unit 3 lesson 2 energy transfer -...

Unit 3 Lesson 2 Energy Transfer

Copyright © Houghton Mifflin Harcourt Publishing Company

Hot and Cold


How are energy and temperature related? • All matter is made up of moving particles and has

kinetic energy. • Temperature is a measure of the average kinetic

energy of particles. • The faster a particle moves, the more kinetic

energy it has.


How are energy and temperature related? • Thermal energy is the total kinetic energy of

particles. • Thermal energy depends on the number of

particles. • The more particles there are in an object, the

greater its thermal energy.



How are energy and temperature related? • How does kinetic energy change as particle

motion increases and decreases?



What is thermal expansion?

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

• The increase in volume that results from an

increase in temperature is called thermal expansion.

• Thermal expansion causes a change in the density

of a substance.



What is thermal expansion?

• Density is the mass per unit volume of a substance.

• Differences in density caused by thermal

expansion can cause movement of matter. • The movement of air in the atmosphere, water in

the oceans, and rock in the geosphere can be caused by thermal expansion.



Getting Warm


What is heat?

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

• When objects at different temperatures come in

contact, energy is transferred between them until they reach the same temperature.

• Energy flows from the object at higher

temperature to that at lower temperature.


Why can the temperatures of land, air, and water differ? • The different rates at which materials become

warmer or cooler are due to specific heat. • Materials with a high specific heat require more

energy to show an increase in temperature. • Water has a higher specific heat than land, which

means water warms up and cools down more slowly than land does.



Heat


How is energy transferred by radiation?

• Radiation is the transfer of energy as electromagnetic waves.

• The sun transfers energy to Earth by radiation. • Radiation can transfer energy between objects

that are not in direct contact with each other.



• Energy from the sun travels as waves and is called electromagnetic radiation.

• Forms of electromagnetic radiation include visible

light, infrared radiation, X-rays, and ultraviolet light.




• How does the sun heat Earth?



Where does radiation occur on Earth?

• The sun is almost 150 million km away from Earth, but it is the major source of energy for processes on Earth.

• Solar radiation is partly reflected and scattered by

Earth’s atmosphere. However, some solar radiation is absorbed by the atmosphere, geosphere, and hydrosphere.



Heating Up


How is energy transferred by convection? • Convection is the transfer of energy due to the

movement of matter. • Convection occurs because most matter becomes

less dense when it gets warmer. • Convection currents form as warm and cool

matter rise and fall due to temperature and density differences.


Where does convection occur on Earth?

• Energy moves through the atmosphere as warm air rises and cool air sinks.

• Ocean water has different densities due to

differences in temperature and the amount of salt in the water.

• Energy is transferred through rock material from

Earth’s core to the surface by convection currents.



Ouch!


How is energy transferred by conduction? • Conduction is the transfer of energy from one

object to another object through direct contact. • When objects at different temperatures touch,

their particles interact.

• The faster-moving particles of the warmer object transfer energy to the slower-moving particles in the cooler object.


Where does conduction occur on Earth?

• Energy is transferred by conduction from the warmer ground to cooler air at Earth’s surface.

• Warm air can transfer energy to cooler water and

cause evaporation. If water vapor transfers energy to the air, the water vapor may condense.

• Inside Earth, energy can be transferred between

rock particles by conduction, but very slowly.



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unit 3 lesson 2 energy transfer -...

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