TEMPERATURE AND HEAT TRANSFER REVIEW HEAT ENERGY REVIEW

TEMPERATURE AND HEAT TRANSFER REVIEW

HEAT ENERGY REVIEW n You have a black cat and white cat. Which is more likely to absorb less heat energy?

HEAT ENERGY REVIEW n White cat because it is a lighter color. Dark colors absorb heat better while light colors reflect more heat energy.

HEAT ENERGY REVIEW n Describe how an egg may be cooked when heat is transferred by conduction.

n The egg is cracked into a pan. The egg is in direct contact with the heated surface of pan and the heat travels through the egg.

n By which method is heat being transferred in a refrigerator? Explain your choice.

answer n Convection; heat is moving from one part of refrigerator to another by moving with the heated and cooled air. the colder air created below the freezer becomes dense and sinks into lower portion of ‘fridge. Warmer air from below rises up to top.

HEAT ENERGY REVIEW n Identify which has a higher kinetic energy. Explain how you know. n A pot of boiling water or a tub of cold water.

HEAT ENERGY REVIEW n The pot of boiling water has more KE because the molecules are moving faster. Temperature measures the KE of the molecules.

HEAT ENERGY REVIEW n Describe how an egg may be cooked when heat is transferred by radiation.

HEAT ENERGY REVIEW n An egg can be cooked by radiation by putting in a microwave or in a solar cooker. The waves travel to egg and cook egg.

n By which method is heat energy largely reaching the man? Explain your choice.

n Radiation-heat travels as electromagnetic waves toward man

n Explain what will happen to the heat energy when a glass of iced tea is placed next to a bowl of soup and allowed to sit for a long while.

n The heat energy will transfer from the soup to the iced tea (and other surrounding matter) until they are all at equal temperatures (thermal equilibrium)

HEAT ENERGY REVIEW n_ _ is transferred between objects of different temperatures.

HEAT ENERGY REVIEW n. HEAT ENERGY

HEAT ENERGY REVIEW n. Give an example of a heat being transferred by radiation.

n__ is the measure of the average kinetic energy of the molecules in a substance

HEAT ENERGY REVIEW ntemperature

HEAT ENERGY REVIEW n. Give an example of a heat being transferred by conduction.

n Answers will vary: some examples—car engine heating up, tires on bike after a ride, hand holding a snowball

HEAT ENERGY REVIEW n Describe how an egg may be cooked when heat is transferred by convection.

HEAT ENERGY REVIEW n An egg may be poached or boiled—placed in a bath of water. The water transfers the heat to the egg because convection currents form when the heat of the burner is turned on.

HEAT ENERGY REVIEW n_ _ is the expansion of molecules due to an increase in heat energy.

HEAT ENERGY REVIEW n. THERMAL EXPANSION

HEAT ENERGY REVIEW n __ __ occurs when the heat energy between 2 or more substances (of varying temperatures) is exchanged until all of the substances have the same temperature

HEAT ENERGY REVIEW nthermal equilibrium

n __ is the transfer of heat between two or more objects or within a substance (molecule to molecule)

n CONDUCTION

n __ is the transfer of heat through a fluid; the matter moves the heat between areas of unequal temperatures

n CONVECTION

n __ is the transfer of heat in the form of waves.

n RADIATION

n __ allow heat to flow through it easily.

n CONDUCTORS

This type of heat transfer can move over great distances in a vacuum (empty space).

n RADIATION

Identify at which point(s) heat is being transferred by conduction

X-conduction (radiation if it is a gas fire) Y-convection Z-conduction

n Give an example of good conductor

Any kind of metal

n Give an example of a good insulator

n Answers will vary: air, water, plastic, Styrofoam, feathers, wool, etc.

Explain how heat is being transferred by convection

n The heat travels from the bottom of the pan to the top by moving with the hot, less dense water as it rises.

True or False. Explain your choice. n A good insulator is a poor conductor n

n True. A good insulator is a poor conductor because it delays (slows down) the transfer of heat energy through a substance.

n Describe what happens to the movement and arrangement of molecules in a fluid when heat is lost

n THE MOLECULES MOVE SLOWER AND CONTRACT

Identify where heat is being transferred by conduction.

answer

n Heat always flow from ___ matter to ____ matter.

n From hotter substances to cooler ones

n Describe what happens to the movement and arrangement of molecules in matter when they are heated

n THE MOLECULES MOVE FASTER AND EXPAND

n __ do not allow heat to flow easily through it; they trap heat.

n INSULATORS

Identify where heat is being transferred by radiation.

ANSWER

n In general, which will absorb heat better: a solid, liquid, or gas?

n A SOLID

Identify where heat is being transferred by convection.

answer

n Using what you know about the transfer of heat, explain why air conditioners are often placed up high in a room.

n ACs are placed up high so that the cold, dense air can sink and push the warm, less dense air up (to be cooled)