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Transcript of Heat: Lesson 4 Heat vs. Temperature. What happens to the movement of molecules as they’re heated? ...
Heat: Lesson 4
Heat vs. Temperature
What happens to the movement of molecules as they’re heated?
• http://phet.colorado.edu/en/simulation/energy-forms-and-changes
What is temperature?
• Temperature is the average kinetic energy of matter. The more the molecules move the higher the temperature will be.
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Thermal Energy
• Thermal energy is the total amount of energy in a sample. It involves the temperature and amount of a substance.
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Which sample has more thermal energy?
50 mL at 100 °C 100 mL 100 °C
Sample A Sample B
=thermal energy
Which one has more thermal energy: A or B?
50 mL at 80 ° C 10 mL at 100 ° C
100 mL temp increases from 22 °C to 38 ° C 100 mL temp increases from 22 °C to 29 ° C
A B
Law of Conservation of Energy
System Surroundings
• The amount of energy released or absorbed by a process can be quantified by the following equation:
q = m x x ΔT• q = • m = • ΔT = • 1 calorie is the amount of energy that it takes
to raise 1 gram of water 1°C .
PRACTICE:A 100 gram sample of water is at 50°C . The water sample cools to 25°C. How many calories did the sample lose to the surroundings?
q = m x x ΔT
q =
m =
ΔT = (Tfinal– Tinitial)
= (___ – ___)
= ( _____ )
PLUG IN AND SOLVE:
PRACTICE:200 mL of 50°C water is mixed with 75 mL of 90°C water. The final temperature of the water is 60.9°C. How much heat did the 50 °C water gain?
q = ______
m = ______
ΔT = (Tfinal– Tinitial)
= (___ – ___)
= ( _____ )
q = m x x ΔT
PLUG IN AND SOLVE:
PRACTICE: 200 mL of 50°C water is mixed with 75 mL of 90°C water. The final temperature of the water is 60.9°C. How much heat did the 90°C water lose?
q = ______
m = ______
ΔT = (Tfinal– Tinitial) = (___ – ___)
= ( _____ )
q = m x x ΔT
PLUG IN AND SOLVE:
This example proves the _________________________because the energy ________ by the _______ water, 2180 calories, is equal to the energy _______ by the _______ water, 2180 calories.
Hot Water Cold Water