Chapter 5

Question 1

Kinetic theory

Answer 1

Matter is made up of tiny particles which are constantly in motion. The particles attract each other strongly when close together, but this attraction weaken when they are further apart.

Question 2

Particles in a solid (according to kinetic theory)

Answer 2

Fixed shape and volume, vibrate around fixed positions, very close together, very strong attraction

Question 3

Particles in a liquid (according to kinetic theory)

Answer 3

Has a fixed volume no fixed shape, particles are close and attract eachother, can change positions

Question 4

Particles in a gas (according to kinetic theory)

Answer 4

Has no fixed shape or volume, particles are far apart and do not attract eachother

Question 5

Brownian Motion

Answer 5

Random movement of particles due to collisions with other particles

Question 6

Random movement of particles due to collisions with other particles

Answer 6

Brownian Motion

Question 7

Internal energy

Answer 7

The total kinetic and potential energies of all the atoms or molecules of a material, sometimes the term is used interchangeably with thermal energy

Question 8

Liquid-in-glass thermometers

Answer 8

The liquid expands and moves up a tube when temperature rises

Question 9

Thermistor thermometer (thermistor)

Answer 9

Becomes a better electrical conductor when its temperature rises, causing a (higher) current to flow (which can cause a higher reading on a meter)

Question 10

Thermocouple thermometer

Answer 10

two different metals are joined to form two junctions, a greater difference in temperature between the two junctions causes a voltage which makes a current flow

Question 11

What is temperature?

Answer 11

the temperature of a material is the average kinetic energy of all the particles in the material. Individual molecules cannot have temperature.

Question 12

properties of liquid-in-glass thermometers

Answer 12

• sensitivity, how far the thread moves for a constant temperature change
• range, how high and low the thermometer can show
• responsiveness, how fast it responds to a change in temperature
• linearity, how well the calibration agrees with the true value

Question 13

How to make a thermometer more sensitive

Answer 13

Thinner tube

Question 14

How to make a thermometer more responsive

Answer 14

Thinner glass, smaller bulb

Question 15

Range of alcohol thermometers

Answer 15

-115 to 80 degrees

Question 16

Range of mercury thermometers

Answer 16

-40 to 500 degrees

Question 17

What is thermal expansion

Answer 17

The expansion of a material when it is heated due to particles having more energy and therefore vibrating more violently, which takes up more space

Question 18

What is a bimetal strip

Answer 18

Strips of two different metals merged together. When heated, one type of metal expands more than the other, making the strip bend.

Question 19

In terms of momentum, why does the pressure of a gas increase with temperature?

Answer 19

• Molecules move faster due to more energy
• So there is an increase in velocity
• So that means there is a greater change in momentum
• Which means there is a larger force
• Which means there is a larger pressure

Question 20

Conduction

Answer 20

Energy from faster-moving particles is passed on by passing on extra motion to slower particles, and by free electrons (in metals)

Question 21

How to increase conduction

Answer 21

• increase temperature difference
• increase cross-sectional area of the object
• reduce the length of the object
• change the material of the object

Question 22

How to increase amount of thermal radiation given out

Answer 22

• higher surface temperature

- higher surface area

Question 23

Emitters

Answer 23

Surfaces that are best at emitting thermal radiation
Good emitters are also good absorbers
-matt black surfaces are best
-shiny surfaces are worst

Question 24

Absorbers

Answer 24

Surfaces that are best at absorbing thermal radiation
Good absorbers are also good emitters
-matt black surfaces are best
-shiny surfaces are worst

Question 25

Reflectors

Answer 25

Surfaces that are best at reflecting thermal radiation
Good reflectors are poor emitters and absorbers
-shiny surfaces are best
-matt black surfaces are worst

Question 26

Features of a vacuum flask

Answer 26

• a stopper to reduce conduction and convection
• A double-walled container with a vacuum between the two, air has been removed to reduce conduction and convection
• Walls with silvery surfaces to reduce thermal radiation

Question 27

How to increase evaporation

Answer 27

• Increase the temperature
• Increase the surface area
• Blow air across the surface

Question 28

thermal capacity =

Answer 28

thermal capacity = mass x specific heat capacity

thermal capacity = energy/temperature change

Question 29

energy transferred in fusion/vaporization =

Answer 29

energy transferred in fusion/vaporization = mass x specific latent heat

Question 30

Meaning of specific latent heat

Answer 30

Specific latent heat, measured in J/kg, is the amount of energy needed to change each kilogram of a substance into a different form

Question 31

Meaning of thermal (heat) capacity

Answer 31

Thermal capacity, measured in J/°C, is the amount of energy that must be supplied to raise the temperature of a material by 1°C

Question 32

Meaning of specific heat capacity

Answer 32

Specific heat capacity, measured in J/kg°C, is the amount of energy needed to raise the temperature of 1kg of a substance by 1°C

Question 33

Why do gases expand more than liquids, and liquids expand more than solids when heated?

Answer 33

In a solid, the attractions are very strong so they do not move very far apart. In a liquid they are less strong and in a gas they are almost non-existent so particles can move very far away from eachother.

Question 34

Explain latent heat

Answer 34

While changing state, the material continues to absorb energy, but it does not change temperature as this energy is being used to separate particles rather than increase the temperature. This energy absorbed is known as latent heat.