14-3 & 14-4 Thermal 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 Door Ticket out the Door On 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.

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