P6 - Molecules And Matter✔️

Question 1

What is the density?

Answer 1

The density of a substance is defined as its mass per unit volume - caculated by mass/volume

Question 2

Equation for density?

Answer 2

ϱ = m/v
density = mass/volume

ϱ=density in kg/m^3
m=mass
v=volume

Question 3

Does the mass of a substance change when it changes state?

Answer 3

When a substance changes state the number of particles in the substance stays unchanged so the mass of the substance after the change of state is the same as the mass before the change of state.

Mass of substance is conserved when it changes state

Question 4

Particles of a substance in solid state?

Answer 4

Particles held next to each other in fixed positions - vibrate about their fixed position - solid keeps its own shape

Question 5

Particles of a substance in liquid state?

Answer 5

Particles are in contact with each other - move about at random so a liquid doesnt have its own shape.

Question 6

Particles of a substance in Gas state?

Answer 6

Particles move about at random - much faster then they do in a liquid-further apart so density of gas lot less then that of solid or liquid

Question 7

Do particles of solid,gas and liquid all have same amount of energy?

Answer 7

No - they have different amounts of energy - for a given amount of substances its particles have more energy in the gas state then they have in the liquid state - more energy in liquid state then solid state

Question 8

What happens to temperature of pure substance as it changes state?

Answer 8

Any pure substance undergoing a change of state its temperture remains the same while the change takes place

Question 9

What is melting point?

Answer 9

Point at which a solid changes state to a liquid

Question 10

What is boiling point?

Answer 10

Temperature at which a liquid turns to gas

Question 11

What is freezing point?

Answer 11

Point at which a liquid changes to a solid - same temperature as melting point of solid

Question 12

What effects melting point of substance?

Answer 12

The melting point of a liquid or solid are affected by impurities in the substance - melting pint of water is lowered if you add salt to the water

Question 13

Why is salt added to the grit used for gritting roads in frezzing weather?

Answer 13

The salt lowers the freeing temperature of the moisture in the ice - causing it to melt away

Question 14

What is latent heat?

Answer 14

Latent heat - energy transferred to the substance when it changes state

Question 15

Whats the difference between boiling and evaporation?

Answer 15

Boiling occurs throughout a liquid at its boiling point - evaporation occurs from the surface of a liquid when its temperature is below it boiling point

Question 16

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

Answer 16

Flat section gibes the melting point or the boiling point of a substance

Question 17

What is internal energy?

Answer 17

Internal energy - energy stored by the particles of a substance

Question 18

What causes internal energy?

Answer 18

Energy of particles is caused by their indivisual motion and positions - internal energy is sum of kinetic energy and potential energy

Question 19

What is kinetic energy

Answer 19

Energy it has due to the motion of the internal particles

Question 20

What is potential energy?

Answer 20

Energy particles have due to their position

Question 21

Characteristics of a solid?

Answer 21

-strong forces of attraction between particles - bond particles in fixed positions
-each particles vibrates about a fixed position
-solid is heated - particles energy store increase - particles vibrate more

Question 22

Characteristics of a liquid?

Answer 22

-forces of attraction not strong enough to hold particles in fixed position - stong enough to stop them moving away completley
-when heated - partiles break away - particles that escape are in a gas state

Question 23

Characteristics of a gas?

Answer 23

-particle move at high speed in random directions - colliding with eachother and internal surface - which causes the pressure of gas in container
-heated - particles gain kinetic energy move faster causes pressure to increase

Question 24

How does temperature affect pressure in gas?

Answer 24

Increase in temperature causes particles to gain kinetic energy and as a result move at higher speeds colliding with each other and the internal surface of ther container more often therefore inreasing pressure

Question 25

What is specific latent heat of fusion?

Answer 25

The energy needed to change state of 1kg of the substance from solid to liquid at its melting point
Unit: (J/kg)

Question 26

Equation for specific latent heat of fusion (Lf)?

Answer 26

Specific latent heat of fusion Lf = energy / mass

Specific latent heat of fusion: joules per kilogram - J/kg
Energy:Joules - J
Mass:killograms - kg

Question 27

What is specific latent heat of vaporisation?

Answer 27

Is the energy needed to change the state of 1kg of a substance from liquid to vapour at its boiling point - without changing temp

Question 28

Equation for specific latent heat of vaporisation Lv?

Answer 28

Specific latent heat of vaporisation Lv = energy/mass

Specific latent heat of vaporisation: joules per kilogram - J/kg
Energy:Joules - J
Mass:killograms - kg

Question 29

What is boyles law?

Answer 29

Pressure(p) x volume(V) = constant

Pressure = Pa
Volumes = m^3

P = constant / v

Question 30

Why does pressure increase if volume is reduced?

Answer 30

The space between each mollecules is smaller so they dont travel as far between each impact with the surface of the container

Question 31

Word Equation for specific latent heat of vaporisation?

Answer 31

specific latent heat of vaporisation = energy / mass

Question 32

Word Equation for specific latent heat of fusion?

Answer 32

specific latent heat of fusion = energy/mass