Heating and Cooling Curves of Water

Special Info about the Heating and Cooling Curves of Water

• heating curve of water animation• Since Temperature is a measure of "Average Kinetic

Energy", any change in temperature is a change in Kinetic Energy.

• ↑ temp= ↑ KE• ↓ temp= ↓ KE• The total energy absorbed in the heating curve is

equal to the total energy released in the cooling curve of water

More Special info

• Temperature does not change during a phase change

• So, the graphs have 2 main plateau areas where phase changes are occurring

• Melting/freezing pt: occur at same temperature

• Boiling/condensation pt: occur at same temperature

Changes in State (phase changes)

Melting - solid to liquid

a. Substance is absorbing energy from the surroundings (endothermic)

b. Particles get more kinetic energy and begin rotating around each other.

c. The IF’s begin to weaken (intermolecular forces) to then form a liquid.

d. The energy required to melt a solid is called the heat of fusion.

Vaporization - liquid to gas

a. Types:

1) Boiling - rapid; gas bubbles are produced throughout.

2) Evaporation - slow; occurs at the surface.

b. Liquid particles gain enough kinetic energy to overcome IF’s between the particles and they begin translational motion; this energy is called the heat of vaporization.

Evaporation is a cooling process.

a. Particles in a liquid gain kinetic energy.

b. They leave as gas particles (taking the energy away with them).

c. This leaves less energy in the liquid, therefore cooling down what is left.

Sublimation - solid to gas a. Dry ice - carbon dioxide b. Iodine c. Frost*During phase changes there is no change of temperature!

Cooling Curve of Water

Condensation - gas to liquid

a. Particles lose kinetic energy, slow down, and come closer together.

b. IF’s become strong enough to make particles merely rotate around each other.

c. The energy they lose to turn into a liquid is the heat of vaporization.

Substance is releasing energy to the surroundings (exothermic)

Freezing - liquid to solid-.

a. Particles lose kinetic energy

and slow down.

b. Substance releases energy to surroundings

(exothermic)

c. IF’s b/w particles become stronger than the particles’ motion, so the particles begin merely vibrating in place to form a solid.

d. The amount of heat the particles must lose to turn into a solid is called the heat of fusion.