Thermal Energy and Heat

Kinetic Theory of Matter ALL particles that make up matter are constantly in motion. ALL particles that make up matter are constantly in motion. ALL particles in matter have kinetic energy. ALL particles in matter have kinetic energy. Within a substance, not all particles move at the same rate. Within a substance, not all particles move at the same rate.

Temperature A measure of the average kinetic energy of the individual particles of matter A measure of the average kinetic energy of the individual particles of matter Depends on mass as well as speed Depends on mass as well as speed

Temperature Thermometer is used to measure temperature Thermometer is used to measure temperature 3 common scales 3 common scales Fahrenheit Fahrenheit Celsius Celsius Kelvin Kelvin

Fahrenheit Scale Most common in the U.S. Most common in the U.S. 32 o = water freezes 32 o = water freezes 212 o = water boils 212 o = water boils Intervals in between are divided into 180 equal intervals called degrees Fahrenheit ( o F) Intervals in between are divided into 180 equal intervals called degrees Fahrenheit ( o F) Absolute zero = -459 degrees Absolute zero = -459 degrees

Celsius Scale Used in most of the world Used in most of the world 0 o = water freezes 0 o = water freezes 100 o = water boils 100 o = water boils Intervals divided into 100 equal parts called degrees Celsius ( o C) Intervals divided into 100 equal parts called degrees Celsius ( o C) Absolute zero = -273 degrees Absolute zero = -273 degrees

Kelvin Scale Most commonly used in physical science Most commonly used in physical science 273 degrees = water freezes 273 degrees = water freezes 373 degrees = water boils 373 degrees = water boils Kelvin scale is designed so that 0 = absolute zero Kelvin scale is designed so that 0 = absolute zero

Conversion between Celsius and Fahrenheit

Thermal Energy The total energy of all of the particles in a substance or material The total energy of all of the particles in a substance or material The more particles a substance has at a given temperature; the more thermal energy it has The more particles a substance has at a given temperature; the more thermal energy it has

Thermal Energy Example: 2L of hot chocolate at 75 o has more thermal energy than 1.5L of hot chocolate at 75 o Example: 2L of hot chocolate at 75 o has more thermal energy than 1.5L of hot chocolate at 75 o

Thermal Energy Thermal energy depends on: Thermal energy depends on: temperature temperature # particles in a substance # particles in a substance how the particles are arranged how the particles are arranged

Heat Movement of thermal energy from a substance at a higher temperature to another at a lower temperature Movement of thermal energy from a substance at a higher temperature to another at a lower temperature

Heat When energy flows from one object to another; the thermal energy of BOTH objects changes When energy flows from one object to another; the thermal energy of BOTH objects changes Ex: ice cube in bowl Ex: ice cube in bowl

Measuring Heat Calorie Calorie Amount of energy needed to raise the temp. of 1g of water by 1 degree Celsius Amount of energy needed to raise the temp. of 1g of water by 1 degree Celsius Joule Joule SI unit for energy SI unit for energy One calorie = 4.18J One calorie = 4.18J

Measuring Heat 1 C = 1kilocalorie (1000 calories) 1 C = 1kilocalorie (1000 calories) Each calorie of food contains 1000 calories of energy Each calorie of food contains 1000 calories of energy Measured by a calorimeter Measured by a calorimeter

Specific Heat A quantity to measure the relationship between heat and temperature change A quantity to measure the relationship between heat and temperature change Amount of energy required to raise the temperature of 1g of a substance by 1 o C Amount of energy required to raise the temperature of 1g of a substance by 1 o C Every substance has its own specific heat Every substance has its own specific heat

Heat Transfer 3 ways heat can be transferred: 3 ways heat can be transferred: Conduction Conduction Convection Convection Radiation Radiation

Conduction Heat is transferred without the movement of matter itself Heat is transferred without the movement of matter itself Heat is transferred by touching Heat is transferred by touching

Convection Transfer of heat by the movements of a fluid Transfer of heat by the movements of a fluid Gas or liquid Gas or liquid

Convection Current Movement of a fluid caused by differences in temperature Movement of a fluid caused by differences in temperature

Radiation Transfer of energy by electromagnetic waves Transfer of energy by electromagnetic waves Feel radiation from a bonfire; heat lamp Feel radiation from a bonfire; heat lamp DOES NOT require matter to transfer thermal energy DOES NOT require matter to transfer thermal energy

Heat Transfer Heat flows into a substance; thermal energy increases; as thermal energy increases, temperature increases Heat flows into a substance; thermal energy increases; as thermal energy increases, temperature increases Heat will flow until 2 substances have same temperature Heat will flow until 2 substances have same temperature

Heat Transfer Example: ice cream Example: ice cream Heat from ingredients flows to the ice Heat from ingredients flows to the ice

Conductors A material that conducts heat well A material that conducts heat well Metals: silver, copper, stainless steel Metals: silver, copper, stainless steel

Insulators A material that does not conduct heat well. A material that does not conduct heat well. Wool, straw, paper, cork Wool, straw, paper, cork Gases: air Gases: air

Changes in State Three states of matter Three states of matter Solid Solid Liquid Liquid Gas Gas

Changes in State Physical change is a change of state from one form to another Physical change is a change of state from one form to another Most often occurs between solid & liquid; liquid & gas Most often occurs between solid & liquid; liquid & gas

Changes in State Matter will change from one state to another if thermal energy is absorbed or released. Matter will change from one state to another if thermal energy is absorbed or released.

Changes in State The addition or loss of thermal energy changes the arrangement of the particles. The addition or loss of thermal energy changes the arrangement of the particles. The average kinetic energy DOES NOT change. The average kinetic energy DOES NOT change.

Changes in State Melting: solid to liquid Melting: solid to liquid Melting point: temperature at which a solid changes to a liquid Melting point: temperature at which a solid changes to a liquid

Changes in State Freezing: liquid to a solid Freezing: liquid to a solid Freezing point: when a substance loses thermal energy; temperature at which a liquid changes to a solid Freezing point: when a substance loses thermal energy; temperature at which a liquid changes to a solid

Changes in State Vaporization: liquid to a gas Vaporization: liquid to a gas Evaporation: at the surface Evaporation: at the surface Boiling: below the surface Boiling: below the surface Boiling point: temperature at which liquid becomes a gas (boils) Boiling point: temperature at which liquid becomes a gas (boils)

Changes in State Condensation: gas becomes liquid Condensation: gas becomes liquid

Changes in State Thermal Expansion: expanding of matter when it is heated Thermal Expansion: expanding of matter when it is heated As thermal energy of a substance increases, its particles spread out. As thermal energy of a substance increases, its particles spread out. True even when a substance is not spreading out True even when a substance is not spreading out

Changes in State Examples of thermal expansion: Examples of thermal expansion: Thermometer Thermometer Teeth (fillings) Teeth (fillings) Thermostats (heat- regulating device) Thermostats (heat- regulating device)

Uses of Heat Heat engine Heat engine Conversion of thermal energy to mechanical energy requires a heat engine Conversion of thermal energy to mechanical energy requires a heat engine Make use of combustion: burning fuel (coal, gasoline) Make use of combustion: burning fuel (coal, gasoline)

Heat Engine During combustion, chemical energy is converted to thermal energy During combustion, chemical energy is converted to thermal energy Heat engine converts the thermal energy into mechanical energy Heat engine converts the thermal energy into mechanical energy

Heat Engine Classified according to whether combustion takes place outside the engine or inside the engine Classified according to whether combustion takes place outside the engine or inside the engine

Heat Engine External combustion engine External combustion engine Fuel is burned outside the engine. Fuel is burned outside the engine. Steam engine Steam engine

Heat Engine Internal combustion engine Internal combustion engine Fuel is burned in cylinders inside the engine Fuel is burned in cylinders inside the engine Automobiles Automobiles