Particle model of matter

What is density?

The amount of mass in a certain volume

What is the formula for density?

Mass = Density * Volume

What is the particle model of solids?

Densely packed molecules in a fixed regular pattern, immovable, only able to vibrate

What is the particle model of liquids?

Particles close together, but not packe together, allowing them to slide and move over each other (flowing). They have no fixed volume, they take the shape of the container it is in

What is the particle model of gases?

Random and far apart molecules that can move quickly. Heating causes faster movement. No fixed volume. Expands easily

What is always conserved when a product undergoes a change in state?

Mass

What is melting?

solid-liquid

What is boiling?

liquid-gas

What is sublimation?

solid-gas

What is condensation?

gas-liquid

What is freezing?

liquid-solid

What is deposition?

solid-gas

What is internal energy?

Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

How does heating affect the energy of a substance?

• Heating transfers energy to the substance

• Increases the energy of the particles that make up the substance

What 2 things can heating a substance do?

• Raise its temperature

• Change state of the substance

What three factors determine the temperature change of a system?

• Mass of substance being heated

• Type of material (Specific heat capacity)

• Energy inputted into the system

What is the specific heat capacity formula?

∆T = mc∆θ

What is specific heat capacity?

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

What is specific latent heat?

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

What is the specific latent heat formula?

E = mL

What is the movement of molecules of gas?

They are in constant random motion

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

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 force increases as pressure increases

What is Boyle’s law?

Boyle's law states that the pressure of a gas is inversely proportional to its volume when the temperature and mass stay the same:

P₁ V₁ = P₂ V₂

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

• Molecules become more spread out and so time between collisions increases

• 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?

It is constant, pV = constant

What increases when you do work on a gas?

• 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?

• 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