Particle model of matter

particles are very close together • particles are arranged in a regular pattern • particles vibrate but they do not move from place to place

• particles are close together • particles are not arranged in a regular pattern • particles can move around each other

• particles are very far apart • particles are not arranged in any pattern • particles are moving very rapidly

Density of a material tells us the mass for a given volume

A brick has very high density. it has lots of mass packed into its volume

the density for a polystyrene block is low. it has a lower mass packed into its volume

density p kg/m^3 = mass (kg) / volume (m^3)

150/0.3=500kg/m^3

solids have a very high density because the particles are very closely packed together solids have lots of mass for their volume.

liquids usually have high density because the particles are close together, liquids have alot of mass for their volume

gases have a low density because the particles are far apart so gases only have a small mass for their volume.

this is because polystyrene has a very open structure and is full of air spaces. it has a small mass for its volume.

regular objects have dimensions we can easily measure with a ruler irregular objects- cannot easily measure dimensions regular objects density- first determine the mass using a balance. next work out volume by using a ruler to measure length of each side. volume of a cube= length of side^3

because we cannot easily measure the dimensions instead we have to determine the volume using displacement.

first, measure mass of object using a balance. fill a eureka can with water. eureka can has a spout so that water can flow out through the spout. place the object in water. this will cause water to be displaced as it will flow through the spout collect water in a beaker and then transfer to measuring cylinder to measure the volume of water displaced. once you have determined the volume, use it to calculate the density of the object using the equation density kg/m^3= mass (kg)/volume (m^3) key point- the volume of water displaced is the volume of the object.

-kinetic energy= all these particles have kinetic energy (due to particles movement) potential energy= ( intermolecular forces or chemical bonds if they are a molecule)

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

if we heat a solid, we are increasing the internal energy. at some point the solid can turn into a liquid (melting)

it increases

when we heat a liquid, again the internal energy increases, at some point the liquid turns into a gas (boiling)

the internal energy reduces the gas turns into a liquid at some point (condensing) if we cool down the liquid further, we reduce the internal energy even more eventually the liquid turns into a solid ( freezing)

sublimination

we are not adding or taking away particles

physical changes if we reverse the change, the material recovers its original properties.