Phase Changes in Water
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Transcript of Phase Changes in Water
Phase Changes in WaterAIM: How does the Atmosphere store energy?
• Water exists on Earth in three states: solid (ice), liquid, and gas (water vapor)
• These “states of matter” can also be called “phases of matter”
• How do temperatures on our planet allow us to experience all three states of matter?
The Water Cycle!
• When water changes from one phase to another, a great deal of energy is involved
Energy gained – melt and vaporize
Energy released – condense and freeze
Notice temperature does not increase or decrease during a phase change.
• We call this latent heat = hidden energy that is absorbed or released when matter changes state
• A type of potential energy required to rearrange molecules only – not change temperature.
Animation
How do we measure energy?
• Scientists use joules (J) to measure energy• Named for the scientist who discovered that heat is a
form of energy
• ***Notice – more energy to boil (vaporize) and condense than to melt or freeze
James Prescott Joule
Specific Heat
• Different substances absorb different amounts of energy as their temperatures change…WHY?
• The reason is because they have different specific heats = the energy needed to raise the temperature of 1 gram of a substance 1C, without changing its state
• The higher the specific heat of a substance, the more energy needed to raise its temperature
• For example, it takes about 33 times as much energy to heat 1 g of water at 1C than it takes to hear 1 g of lead at 1C (the same amount of substance at the same temperature)