# scinece revision

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density and changes of state

density tells us how much mass there is in a certain volume it is a property of a material

the relationship between density, volume and mass can be summed up in the following equation:    density = mass divide volume

density, p, is mesaured in kilograms per metre cubed (kg/g)

mass, m, is mesaured in kilograms (kg)

volume, v, is mesaured on metres (m)

density is the mass per unit volume of a material, or the mumber of kilograms (Kg) contained in 1m of the material.

DENSITY AS A PROPERTY OF A MATERIAL

the density of a marterial does not change when we change the volume of an object

for example we could take a 1m block of material that weights 1000kg. its density is: 1000 didivde 1 = 1000(kg/m)

if we stick another identical block onto this, the volume is now doubled to 2m but so the mass. the density can be caluclated again: 2000 didvide 2 = 1000kg/m. its stays the SAME.

COMPARING DENSITIESB OF MATERIALS

we can easily compare the density of diffrent materials using a balance

we can see that the density of the red object is 10 times that of the green

they have the same mass but it is contained in a much smaller volume for the red object.

MEASURING MASS

in order to calculate the density of an object, the volume and mass of the object must first be measured

measuring mass is easy. we can use an electronic BALANCE

MEASURING VOLUMES

measuring the volume of regular shapes can be done using mathematical formulae

for example, for a cube w ecan simply mulitply the lengths of the sides, for a sphere we can use a mathematical formula the dimensions of an object can be mesaured using a ruler a vernier callier or a micromenter, depending on the size.

we can then divide the mass by the volume to find the density.

MEASURING IRREGULAR VOLUMES

there is no mathematical formula to find the volume of irregular shapes. instead a simple experiment