C Heat and Temperature Flashcards
What is heat?
- energy, not a substance
- heat energy travels from matter at higher temperatures to matter at lower temperatures
heat is a term used to mean the energy that is transferring between substances and implies that the energy is transferred
use kinetic energy instead if you want to talk about the general movement of particles within a substance
What is the official unit of heat energy?
joule (J)
What are examples of heat related technologies?
- forced-air heating
- electric heaters
- air conditioners
- fire
- central heating
- chimneys
- cast-iron stoves
rough sequence of heating technology inventions:
fire –> central heating but not with coal –> chimneys –> fireplaces in walls –> cast-iron stoves –> central heating with coal –> forced-air heating –> electric heaters
sustainable
something can be maintained or continued
states of matter
- solid
- liquid
- gas
melting point
the temperature at which the matter changes from solid to liquid
boiling point
temperature at which matter changes from liquid to gas
particle model of matter
a) all matter is made up of TINY particles
b) the particles are always MOVING
c) adding heat makes the particles move FASTER
d) there is SPACE between the particles
kinetic energy
energy of movement
(not to be confused with heat, which is energy that is moving from hot to cold)
compare different states of matter
- solid has least amount of particle movement, gas has the most
- solids have particles that are attached to each other in all directions so can only vibrate but not travel
- liquids have loose attractions between particles
- gases have no set shape and particles are not connected
- solids and liquids have definite volume (vs. gases fill the container and change density)
temperature
how hot or cold matter is measured on a scale (such as degrees Celcius)
thermal energy
sum of all kinetic energy that the substance contains, so if you have more of the substance at the same temperature, the thermal energy will be higher
thermal energy
sum of all kinetic energy in a substance
this means that more of the substance at the same temperature makes more thermal energy
thermal expansion
when a substance takes up more space because of an increase in thermal energy
What happens when the thermal energy of a solid decreases?
- solid contracts
- volume decreases
methods of heat transfer
- conduction
- convection
- radiation
conduction
- transfer of heat energy between substances that are in contact with each other
conductor
- material that allows easy transfer of heat
- metals are good conductors
insulator
material that does not allow easy transfer of heat
- styrofoam is a good insulator
convection currents
- hot matter rises because it is less dense than cold matter of the same type
- this causes a vacuum underneath the hot matter that is rising so substance will come in from the sides to fill the space
- if you heat something from below (such as sun heating the ground or a pot of water on the stove being heated by the element) then a current will occur since the matter is being heated more lower down and that will push up starting the current
- convection currents happen in liquids and gases such as air or water
radiation
- does not require movement of particles to transfer energy
- radiant energy is transfered with invisible waves
infrared waves
- the method of energy transfer for radiant energy
good reflectors of radiant energy
- light colours or white
- shiny
Natural sources of thermal energy
- sun
- geothermal energy (center of the Earth)
- fires
- decay
passive vs. active heating system
- passive means to reduce heat loss and let the building have lots of windows facing south
- active is using technology to pump hot into colder places or to light a fire and then direct the heat towards something cold
three components of active solar heating
- collector
- heat storage unit
- heat distribution system
thermostat
- maintains the heat at a consistent temperature
local heating system
- provides heat for only one room
central heating system
heat transfers through pipes, ducts, or vents or openings to other places around the building
e.g. forced-air heating or hot-water heating are two different examples
refrigerant
- evaporates at a very low temperature creating freezing temperatures inside the refrigerator
- evaporation is a process that absorbs heat so when the refrigerant evaporates, that heat is taken with it
thermal conductivity
the ability to transfer heat by conduction
alternatives for thermal energy (instead of burning fossil fuels)
- wind energy
- nuclear energy
- hydro-electric power
cogeneration
- the production of two forms of energy at the same time from one energy source
electricity and heat could be generated together and is common
