P6-Molecules and matter

Question 1

what is the density equation

Answer 1

Density =the mass per volume

Question 2

what is density

Answer 2

Density in lay man terms = how crowded/packed the particles are

Compare a tennis ball and a cricket ball. What is similar about them and what is different about them?
They both have the same volume, but one has more mass than the other. The cricket ball is a lot more dense because it has a lot more mass even though it has the same volume.

Question 3

how to find volume of regular shaped object

Answer 3

Regularly shaped - measure the relevant parameters using a mm ruler or a vernier calliper, and calculate the volume with the right equation

Question 4

how to find volume of irregular shaped object

Answer 4

Irregularly shaped: tie the object with a piece of thread, and lower it into a measuring cylinder filled with wate. The volume of the object determines the rise of the water level. Find the volume of water by finding the rise in the water level.

Question 5

what is density represented as

Answer 5

density is repped as ‘p’

Question 6

describe organisation of solids

Answer 6

Solid- Regularly arranged and particles always touching. Solids vibrate about a fixed point

Question 7

describe organisation of liquids

Answer 7

Liquid- Irregularly arranged with particles always touching.. Particles flow randomly, with the particles always in contact.

Question 8

describe organisation of gas

Answer 8

Gas- Irregularly arranged with particles never touching. Move freely and randomly, bouncing off each other and other surfaces

Question 9

what are fluids

Answer 9

Fluids= things that flow ⟶ liquids and gases

Question 10

why cant solids and liquids be compressed

Answer 10

Solids and liquids can’t be compressed (this is because their particles are always in contact, so there is no space to move the particles closer.

Question 11

what is sublimation

Answer 11

Sublimation = when a gas becomes solid or a solid becomes gas

Question 12

what are MP and BP affected by?

Answer 12

MP and BP of liquids are affected by any impurities in the substances

Question 13

what happens to temprature when change of state is happening

Answer 13

However, when the substance is changing state, the temperature of the system remains constant as the energy is being transferred to the particles allowing them to vibrate faster, with more energy, separating apart, causing the density of the substance to change, leading to the overall state change

Question 14

what is latent heat

Answer 14

Latent heat = the energy transferred to a substance when it changes its state

Question 15

why does water bubble when we boil it

Answer 15

When a liquid reaches its BP, the particles that change into gas appear as bubbles, rise to the surface, and get released

Question 16

what is internal energy

Answer 16

Internal energy = the energy stored by the particles of a substance

It’s the sum of:
1. the kinetic energy that the particles have due to their individual motions relative to each other
2. the potential energy that they have due to their individual positions relatvie to each other

Question 17

what keeps particles in fixed positions?

Answer 17

1. There are strong forces of attraction between the particles ⟶ these keep the particles in their fixed positions

Question 18

what happens when a solid is heated

Answer 18

When a solid is heated, particle’s energy stores increase and they vibrate more, and when heated enough, it melts ⟶ particles have gained enough energy to break their structure

Question 19

what is latent heat

Answer 19

Latent heat = the energy needed by the particles to break free from each other

Question 20

what does lf stand for and what does it mean

Answer 20

Lf = Latent heat of fusion
Lf = the energy needed to change 1kg of a substance from solid to liquid at its melting point

Question 21

what does lv stand for

Answer 21

Lv = latent heat of vapourisation
Lv = the energy needed to change 1kg of a substance from liquid to gas at its boiling point

Question 22

what is the equation for lf and lv

Answer 22

For both fusion and vapourisation, the equation is energy/mass, so the unit for both is

Question 23

what does pressure mean

Answer 23

Pressure = the total of all the forces exerted on the walls of the container by gas particles ⟶ gas particles bouncing off each other does NOT contribute to pressure

Question 24

what happens if you heat a sealed container with gas

Answer 24

When you increase temperature of sealed gas container, you increase the pressure of the gas inside
As:
1. average kinetic energy of the gas molecules increases when the temperature increases
2. pressure of the gas container increases, as there will be more collisions against the surfaces of the containers

Question 25

what is the motion gas particles move in

Answer 25

Gas particles have a random motion called Brownian motion ⟶ you see this motion when you shine light on smoke particles

Question 26

When a gas is stored in a tube and a piston is pushed in, the air is compressed and the volume decreases

Answer 26

what happens when a gas is stored in a tube and a piston is pushed in

Question 27

what happens if you push the piston in slowly

Answer 27

By pushing the piston in slowly, the gas loses energy to the surroundings at the same rate as energy being transferred to it ⟶ SO the internal energy doesn’t change

Question 28

how is pressure and force associated

Answer 28

pressure and force have a directly proportional SO the number of impacts against the container wall is going to increase, so the total force of impacts per square metre is going to increase, so when you decrease volume pressure is will increase

Question 29

what is Boyel's law

Answer 29

Boyle’s Law = FOR A FIXED MASS OF GAS AT A FIXED TEMPERATURE: p x V = constant