Question

As a sample of water is heated, the energy is used to overcome the attractions between the molecules so that they are no longer held close together and can move in random directions. Then, the kinetic energy of its molecules increases. Which sections of the heating curve illustrate this process?

Answer 1

The sections of the heating curve that demonstrate an increase in the kinetic energy of water molecules while overcoming molecular attractions are the melting and boiling phases, distinguished by flat line segments at constant temperatures of 0°C and 100°C respectively.

Step-by-step explanation:

The process of heating a sample of water that leads to an increase in the kinetic energy of its molecules while overcoming attractions between the molecules occurs during two key stages on a heating curve. The first is during the melting phase where the solid converts to liquid at a constant temperature of 0°C, which corresponds to a flat section of the curve. The second is during the boiling phase where liquid changes to gas, also at a constant temperature, but this time at 100°C. Each of these sections represents an increase in kinetic energy without an increase in temperature as the added energy is used to overcome molecular attractions rather than increase motion.

Answer 2

B. This is an example of a graph showing the phase changes of a certain material in this case water. Before A, a solid (ice) is being heated and then at A all of the energy provided or the heat provided to the solid to cause it to melt goes into breaking the bonds between the molecules of the solid. At C, the liquid (water) is heating up again and then at B the liquid is vaporizing into a gas (water vapor), which fits the description given. At D the gas is continuing to heat up and it will continue to heat up as long as heat is provided to it.