1.1 What is Chemistry?

http://www.ck12.org Chapter 15. Water

Heat Capacity

Theheat capacityof a substance measures how much heat it needs to absorb to cause a certain increase in
temperature. Substances with high heat capacities can absorb large amounts of heat with only a minimal temperature
increase. Compared to other common liquids, water has a relatively high heat capacity. The heat capacities of some
common substances are listed inTable15.2.

TABLE15.2: Heat Capacity of Common Materials

Material Heat capacity (calories•g−^1 •°C−^1 )

Acetone 0.51

Aluminum 0.22

Ammonia 1.13

Copper 0.09

Grain alcohol 0.23

Lead 0.03

Mercury 0.03

Silicon 0.18

Silver 0.06

Water 1.00

Example 15.3

How much heat must be absorbed by 1 gram of water to raise its temperature by 5°C?

Answer:

Water has a heat capacity of 1.00 calories•g−^1 •°C−^1. Raising the temperature of 1 gram of water by 5°C would
require the absorption of 5 calories of energy.

Steam –H

Water vapor, or steam, can be produced either through the vaporization of liquid water (i.e., H 2 O(l)→H 2 O(g)
or the sublimation of solid water (i.e., H 2 O(s)→H 2 O(g)). When water changes from a liquid to a gas at normal
temperatures and pressures, we refer to the process as evaporation. When we sweat, we take advantage of this
process. Vaporization requires an input of energy, so when our sweat evaporates, it absorbs some of the energy from
our bodies, thus cooling us. When water is vaporized by heating it to its boiling point, we generally refer to it as
boiling instead.

Steam is a very useful form of water that can be used to do mechanical work, like powering steam engines and
turbines. Such devices are important for the generation of electricity.

Lesson Summary

• Water can exist in all three states under normal pressures and temperatures. It is tasteless, odorless, and exists
  as a liquid at room temperature and standard atmospheric pressure.


• In its solid form, water is frequently referred to as ice. The terms snow, sleet, hail, or frost may also be used,
  depending on the conditions under which the water solidified. Ice can exist as an amorphous solid or as a
  crystalline solid.