Thermal properties and temperature

Question 1

What happens when a material receives heat energy, in terms of expansion?

Answer 1

molecules move faster, molecules separate further. the material will expand

Question 2

What happens when a material loses heat energy, in terms of expansion?

Answer 2

molecules move slower, molecules come close together. the material will contract

Question 3

Which state of matter expands most, for the same amount of heat energy?
Why?

Answer 3

gases, no forces of attraction between molecules, molecules have enough energy to overcome the weak intermolecular forces

Question 4

Which state of matter expands the least, for the same amount of heat energy?
Why?

Answer 4

solid, because the molecules cannot overcome the strong intermolecular forces holding the molecules together

Question 5

If a gas and a solid are subject to the same amount of heat energy, which will expand more?

Answer 5

gas

Question 6

What are 3 applications of thermal expansion in everyday life?

Answer 6

gaps in railway tracks
fitting metal tyres onto railway train wheels
bimetallic strips
thermometers

Question 7

Why are there gaps in railway tracks?

Answer 7

because it leaves space for solids to expand into when temperature increases

Question 8

How is thermal expansion used to fit metal tyres onto railway train wheels?

Answer 8

since the wheel is bigger than the tyre, the tyre is heated so it expands. this will make it possible for it to fit over the wheel. then it is cooled to contract.

Question 9

How does a bimetallic strip work?

Answer 9

two different materials on either side of a strip. when it is heated, the material which expands more will expand and cause the strip to bend (vice verse for cooling)

Question 10

What is the relative order of magnitudes of the expansion of solids, liquids and gases?

Answer 10

(least expansion) solid - liquid - gas (most expansion)

Question 11

What causes an increase in internal energy?

Answer 11

rise in temperature of an object

Question 12

In terms of molecules, what does an increase in temperature mean?

Answer 12

increased average kinetic energy of molecules of a substance

Question 13

Define the term ‘specific heat capacity’.

Answer 13

the heat energy needed for a body of mass given to increase its temperature (by 1 degree)

Question 14

What is the equation for specific heat capacity?

Answer 14

c= ∆E / m∆θ

Question 15

Describe an experiment to find out the s.h.c of water.

Answer 15

1. connect a power pack to an ammeter, voltmeter and an electric heater
2. measure starting temperature and mass of water (which should be in calormeter cup, with insulating air and another metal cup)
3. turn heater on and measure the current and voltage
4. turn heater off after 5 min, wait and measure maximum temperature
5. find the find energy using the H = VIt formula
6. plug results in s.h.c formula

Question 16

How do thermometers use thermal expansion?

Answer 16

mercury expands as the temperature increases

Question 17

What happens to the temperature of a substance as it goes from a solid to a liquid?

Answer 17

it will increase until the melting point is reached. the temperature stays constant until the substance is a liquid.

Question 18

What happens to the temperature of a substance as it goes from a liquid to a gas?

Answer 18

it will increase until the boiling point is reached. temperature stays constant until the substance is a gas.

Question 19

Name 3 differences between boiling and evaporation.

Answer 19

boiling only occurs at boiling point
evaporation is much slower
evaporation is only at the surface, unlike boiling which is throughout surface
boiling forms bubbles
boiling requires an external thermal energy source

Question 20

What is condensation, in terms of particles?

Answer 20

when a gas cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a liquid

Question 21

What is solidification, in terms of particles?

Answer 21

when a liquid cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a solid

Question 22

Define ‘evaporation’.

Answer 22

the escape of more energetic particles from the surface of a liquid

Question 23

Evaporation has a ______ effect.

Answer 23

cooling

Question 24

How does evaporation cool down a liquid?

Answer 24

molecules with a higher KE escape, leaving behind molecules with less KE. this causes the liquid to cool down.

Question 25

What is one example of evaporation’s cooling effect in real life?

Answer 25

sweating

Question 26

How does sweating work?

Answer 26

water evaporates from our skin, the temperature of the water falls, and removes heat energy from our body

Question 27

What are factors that influence the rate of evaporation?

Answer 27

temperature
wind
surface area

Question 28

How does temperature influence the rate of evaporation?

Answer 28

molecules move faster, can escape surface of liquid
increased temperature, increased rate of evaporation

Question 29

How does wind influence the rate of evaporation?

Answer 29

decreases number of molecules above the liquid surface, leaving space for them
increased wind, increased rate of evaporation

Question 30

How does surface area influence the rate of evaporation?

Answer 30

more molecules are positioned at the surface and can escape
increased surface area, increased rate of evaporation