Heat and Energy

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Heat and Energy

What is energy?

The ability to do work or produce heat.

Define potential Energy

Energy due to composition- BONDS- or position

Define Kinetic Energy

Energy of motion

Kinetic energy is directly related to…

Constant random motion of atoms or molecules..

And is proportional to ….

Temperature

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

State the Law of Conservation of Energy

Energy cannot be created or destroyed but can change from one form to another.

Describe how octane contains chemical potential energy

Strength of stored energy in bonds between C-H

What symbol is used to represent heat?

Q

Define heat

The transfer of energy from warmer objects to cooler.

Define calorie

The heat required to raise 1 gram of pure water 1 degree celsius

What is another name for a nutritional Calorie?

Kilocalorie

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.

If a food has 10,000 calories, how many Calories does it contain?

10,000 cal x 1 Cal = 10Cal

1000 cal

What is the SI unit of heat and energy?

Joule

One joule = .2390 calories

One calorie = 4.184 joules

.A fruit and oatmeal bar contains 142 nutritional Calories. Convert to calories.

142 Calories x 1000 calories = 142,000 calorie

1 Calorie

Define specific heat

The amount of heat required to raise the temperature of

1 gram of a substance 1 degree celsius.

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

What is the specific heat of

A. Water- 4.184B. Ice- 2.03C. Iron- .449D. Gold- .129

What can water do because of its high specific heat?

Absorb large amounts of heat and cold.

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.

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)

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 )

Q= xM= 34.4C= 2.44∆T= (78.8 – 25.0)

Q = M x C x ∆T

Q= 2.44 x 34.4 x 53.8

Q= 4515.75 J

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?

Q = M x C x ∆T

Q = 5696 JM = 155 gC = X∆T = (40 °C– 25°C)

Q = M x C x ∆T

5696 J = 155 g x C x 15°C

C = 2.45 j/g°C

Calorimeter

A device used to measure heat content.