OCR A GCSE Physics: P1 Matter

For assessment in November, flashcards from PMT

How did the plum-pudding model describe the atom?

A ball of positive charge, with negatively charged electrons distributed evenly throughout it.

Prior to the discovery of the electron what was believed about the atom?

The atom was believed to be indivisible.

Which experiment led to the plum-pudding model being discarded?

Rutherford’s alpha-scattering experiment.

What is the name given to the currently accepted model of the atom?

The Bohr nuclear model.

What are the three subatomic constituents of an atom?

Proton, Neutron, Electron

Describe the arrangement of protons, neutrons and electrons in an atom.

The protons and neutrons are found in the atom’s nucleus. The electrons are found in discrete energy levels around the nucleus.

What type of charge does the nucleus of an atom have? Why?

Positive charge. The nucleus contains protons (positive) and neutrons (no charge), so the overall charge is positive.

Where is most of the mass of an atom concentrated?

In the nucleus.

Approximately what proportion of the total radius of an atom is the radius of the nucleus?

1/10,000

Give an approximation for the radius of an atom.

1x10⁻¹⁰ metres

What is the definition of density? State the relevant equation with units.

The mass per unit volume of a material. ⍴=m/v. Density (kg/m³), Mass (kg), Volume (m³)

Describe the particle arrangement of a solid.

Tightly packed in a regular arrangement. Particles can only vibrate on the spot.

Describe the particle arrangement of a liquid.

Close together, but irregular arrangement. They can flow past each other.

Describe the particle arrangement of a gas.

Separated, with no regular arrangement. Particles can move freely.

Give the different states of matter in order (least to most) of density of atoms.

Gas (Least dense), Liquid, Solid (Most dense)

What is always conserved when a substance undergoes a change of state?

Mass

What are the 5 main ways that a substance can change state?

Melt, Freeze, Evaporate, Condense, Sublimate

What is sublimation?

When a substance transitions from a solid straight to a gas without transitioning into a liquid in between.

What is always conserved when a substance changes state?

Mass

How does a change of state differ from a chemical change?

In a change of state, the material can return to having its previous properties if the change is reversed.

What two things can heating a substance do?

Raise its temperature, Change the state of the substance

Define specific heat capacity.

The amount of energy needed to increase the temperature of 1kg of a substance by 1°C.

What can be said about a material if it has a higher specific heat capacity?

For a constant mass, the material will need more energy to achieve a given temperature change.

Define specific latent heat.

The amount of energy needed to change the state of 1kg of a substance with no change in temperature.

State the equation for the energy required to change state. Give appropriate units.

E = mL. Energy to change state = mass x specific latent heat. Energy (J), Mass (kg), Specific latent heat (J/kg)

What is the internal energy of a substance?

The energy stored by the particles. The sum of the total kinetic and potential energies that make up the system.

Describe the motion of molecules in a gas.

They are in constant random motion.

What is the unit used for pressure?

Pascal (Pa).

How can the pressure of a gas be increased whilst kept at constant temperature?

The volume can be decreased.

How can the pressure of a gas be decreased whilst kept at constant temperature?

The volume can be increased.

What effect does increasing temperature have on the pressure of a gas when held at constant volume?

Pressure of the gas will increase as the temperature increases.

Why does pressure increase as temperature increases (at a constant volume)?

Kinetic energy of molecules increases. Collisions between molecules becomes more frequent. Greater rate of change of momentum. Greater force and therefore pressure.

If gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?

There are more collisions per second in gas B than in gas A. The rate of collisions is higher in B.

Describe the force that the pressure of a gas exerts on the walls of its container.

The net force acts at right-angles to the container’s surface. The magnitude of the force increases as pressure increases.

Explain how increasing the volume of a gas results in a decrease of pressure.

Molecules become more spread out so collisions become less frequent (more time between them). This reduces the rate of collisions. Rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure.

What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature? (Higher)

It is constant. pV = constant

What increases when you do work on a gas? (Higher)

The internal energy of the gas. This can also lead to an increase of temperature.

Why does the temperature of air inside a bike pump increase when it is pumped? (Higher)

Work is done on a gas when it is compressed. Doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules. Temperature increases with an increase of average kinetic energy.

Why does atmospheric pressure decrease as you move higher above the Earth’s surface?

The atmospheric pressure at a point is equal to the weight of the air in the column above that point, as you move higher above the Earth the amount of air in said column decreases - resulting in less weight above and as a result less pressure at the point.

What does an object in a fluid experience as a result of pressure?

Forces at right angles to all of its surfaces.

Pressure in a fluid increases with depth. Why? (Higher)

Increases, because it is caused by the gravitational force on the fluid above that point. The deeper you go, the greater the weight of water above you, and so a higher force and pressure.

What equation is used to calculate the pressure at a given depth of liquid? (Higher)

pressure = depth x liquid density x gravitational field strength. p = hρg

What is upthrust? (Higher)

The upwards force that an object experiences in a fluid as a result of a greater pressure below the object than above it.

Under what circumstances will an object float? (Higher)

When the object’s upthrust equals its weight.

Under what circumstances will an object sink? (Higher)

When the object’s upthrust is less its weight.

When you submerge an object in a liquid, what is the upthrust acting on the object equal to? (Higher)

The weight of the volume of liquid displaced as it is submerged.

What can be said about the density of an object that sinks in water? (Higher)

The object’s density is greater than the density of water.