Sci ~ Ch.40 Heat

Question 1

An example of heat energy changing into any other form of energy

Answer 1

Heat ➡️ kinetic energy

Heat➡️ light and sound

Question 2

What is heat measured in?

Answer 2

Joules (symbol:J)

Question 3

When solids,liquids and gases is heated,they _____.

Answer 3

Expand

Question 4

When solids,liquids and gases are cooled,they ______.

Answer 4

Contract

Question 5

Disadvantages of expansion and contraction:

Answer 5

• railway tracks need tapered joints
• slabs of concrete buckle in the heat if it has no room.
• bridges can get longer in summer than in winter

Question 6

Advantages of expansion and contraction:

Answer 6

• thermometers
• Bimetallic strips➡️ used to trigger alarms and switch off heating. Made from 2 metals joined together.One metal expands faster than the other causing the strips to bend and break/complete circuit.
• expansion can be used in the car engine and in rockets

Question 7

Why is it different with water?

Answer 7

Water contracts on cooling,only until it reaches 4 degreesC and if further cooled,water expands.

Question 8

Advantages of water expanding when freezed

Answer 8

• fish can survive in lakes in the cold since water is most dense at 4*C and this “warm” water sinks and “colder” water is less dense and floats on top.

Question 9

Disadvantage of water expanding when freezed

Answer 9

Water pipes can et burst if the water freezes.

Question 10

Heat moves from a _____ object to a ____ object.

Answer 10

Warm ↪️ colder

Question 11

3 ways that heat can be transferred is:

Answer 11

• conduction
• convection
• radiation

Question 12

What is conduction?

Answer 12

Conduction is the method by which heat travels from particle to particle through a solid. E.g metals

Question 13

What is an insulator?

Answer 13

An insulator is a substance which does not allow heat to flow through it easily. E.g. Wooden spoon
Gases (trapped air)

Question 14

An example of a poor conductor of heat:

Answer 14

Water

Question 15

Convection?

Answer 15

The transfer of heat through a liquid or gas when the particles of the liquid or gas move and carry the heat with them.

Question 16

What is used to show convection currents in air?

Answer 16

A smoke box

Question 17

Explain how a smoke box works.

Answer 17

1. A taper ➡️ lit ↪️ blown out
2. taper placed above the hole on the right
3. Air above candle on the left heated➡️ expands↪️ less dense and rises
4. colder air move in its place.

Question 18

What chemical is required to test for convection in water?

Answer 18

Potassium permanganate crystal (purple dye)

Question 19

Conclusion of testing for convection in water:

Answer 19

Water near crystal receive heat and expand first becoming less dense ↪️ floats to the top.their path is shown by the purple dye. Denser colder water replaces it➡️heated ↪️↪️ continues until all are heated. (Convection currents)

Question 20

Radiation?

Answer 20

Radiation is the rapid transfer of heat from a hot object without needing a medium.

Question 21

What is temperature?

Answer 21

A measure of the level of heat in an object

Question 22

Whats the freezing point of water

Answer 22

0*C

Question 23

Boiling point of water

Answer 23

100*C

Question 24

When the pressure on water increases:

Answer 24

The boiling point increases.

Question 25

When the pressure on water decreases:

Answer 25

The boiling point decreases

Question 26

Each substance has its own ____ and ___

Answer 26

Melting and boiling point

Question 27

Latent heat?

Answer 27

Latent heat is the heat taken in or given out when a substance is changing state without changing temperature.

Question 28

What is heat?

Answer 28

Hear is a form of energy that can do work and change into other forms of energy.