Heat Energy

Heat is energy caused by the internal motion of molecules of matter Heat is energy caused by the internal motion of molecules of matter Heat energy moves from warmer objects to cooler objects Heat energy moves from warmer objects to cooler objects Some objects transfer heat better than others Some objects transfer heat better than others

Heat Transfer Heat may be transferred in 3 ways: conduction, convection, and radiation Heat may be transferred in 3 ways: conduction, convection, and radiation

Conduction Conduction – Heat energy is transferred through a substance or from one substance to another by direct contact between molecules Conduction – Heat energy is transferred through a substance or from one substance to another by direct contact between molecules When fast-moving molecules collide with slow-moving molecules, heat energy is transferred, causing the slower molecules to speed up When fast-moving molecules collide with slow-moving molecules, heat energy is transferred, causing the slower molecules to speed up May take place in solids, liquids, and gases May take place in solids, liquids, and gases

Heat Transfer Objects that transfer heat well are good conductors of heat Objects that transfer heat well are good conductors of heat Objects that do not transfer heat well are called insulators Objects that do not transfer heat well are called insulators

Convection Convection – Heat energy is transferred through liquids and gases by up-and-down movements called convection currents Convection – Heat energy is transferred through liquids and gases by up-and-down movements called convection currents As a gas or liquid is heated, the molecules move farther apart, making it less dense and causing it to rise, carrying heat with it As a gas or liquid is heated, the molecules move farther apart, making it less dense and causing it to rise, carrying heat with it Takes place in liquids, and gases Takes place in liquids, and gases

Radiation Radiation – Heat energy is transferred through empty space Radiation – Heat energy is transferred through empty space Explains heat from the sun or fires Explains heat from the sun or fires Takes place in liquids, and gases Takes place in liquids, and gases

Measuring Heat When temperature increases, heat is being added When temperature increases, heat is being added When temperature decreases, heat is being removed When temperature decreases, heat is being removed Heat is measured in calories Heat is measured in calories

Calories 1 calorie is the amount of heat needed to raise 1 gram of water 1°C 1 calorie is the amount of heat needed to raise 1 gram of water 1°C Example – 1 calorie is needed to raise the temperature of 1g H 2 O from 24°C to 25°C Example – 1 calorie is needed to raise the temperature of 1g H 2 O from 24°C to 25°C 1 cal = 4.19J 1 cal = 4.19J The amount of heat needed to increase the temperature of an object depends on the mass of the object The amount of heat needed to increase the temperature of an object depends on the mass of the object

Specific Heat Capacity

Coffee Cup Calorimeter The heat lost by one substance is the amount of heat gained by another substance The heat lost by one substance is the amount of heat gained by another substance A calorimeter is a device used to measure the heat given off in chemical reactions A calorimeter is a device used to measure the heat given off in chemical reactions Coffee Cup Calorimeter Coffee Cup Calorimeter