P1 - Matter

Question 1

P1.1
Describe how and why the model of the atom has changed

Answer 1

• John Dalton: Thought that atom could explain his experiment results. Small indestructible sphere.
• J.J.Thompson: He made the plum-pudding model. (+) mass with (-) electrons embedded in it.
• Rutherford: Found the nucleus (protons (+) and neutrons (0)) with electrons on the outside
• Bohr: Modern day model. He discovered shells where electrons are known to be.

Question 2

P1.1
Describe the structure of an atom

Answer 2

• Nucleus containing protons and neutrons
• Electrons moving around nucleus on shells

Question 3

P1.1
State the order of magnitude sizes of the atom and small molecules

Answer 3

An atom = 0.0000000001m in diameter. Can be written as 10 ^ -10m or 1x10 ^ -10m.
Small molecule = 100 atoms x 10 ^ -10m/atom
= 10 ^ -8m

Question 4

P1.2
Explain what density means.

Answer 4

Tells you how much mass there is in a certain volume

Question 5

P1.2
State the equation linking density, mass, and volume.

Answer 5

Density (kg/m^3) = Mass (kg) / Volume (m^3)

Question 6

P1.2
Explain why substances in different states have different densities.

Answer 6

In a 1cm^3 of a substance in the solid state there are more particles than in 1cm^3 of the same substance as a gas. The mass of 1cm^3 of the solid is greater, so its density is also greater.

Density doesn’t only depend only on the particle arrangement, but also on the mass of the particles

Question 7

P1.2
Describe the differences between energy and temperature.

Answer 7

• The energy in a thermal store is measured in Joules ( J ). It depends on the arrangement of the particles and how fast they are moving or vibrating.
• Temperature tells you about the average kinetic energy of the particles.

Question 8

P1.2
Describe the differences between physical and chemical changes.

Answer 8

A physical change is different from a chemical reaction. Chemical reactions, such as burning, involve joining atoms together in different ways. You cannot easily reversed a chemical change.

Question 9

P1.2
Describe what specific heat capacity is.

Answer 9

The energy needed to raise the temperature of 1 kg of a material by 1 degree.

Question 10

P1.2
What is the equation for specific heat capacity.

Answer 10

Change in thermal energy ( J ) = Mass ( kg ) x Specific heat capacity ( J/kg °C ) x Change in temperature ( °C )

Question 11

P1.2
Describe what happens in state changes.

Answer 11

Melting : Solid -> Liquid
Boiling : Liquid -> Gas (evaporation)
Condensing : Gas -> Liquid
Freezing : Liquid -> Solid
Subliming : Solid -> Gas

Question 12

P1.2
What is the equation for specific latent heat.

Answer 12

Thermal energy for a change in state ( J ) = Mass ( kg ) x Specific latent heat ( J/kg )

Question 13

P1.2
Compare specific heat capacity and specific latent heat.

Answer 13

• Specific heat = energy needed to change 1 kg of a material by 1°C.
• Latent heat = energy needed to change the state of 1 kg of material

Question 14

P1.3
Explain how a gas exerts a pressure

Answer 14

• When you blow up a balloon it gets bigger.
• You are increasing the number of air particles in the balloon.
• The particles collide with the inside surface of the balloon.
• Each collision produces a very small force.
• There are many collisions, each producing force over a certain area. This produces a gas pressure.

Question 15

P1.3
Describe the relationship between the temperature of a gas and its pressure.

Answer 15

• If the temperature of a gas increases, the gas particles have a higher average speed.
• They collide more frequently with the sides of the container.
• The collision is produced over certain area.
• This produces a bigger pressure

Question 16

P1.3
Explain the relationship between pressure and volume for a gas at constant temperature.

Answer 16

If you seal the end of a syringe and press the plunger, the volume of the gas decreases. You have increased the pressure:
- As the volume doubles the pressure halves
- As the volume halves the pressure doubles

Question 17

P1.3
What is the equation linking the pressure and volume of a gas

Answer 17

Volume = constant / pressure

Question 18

P1.3
Describe a model of the earth’s atmosphere

Answer 18

You can think of that must feel as a single layer of gas that covers the Earth to a height of about 700 km. In the simplest model of the atmosphere, scientists assume that the density of the atmosphere is the same in all parts of the atmosphere

Question 19

P1.3
Describe what atmospheric pressure is.

Answer 19

The pressure the gasses of the atmosphere exert.

On the surface of the Earth atmospheric pressure is 101325 Pa, which is about 100000 Pa, or 100kPa

Question 20

P1.3
Describe how atmospheric pressure changes with height.

Answer 20

As you go higher, the atmospheric pressure decreases because there is less air above pushing down.