Topic 4Thermal Energy

I. Temperature, Thermal Energy, and Heat

A. Thermal Energy - the total kinetic and potential energy of

all the particles in an object.

1. Depends on the amount of a substance (more of a

substance, more thermal energy)

2. thermal equilibrium - energy is transferred from high to

low, until they reach the same point

B. Heat - energy that is transferred between to objects (joules)

C. Temperature – the average amount of kinetic energy in the

particles of an object.

1. Kinetic Energy – the amount of kinetic energy is

directly related to its temperature.

a. more kinetic energy = more temperature

b. less kinetic energy = less temperature

2. Average Measure – the temperature is a measure of

the average kinetic energy of the particles.

a. Some particles of an object may have more

kinetic energy than other particles.

b. Temperature is not determined by the amount of

a substance.

3. Measuring Temperature

a. thermometer – measures the temperature of a

substance using mercury or alcohol.

b. temperature scales – Kelvin vs. Celsius

WATER Celsius Kelvin

Freezing Point 0 273

Boiling Point 100 373

II. Heat Transfer - transfer of energy between objects that are a

different temperature

A. Conduction

1. transfer of thermal energy from one substance to

another through direct contact.

2. can occur within a substance

3. transfers until all substances have the same

temperature.

B. Convection

1. transfer of the thermal energy by the movement of a

liquid or a gas.

2. Warmer gasses or liquids are less dense, and therefor

rise. As it rises, it cools, becomes more dense, and

sinks.

3. Convection current – circular motion of liquids or

gasses

C. Radiation

1. transfer of energy through matter or space as

electromagnetic waves.

2. All objects radiate electromagnetic waves

III. Heat and Materials

A. Conductors and Insulators

1. conductors - materials that conduct heat well; metals

2. Insulators - materials that do not conduct heat well;

air, wool

B. Specific Heat - the amount of energy required to raise the

temperature of 1 kilogram of a material by 1 Kelvin

1. (joules per kilogram-kelvin or J/(kg-K)

2. Energy Change = mass x specific heat x

temperature

3. a material with a high specific heat can absorb a

great amount of energy without much temperature

change.

C. Thermal expansion

1. increase in volume of a substance due to its increase

in temperature.

2. Expansion joints – parts of bridges or roads that allow

the road to expand due to changes in temperature

3. Thermostat – bimetallic strip coils and uncoils in

response to temperature changes in your house

IV. Change of State Graphs

A. Changes of State – Melting, Freezing, Boiling, Condensing

B. During ACTUAL change of state, temperature does not

increase or decrease. The energy is being used to change

the arrangement of the particle.