Particle Model of Mater

What is density?

the mass per unit volume of a substance (g/cm³) (kg/m³).

What is the equation for density?

density = mass/volume

What is a displacement vessel/eureka can?

A device used to measure the volume of an irregularly shaped object by determining the amount of liquid displaced when the object is submerged.

Solid

• very strong intermolecular forces between particles in a solid

• fixed position, close together

• held in a uniform arrangement

• vibrate on the spot

liquid

• quite strong intermolecular forces between particles

• close together

• non uniform arrangement

• move past eachother

• have a definite volume but take the shape of their container.

gas

• very weak/no forces between particles in the gas

• spread out

• irregular arrangement

• move randomly in all directions

internal energy

kinetic energy of particles + potential energy of particles

kinetic energy

• when the store of energy increases the particles in a substance begins to move faster

potential energy

when the store of energy increases the particles in a substance are further apart and intermolecular forces weaken

Adding energy to a solid

• increases kinetic energy/ temperature of particles

• increases internal energy

• reaches melting point which weakens intermolecular forces

• increases potential energy

• changes state to liquid

Adding energy to a liquid?

• increase in temperature (kinetic energy) until boiling point

• intermolecular bonds are broken/weakend

• at boiling point turns into gas (increase in potential energy)

What happens to the internal energy store in melting ice?

the temperature remains constant

What happens to the internal energy when warming water?

increase in temperature

What happens to the internal energy in boiling water?

the temperature remains constant

the process of specific latent heat

• when a substance reaches boiling point the temperature can’t increase so instead the potential energy is increased

• the energy change is hidden in the changing structure of the liquid

• hidden energy/latent heat is needed to overcome intermolecular forces to vaporise the liquid

• change of state occurs and is now a gas

latent heat

the energy required for a phase change without a change in temperature.

needed to overcome intermolecular forcesthat hold the molecules together in a solid or liquid state.

specific latent heat

the amount pf energy needed to change state of 1kg of a substance without a change in temperature.

Equation for specific latent heat

energy = mass x specific latent heat

Specific latent heat of fusion

when a solid reaches melting point

specific latent heat of vaporisation

when a liquid reaches boiling point

evaporation

• does not happen at boiling point

• process that happens when particles have enough energy to evaporate over time

pressure and volume relationship for gases

As the volume decreases pressure increases and as the volume increases the pressure decreases

gases at a constant temp

• gas volume is indirectly to gas pressure

• gas volume decreases, pressure increases.

• p x V = constant

pressure

the force acting on an object

Pressure & volume of gases 4 markers

• pressure caused by collisions of gas particles & walls of container

• increases frequency of collisions

• faster particles

• increases force and increases pressure

Compressing gas

• increases pressure

• increases frequency of collision between particles & the container

• increases force of each collision

• increases force per unit of area which increases pressure

Heating gas

• increases kinetic energy of particles

• increases frequency of collisions with container walls

• increases the amount of force per second so with each collision force is increased

• increases force per unit area which increases pressure