1.Unit of heat is

2. convert cal to J

3.convert kcal to kJ

1.calorie(cal)

2. 1 kcal * 4.186 x 10³ J

3. 1 kcal= 4.186 kJ

Heat is energy transferred from one object to another because of a difference in temperature.

*Remember that the temperature of a gas is a measure of the kinetic energy of its molecules.

u=3/2nRT

(remember this is kinetic energy in terms of temperature and moles of gas)

Internal energy:

If the gas is molecular rather than atomic, what other energy needs to be taken into account as well? (2)

Specific Heat def

Specific Heat formula

and unit

Q=mcΔT

where

c=specific heat for the material

unit: J/kg• C

Calorimetry – Solving Problems

Closed system def

mass + energy

may transfer as well 

closed system, no energy in any form is transferred

   *heat lost = heat gained

or 

Energy OUT of one part = energy INTO another part

e.g. kettle to the mug

You accidently leave a frying pan on the hot stove and get its very hot, almost 200C,

1.What happens when you dunk the pan in a few inches of cool water in the sink?

2.Will the water boil?

3.Will the final temp be midway btwn the initial temps of the water & the pan?

1.The water will warm up a few degrees (10 to 12) but will NOT boil b/c the mass of water is mostly equal to the pan & iron has a SMALLER specific heat than water)

(*compare this to the sizzle u hear when you place a drop of water on a hot pan)

3. As heat leaves the pan and enters the water the pan will experience a greater temp change (ten times more than water).

T /F:

Energy is required for a material to change phase, even though its temperature is not changing.

The values for :

Heat of fusion (LF) & vaporization, (LV) are also called?

Latent Heat

(involves changes in phase & the release of energy)

Q=mL

Q= heat added or released (J)

total mass: kg

L: latent heat (J/kg)

write the phase equation for the following situation: 

water reduces from 20 C to 0C

in this situation energy is being LOST

Q=m_water c_w (20 C-0 C)

(Template)Q=mc (T_i-T_f)

write the phase equation for the following situation: 

water is heated from 0C to 5 C

in this situation energy is being GAINED

Q=m_water c_w (5C-0 C)

(Template)Q=mc (Tf-Ti)

 evaporation &boiling

(aka it takes a certain energy threshold for these processes to occur)

Sample B:

The heat of vaporization of water rises slightly as the temperature decreases.

T or F: A  phase change to occurs because heat increases the kinetic energy of the individual molecules

Heat conduction formula

& include unit

Q/t= kA T₁- T₂

             l

A:area of object

k:thermal conductivity constant

unit: J/s

T: can leave in C

The heat flow per unit time

1.Materials with large k are called  

2. small k are called 

1.conductors

2.insulators

1.R−values formula

2.r values increse directly with ______

1.R= l/k

2. material thickness

Convection occurs when heat flows by:

the mass movement of molecules from one place to another.

It may be natural or forced.

ex. boiling pot of water

hot water on bottom b/c stove is heating it, cold water on top, will  continue to cycle till all is hot

Many home heating systems are forced hot-air systems; these have a fan that blows the air out of registers, rather than relying completely on natural convection.

In heat conduction, energy is transferred from molecule to molecule by direct contact; the molecules themselves do not necessarily change position, but simply vibrate more or less quickly against each other.

Heat conduction can be visualized as occurring through molecular collisions. 

false;

the sun's energy transfer is in the form of heat and occurs over an EMPTY space

The most familiar example of radiation is our own Sun, which radiates energy in the form of heat to Earth  at a temperature of almost 6000 K

give radiation formula

& unit

ΔQ/Δt=

eσAT⁴

or if 2 temps:

eσAT₁⁴-T₂⁴

unity: Watts (J/s)

σ : Stefan-Boltzmann constant

e: emissivity

A: area

T: Temp (K)

1.black objects have an emissivity 

2.shiny objects

1. near 1

(they absorb nearly all the radiation)

2.near 0

(they reflect almost all the radiation)

If you are sitting in a place that is too cold, your body radiates more heat than it can produce.

*You will start shivering and your metabolic rate will increase unless you put on warmer clothing.

T or False:

A good absorber is a bad emitter.

False,

a good absorber is a good emitter.

 EX. light colors absorb little or no radiation they are exposed to and thus emit very little.

so ΔQ/Δt= 0

when T1=T2

T1 >T2

What will occur?

the net flow of heat is from the object (T1) to the surroudings (T2)

=

the object cools

T1 <T2

What will occur?

the net flow of heat is from the surroundings (t2) to the object(t1)

=

object's temp raises

ΔQ/Δt= (1000W/m²)eAcosθ

θ= angle btwn the sun's rays& a line perpendicular to the area A.

*cosθ effect is also responsible for the seasons.