with each other

• smoke particles reacting with oxygen molecules in the air

The same quantity of thermal energy is supplied to two solid objects X and Y. The temperature increase of object X is greater than the temperature increase of object Y. Which statement explains this?

• X has a lower melting point than Y.

• X has a lower density than Y.

• X has a lower thermal capacity than Y.

• X is a better thermal conductor than Y.

Air in a sealed syringe is slowly compressed by moving the piston. The temperature of the air stays the same. Which statement about the air is correct?

• The pressure of the air decreases because its molecules now travel more slowly.

• The pressure of the air decreases because the area of the syringe walls is now smaller.

• The pressure of the air increases because its molecules now hit the syringe walls more frequently.

• The pressure of the air increases because its molecules now travel more quickly.

Which statement describes what happens as ice at 0°C starts to melt to become water?

• Energy is absorbed and the temperature remains constant.

• Energy is absorbed and the temperature rises.

• Energy is released and the temperature remains constant.

• Energy is released and the temperature rises.

Which row is correct for the evaporation of a liquid?

• A

• B

• C

• D

A liquid at room temperature fills a flask and a glass tube to level X. The flask is now placed in ice, and the liquid level in the tube falls to level Y. Why does the level fall?

• The flask contracts.

• The flask expands.

• The liquid contracts.

• The liquid expands.

The diagrams represent the molecules in two different states of matter. The arrows show the motion of the molecules.

• A

• B

• C

• D

A 15.75-g piece of iron absorbs 1086.75 joules of heat energy, and its temperature changes from 25°C to 175°C. Calculate the specific heat capacity of iron.