Page 180 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

l water (liquid) to ice (solid) is called freezing (solidification)
l ice (solid) to steam (gas) is known as sublimation
l steam (gas) to ice (solid) is known as deposition.

Steam
Sublimation (ice directly to steam) Water Evaporation Energy Condensing

Deposition (steam directly to ice)
Energy

Melting Energy Freezing Energy

Ice

p Figure 3.15 States of matter

Sensible and latent heat of liquids
and gases

Sensible heat of liquid and gases

When heat is applied to a liquid, its temperature will rise as heat is added
without a change of state. The resulting increase in heat is known as sensible
heat. This process can be reversed. When heat is removed from the liquid and
its temperature decreases, the heat that is removed is also called sensible heat.
Therefore, any heat that causes a change in temperature without a change of
state is known as sensible heat.
Latent heat of liquid and gases

Changes of state, as we have already seen, are the result of a change in temperature.
Solids can become liquids, liquids can become gases and each change of state is
reversible. The heat that causes any change of state is known as latent heat. Latent
heat, however, does not affect the substance’s temperature. For example, water
boils at 100°C. The heat required to raise the water to its boiling point of 100°C is
called sensible heat. The heat required to keep it boiling at 100°C is latent heat.
Steam

Evaporation Energy at 100ºC. A change in temperature
Water is heated from 0ºC to water
but no change of state. This is
Water sensible heat.

The ice remains at 0ºC and
melts to become water at 0ºC.
A change of state without a change Melting
in temperature. This is latent heat. Energy
Ice

p Figure 3.16 How sensible and latent heat work together
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