P1 Matter Flashcards

1
Q

What is the billiard ball model?

A

-Discovered by dalton in 1803.
-Different elements have different atoms.
-Atoms of the same element are identical.
-Atoms can’t be divided.
-Atoms can join to make new substances.
-Atoms make up all substances.

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2
Q

What is the plum pudding model?

A

-Discovered by JJ Thompson in 1897.
-The atom is a weak, positively charged sphere embedded with negative electrons.

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3
Q

How was the plum pudding model discovered?

A

-JJ Thompson used a cathode-ray tube to conduct an experiment which showed that there are small particles inside atoms.
-This disproved Dalton’s theory about atoms not splitting.

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4
Q

What is the planetary model?

A

-Discovered by Rutherford in 1911.
-The atom has a small, central nucleus of concentrated positive charge.
-Electrons orbited around the nucleus.
-He also discovered protons.

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5
Q

How was the planetary model discovered?

A

-Rutherford and his 2 students, Geiger and Marsden, fired positive alpha particles at thin, gold foil.
-They were supposed to go straight through however some particles deflected or rebounded back.

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6
Q

What is Bohr’s model?

A

-Discovered in 1913.
-Electrons orbited around the nucleus in fixed shells.
-This prevents the atom from collapsing due to electrons being attracted to the nucleus if there were no shells.

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7
Q

Who discovered neutrons?

A

Chadwick discovered neutrons in 1932.

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8
Q

What is the atom?

A

Has a positively charged nucleus orbitted by negatively charged electrons.

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9
Q

What is the radius of a nucleus?

A

1 x 10-15m

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10
Q

What is the radius of an atom?

A

1 x 10-10m

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11
Q

Why is most of the atom’s mass in the nucleus?

A

Contains subatomic particles which are heavier than electrons.

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12
Q

What is density?

A

How much mass is contained within a certain volume.

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13
Q

What is the formula for density?

A

Density = Mass / Volume

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14
Q

Why do solids and liquids have similar, higher densities?

A

-Particles are arranged closely together due to electrostatic forces of attraction.
-The space between particles doesn’t change significantly.
-Liquids tend to have lower densities than solids but water is denser than ice.

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15
Q

Why do gases have much lower densities than solids and liquids?

A

-The spacing between atoms is much greater.
-Particles have a lot of energy to move so they occupy a greater volume and are less dense than solids and liquids.

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16
Q

Why does a higher density mean a higher pressure?

A
  1. There are more particles in the volume of space.
  2. There are more collisions between the particles.
  3. Collisions increase the pressure.
  4. Therefore a higher density means a higher pressure.
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17
Q

What is the conservation of mass?

A

Mass is conserved when a substance changed state therefore the substance’s volume will change, resulting in a different density, but the mass remains constant.

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18
Q

What are physical changes?

A

-Reversible and require an energy change as well as a change in state.
-Examples: changes in state.

19
Q

What are chemical changes?

A

Irreversible and require a chemical reaction so that what you produce is chemically different from what you react.

20
Q

What is the difference between temperature and heat?

A

A measure of the average kinetic energy of particles in a system whereas heat is a form of energy.

21
Q

What 2 things could happen when a substance gains heat energy?

A

-Could raise in temperature but remain the same state.
-Could remain the same temperature but change state.

22
Q

What is specific heat capacity?

A

-The energy required to raise the temperature of 1kg of a substance by 1 degree celsius or 1 kelvin.
-Describes the energy to melt / freeze.

23
Q

What is the equation for specific heat capacity?

A

Energy = mass x specific heat capacity x change in temperature

24
Q

What is specific latent heat?

A

-The energy required to change the state of 1kg of a substance without a change in temperature.
-Describes the energy to boil / condense.

25
Q

What is the formula for specific latent heat?

A

Energy = mass x specific latent heat

26
Q

What is pressure?

A
  1. Particles in a liquid / gas move randomly in every direction.
  2. This causes pressure, producing a net force at right angles to any surface.
27
Q

What is the formula for pressure?

A

Pressure = force / area

28
Q

How do changes in pressure affect gases?

A

Gases can be compressed / expanded.

29
Q

Why are temperature and pressure proportional to each other when volume is constant?

A
  1. Increasing the temperature gives more energy to particles in a fluid.
  2. This thermal energy is transferred to kinetic energy so particles move faster.
  3. Therefore collisions of particles within the container walls become more frequent and forceful.
  4. As a result, the pressure of the fluid increases.
30
Q

Why are volume and pressure inversely proportional at a constant temperature?

A

-As pressure increases, greater force is applied per unit area during collisions so the particles occupy a smaller volume.
-As volume increases, the area over which the particles collide is larger than the force therefore the pressure decreases.

31
Q

Why are the temperature and volume of a liquid / gas proportional at a constant temperature?

A
  1. As the temperature increases, a greater force is exerted on the walls as particles have more kinetic energy.
  2. For the pressure to stay constant, the area of the container must also be greater as the particles exert a greater force, therefore the volume increases.
32
Q

What is the formula for work done?

A

Work done = force x distance

33
Q

What happens when work is done, a force is applied, to a fluid?

A

The temperature increases and there are two ways this can happen.

34
Q

How does the temperature increase when work is done to a fluid?

A

METHOD 1:
1. Introduce more gas to the same volume.
2. More particles are present.
3. More collisions occur.
4. The pressure increases.
5. This transfers energy to the particles.
6. The fluid heats up.

METHOD 2:
1. Reduce the volume of the fluid.
2. Particles collide with the container walls more frequently.
3. Increases the pressure and kinetic energy of each particle.
4. The fluid heats up.

35
Q

What are features of the Earth’s atmosphere?

A

-Isothermal (all the same temperature).
-Assumed to have uniform density.

36
Q

What is atmospheric pressure?

A

-The total weight of the air above a unit area at a certain altitude.
-Decreases as the height above the Earth’s surface increases.

37
Q

Why does atmospheric pressure decrease as the height above the earth’s surface increases?

A
  1. At higher elevation, there’s fewer air molecules in a given area.
  2. This means there’s a smaller weight of air.
  3. Therefore, there is less pressure.
38
Q

When does an object float?

A

If its weight is less than the weight of the fluid it displaces.

39
Q

When does an object sink?

A

When its weight is greater than the weight of the fluid it displaces.

40
Q

Why does pressure in a liquid increase with depth and density?

A
  1. The depth of the liquid increases.
  2. There are more particles above this depth.
  3. This means the weight of the party does is on top of the liquid.
  4. This weight adds to the pressure in the liquid.
  5. Therefore as the depth increases, so does the pressure.
41
Q

What does pressure in a liquid increasing with depth and density lead to?

A

-Leads to the liquid exerting an upwards force on a partially submerged object.
-Known as buoyancy force.

42
Q

What is the buoyancy force?

A

Counteracts the weight of the floating object.

43
Q

What is the formula for pressure due to a column of liquid?

A

Pressure due to a column of liquid = height of column x density of liquid x gravitational acceleration

44
Q

What is gravitational acceleration of Earth?

A

Always 10 unless question states otherwise.