P1 - Matter

Question 1

What was Dalton’s model?

Answer 1

• A very small indestructible sphere
• he believed that different elements contained different types of atoms and all the atoms in 1 element were the same

Question 2

What was J. J Thomson’s model?

Answer 2

• He figured out that atoms weren’t solid spheres
• He discovered electrons
• His model is called the ‘plum pudding model’ with discrete electrons in spread out positive mass

Question 3

What was the experiment that J. J Thomson carried out that led him to his theory? (extra)

Answer 3

• He was investigating rays given out by hot metals called cathode rays
• He discovered that cathode rays are made of particles less than one thousandth of the mass of a hydrogen atom
• He found a particle which he called an electron that must have come from inside an atom
• He worked out that the charge on an electron is negative
• Thomson thought that part of an atom must be positive as overall, the charge on an atom is neutral

Question 4

What was the experiment Rutherford carried out that caused him to form his model?

Answer 4

• He fired positive alpha particles at an extremely thin sheet of gold foil
• He expected all of them to pass straight through, but instead, some of them were deflected to the left and right, and some even deflected backwards

Question 5

What did Rutherford’s experiment prove?

Answer 5

• It proved that the plum pudding model was wrong because the positive mass couldn’t be spread out and instead had to be concentrated in order for the atom to be deflected

Question 6

What was Rutherford’s model?

Answer 6

• He came up with the theory of the nuclear atom –> he suggested that atoms were made up of tiny, positively charged nuclei surrounded by a ‘cloud’ of negative electrons

Question 7

What was the problem with Rutherford’s model?

Answer 7

• If electrons were surrounding the nucleus in a ‘cloud’, they would be attracted to the nucleus and cause the atom to collapse

Question 8

What is Bohr’s model?

Answer 8

• He introduced electron shells and suggested that electrons can only move in a fixed orbit
  –> this would provide a reason as to why the electrons don’t rush in towards the nucleus and cause the atom to collapse

Question 9

How big is an atom’s diameter?

Answer 9

1 x 10 to the power of -10 m

Question 10

Why is a substance denser as a solid than as liquid or gas?

Answer 10

In 1cm cubed of a solid substance, there are many more particles than in 1cm cubed of that same substance as a liquid or gas
- The mass is greater so the density is also greater

Question 11

If you have 2 different sized blocks of the same element the density of the blocks are ___ because ___

Answer 11

the same because density is a property belonging to the material and not of the object

Question 12

What is the conservation of mass?

Answer 12

• You have to add or remove material for the mass of a system to change
• Particles don’t appear or disappear
• For example, if 1g of ice melts then 1g of water will be made

Question 13

What are physical changes and are they easy to reverse?

Answer 13

Physical changes are changes in which new substances are not made and the particles are just rearranged, like in a change of state
- They’re easily reversible

Question 14

What are chemical changes and are they easy to reverse?

Answer 14

Chemical changes involve atoms from the reactants breaking and joining in a different way to form new substances
- They are either hard to reverse or irreversible

Question 15

What is the definition of specific heat capacity?

Answer 15

The energy needed to raise the temperature of 1kg of a material by 1 degree

Question 16

Solid to gas is called ___ and gas to solid is called ___

Answer 16

subliming and deposition

Question 17

When a substance is changing state, the temperature ___

Answer 17

remains constant

Question 18

What does the energy provided do when a substance is changing state?

Answer 18

• Increases internal energy
• Energy used to break / join attractive forces between molecules

Question 19

What is the specific latent heat of fusion?

Answer 19

The energy transferred when 1kg of a substance changes from the solid state into the liquid state or from the liquid state into the solid state

Question 20

What is the specific latent heat of vaporisation?

Answer 20

The energy transferred when 1kg of a substance changes from liquid to gas

Question 21

How does temperature affect gas pressure?

Answer 21

• If the temperature of a gas increases, the gas particles have a higher average speed
• This means they collide more frequently with the sides of the container
• These collisions produce a bigger force over a certain area which produces a bigger pressure

Question 22

What is the relationship between volume and pressure?

Answer 22

Pressure and volume are inversely proportional
- Volume halves, pressure doubles
- Volume doubles, pressure halves

Question 23

Why are pressure and volume inversely proportional?

Answer 23

• The collisions of the gas particles produce forces at right angles to the surface
• If you halve the volume, you double the number of collisions per second between the gas particles and the container

Question 24

What is the equation realating pressure and volume?

Answer 24

Pressure (Pa) x volume (m cubed) = constant

Question 25

How does doing work on a gas affect temperature in terms of using a bicycle pump?

Answer 25

- If you apply a force to the pump, the average speed of the particles will increase because their kinetic energy increases when they collide with the moving piston --> so the temperature is higher

Question 26

What are the 2 ways in which you can increase the internal energy of a gas?

Answer 26

- Heating it - Doing work on it

Question 27

What is atmospheric pressure?

Answer 27

- The gases of the atmosphere exert a pressure called atmospheric pressure

Question 28

On the surface of the Earth, atmospheric pressure is around ___ Pa which means that there's a force of around ___ N on each square metre of the Earth's surface (which is the weight of 10 cars)

Answer 28

100,000 Pa 100,000 N

Question 29

Why does a can collapse if you take the air out of it and why does it keep its shape when it contains air?

Answer 29

- When you have an open can, the forces on the can are equal in all directions so the shape doesn't change - If you pump the air out, the can collapses because the atmospheric pressure is bigger than the pressure inside the can

Question 30

What happens to atmospheric pressure as you go up?

Answer 30

- As you go up, atmospheric pressure decreases because there is less air above pushing down

Question 31

What is liquid pressure and what do water molecules collide with?

Answer 31

- Water in an ocean exerts a liquid pressure - Water molecules are very close together and so collide with each other, the container and anything in the water

Question 32

In which direction does liquid pressure act in?

Answer 32

All directions

Question 33

What happens to liquid pressure as you go deeper?

Answer 33

- The deeper you are, the higher the liquid pressure is as there is more water pushing down on you

Question 34

What happens to pressure in liquids of different densities?

Answer 34

- The pressure at a particular depth will always be greater in the denser liquid - This is because the denser the liquid is, the greater the weight of particles pushing down is

Question 35

Why is there an upwards force / upthrust on a floating object?

Answer 35

- Anything that's floating must have an upwards force on it to balance its weight - When you are floating on the surface of a swimming pool, you are in contact with the water and the air --> the water exerts a bigger upwards force on you than the downwards force exerted by the air (net force is upwards)

Question 36

Why do some objects float and others sink?

Answer 36

If the pressure difference x area is big enough, the net force will be enough to balance the weight