Physics-Particles

Question 1

What is the definition of ‘Thermal energy’ in terms of particles?

Answer 1

It is the total kinetic energy of the particles in an object.

Question 2

What is the definition of ‘Internal energy’ in terms of particles?

Answer 2

It is the total kinetic and potential energy of the particles in an object.

Question 3

What is the definition of ‘Temperature’ in terms of particles?

Answer 3

It is a measure of the average kinetic energy of the particles in an object.

Question 4

Why does the temperature of a substance remain constant during melting, even though it is being heated?

Answer 4

The energy supplied increases the potential energy of the particles to overcome intermolecular forces, while their average kinetic energy remains the same.

Question 5

When a substance changes state from solid to liquid, energy is required to overcome the _____ forces.

Answer 5

intermolecular

Question 6

During a change of state, such as melting or boiling, the energy supplied increases the _____ energy of the particles, but not their kinetic energy.

Answer 6

potential

Question 7

What is the formula that links energy needed for a state change (E), mass (m), and specific latent heat (L)?

Answer 7

$E = mL$

Question 8

What does ‘specific latent heat of fusion’ refer to?

Answer 8

The energy required to change 1kg of a substance between the solid and liquid states without a change in temperature.

Question 9

What does ‘specific latent heat of vaporisation’ refer to?

Answer 9

The energy required to change 1kg of a substance between the liquid and gas states without a change in temperature.

Question 10

How does the body use the concept of specific latent heat to cool down?

Answer 10

The energy needed for sweat (water) to evaporate into a gas is taken from body heat, thereby cooling the skin.

Question 11

On a heating curve graph (Temperature vs Heat), what do the flat, horizontal sections represent?

Answer 11

A change of state is occurring (e.g., melting or boiling).

Question 12

On a heating curve graph, what is happening to the substance on the sloped sections where temperature is increasing?

Answer 12

The substance is being heated in a single state (solid, liquid, or gas), and the kinetic energy of its particles is increasing.

Question 13

What term describes the random motion of particles suspended in a fluid resulting from their collision with fast-moving atoms or molecules?

Answer 13

Brownian motion

Question 14

How are the particles in a gas described as moving?

Answer 14

They move in random directions with a range of speeds.

Question 15

What is the cause of gas pressure in a container?

Answer 15

It is caused by the collisions of the gas particles with the walls of the container.

Question 16

What is the formula that links pressure (P), force (F), and area (A)?

Answer 16

$P = \frac{F}{A}$

Question 17

If the temperature of a gas in a sealed container of constant volume is increased, what happens to the pressure and why?

Answer 17

The pressure increases because the particles gain kinetic energy, move faster, and collide with the container walls more frequently and with more force.

Question 18

If more gas particles are added to a sealed container of constant volume and temperature, why does the pressure increase?

Answer 18

There are more particles in the same space, leading to more frequent collisions with the container walls.

Question 19

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

Answer 19

Pressure is inversely proportional to volume.

Question 20

What is the equation that describes the relationship between the pressure (p) and volume (V) of a fixed mass of gas at constant temperature?

Answer 20

$pV = \text{constant}$

Question 21

A graph of pressure against volume (P vs V) for a fixed mass of gas at constant temperature shows what shape of curve?

Answer 21

A downward sloping curve, showing that as volume increases, pressure decreases.

Question 22

A graph of pressure against 1/volume (P vs 1/V) for a fixed mass of gas at constant temperature shows what shape of line?

Answer 22

A straight line through the origin, showing that pressure is directly proportional to 1/volume.

Question 23

What happens to the internal energy of a gas when work is done on it, for example by compressing it with a pump?

Answer 23

The internal energy of the gas increases, which can also lead to an increase in its temperature.

Question 24

Why does a bicycle pump get warm when you use it to inflate a tyre? (Higher Tier)

Answer 24

Work is done on the gas (air) to compress it, which increases the internal energy and temperature of the gas.

Question 25

What is the term for the amount of energy required to raise the temperature of 1kg of a substance by $1^{\circ}C$?

Answer 25

Specific heat capacity.

Question 26

What is the term for the amount of energy needed to change the state of 1kg of a substance without a change in temperature?

Answer 26

Specific latent heat.

Question 27

Why is mass conserved during a change of state?

Answer 27

The number of particles does not change; only their arrangement and energy levels are altered.

Question 28

Are changes of state physical or chemical changes, and are they reversible?

Answer 28

They are physical changes and are reversible.

Question 29

Describe the arrangement and movement of particles in a solid.

Answer 29

Particles are held in fixed, regular positions and vibrate about these points.

Question 30

Describe the arrangement and movement of particles in a liquid.

Answer 30

Particles are closely packed in an irregular arrangement and are able to move past one another.

Question 31

Describe the arrangement and movement of particles in a gas.

Answer 31

Particles are far apart, move randomly and rapidly, and have negligible forces of attraction between them.

Question 32

Which state of matter is generally the least dense and why?

Answer 32

Gas, because the particles are spread far apart, meaning there is a small mass in a large volume.

Question 33

How do you calculate the density of a material if you know its mass and volume?

Answer 33

By using the equation: density = mass / volume, or $\rho = \frac{m}{V}$.

Question 34

What equipment is used to measure the mass of an object when determining its density?

Answer 34

A balance (or top-pan balance).

Question 35

How would you determine the volume of a regularly shaped object, like a cube, for a density calculation?

Answer 35

Measure its length, width, and height with a ruler and then calculate the volume by multiplying these dimensions together.

Question 36

What is the name of the apparatus used to find the volume of an irregularly shaped object by water displacement?

Answer 36

A eureka can (or displacement can).

Question 37

Describe the procedure for finding the volume of an irregular object using a eureka can.

Answer 37

Fill the can with water up to the spout, submerge the object, and collect the displaced water in a measuring cylinder to measure its volume.

Question 38

In a sealed gas container, the force exerted by particle collisions is at _____ angles to the wall of the container.

Answer 38

right

Question 39

What happens to the boiling point of water as altitude increases, and why?

Answer 39

The boiling point decreases because the external air pressure is lower, so less energy is needed for the water particles to overcome it and escape as a gas.

Question 40

What quantity is related to the average kinetic energy of the molecules in a gas?

Answer 40

The temperature of the gas.

Question 41

In the context of the particle model, what is meant by 'potential energy'?

Answer 41

The energy stored in the bonds or intermolecular forces between particles.

Question 42

When a gas expands, does it do work on its surroundings or is work done on it?

Answer 42

It does work on its surroundings, which causes its internal energy to decrease.

Question 43

What is the unit for specific latent heat?

Answer 43

Joules per kilogram (J/kg).

Question 44

What are the units for density, mass, and volume in the SI system?

Answer 44

Density is in kilograms per metre cubed ($kg/m^3$), mass is in kilograms (kg), and volume is in metres cubed ($m^3$).

Question 45

The specific latent heat of _____ is for the change of state from solid to liquid.

Answer 45

fusion

Question 46

The specific latent heat of _____ is for the change of state from liquid to gas.

Answer 46

vaporisation

Question 47

If the volume of a gas is halved at constant temperature, what happens to its pressure?

Answer 47

The pressure is doubled.

Question 48

Why does increasing the volume of a gas at constant temperature decrease its pressure?

Answer 48

The particles are more spread out, so they collide with the container walls less frequently.

Question 49

The total internal energy of a system is the sum of the _____ energy and _____ energy of all its particles.

Answer 49

kinetic, potential

Question 50

What must be overcome for a liquid to change into a gas?

Answer 50

Intermolecular forces (bonds) between the particles.