SP14 Particle Model

Question 1

Define density

Answer 1

The mass per unit of volume

Question 2

How do we calculate density?

Answer 2

mass/volume

Question 3

What are the units for density?

Answer 3

g/cm^3 or kg/m3

Question 4

What are the three states of matter?

Answer 4

Solids, liquids and gas

Question 5

Why do solids and liquids have similar densities?

Answer 5

The space between the particles don’t change significantly

Question 6

Describe the following for solids:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility

Answer 6

a) very strong
b) close together, regular pattern
c) vibrate around a fixed point in space
d) fixed for both
e) not compressible

Question 7

Describe the following for liquids:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility

Answer 7

a) moderately strong
b) close together, randomly arranged
c) move around each other
d) takes shape of the container, fixed
e) almost negligible

Question 8

Describe the following for gas:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility

Answer 8

a) negligible
b) far apart, random arrangement
c) move quickly, in a straight line, in random directions until they collide: causing them to change directions
d) takes shape of container, expands to fill container
e) highly compressible

Question 9

Why are gases compressible?

Answer 9

• large gaps between the particles
• makes it easier to push them as compared to solids and liquids

Question 10

What doesn’t change during a change of state?

Answer 10

• mass
• number of molecules in the substance

Question 11

What does change during a change of state?

Answer 11

• the state of matter of the substance
• the energy that the substance has

Question 12

What happens when you heat up a system?

Answer 12

• the amount of kinetic energy that the particles have increases
• particles vibrate more
• temperature of the system increases / substance changes state

Question 13

What are the two types of energy that molecules within a substance possess?

Answer 13

• kinetic energy
• potential energy

Question 14

Define internal energy

Answer 14

The total energy stored inside a system due to their motions and position

Question 15

What happens when a substance changes state?

Answer 15

• potential energy of molecules increases, breaking bonds between them and becoming further apart
• kinetic energy remains the same, which means that temperature remains the same, despite the substance continuing to be heated

Question 16

Define specific heat capacity

Answer 16

The amount of energy required to raise the temperature of 1kg of a substance by 1degree celsius

Question 17

What does the increase of temperature of a system depend on?

Answer 17

• mass
• type of material
• energy input into the system

Question 18

What is a low heat capacity?

Answer 18

A substance that takes less energy to change its state: it heats up and cools down fast

Question 19

What is a high heat capacity?

Answer 19

A substance that takes more energy to change its state: will heat up and cool down slowly

Question 20

Define specific latent energy

Answer 20

The amount of energy that it takes to make 1 kg of a substance to change its state without a change in temperature

Question 21

What are the two types of specific latent heat?

Answer 21

• fusion
• vapourisation

Question 22

What are the units of specific latent heat?

Answer 22

joules per kilogram J/kg

Question 23

Define specific latent heat of fusion

Answer 23

The thermal energy used to convert 1kg of solid into a liquid with no change in temperature

Question 24

Define specific latent heat for vaporisation

Answer 24

The thermal energy required to convert 1kg of liquid to gas with no change in temperature

Question 25

How do we calculate specific latent heat?

Answer 25

energy/mass = specific latent heat

Question 26

What is the difference between specific latent heat and specific heat capacity?

Answer 26

- specific heat capacity = change in temperature **in the same state** - specific latent heat = change in **state, not in temperature**

Question 27

Name an equation involving specific heat capacity

Answer 27

change in thermal energy = mass x specific heat capacity x change in temperature

Question 28

What is **insulation** used for?

Answer 28

To slow down the rate at which heat transfers from an object to its surroundings

Question 29

How do we reduce conduction and convection?

Answer 29

Use thermal insulators

Question 30

How do we reduce radiation?

Answer 30

Using shiny and reflective coatings to reflect IR radiation back into the system

Question 31

Define **pressure**

Answer 31

Force exerted per unit area

Question 32

What is the unit used to measure pressure?

Answer 32

Pascals (Pa)

Question 33

Pressure produces a force to...

Answer 33

right angles of a surface

Question 34

How is pressure of a gas caused?

Answer 34

Pressure is caused due to the force on the walls of a container caused by moving particles hitting a wall

Question 35

Describe the relationship of the temperature and the pressure of a gas

Answer 35

- higher the temperature of the gas = the more energy the molecules have - collisions happen more often - and happen with greater impact - which increases the pressure

Question 36

Define **absolute zero**

Answer 36

Particles at this temperature have no kinetic energy at all, so they remain perfectly still and don't vibrate at all

Question 37

What is the temperature of absolute zero?

Answer 37

-273 degrees celsius, or 0 kelvin

Question 38

How do we convert between celsius to kelvin?

Answer 38

add 273

Question 39

How do we convert from kelvin to degrees celsius?

Answer 39

subtract 273

Question 40

What happens to the volume when a gas is compressed?

Answer 40

It decreases

Question 41

What happens to the volume when the gas is expanded?

Answer 41

It increases

Question 42

What is the equation involving pressure and volume?

Answer 42

P1 X V1 = P2 X V2

Question 43

What is **work done**?

Answer 43

The transfer of energy through a force

Question 44

How is work done on a gas?

Answer 44

- through compression - force used to push a piston by a certain distance - which decreases the volume of gas - causing the molecules to move faster = more kinetic energy = increase in temperature

Question 45

How does a gas do work?

Answer 45

- when a gas expands - it loses energy - resulting in a decrease of temperature