P6 Molecules and Matter

Question 1

What happens when atoms absorb radiation

Answer 1

Electrons move to higher energy levels, further away from the nucleus

Question 2

What happens when atoms emit radiation

Answer 2

Electrons drop to a lower energy level, closer to the nucleus

Question 3

What is Thomson’s plum pudding model

Answer 3

Thomson modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the ‘dough’

Question 4

What is Rutherford’s nuclear model

Answer 4

Rutherford concluded that an atom’s mass is concentrated in the atom’s centre

This was called the “nucleus” and it contained positively charged particles called protons.

Question 5

What is the modern model

Answer 5

Niels Bohr discovered that electrons orbit (fly around) the nucleus at fixed distances

In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons

Question 6

What is density

Answer 6

The amount of mass in a volume

Question 7

What is the formula for density

Answer 7

ρ=m/V

Question 8

What is upthrust

Answer 8

An object floats in a fluid if the density of the object is lower than the density of the fluid

The force that keeps the object afloat is called upthrust

Question 9

What is the law of displacement

Answer 9

The Law of Displacement says that an object completely submerged in a fluid will replace an amount of fluid equal to its own volume.

Question 10

How are particles in a solid arranged

Answer 10

Solids are the densest state of matter

The particles are packed tightly together

Question 11

How are particles in a gas arranged

Answer 11

Gases are the least dense state of matter

The particles are free to move with negligible forces between particles

Question 12

How are particles in a liquid arranged

Answer 12

Liquids are less dense than solids but denser than gases

The particles in liquids can move around each other

Question 13

What is the conservation of mass

Answer 13

When a substance changes state, its mass is conserved

Question 14

What is a physical change

Answer 14

Changes of state are physical changes because the material recovers its old properties if the change is reversed

Question 15

What is condensation

Answer 15

When the temperature of a gas decreases to the boiling point, the strength of the forces between particles increases and the particles condense to become a liquid

For the same material, its boiling point is the same as its condensing point

Question 16

What is boiling

Answer 16

If we heat a liquid, the liquid particles move more energetically until they have enough energy to escape completely from the forces between them

The particles become a gas and move completely freely

The temperature needed for this to happen is the boiling point. Boiling can be called vaporisation

Question 17

What is solidifying

Answer 17

When the temperature of a liquid decreases to the melting point, the strength of the forces between particles increases and the liquid solidifies to become a solid

For the same material, its melting point is the same as its freezing point

Question 18

What is melting

Answer 18

If we heat a solid, the solid particles vibrate more energetically, until they have enough energy to overcome the forces between them

This is when the solid melts

The temperature needed for this to happen is the melting point.
Melting is sometimes also called fusion

Question 19

What is the internal energy store

Answer 19

The amount of energy in an object’s internal store is the sum of the kinetic and chemical stores of the object’s particles

Question 20

What is the potential energy store

Answer 20

The energy in an object’s potential store comes from the potential energy stored in the bonds between particles

Question 21

What is the kinetic energy store

Answer 21

The energy in an object’s kinetic store comes from the random motion of its particles

The temperature of a body is a measure of the energy in the kinetic stores of its particles

Increasing a body’s temperature increases the energy in the kinetic stores of the body’s particles, which means that the energy in the body’s internal store also increases

Question 22

How to calculate change in internal energy

Answer 22

mass * specific heat capacity * temperature change

Question 23

How to calculate thermal capacity

Answer 23

mass * specific heat capacity

Question 24

What is latent heat

Answer 24

The energy that is transferred to a substance without the substance’s temperature changing

Question 25

Where does latent heat go

Answer 25

Energy is absorbed to create or weaken bonds, rather than transfer kinetic energy to a substance’s particles

Question 26

What is specific latent heat

Answer 26

Latent heat / 1kg of mass

Question 27

What is latent heat of fusion

Answer 27

Latent heat in melting or freezing

Question 28

What is latent heat of vaporisation

Answer 28

Latent heat in boiling or condensing

Question 29

How to calculate energy change for change of state

Answer 29

Energy = mass * specific latent heat

Question 30

What happens when gas is heated

Answer 30

Energy is transferred to kinetic energy store

Particles move faster

Particle collide with the container more of ten and with more force, increasing pressure

Question 31

What is the equation for change in momentum

Answer 31

Δp = force × time = impulse

Question 32

What happen when work is done on gas

Answer 32

Gas’ internal energy increases