Topic 3- Density and states of matter

Question 1

What is density?

Answer 1

The measure of compactness of a substance

Question 2

Describe the arrangement of particles in a solid

Answer 2

• strong forces of attraction hold particles close together
• fixed, regular arrangement
• Particles don’t move much and vibrate about fixed positions

Question 3

Describe the arrangement of particles in a liquid

Answer 3

• Weaker forces of attraction between particles in a liquid
• Partices are close together but can move past eachother
• They move random directions at low speeds

Question 4

Describe the arrangement of particles in a gas

Answer 4

• almost no forces of attraction between the particles
• more energy than liquids or solids
• free to move and travell in random directions at high speeds

Question 5

What is the internal energy of a system?

Answer 5

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

Question 5

Why are gasses compressable?

Answer 5

The particles in a gas are very spread out and therefore by compressing a gas you are simply reducing the distance between particles.

Question 6

What is internal energy?

Answer 6

The sum of all the individual kinetic and potential energy stores of the particles.

Question 7

When changing state, when does potential energy increase?

Answer 7

As particles become further apart (during changing states)

Question 8

When changing state, when does kinetic energy increase?

Answer 8

As particles vibrate more / move faster (when the temperature increases)

Question 9

What is temperature a measure of?

Answer 9

The average kinetic energy of the particles in a substance.

Question 10

What is the average kinetic energy of a substance at zero Kelvin?

Answer 10

zero

Question 11

What is 0 Kelvin in degrees Celsius?

Answer 11

-273°C

Question 12

What is specific heat capacity?

Answer 12

Specific heat capacity is the amount of energy required to raise the temperature of one kilogram of a substance by 1°C.

Question 13

What unit is used to measure specific heat capacity?

Answer 13

J / Kg / °C.

Question 14

What is the equation for power?

Answer 14

Power = energy / time

Question 15

What is the latent heat of fusion?

Answer 15

The latent heat of fusion is the energy required to change 1kg of a substance from a solid to a liquid without changing the temperature.

Question 16

What is the latent heat of vaporisation?

Answer 16

The latent heat of vaporisation is the energy required to change 1kg of a substance from a liquid to a gas without changing the temperature.

Question 17

What is the equation for latent heat?

Answer 17

Latent heat= Energy supplied to change state / mass

L = Q / M

Question 18

What is the unit used to measure latent heat?

Answer 18

J/kg

Question 19

What is the equation for pressure?

Answer 19

Pressure = Force / Area

P = F / A

Question 20

What is the unit for pressure?

Answer 20

N/cm^2 or Pascals (N/m^2)

Question 21

What is Pascals equal to?

Answer 21

N/m^2

Question 22

What is the equation for density?

Answer 22

Density = mass / volume e = M / v

Question 23

What is the unit for density?

Answer 23

Often given in g/cm^3 but needs to be in g/m^3 before using in other formula.

Question 24

Explain what happens when a gas particle hits the walls of its container.

Answer 24

1. Gas particle hits the wall of its container.
2. It changes direction, therefore accelerates.
3. Therefore the particle has had a force exerted on it by the container.
4. Therefore by Newton III the particle exerts an equal and opposite force on the container.
5. Therefore as P=F/A, a pressure is exerted on the container.

Question 25

What does how high air pressure is, depend on?

Answer 25

Air pressure depends on the speed of the particles and the number of collisions per second (frequency of collisions.)

Question 26

Why does the pressure of a gas increase when the temperature increases?

Answer 26

Temperature is the measure of kinetic energy of the particles. If the particles have more kinetic energy, speed increases causing more frequent collisions. The gas particles exert a greater force on the box because they exert greater forces in collisions therefore increasing pressure.

Question 27

What is the equation for Boyle’s law?

Answer 27

Pressure = constant / volume (P=K/V)
Pressure and volume are inversely proportional-

• increasing volume will result in a decrease in pressure
• decreasing volume will result in an increase in pressure

Question 28

What happens when you compress a gas?

Answer 28

1. Compressing a gas causes you to do work on it (force to move a piston to push on the gas.)
2. Work done = energy transferred to thermal store of gas.

Question 29

What will happen to a baloon if the atmospheric pressure around the balloon decreases?

Answer 29

The balloon will expand until the pressure inside drops to the same as the atmospheric pressure.