*10 Transfer of Heat Energy and Its Effects Flashcards
What is the SI unit for temperature?
What are some other units of temperature?
kelvin (K)
Some other units of temperature includes degree Celsius (oC) or degree Farenheit (oF).
What does a change in temperature means?
It means a gain in heat (temperature increases) or a loss in heat (temperature decreases)
How is heat energy transferred?
Think in terms of high temperature and low temperature.
You can also think about the transfer in the terms of hot and cold objects.
Heat transferred from an object of high temperature to an object of low temperature.
Heat transfered from a hot object to a cold object.
What is the effect of heat on objects?
In terms of both heat gain and heat loss.
Objects gain heat and expand.
Objects lose heat and contract.
Why must there be gaps in train tracks?
These gaps allows the tracks to expand during a hot day without damaging the tracks.
Most roads and bridges have similar gaps to allow for the same expansion.
Why must there be flexible bends in pipes that carries hot gases or liquids?
The flexible bends allows the pipes to expand without breaking the pipes when they are carrying hot gases or liquids.
Why does the bimetallic strip bends when heated?
A bimetallic strip is made of two different metals joined together. One metal expands more that the other when heated. This causes it to bend.
The same explanation can also be used for cooling down.
What are the three methods of heat transfer?
conduction
convection
radiation
What is conduction?
The transfer of heat without the physical movement of a medium.
Conduction happens best in solids.
Why does metal feels colder than wood at the same temperature?
Think conduction in metal and in wood.
Metal is a better conductor of heat than wood. Thus metal conducts heat away from your hand faster than wood which causes your hand to feel colder.
Why are solids better conductor of heat than liquid or gas?
Particles in solid are arranged closer together than particles in liquid or gas. This allows heat to transfer more quickly.
What is convection?
The transfer of heat by the physical movement of a medium.
Liquid and gas are able to convect heat very well as both states of matter can flow.
How does a hot air balloon rises when the air inside is heated?
Think in terms of the density of air.
AIr inside the hot air balloon expands when heated. This causes the density of the air inside the balloon to be lower than the outside. The difference in density causes the hot air balloon to rise.
Explain how convection heats up a beaker of water.
Think in terms of the density of hot/cold water.
The heated water at the bottom expands and becomes less dense and it rises up.
The cooler water at the top is denser and it sinks to the bottom.
This process repeats and forms a convection current to heat up the beaker of water.
The same explanation can also be used to explain how air convects heat.
What is radiation?
The transfer of heat without the need of a medium.
This is why radiation can happen through a vacuum.
Why does the wax melts faster at the copper rod?
You can also explain why wax melts the slowest at the wooden rod.
Copper is the best conductor of heat. Heat transfer fastest from one end of the copper rod to the other end. This causes the wax to melt the fastest.
You can use the same explantion for the wooden rod.
Why does the ice not melt when the water at the top of the test tube is heated?
Water is a poor conductor of heat. The ice at the bottom remains at a low temperature even though the top is heated.
Explain why the black container becomes hotter in the sun.
1) Black surface is a good absorber of radiant heat.
2) The container heats up faster and thus becomes hotter than the white container.
Explain why the black container becomes cooler faster in the shade.
1) Black surface is a good radiator of radiant heat.
2) The container cools down faster and thus becomes cooler than the white container.
