Solids, Liquids And Gases

Question 1

What is pressure?

Answer 1

Measure of the weight acting down on a surface.

Question 2

What is Brownian motion?

Answer 2

• movement of particles
• large particles can be moved by smaller particles travelling at high speeds
• this is why smoke particles appear to move rapidly and randomly
• supporting evidence of particle theory

Question 3

What is absolute zero and why do we have it?

Answer 3

0 kelvins = -273 degrees

• the coldest anything can ever get
• point at which particles stop moving and vibrating

Question 4

How do you measure the density of an object?

Answer 4

Take the mass and the volume

Question 5

What do each of these units stand for?
K
J
kg
kg/m3
m
m2
m3
m/s
m/s2
N
Pa

Answer 5

Kelvin
Joule
Kilogram
Kilogram per metre cubed
Metre
Metres squared
Metres cubed
Metres per second squared
Newton
Pascals

Question 6

What is the equation for density?

Answer 6

Density = mass / volume

Question 7

Describe experiments to measure density using direct measurements of mass and volume.

Answer 7

Measuring density of a liquid:

• use measuring cylinder to measure volume
• use a balance to measure the mass of liquid
• mass of liquid = measured mass - mass of cylinder
• work out density (= mass / volume)

Measuring density of a regular shape:

• measure the dimensions (height, length and width) with a ruler and calculate the volume (= h x l x w)
• use a balance to measure the mass of the object
• work out density (= mass / volume)

Measuring density of an irregular shape:

• use a balance to measure the mass
• volume of liquid displaced from a displacement can when object is put in it = volume of object
• work out density (= mass / volume)

Question 8

What is the equation for pressure?

Answer 8

Pressure = force / area

Question 9

What happens to pressure in a gas or liquid at rest?

Answer 9

It acts equally in all directions at a point.

Question 10

What is the equation for pressure difference?

Answer 10

Pressure difference = density x strength of gravity x height

Question 11

What happens when a solid melts to a liquid?

Answer 11

• melting
• some bonds break
• particles are more free to move

Question 12

What happens when a liquid evaporates or boils to a gas?

Answer 12

• evaporation
• bonds break
• particles move far apart

Question 13

Describe the arrangement and motion of particles in solids, liquids and gases.

Answer 13

Solids:

• strong forces between atoms and molecules
• v little motion
• v little kinetic energy

Liquids:

• some forces
• some kinetic energy
• some motion

Gases:

• little forces
• lots of kinetic energy
• lots of motion

Question 14

Describe the molecules in a gas.

Answer 14

• moving randomly
• collide with wall
• momentum changes
• force in molecule from wall
• equal and opposite force on wall from molecule
• averages over time to a constant force on wall
• force per unit area of wall is the pressure

Question 15

What is the Kelvin scale and how do you convert between kelvin and degrees Celsius?

Answer 15

• Kelvin scale takes point of absolute zero temperature to be its 0K position

K = degrees C + 273

Question 16

What happens as temperature increases in a gas?

Answer 16

Particles move faster.

Question 17

What is the kelvin temperature of a gas proportional to?

Answer 17

The average kinetic energy of the gases molecules.

Question 18

What is the relationship between the pressure and kelvin temperature of a fixed mass of gas at a constant volume?

Answer 18

As pressure increases, kelvin temperature increases.

p1 / T1 = p2 / T2

Pressure / temperature = constant

Question 19

What is the relationship between the pressure and volume of a fixed mass of gas at a constant temperature?

Answer 19

p1 x V1 = p2 x V2

Pressure x volume = constant