Bell Ringer

• How is kinetic energy directly related to thermal energy?

Thermal Energy

A. Temperature & Heat

1. Temperature is related to the average kinetic energy of the particles in a substance.

2. SI unit for temp. is the Kelvin (273 degrees different than Celsius)

-273 Absolute ZeroCelsius

Most common scale world wideFreezing point of H2O is 0Boiling point of H2O is 100

FahrenheitUsed generally in the U. S.Freezing point is 32/ Boiling point is 212

Scales• The relationships

between the different temperature scales are:

• oK = 273.15 + oC      

•   oC = (5/9)*(oF-32)       

• oF = (9/5)*oC+32       

4. Thermal Energy – the total of all the kinetic and potential energy of all the particles in a substance.

Depends on 3 Things:

Mass (cup vs. pot)

Temperature

Phase( solid, liquid, gas)

5. Thermal energy relationships

a. As temperature increases, so does thermal energy (because the kinetic energy of the particles increased).

b. Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy).

6. Heat

a. The flow of thermal energy from one object to another.

b. Heat always flows from warmer to cooler objects. Ice gets

warmer while hand gets

cooler

Cup gets cooler while hand gets

warmer

7. Specific Heat

a. Some things heat up or cool down faster than others.

Land heats up and cools down faster than water

b. Specific heat is the amount of heat required to raise the temperature of 1 kg of a material by one degree (C or K).

1) C water = 4184 J / kg C

2) C sand = 664 J / kg C

This is why land heats up quickly during the day and

cools quickly at night and why water takes longer.

Why does water have such a high specific heat?

Water molecules form strong bonds with each other; therefore it takes more heat energy to break them. Metals have weak bonds

and do not need as much energy to break them.

water metal

How to calculate changes in thermal energy

Q = m x T x Cp

Q = change in thermal energy

m = mass of substance

T = change in temperature (Tf – Ti)

Cp = specific heat of substance

• What would the change in T.E. be if the temperature of 12 g of water increased by 20C

• What is the change in T.E. when 500 grams of water cools from 45 C to 35 C

• What is the change is Thermal Energy when a 55 g iron nail cools from 90c to 25C

• What mass of water will change it’s temperature by 3.0 C when 525 j of heat is added to it?

• A 42 g ball of aluminum foil cools from 30C to 15C. What it’s change in thermal energy, specific heat of aluminum is .920 j/g

• To release a diamond from it’s setting, a jeweler heats a 10 g silver ring by adding 23.5 j of heat. How much does the temp increase? Silver is .235 j/g

• The temperature of a 32-gram silver spoon increases from 20C to 60 C. What is the change in Q?

• What is the mass of water that will change it’s temperature by 8.0 when 1500 J of heat is added to it?

• PVC Piping has a specific heat of 2.09. What is the change in thermal energy when a 700 g pipe changes temp from 82C to 112C

c. A calorimeter is used to help measure the specific heat of a substance.

First, mass and temperature of

water are measured

Then heated sample is put

inside and heat flows into

water

T is measured for water to help get its heat gain

This gives the heat lost by

the substance

Knowing its Q value, its mass, and its T, its Cp can be calculated

Calorimeter Lab

Go to back of room today, gather equipment.

Convection Current

• The movement of a substance that is caused by differences in temperature and density.

• EXAMPLES: wind boiling water

• NATURE WANTS

EVERYTHING TO BALANCE ! !

• The transfer of heat by direct contact between objects or particles.

• Transfer of energy by particles colliding. Heat from hand to the snow

• Happens best in Solids

• Heat transferred through space.

• Happens best in gases• EXAMPLE: The

sun’s rays causing a sunburn.

• An insulator is a material that does not transfer heat easily.

• Examples: • liquids and gases• A jacket