Heat Unit Study Guide
1.
2.
What is the difference between heat and temperature?
Temperature is a measure of the speed of the molecules
and heat is a measure of all the energy in a substance.
Temperature is measured in degrees and heat is
measured in calories or Joules.
What happens to the atoms and molecules of a substance when they
increase in temperature?
When a substance increases in temperature the molecules
and atoms are speeding up. Two substances at the same
temperature have molecules moving at the same speed​.
3.
4.
What is specific heat?
Specific heat is a measure of how quickly a substance can
absorb or lose heat. It measures how fast or slow a
substance will heat up or cool down.
When an object has a low specific heat it:
a. heats up quickly and cools down slowly
b. heats up quickly and cools down quickly
c. heats up slowly and cools down slowly
d. heats up slowly and cools down quickly
“low” specific heat means a small number. Substances
with small specific heats heat up fast and cool down fast
= B.
5.
Think of some real-world examples which demonstrate that water
has a high specific heat and most metals have a low specific heat.
An example: that water in the Boundary waters does not
heat up until late June or July or that lake Superior never
does heat up even in the summer because there is so
much water and it takes a lot of heat to raise its temp.
Putting a pot of boiling water on the stove - turning on stove
- come back after only 2-3 minutes. The water is not
boiling yet & you could touch it without getting burned, but
6.
the pot is very hot already - you would not want to touch
it!
How are conduction, convection and radiation similar?
These are all ways that heat moves around our universe.
7.
How are conduction, convection and radiation different?
Conduction is the movement of heat through a solid.
Convection is the movement of heat through a fluid - like air
or water.
Radiation is the movement of heat through light, such as
flames, a light bulb, or our sun.
8.
Why are materials that are good conductors of heat also poor
insulators?
Good conductors (like metals) have molecules that are
close together and heat can move through them easily.
Good insulators (like air) have molecules that are far
apart and heat has a tough time moving from molecule to
molecule.
That puffy jacket you own does not heat your body at all.
The “puffy” parts are simply is filled with air and that
prevents you from losing your heat. The puffy jacket is a
good insulator.
9. What is the formula for heat? ​Q=mcΔT
(Q) Heat​(calories)​ = mass X specific heat X change in temp = ​mc​ΔT
Use the table below (FILL IT IN) to answer questions 10 & 11!
10. 100 ml of water at 50​°​C is mixed with 500 ml of water at 20​°​C. The
final temperature of the mixture is 25​°​C.
Cold water
mass
500 g
#10
#11
X
Hot
water
mass
Cold
water
Temp.
Hot
water
temp.
Final
water
temp.
Temp
change
of cold
water
Temp
change
of hot
water
Heat gained
by cold water
100 g
20°C
50°C
25°C
5°C
25°C
2500 cal
75,000 g
15°C
70°C
40°C
25°C
30°C
2,250,000
cal
see formula
Heat lost by
hot water ​see
formula
2500 cal
2,250,000 cal
How much heat did the cold water gain?
2500 calories
How much heat did the hot water lose?
2500 calories
11.
A bathtub contains 75 kg of water at 70​°​C – which is too hot. How
much water at 15​°​C must be added to end up with a bearable bath at
40​°​C? ​
75 kilograms = 75,000 grams
Solve for the heat lost by the hot water. Once you have
this answer, you can work backwards to solve for the
mass of the cold water.
The answer is 90,000 grams (90 kg) of cold water. Make
sure you can get the answer on your own!
These are heat problems. Please use the heat formula.
12. How many calories of heat are required to heat 12g of iodine from 16​°​C
to 30​°​C? Specific Heat of Iodine = 0.052 cal/g​o​C
13. What is the specific heat of silver if 112 calories are required to raise
the temperature of 80 g of silver from 25​°​C to 50​°​C?
14. How many calories of heat are needed to completely change 5 g of
water at 0​°​C to 100​°​C? Specific Heat of Water = 1 cal/g​o​C
15. What is the mass of silver that can be heated 500 degrees when
2000 calories are added to it? Specific Heat of Silver = 0.057 cal/g​o​C