Energy review

Energy review

Conduction, convection and radiation

Conduction

Energy transfer by particles bumping into each other

In the next slide, you will see 10 statements about conduction in metals.

• Grab some paper - you will need it.

• Sort the 10 statements into two groups of five statements.

• For each group, put the statements into order to describe how thermal conduction works.

Multiple Choice

Which box has a higher density?  

• Box A
• Box B
• cannot be determined
• they are the same

Multiple Choice

Less dense fluids _______ in more dense fluids

• float

• sink

Multiple Choice

When a gas is heated, it...

• shrinks

• does not change

• expands

Multiple Choice

If a fluid's particles are further apart, the fluid is now...

• heavier

• less dense

• more dense

• lighter

Convection

Energy transfer by movement of energetic particles

Multiple Choice

A candle flames moves the air around it.

It makes the particles move more quickly and spread out.

How do air particles move above a candle flame?

Multiple Choice

KMnO₄ is a purple solid. It dissolves very easily in water. It can be used to show how water moves when it is heated.

Which diagram do you think shows how the water moves when it is first heated?

Radiation

Energy transfer by light waves

Multiple Choice

Which is an example of something that transfers heat by radiation?

• the sun

• a hot air balloon

• a Bunsen burner

• wind currents

Multiple Choice

Which best describes radiation?

• heat moving water

• heat moving air

• metals touching a fire

• electromagnetic rays

Multiple Choice

Which is the best example of radiation?

• a hairdryer drying hair

• a microwave cooking food

• melting ice cubes in your hand

• baking bread in the oven

Multiple Choice

Which method of energy transfer by heating does NOT require particles?

• convection

• conduction

• radiation

Multiple Choice

Which is BEST surface for absorbing and emitting energy by radiation?

• matte black

• shiny black

• matte silver

• shiny silver

Temperature

A quick recap

Temperature measures the AVERAGE energy in the kinetic energy stores of the particles in an object

An object's thermal energy store tells us the TOTAL energy in the kinetic energy stores of the particles making up the object.

Multiple Choice

When we measure the temperature of something, we are measuring the ________ energy in the kinetic energy stores of all the particles in that substance.

• average

• total

Multiple Choice

When an object has energy in its THERMAL energy store, its particles have energy in their:

• kinetic energy stores

• elastic potential energy stores

• nuclear energy stores

Multiple Choice

In a hot fluid (that is, a hot liquid or gas), particles move ________ than in a cold fluid.

• more slowly

• faster

• more elegantly

• more erratically

Multiple Choice

Why does the temperature of boiling water stay at 100^oC until it has all evaporated, even though we are transferring energy into it by heating? What happens to the additional energy?

• It helps the particles overcome forces keeping them together as a liquid

• The additional energy is destroyed

• Additional water is created

• The additional energy is lost

Multiple Choice

The temperature of a cup of tea is measured with a thermometer. There is a red liquid inside the thermometer.

What happens to the liquid in the thermometer when it is put into the cup of hot tea?

• Its temperature goes up and it expands (gets bigger)

• Its temperature goes up

• Its temperature goes up and it contracts (gets smaller)

Multiple Choice

Which answer best explains why the liquid in the thermometer changes in this way?

• The particles move more quickly

• The particles expand (get bigger)

• The particles break up

• The temperature of each particle goes up