Convection and Conduction
All matter is made of tiny particals called atom and molecules
Held together by chemical bonds…all of those particals are in motion constantly
Make up all things in the universe
“shivers to get warm”body mechanizam of staying warm
All particals in universe have Kinetic Energy
The Kinetic Theory states that all partical are in constant motion and there are forces of attraction bw particles without that attraction forces the particles would drift apart
How much energy is in a sample of matter (need to know)
The faster the motion the more KE…the measure of the average KE is what we call temperature
High KE High Energy High Temperature
Low KE Low Energy Low Temperature
Temp is measured in degrees kelvin (K)
1 C = 273 K
Celcius= 5/9(F +40)-40
Farenheit= 9/5(C+40)-40
33C=_91.4___ F=_306___K
90F= ___32.2_C = _305.2_K
C: 30 is hot 20 is nice 10 is cool 0 is ice
Temperature and heat are different but are related
Temp is the avg KE of the particles in matter
Heat and Thermal energy total energy of all the particle in a sample of matter KE + PE
Heat depends on the average KE and how many particles there are
Measure how much energy is add to or taken out
Amt of energy transferred bw objects with different temperatures is heat
Heat and temp are related but they are NOT the same
If the mass of an object increase then the thermal energy it has
Heat only flow from hot to cold High to low
Diffe. Substance have diff capacities for absorbing heat
Amt of heat energy to raise the temp of 1 g of a substance 1C is specific heat
Specific heat is a measure of the ability of a substance to absorb heat
Every substance has its own specific heat
|
Substance |
Specific heat (j/gC) | Specific Heat (J/KgK) |
| Al | .90 | 900 |
| Cu | 38 | 380 |
| Au | .13 | 130 |
| Ice | 2.06 | 2060 |
| Fe | .45 | 450 |
| Pb | .13 | 130 |
| Steam | 2.06 | 2060 |
| H2O | 4.184 | 4184 |
| Alcohol | 2.45 | 2450 |
| C(Graphite) | 7.10 | 7100 |
| Sand | 6.64 | 6640 |
Water is used as a coolant bc it has a high specific heat
Takes longer for water to heat up and to cool down
www.engineeringtoolbox.com/specific-heat-solids-d_154.html
thermal energy of an object changes when heat flows into or out of a substance
that heat flow change in thermal energy is related to the mass of the object the obj specific heat and its change in temperature
Q=mC(Tf-Ti)
Q=change in thermal energy
m=mass of object
C=specfic heat
Tf= final temperature
Ti= initial temperature
32g Au spoon heats from 20C to 60C what is its change in thermal energy
Q= (32g)(.23J/gC)(60C-20C)
Q=294.4 J
A 45kg brass structure gains 180,480J with a change in temperature from 40C-28C
Dulong-Petit Law: The specific heat of an element is inversley related to it atomic mass
Heat of fussion: The amt of heat needed to change a solid at its melting pt to a liquid at the the same temp
The heat of vaporization: the amt of heat energy that will change a liquid at its boiling pt to a gas at the same temperature
http://energyconcepts.tripod.com/energyconcepts/boilerstean.htm
direct contact – hands/snow . . . .hands/coffee cup
Table of tables http://hyperphysics.phy-astr.gsu.edu/hbase/tables/ttab.html
Convection: transfer of energy of the motion of heated particles in a fluid
As the particles move faster the fluid expands…density decrease…density of warmer fluid it less than that of the surrounding cooler fluid
Convection currents transfer heat from warmer to cooler parts of the fluid
Conduction:
Radiation:
When radiation is absorbed thermal energy is increased…heat is
