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Question 1

Prior to the discovery of the electron, what was

believed about the atom?

Answer 1

The atom was believed to be indivisible.

Question 2

Approximately what proportion of the
total radius of an atom is the radius of
the nucleus?

Answer 2

1/10,000

This equals 0.01%. The nucleus is very small compared to the whole atom.

Question 3

Give an approximation for the radius of an atom.

Answer 3

1x10⁻¹⁰ metres

Question 4

What is the definition of density? State

the relevant equation with units

Answer 4

● The mass per unit volume of a material
● ⍴=m/v
● Density (kg/m³), Mass (kg), Volume (m³)

Question 5

Give the different states of matter in order (least to most) of density of atoms

Answer 5

● Least dense: Gas
● Liquid
● Most dense: Solid

Question 6

What is always conserved when a substance

undergoes a change of state?

Answer 6

Mass

Question 7

What are the 5 main ways that a substance can change state?

Answer 7

1. Melt
2. Freeze
3. Evaporate
4. Condense
5. Sublimate

Question 8

What is sublimation?

Answer 8

When a substance transitions from a solid straight to a gas without transitioning into a liquid in between.

Question 9

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

Answer 9

Change of state - reversible

Chemical state - irreversible

Question 10

What two things can heating a substance do?

Answer 10

1. Raise its temperature

2. Change the state of the substance

Question 11

Define specific heat capacity

Answer 11

The amount of energy needed to increase the temperature of 1kg of a substance by 1°C.

Question 12

What can be said about a material if it has a higher

specific heat capacity?

Answer 12

For a constant mass, the material will need more energy to achieve a given temperature change

Question 13

Define specific latent heat.

Answer 13

The amount of energy needed to change the state of 1kg of a substance with no change in temperature.

Question 14

State the equation for the energy required to change state. Give appropriate units.

Answer 14

E = mL:

● Energy to change state = mass x specific latent heat
● Energy (J), Mass (kg), Specific latent heat (J/kg)

Question 15

What is the internal energy of a substance?

Answer 15

● The energy stored by the particles

● The sum of the total kinetic and potential energies that make up the system

Question 16

What is the unit used for pressure?

Answer 16

Pascal (Pa).

Question 17

How can the pressure of a gas be increased whilst kept at constant temperature?

Answer 17

The volume can be decreased (when the gas is compressed).

Question 18

How can the pressure of a gas be decreased whilst kept at constant temperature?

Answer 18

The gas can be expanded (the volume is increased)

Question 19

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

Answer 19

Pressure increases as temp increases

Question 20

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

Answer 20

● Kinetic energy of molecules increases
● Collisions between molecules becomes more frequent
● Greater rate of change of momentum
● Greater force and therefore pressure

Question 21

Describe the force that the pressure of a gas exerts

on the walls of its container.

Answer 21

● The net force acts at right-angles to the container’s surface
● The magnitude of the force increases as pressure increases

Question 22

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

Answer 22

● Molecules become more spread out so collisions become less frequent (more time between them)
● This reduces the rate of collisions
● Rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure

Question 23

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

Answer 23

It is constant.

p V = constant

Question 24

What increases when you do work on a gas?

Answer 24

● The internal energy of the gas

● This can also lead to an increase of temperature

Question 25

Why does atmospheric pressure decrease as you move higher above the Earth’s surface?

Answer 25

● As you move higher, the quantity of air above you decreases, meaning the force (weight) acting on you decreases.
● This results in a lower pressure.

Question 26

What does an object in a fluid experience as a result of pressure?

Answer 26

Forces at right angles to all of its

surfaces.

Question 27

Why does pressure in a fluid increase with depth?

Answer 27

the deeper you go, the greater the weight of the water above you, and so a higher force and pressure

Question 28

What equation is used to calculate the pressure at a

given depth of liquid?

Answer 28

pressure = depth x liquid density x gravitational field strength
p = hρg

Question 29

What is upthrust?

Answer 29

The upwards force that an object experiences in a fluid as a result of a greater pressure below the object than above it.

Question 30

Under what circumstances will an object float?

Answer 30

When upthrust = weight

Question 31

Under what circumstances will an object sink?

Answer 31

When upthrust is less than weight

Question 32

When you submerge an object in a liquid, what is the

upthrust acting on the object equal to?

Answer 32

The weight of the volume of liquid displaced as it is submerged.

Question 33

What can be said about the density of an

object that sinks in water?

Answer 33

The object’s density is greater than the density of water.