P6-Density

Question 1

How do you calculate the density of a regular object

Answer 1

• Calibrate your scales and measure the mass of the object
• Calibrate your calliper and measure the length and width of the object . Multiply these values to get a volume for the object
• Use your equation to work out the density of the object from these values

Question 2

How do you calculate the density of an irregular object

Answer 2

• Calibrate the scales and measure the mass of the object
• Fill the eureka can to the top with water. Then let the excess water drip out until the water settles just under the hole.
• Place the measuring cylinder under the nosel. Then place your object into the eureka can. Make sure no water splashes and maybe place your object in with string so your fingers dont displace any water
• Measure the volume of displaced water that has gone into the measuring cylinder. Making sure to measure from the bottom of the meniscus
• Use the equation density = mass divided by volume to work out the density

Question 3

How do you measure the mass of a liquid

Answer 3

• Place a measuring cylinder on the scales and zero the scales
• Place 10 cm3 of the liquid into the measuring cylinder and record the mass of the liquid
• Place another 10 cm3 of liquid into the measuring cylinder and measure the mass of the liquid again
• Use the mass and volume to calculate a density for each of the measurements and find out an average density for the liquid

Question 4

What is the equation for density

Answer 4

Density = mass divided by volume

Question 5

Describe the features of particles in a solid

Answer 5

• Strong forces pf attraction hold the particles in a solid in a fixed regular arrangement
• The particles have little energy and just vibrate round their fixed positions
• The density of a solid is highest because the particles are closest together

Question 6

Describe the features of particles in a liquid

Answer 6

• There are weaker forces of attraction between particles so the particles are able to move past each other and form irregular arrangements. They are still close together though
• The particles have more energy than the particles in solids so they are able to move in random directions at high speeds
• Liquids are less dense than solids

Question 7

Describe the features of particles in a gas

Answer 7

• There are almost no forces of attraction between the particles in a gas
• The particles have more energy than particles in liquids and solids. They are free to move in random directions at high speeds
• Gases have the lowest densities as the particles are the least close together

Question 8

What is the internal energy store of a substance

Answer 8

The internal energy store of a substance is the total energy that the particles have in their kinetic and potential energy stores

The energy in the particle’s potential energy store is due to the positions of the particles

The energy in the particle’s kinetic energy store is due to the motion( vibration and movement )of individual particles

Question 9

How does heating affect a particles internal energy store

Answer 9

Heating transfers energy to the particles in the substance. This energy goes into the kinetic energy store of the particles and the particles move faster.This increases the internal energy of the substance

Question 10

When will a change in state happen

Answer 10

A change in state will happen if particles have been heated enough. The particles will have enough energy in their kinetic energy store to break the intermolecular forces of attraction that are holding them together .

Question 11

How does mass of a substance change when a change of state occurs

Answer 11

The mass of a substance does not change.

• This is because when a change if state occurs the number of particles doesnt change they are just arranged differently.
• This means mass is conserved

Question 12

What happens if you reverse a change in state

Answer 12

If you reverse a change in state the particles return to their original form and go back to their original properties

Question 13

What happens to the temperature of a substance when it is melting or boiling

Answer 13

When a substance is actually melting or boiling , energy is being put into the substance so the internal energy of the substance is increasing. But the energy is being used to break the intermolecular forces of attraction rather than to increase the temperature of the substance

This means that the temperature does not change

Question 14

What happens to the temperature of a substance when it is freezing or condensing

Answer 14

When a substance is freezing or condensing, energy is being released because bonds are being made. This decreases the internal energy of the substance but does not decrease the temperature as the energy is being used to make the bonds rather than to change the temperature

Question 15

What is latent heat

Answer 15

Latent heat is the amount of energy needed to change the state of a substance

Question 16

What is specific latent heat of fusion and what is the equation for it

Answer 16

Specific latent heat of fusion refers to the energy needed to change a 1kg substance from a solid state to a liquid state

Specific latent heat of fusion= energy (j) divided by mass (kg)

Question 17

What is specific latent heat of vaporisation

Answer 17

Specific latent heat of vaporisation refers to the energy needed to change 1kg of a substance from a liquid to a gas

Specific latent heat of vaporisation = energy(j) divided by mass (kg)

Question 18

How does pressure exerted by a gas increase as temperature increases

Answer 18

When a substance is heated its particles gain kinetic energy and move faster. The molecules therefore collide with surfaces more frequently and with more force .

Therefore pressure increases as temperature increases

Question 19

What is the equation for pressure

Answer 19

Pressure(N/m2) = force(N) divided by area (m2)

Question 20

What is pressure

Answer 20

Pressure is the continuous colliding of particles with a surfaces

More particles= higher pressure

Less particles=lower pressure

Question 21

What equation links pressure and volume

Answer 21

Pressure x volume = constant

P1xV1=P2xV2

Question 22

What is Boyles law

Answer 22

Boyles law states that for a fixed amount of gas at a fixed temperature , pressure is inversely proportional to volume.

As pressure increases volume decreases and vica versa

Question 23

Why does pressure increase as volume decreases

Answer 23

Due to having a smaller volume the particles collide more frequently with the internal surface. Thsi increases the force per unit area therefore increasing the pressure

Question 24

What would happen to pressure if the volume of the container increased

Answer 24

Pressure would decrease if the volume of the container increased .

• This would be because there would be more space between the particles and the internal surface and overall less frequent collisions with the internal surface.
• This would ultimately mean that there would be less force over a larger area so less pressure

Question 25

How does doing work on a gas increase temperature

Answer 25

If you transfer energy by applying a force then you do work on a gas.
Doing work on a gas transfers energy to its internal energy store .

This increases the energy in the kinetic energy stores of the particles within the gas

By increasing the energy in the kinetic energy store you increase the temperature of the gas (temperature is average kinetic energy)

So overall doing work on a gas increases temperature