P3 - Changes of State and Particle Model

space - minimal/no space between the particles

movement - vibrate around a fixed point

shape - don't change shape/fixed shape

volume - has a fixed volume

forces - strong forces between the particles

space - has minimal gaps

movement - slide and flow past eachother

shape - changes shape according to the container 

volume - has a fixed volume

forces - medium forces between the particles

space - large gaps between particles

movement - random directions at varying speed

shape - changes shape freely around the container

volume - doesn't have a fixed volume

forces - weak/no forces between the particles 

solid into liquid - melting

liquid into gas - evaporation

gas into liquid - condensation

liquid into solid - solididifying

solid into gas - sublimation

density relates to the mass of an object and how tightly packed the particles are.

it is the mass per unit volume.

density = mass/volume

density equation= ρ (kg/m^3) = m(kg) / v(m^3)

1) use a balance to measure the object's mass

2) if it is a regular solid, measure the length, width and height with a ruler then multiply together to find the volume

3) if the solid is irregular, you can use the displacement method. fill a eureka can with water, submerge the object in it, and collect the water in a measuring cylinder. the total water that is displaced is the object's volume.

4) convert any values into the correct units, and find the density by using the equation mass/volume

internal energy is caused by two things:

• the amount of kinetic energy particles have depending on their individual motion
• the potential energy particles have due to molecular attraction

heating a system causes transfers energy to its particles (they gain energy inn their kinetic stores so move faster) which increases the internal energy.

this leads to a change in temperature, or a change in state.

when the temperature of a system changes, the size of that change depends on the mass of the substance, its specific heat capacity (what it is made of) and the energy input.

a change in state occurs when the particles have enough energy from being heated in their kinetic energy stores to break the bonds between them.

remember: the specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of that substance by 1°C.

energy = mass * SHC * temp change

E (J) = m (Kg) * C (J/Kg°C) * θ (°C)

the temperature of a substance doesn't change while it is changing state because the energy that is being transferred is being used to change the state.

the specific latent heat of a substance tells us how much energy is needed to change the state of 1Kg of a substance at a constant temperature.

specific latent heat of fusion = solids --> liquids

specific latent heat of vaporisation = liquids --> gases

energy (J) = mass (Kg) * SLH (J/Kg)

when a particle hits a surface this creates a force on the surface, which creates the pressure of the gas.

factors which affect pressure:

• temperature - the higher the temperature, the more internal energy the particles have. they move around faster and collide with each other and the surface more often, causing the pressure to increase
• volume - the smaller the volume of the container, the less space the particles have to move around, resulting in more collisions with the surface and each other, therefore increasing the pressure
• number of particles - the more particles in the container, the more often they will collide with each other and the container, resulting in higher pressure

boyle's law states that the pressure of a gas is inversely proportional to its volume (at a constant temperature and amount of gas)

as pressure increases, volume of the gas decreases by the same factor

p1 * v1 = p2 * v2