Heat and Energy
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Transcript of Heat and Energy
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• QUIZ ON ACIDS & BASES AT THE BEGINNING OF CLASS. TAKE A FEW MINUTES AND STUDY!!
PICK UP THE TWO HANDOUTS
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Heat and Energy
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What is energy?
The ability to do work or produce heat.
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Define potential Energy
Energy due to composition- BONDS- or position
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Define Kinetic Energy
Energy of motion
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Kinetic energy is directly related to…
Constant random motion of atoms or molecules..
And is proportional to ….
Temperature
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What 3 things does the potential energy of a substance depend upon?
1. The type of atoms in the substances
2. Numbers and type of chemical bonds
3. Particular way atoms are arranged
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State the Law of Conservation of Energy
Energy cannot be created or destroyed but can change from one form to another.
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Describe how octane contains chemical potential energy
Strength of stored energy in bonds between C-H
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What symbol is used to represent heat?
Q
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Define heat
The transfer of energy from warmer objects to cooler.
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Define calorie
The heat required to raise 1 gram of pure water 1 degree celsius
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What is another name for a nutritional Calorie?
Kilocalorie
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What is the difference between 1 nutritional Calorie and 1 calorie?
1C = 1000cC is a food calorie. Little c is defined as the heat required to raise 1 gram of pure water 1 degree celsius.
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If a food has 10,000 calories, how many Calories does it contain?
10,000 cal x 1 Cal = 10Cal
1000 cal
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What is the SI unit of heat and energy?
Joule
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One joule = .2390 calories
One calorie = 4.184 joules
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.A fruit and oatmeal bar contains 142 nutritional Calories. Convert to calories.
142 Calories x 1000 calories = 142,000 calorie
1 Calorie
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Define specific heat
The amount of heat required to raise the temperature of
1 gram of a substance 1 degree celsius.
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How many joules must be absorbed by each gram of water to raise the temperature of one gram of a substance one degree celsius?
4.184 j/g°C
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What is the specific heat of
A. Water- 4.184B. Ice- 2.03C. Iron- .449D. Gold- .129
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What can water do because of its high specific heat?
Absorb large amounts of heat and cold.
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Why is it good to plant vineyards and orchards near large bodies of water?
Water absorbs the temperature of the surrounding air to keep the temperature constant.
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Q= M x C x ∆T
Q = heat (Calorie or Joules)
M = mass (grams)C = specific heat (j/g°C)∆T = change in
temperature (°C)
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If the temperature of 34.4 g of ethanol increased from 25.0 C to 78.8 C, how much heat has been absorbed by the ethanol? (C= 2.44 j/g°C )
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Q= xM= 34.4C= 2.44∆T= (78.8 – 25.0)
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Q = M x C x ∆T
Q= 2.44 x 34.4 x 53.8
Q= 4515.75 J
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A 155 g sample of an unknown substance was heated from 25.0 °C to 40.0 °C. In the process, the substance absorbed 5696 J of energy. What is the specific heat of the substance?
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Q = M x C x ∆T
Q = 5696 JM = 155 gC = X∆T = (40 °C– 25°C)
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Q = M x C x ∆T
5696 J = 155 g x C x 15°C
C = 2.45 j/g°C
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Calorimeter
A device used to measure heat content.