Heat is a form of energy,
We know things to be either hot or cold.
Something hot has a lot of heat energy, cold has less heat energy but it always has some.
Heat travels from warm places to cold places.
It is this transfer of heat can causes injury
This transfer of energy is how we get useful energy liberated
the following questions come from thephysicsteacher.ie
Questions to make you think
1. The foil and the cotton towel are both at the same temperature – so why does the foil feel colder?
2. A candle needs oxygen to burn, which is why if we want to resuscitate a dying fire we blow on it.
So why does blowing on a candle put it out?
3. Why does it get colder as you climb up a mountain, even though you’re getting closer to the sun?
4. When pouring boiling water into a glass, it is advised to first place a metal spoon in the glass. Why?
5. Why might a glass crack when you pour boiling water into it?
6. If you lick a frozen pipe why will your tongue stick to the pipe?
7. Why are ice cubes much better at cooling a drink that the equal amount of iced water?
8. Why is a scald from steam much more serious that a burn from boiling water?
9. Why do hurricanes pick up energy when they pass over oceans?
10. Why does a glass beaker often crack when you pour in boiling water?
11. How come a shiny material is both a bad absorber of heat and a bad radiator of heat?
12. When stepping out of bed on a cold morning, why does it feel colder if your feet touch say, a marble floor rather than a floor with carpet even though both are at the same temperature?
13. Why do footpaths/ rail-tracks/ bridges have gaps in them (hint: sometimes you see the gaps in footpaths or roads filled with a piece of rubber)?
14. Why does water rise when heated?
15. How does perspiration (sweating) help to keep us cool?
16. Many Arabs wear dark clothing in warm weather, even though dark clothes are better at absorbing heat than white clothes. Any idea why?
17. Heat can be transferred by conduction, convection or radiation. A thermos flask tries to keep hot liquids hot by preventing heat loss. Any idea how it minimises each of these three methods of heat transfer?
18. When cooking potatoes on a gas cooker you put the gas supply onto ‘max’ to boil the water as quickly as possible.
The water is now boiling.
If you turn the gas down will it take longer for the potatoes to cook or will it not make any difference?
1. Concept of temperature
2. Thermometric properties
Concept of heat
Heat as a form of energy that causes a rise in temperature when added or a fall in temperature when withdrawn.
The difference between Temperature and Heat
Temperature is the average Kinetic Energy of the particles within a body.
Heat is the sum of the energies in a body.
Thus as the amount of heat in a body increases so too does the temperature, but if two bodies have the same temperature it cannot be said that they have the same heat.
QUANTITY OF HEAT
Using the data that follow, how much energy would be required to change 200g of ice @ -50oC to steam @ 120oC (assume standard temperature & pressure)
C(ice) = 2090 J/kg K
C(water) = 4180 J/kg K
C(steam) = 1865 J/kg K
L(fusion) = 334,000 J/kg
L(vaporisation) = 2,230,000 J/kg
A car radiator is a good example of heat transfer!
Conduction convection and even a little radiation
Draw a diagram
Place the hot object on one side
Place the cold object on the other side
Write in all the values
Draw a line
write out an increasing energy equation
write out an decreasing energy equation
allow them to equal and solve.
Heat crossword to do
The Carnot Cycle as put to you by Micheal Fowler
Heat Engines: the Carnot Cycle
And also by Fowler is this applet about the carnot cycle
- To demonstrate the concept of supercooling in physics classes. Melted sodium thiosulfate is very easy to overcool to room temperature and when crystallization is forced, the sudden temperature jump to 48.3°C can be experienced by touch.