Heat and EnergyHeat and Energy

Chapter 3 section 2Chapter 3 section 2Key Concept: Heat flows in a Key Concept: Heat flows in a

predictable way from warmer objects predictable way from warmer objects to cooler objects until all the objects to cooler objects until all the objects

are the same temperature.are the same temperature.

What You Will LearnWhat You Will Learn

Temperature is a measure of the Temperature is a measure of the average kinetic energy of particles in average kinetic energy of particles in an object.an object.

Heat is energy that is transferred Heat is energy that is transferred between objects.between objects.

Heat flows by conduction, Heat flows by conduction, convection, and radiation.convection, and radiation.

What is temperature?What is temperature? TemperatureTemperature is a is a

measure of the measure of the average kinetic average kinetic energy of the particles energy of the particles in an object.in an object.

All matter is made up All matter is made up of constantly moving of constantly moving particles, such as particles, such as atoms or molecules.atoms or molecules.

When a particle is in When a particle is in motion, it has motion, it has kinetic kinetic energyenergy..

The The fasterfaster particles particles move, the more kinetic move, the more kinetic energy they have.energy they have.

The temperature of a The temperature of a substance depends on substance depends on the kinetic energy of the kinetic energy of all of its particles.all of its particles.

The more kinetic The more kinetic energy the particles energy the particles have, the higher the have, the higher the temperature of the temperature of the substance.substance.

The substance The substance on the right has on the right has a higher a higher temperature temperature because its because its particles have a particles have a higher average higher average kinetic energy.kinetic energy.

Particles in a substance move at Particles in a substance move at random and at different speeds.random and at different speeds.

The average of all these speeds is The average of all these speeds is the average kinetic energy.the average kinetic energy.

When you measure temperature, you When you measure temperature, you are measuring average kinetic are measuring average kinetic energy.energy.

Temperature does not Temperature does not depend on the amount of depend on the amount of particles in a substance.particles in a substance.

A teapot holds more tea A teapot holds more tea than a tea cup.than a tea cup.

But if the atoms of tea in But if the atoms of tea in both containers have the both containers have the same kinetic energy, same kinetic energy, then the tea in both then the tea in both containers has the same containers has the same temperature.temperature.

Thermal ExpantionThermal Expantion When particles move When particles move

faster, they move apart.faster, they move apart.

As the space between As the space between the particles increases, the particles increases, the substance expands.the substance expands.

Therefore, an increase Therefore, an increase in temperature leads to in temperature leads to an increase in volume. an increase in volume. This is called This is called thermal thermal expansionexpansion..

What is heat?What is heat?

HeatHeat is the energy that is is the energy that is transferred between objects transferred between objects that are at different that are at different temperatures.temperatures.

Heat energy is always Heat energy is always passed from an object with passed from an object with a higher temperature to one a higher temperature to one with a lower temperature.with a lower temperature.

When you touch something When you touch something hot, heat flows from the hot, heat flows from the object to your finger.object to your finger.

Thermal energyThermal energy is is the total kinetic the total kinetic energy of the particles energy of the particles that make up a that make up a substance.substance.

Thermal energy, which Thermal energy, which is expressed in joules is expressed in joules (J), depends partly on (J), depends partly on temperature.temperature.

Something at a high Something at a high temperature has more temperature has more thermal energy than thermal energy than something at a low something at a low temperature.temperature.

Thermal energy also Thermal energy also depends on the depends on the amount of particles amount of particles in a substance.in a substance.

The more particles in The more particles in a substance at a a substance at a given temperature, given temperature, the greater the the greater the thermal energy.thermal energy.

When things that When things that have different have different temperatures come temperatures come into contact, energy into contact, energy will always be will always be transferred.transferred.

Energy will pass from Energy will pass from the warmer to the the warmer to the cooler object until cooler object until both have the same both have the same temperature.temperature. Ex: Hot soup makes cool bowl

hot.

How is heat transferred?How is heat transferred?

The transfer of heat from The transfer of heat from one object to another one object to another through direct contact is through direct contact is called called conductionconduction..

Heat flows from the Heat flows from the particles of hot soup to particles of hot soup to the part of the spoon that the part of the spoon that is in the soup.is in the soup.

Heat travels from particle Heat travels from particle to particle, from the soup to particle, from the soup all the way up the all the way up the spoon’s handle.spoon’s handle.

The transfer of heat The transfer of heat due to the movement due to the movement of matter is called of matter is called convectionconvection..

When you boil water, When you boil water, heat is passed from heat is passed from the burner to the pot the burner to the pot and from the pot to and from the pot to the water by the water by conduction.conduction.

As the water is As the water is heated, it becomes heated, it becomes less dense.less dense.

Cooler, denser water at the top of Cooler, denser water at the top of the pot sinks.the pot sinks.

This forces the warmer water to the This forces the warmer water to the surface.surface.

Water continues to rise and fall in a Water continues to rise and fall in a circular pattern called a convection circular pattern called a convection current.current.

The transfer of heat or The transfer of heat or other energy as other energy as electromagnetic waves, electromagnetic waves, such as visible light or such as visible light or infrared waves, is called infrared waves, is called radiationradiation..

Radiation can occur Radiation can occur between objects that between objects that are not in direct contact are not in direct contact with each other.with each other.

The sun transfers The sun transfers energy through space energy through space by radiation.by radiation.

States of MatterStates of Matter

The states of matter are the physical The states of matter are the physical forms in which a substance can exist.forms in which a substance can exist.

The three states of matter are solid, liquid, The three states of matter are solid, liquid, and gas.and gas.

A substance’s state depends on the speed A substance’s state depends on the speed of its particles, the attraction between of its particles, the attraction between them, and the pressure around themthem, and the pressure around them

A substance’s chemical composition also A substance’s chemical composition also influences the state it is in at a given influences the state it is in at a given temperature.temperature.

For example, milk is a liquid at room For example, milk is a liquid at room temperature, but butter is a solid.temperature, but butter is a solid.

A change of state occurs when a A change of state occurs when a substance changes from one state of substance changes from one state of matter to another.matter to another.

Changes of state include:Changes of state include:

condensing (gas to liquid)condensing (gas to liquid) freezing (liquid to solid)freezing (liquid to solid) melting (solid to liquid)melting (solid to liquid) evaporating (liquid to gas)evaporating (liquid to gas)

A change of state involves a transfer A change of state involves a transfer of heat from one substance to of heat from one substance to another.another.

When a substance melts or boils, it When a substance melts or boils, it gains energy.gains energy.

When a substance condenses or When a substance condenses or freezes, it loses energy.freezes, it loses energy.