The last unit in our exploration of matter and energy delves into one of the more explosive forms of energy--heat. This corresponds to pages 255 - 271 in the textbook. This unit will involve cool things (like liquid nitrogen) and hot things like possibly rocketry.
Heat is the kinetic energy (motion) of the object’s particles.
The faster the particles move, the hotter the object feels
Usually the object gets bigger to accommodate the increased movement, so most things
expand when heated.
This expansion allows us to measure the heat in a number of ways:
bimetal thermometer - where differential expansion of two metals bends the rod.
alcohol and mercury - where expanding fluid rises up a tube
balloon - where expanding air inflates a balloon
digital and infrared thermometers use different methods.
Once we have expansion, we then need a scale to measure it against. There are three:
Fahrenheit Celsius Kelvin
“absolute zero” -273 0
freezing 32 0 273
boiling 212 100 373
The heat energy always travels from hot to cold in one of the three ways:
Conduction - requires contact with a conductor (metal) through which the heat passes
Convection - Involves the rising-spreading-then-cooling within a fluid (air or water)
Radiation - sending off energy in the form of electromagnetic waves
Insulators are the opposite of conductors and prevent the flow of heat.
A refrigerator is actually a heat generator that uses evaporation and condensation to cool
the inside and heat the outside of the ‘fridge.
Evaporation is a cooling process / condensation is a warming process.
We also talked about home heating systems. We compared hot water (the kind with a
radiator) with hot air (the kind with vents). You were asked to find out which kind you
had at home.
Important things to understand:
What heat is.
How heat is measured.
The ways it can be transferred.
What absolute zero is.