Purple Daisy

The future belongs to those who believe in the beauty of their dreams. Eleanor Roosevelt

Energy Notes from December January 12, 2008

Filed under: Classroom Materials — purpledaisy97 @ 5:41 pm

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


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


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=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


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



When radiation is absorbed thermal energy is increased…heat is


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