Particle Model of Matter

Solid

• strong force of attraction

• fixed, regular structure

• vibrate to transfer energy

• high particle density.

Liquid

• weaker forces of attraction

• particles move past eachother in an irregular structure

• particles have more energy than solids

• less dense than solids

Gas

• almost no forces of attraction

• particles move in random directions randomly

• fill their container

• more energy than other states

• low density

What happens to mass when a substance changes state?

Mass is conserved- it stays the same.

Why does it stay the same?

No particles are removed, only rearranged

What is the key feature of a physical change?

The material can return to its original state and properties

density

mass / volume

how do you find the density of irregular objects

• use balance to find mass

• fill a eureka can with water and place object into the water

• measure the amount of water that is dissplaced

internal energy

the total energy that a system’s particles have in their kinetic and potential energy stores

how does heating affect internal energy?

increases the energy in the particles kinetic energy stores

this leads to an increase in temperature, causing particles to move more rapidly and potentially change state.

As water gets heated…

• particle energy increases

• some matter changes state

• internal energy increases

Specific Latent Heat

The energy needed to change the state of 1Kg of a substance

unit for Specifc Latent Heat

J/Kg

equation for SLH

energy = mass x SLH

Why does temperature plateau (stop increasing) during state change?

All the energy goes into breaking intermolecular bonds instead of increasing temperature.

work done on a gas

• increases internal energy

• may increase temperature

what is pressure?

Force exerted per unit area.

pressure (pascals) x volume (m³) = ?

constant

How do gases move inside a container?

• move randomly

• collide with the walls and other particles

What is pressure in a sealed container?

total force exerted on the walls of the container.

Why does pressure decrease when volume increases?

gas particles have more space and hit the walls less often.

Boyle’s Law

for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional. → If volume increases, pressure decreases. If volume decreases, pressure increases.