Lyons Physical Science
1.
Chapter 6 Study Guide Heat
What are the boiling points & freezing points for the 3 temperature scales?
Scale
2.
Freezing Point
Boiling Point
Kelvin
273
373
Celsius
0
100
Fahrenheit
32
212
You can touch the aluminum pan of a TV. dinner after it has been taken out of the oven, but you will burn your hand if
you touch the food it contains. Explain in terms of the specific heat of aluminum and the water in the food. The water has
a high specific meaning it heats & cools slowly, the aluminum has a low specific heat meaning it heats and cools
quickly
3.
When you heat a substance and the temperature rises, how much it rises depends upon its specific heat.
4.
What are three ways thermal energy is transferred? Describe them. Conduction- requires contact/collision of molecules,
Convection occurs in fluids (gases & liquids) warmer less dense fluid rises – cooler more dense fluid sinks, Radiation
is the transfer of heat by electromagnetic waves.
5.
Calculate the specific heat of a metal if 0.5 kg of the metal absorbs 9 000J of heat as it warms by 10 °C.
Q= mc(final temp. – initial temp.)
6.
1800J/kg °C
Explain why materials that are good conductors of heat. Good conductors like metals have loosely held electrons in their
atoms, they bump into other electrons and easily transfer energy. Insulators like air and rubber conduct heat poorly.
7.
Would plastic foam, which contains pockets of air, be a good conductor or a good insulator? Insulator
8.
What is the second law of thermodynamics? Heat always flows from hot to cold
9.
A wooden block has a mass of 20.0 kg and a specific heat of 1 700 J/kg °C . Find the thermal energy of the block as it
warms from 15° C to 25° C. 340,000J
10.
The thermal energy of water in a mug increases by 12 552 J when the water is heated from 20° C to 40°C. If the specific
heat of water is 4 184 J/kg °C, what is the mass of the water? 0.15kg
11.
If 500 J of energy were added to 1 kg of each of these samples, which would experience the LEAST temperature
increase? aluminum
Substance
-1
Specific Heat (J kg K )
Aluminum
900
Copper
390
Brass
380
Silver
230
Platinum
130
the alcohol. 6258J
-1
12.
A scalpel made of surgical stainless steel is sterilized by heating in a
flame and then quenching in 175 g of ethyl alcohol. The alcohol is
initially room temperature, 23.7°C, warms to 38.6°C. The specific heat
capacity of ethyl alcohol is 2.4 J/(g*K). Calculate the heat released by
13.
Substance
Ammonia
Ethanol
Gasoline
Water
Specific Heat Capacity
J/Kgo C
4700
2440
2220
4186
A liquid has a mass of 18.39g. If 655J of heat are required to change the
temperature from 32.8oC to 18.2oC, what is the identity of the liquid? 2439.5
ethanol
14.
You are walking on a beach and find a mystery piece of metal. You take it back
to your lab and measure its mass to be 0.5 kg. In order to heat the metal 1 degree K, you must add 115 J of heat. Identify the
metal. q =mCΔT 230 silver
Substance
Specific Heat (J kg-1 K1
)
15.
Microwave ovens heat food through the process of radiation
Aluminum
900
16.
Brownies cook faster in a glass baking dish because heat is transferred by radiation &
Copper
Brass
390
380
Silver
230
Platinum
130
18.
conduction. In a metal baking pan heat is mainly transferred by conduction.
17.
True/False Fluids are liquids only.
A thermos has a vacuum between two inner glass walls to prevent heat transfer by conduction & convection. Therefore
the only type of heat transfer that can occur is the one that does not require a medium, which is radiation.
19.
Two units of energy are Joules & Calories.
20.
True/False air is a good conductor.
21.
Energy on Earth radiates back out into outer space.
22.
What does salt do to the freezing point of water? Salt lowers the freezing point of water because it interferes with the
lattice structure of solid water, the result is a liquid below the freezing point of water