P6 - Molecules and Matter - Complete

Question 1

What is the Density equation?

Answer 1

Density = mass/volume (in kg/m3)

Question 2

What precaution would one have to take when measuring the density of a liquid? (When weighing it)

Answer 2

To subtract the weight of the measuring cylinder from the end mass

Question 3

What is the density of pure water?

Answer 3

1000kg/m3

Question 4

If an object’s density is higher than that of water, what will it do?

Answer 4

Sink

Question 5

If an object’s density is lower than that of water, what will it do?

Answer 5

Float

Question 6

What is liquid to gas called?

Answer 6

Evaporation

Question 7

What is gas to liquid called?

Answer 7

Condensation

Question 8

What is solid to liquid called?

Answer 8

Melting

Question 9

What is liquid to solid called?

Answer 9

Freezing

Question 10

Explain, using the Kinetic Theory of Matter, the particles in a solid.

Answer 10

They are held in fixed positions next to each other and are the least energetic of the states of matter

Question 11

What does the conservation of mass mean?

Answer 11

In a closed system, the mass of a substance before and after changing state is the same

Question 12

Explain, using the Kinetic Theory of Matter, the particles in a liquid.

Answer 12

They move about at random and are in contact with each other, they are more energetic than the particles in a solid

Question 13

Explain, using the Kinetic Theory of Matter, the particles in a gas.

Answer 13

They move about at random, they are extremely far apart, and it is the most energetic of the states

Question 14

Where does evaporation occur?

Answer 14

Only on the surface of the solution being heated

Question 15

What does the flat section on a temperature-time graph show?

Answer 15

The ealing point or the boiling point of the substance

Question 16

What is latent heat?

Answer 16

The energy transferred to a substance when it changes state. This is not expressed in its temperature as it is going towards making the change

Question 17

What is the internal energy of a substance?

Answer 17

The total energy in its kinetic and potential energy stores. It does not include the gravitational potential energy its has or the kinetic energy of the whole substance moving one way or another

Question 18

The —– of the —— of —— between particles of a substance explains why it is a solid, liquid or gas

Answer 18

The strength of the forces of attraction between particles of a substance explains why it is a solid liquid or gas

Question 19

When a liquid is heated, what happens to the particles at the surface?

Answer 19

Once they have gained enough energy, they move away almost completely from the surface and are a gas above it. The forces of attraction are so weak that they can barely hold it above the liquid

Question 20

In terms of energy, what happens to a substance when it is heated?

Answer 20

Its kinetic energy increases as it heats up, and if it melts or boils the potential energy of its particles increases

Question 21

What is pressure from a gas caused by?

Answer 21

Particles of a gas hitting a surface

Question 22

What is the equation for the specific latent heat of fusion/vaporisation?

Answer 22

Energy, E, (J)/Mass, m (kg) = specific latent heat of fusion/ vaporisation

Question 23

What is the specific latent heat of vaporisation?

Answer 23

The energy needed to change the state of 1kg of the substance from liquid to vapour, at its boiling point, (without changing its temperature)

Question 24

What is the specific latent heat of fusion?

Answer 24

The energy needed to change the state of 1kg of a substance from a solid to a liquid at its melting point (without changing its temperature)

Question 25

What does the flat part in a temperature/time graph represent?

Answer 25

The substance changing state. The temperature does not increase as the substance needs the energy to change state and break its intermolecular attractions

Question 26

What correlation is their between heating air molecules and pressure?

Answer 26

As the air molecules are heated, they exert more pressure on the objects around them

Question 27

Why does heating increase pressure?

Answer 27

Heating increases pressure because the air particles receive more kinetic energy, causing them to bounce off the objects around them more frequently, and the force with which the bounce off the objects is increased as their velocity is increased

Question 28

What is evidence for the random motion of gas particles?

Answer 28

The unpredictable motion of smoke in a closed environment as the gas particles bounce off the larger smoke particles and so it is constantly moving direction

Question 29

How can you compress or expand a gas?

Answer 29

By instituting pressure changes

Question 30

What would compressing a gas do to its temperature if not done slowly?

Answer 30

Increase it, as the work done needed to overcome the pressure of the gas to compress it would be transferred to the gas - therefore heating it up

Question 31

Why does the pressure increase if you reduce the volume of a fixed mass of gas and increase its temperature?

Answer 31

As: the space the molecules move in is smaller, so they don't travel as far in between collisions with each other and the surroundings, and so impacts per square meter increases, and the the impact pressure increases

Question 32

What equation links pressure and volume?

Answer 32

Pressure, p (Pa) x Volume, V (m3) = Constant, this applies only to when the gas's temperature and mass odes not change