Bulk Properties of Water

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The energy required to change the temperature of the ice is the specific heat of ice

Slide 13

Energy and Phase Change

At 0 C a phase change begins:

Moving from left to right along LEG ‘B’, ice is melting to form liquid water

Moving from right to left along LEG ‘B’, liquid water is freezing to form ice

The distance of LEG ‘B’ along the Energy axis (x-axis) is known as the Heat of Fusion

Note that temperature remains constant during a phase change!

Slide 14

Heat of Fusion

The energy that must be absorbed in order to convert solid to liquid at its melting point

The energy that must be removed in order to convert liquid to solid at its freezing point.

The heat of fusion of water is 334 Joules/gram

Slide 15

Energy and Phase Change

Once ice has completely melted, the temperature begins to increase again (LEG ‘C’), as the energy absorbed by water is no longer going toward changing the phase of the substance.

The energy required to change the temperature of the liquid water is its specific heat

Slide 16

Energy and Phase Change

At 100 C, a second phase change begins:

Moving from left to right along LEG ‘D’, water is boiling to form water vapor

Moving from right to left along LEG ‘D’, water vapor is undergoing condensation to form liquid water

The distance of LEG ‘D’ along the Energy axis (x-axis) is known as the Heat of Vaporization

Note that temperature remains constant during a phase change!

Slide 17

Heat of Vaporization

The energy that must be absorbed in order to convert a liquid to gas at its boiling point.

The energy that must be removed in order to convert a gas to liquid at its condensation point.

The heat of vaporization of water is 2260 Joules/gram

Slide 18

Energy and Phase Change

Once all of the liquid water has vaporized, the temperature begins to increase again (LEG ‘E’), as the energy absorbed by water is no longer going toward changing the phase of the substance.

The energy required to change the temperature of the steam is its specific heat

Slide 19

Latent Heat – Sample Problem

Problem: The heat of fusion of water is 334 J/g.

How much energy is needed to convert

60 grams of ice at 0C to liquid water at 0C?

Mass

of ice

Heat

of