Topic 3- Particle model of matter

Question 1

What are density units?

Answer 1

kg/m³

Question 2

Required practical steps (density of regular shaped objects)

Answer 2

1. Measure mass on a balance
2. Measure length of sides and multiply to find the volume
3. Use the equation to find density

Question 3

Required practical steps (density of irregular shaped objects)

Answer 3

1. Measure mass on a balance
2. Fill large measuring cylinder or a displacement/eureka can
3. Volume of displaced water= volume of object
4. Use equation to find density

Question 4

Required practical steps (density of liquids)

Answer 4

1. To find volume, put in measuring cylinder
2. Find mass on balance, take away mass of empty cylinder
3. Use equation to find density

Question 5

Describe the particle arrangement of a solid

Answer 5

Tightly packed in a regular arrangement.

Particles can only vibrate on the spot

Question 6

Describe the particle arrangement of a liquid

Answer 6

Close together, but with an irregular arrangement.

They can flow over each other

Question 7

Describe the particle arrangement of a gas

Answer 7

Separated, with no regular arrangement.

Particles can move freely

Question 8

What is always conserved when a substance undergoes a change of state?

Answer 8

Mass

Question 9

What are the particle model’s limitations?

Answer 9

Only 2D
We don’t see forces between the particles
We don’t see the movement of the particles

Question 10

How does a change of state differ from a chemical change?

Answer 10

In a change of state, the material can return to having its previous properties if the change is reserved

Question 11

What is sublimation?

Answer 11

When a solid changed into a gas without passing through a liquid state

Question 12

When water boils in an open pan, why does the mass of the pan of water appear to decrease?

Answer 12

Some of the water will evaporate and turn into water vapour

This will leave the pan meaning the mass of the pan will decrease.

The mass of the whole system however, remains constant

Question 13

Explain the processes involved when a bathroom mirror mists up

Answer 13

Hot water evaporates to form water vapour

This water vapour lands on the cooler mirror

The vapour condenses and returns to liquid state on the mirror’s surface

Question 14

What is internal energy?

Answer 14

Energy which is stored by particles (atoms and molecules) within a system

Kinetic energy + potential energy of particles

Question 15

How does heating affect the energy of a substance?

Answer 15

Heating transfers energy to the substance

It increases the energy of the particles that make up the substance

Question 16

What two things can heating a substance do?

Answer 16

Raise its temperature

Change the state of the substance

Question 17

What three factors determine the temperature change of a system?

Answer 17

Mass of substance being heated

Type of material (Specific heat capacity)

Energy inputted into the system

Question 18

Define specific heat capacity

Answer 18

The amount of energy needed to increase the temperature of 1kg of a substance by 1 degree celcius

Question 19

Define specific latent heat

Answer 19

The amount of energy needed to change the state of 1kg of a substance without a change in temperature

Question 20

Define specific latent heat of fusion

Answer 20

The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature

Question 21

Define specific latent heat of vaporisation

Answer 21

The energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature

Question 22

Describe the motion of molecules in a gas?

Answer 22

They are in constant random motion

Question 23

What factor affects the average kinetic energy of gas molecules?

Answer 23

The temperature of the substance

The higher the temperature, the higher the average kinetic energy of the molecules

Question 24

What effect does increasing temperature have on the pressure of a gas when held at constant volume?

Answer 24

Pressure of the gas will increase as the temperature increases

Question 25

Why does pressure increase as temperature increases (at a constant volume)?

Answer 25

Kinetic energy of molecules increases

Collisions between molecules become more frequent

Greater rate of change of momentum

Greater force and therefore pressure

Question 26

If Gas A is at a low pressure and gas B is at a high pressure, what can be said about the rate of collisions in each gas?

Answer 26

There are more collisions per second in gas B than in gas A

The rate of collisions is higher in B

Question 27

Describe the force that the pressure of a gas exerts on the walls of its container

Answer 27

The net force acts at right-angles to the container’s surface

The force increases as pressure increases

Question 28

Explain how increasing the volume of a gas results in a decrease of pressure

Answer 28

Molecules become more spread out and so time between collisions increases

This reduced the rate of collisions

Rate of change of momentum decreases, resulting in a lower pressure

Question 29

What unit is used for pressure?

Answer 29

Pascals (Pa)

Question 30

What increases when you do work on a gas?

Answer 30

The internal energy of the gas

This can also lead to an increase of temperature

Question 31

Why does the temperature of air inside a bike pump increase when it is pumped?

Answer 31

Work is done on a gas when it is compressed

Doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules

Temperature increases with an increase of average kinetic energy

Question 32

What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?

Answer 32

It is constant

p V = constant

Question 33

Explain how the internal energy of the water changes as it is heated

Answer 33

The kinetic energy of the particles increases

Which increases the internal energy of the water

Question 34

A student measure the mass of boiling water that was turned into steam in five minutes

Explain how the student could use this information to estimate the power output of the Bunsen burner in watts

Answer 34

Energy given to water E = mL with quantities defined

power output (of Bunsen burner) = energy transferred (to water)/time

power output = change in mass × specific latent heat time

Time should be converted to seconds or use a time of 300 seconds

Question 35

A student measured the temperature stearic acid over 5 minutes to investigate the change of state from liquid to solid

After having become a solid, the temperature still decreased

Why?

Answer 35

Stearic acid is still hotter than the surroundings

Temperature will decrease until acid becomes room temperatures

Question 36

Explain, in terms of the particles, why gases are easy to compress

Answer 36

Large gaps between particles

So it is easier to push them together

Question 37

Describe the movement of the particles of helium gas inside a balloon

Answer 37

Range of speeds

Moving in different directions

Random movement

Question 38

Explain, in terms of particles, how evaporation causes the cooling of water

Answer 38

The fastest particles have enough energy to escape from the surface of the water

Therefore the mean energy of the remaining particles decreases

The lower the mean energy of particles, the lower the temperature