14-3 & 14-4Thermal Energy & States of Matter

Uses of Heat

What are the three states of matter and how are particles arranged in each state?• Solid• Particles are arranged tightly and vibrate back and forth

• Liquid• Particles are close together – particles can move around; therefore, they do

not have a definite shape, but they do have a definite volume

• Gas• Particles are moving so fast that they don’t stay close together. Gases expand

to fill all available space; therefore, they do not have a definite shape or volume

What is a change of state?

• The state of matter of a substance is determined by the amount of thermal energy it has.• Matter can change from one

state to another when thermal energy is absorbed or released.• The more thermal energy an

object has, the faster the particles move.

What are the changes of state?

• Melting – solid to liquid• Freezing – liquid to solid• Evaporation – liquid to gas• (Boiling is a form of evaporation

that occurs beneath the surface of the liquid because of high temperatures)

• Condensation – gas to liquid• Sublimation – solid to gas• Deposition – gas to solid

Deposition

What is thermal expansion?

• As the thermal energy of matter increases, its particles begin to move faster and they spread out. As a result, the substance expands. • When the substance cools off, the particles slow down and move

closer together. This causes the object to retract.

• Egg in a Bottle

What is a heat engine?

• A device that transforms thermal energy into mechanical energy.

• External combustion engine

• Internal combustion engine

External Combustion Engine

• External combustion engine – an engine that burns fuel outside the engine in a boiler• Example: steam engines

Internal Combustion Engine

• Internal combustion engines burn fuel in cylinders inside the engine• Examples: diesel and gasoline

engines

• Each up or down movement of the piston is called a stroke

Four Stroke Engine

Cooling Systems

• Refrigerators• A device that transfers thermal

energy from inside the refrigerator to the room outside• Transfers thermal energy from a

cool area to a warm area by using a refrigerant to absorb heat from the food

Why does keeping the refrigerator open for long time periods cause the refrigerator to use more electricity?

Cooling Systems

• Air Conditioners• Devices used in cars, homes, and schools – work in the same way as a

refrigerator, but absorbs heat from the air inside of a room or car and transfers it outdoors

Ticket out the DoorOn a sheet of paper, restate the following

statements in your own words.1. Most matter on Earth can exist in three states – solid, liquid, and

gas.2. Matter can change from one state to another when thermal energy

is absorbed or released.3. As thermal energy of matter increases, its particles spread out and

the substance expands.4. Heat engines transform thermal energy to mechanical energy.5. A refrigerator is a device that transfers thermal energy from inside

the refrigerator to the room outside.

Homework

• Workbook pages __________________