# Homework Help: Methods used to measure the density of solid materials and liquids.

1. May 31, 2012

### Aaron9890

1. The problem statement, all variables and given/known data

I have to find two methods used to measure the density of a solid material and one method to measure a liquids density

2. Relevant equations

n/a

3. The attempt at a solution

got one method for the solids and have written this but my teacher wants me to find the accuracy of the method an the sources of error and i am not really sure

a) Pycnometer method –A Pycnometer can be used to determine both the density of solid material and a liquid. A glass pycnometer or a gas pycnometer can be used to measure the density of the solid object. To work out the density of the solid we first have to measure the pyconmeter together with the solid object being used. We add water and determine the weight. The volume of the added water can then be measured using the formula V = m/ ρ. The volume of the measured solid object will therefore be the difference between the volume of water that fills the empty pycnometer and the volume V which = mass of the object – the mass of water / the density of water. Once this is worked out we can then use the formula ρ = m/v.
In steps this involves;
1. Determine the weight of empty pycnometer.
2. Fill about 1/3 of pycnometer volume with solid object or material of your choice and measure the weight
3. Add water so that the pycnometer,as well as capillary hole in the stopper are filled with
water and measure total weight .
4. Empty pycnometer and fill with distilled water only, again measure the weight.
5. Empty pycnometer. Rinse it once with a liquid such as water, which density you will work out next (around 1000kg/m3) Fill pycnometer with the liquid and measure the weight
6. Clean pycnometer after finishing. Rinse it with water and let it dry.
8. Measure the laboratory temperature t, which determines the temperature of examined liquids and solid objects.
9. Calculate the weight of water using by deducting its mass inside the pycnometer from the mass of the pycnometer and find its density using ρ = m/v
10. Calculate the weight of solid object using the same method as the water,
11. Calculate solid objects volume using the equation V = mass of the object – the mass of water / the density of water and the objects density using ρ = m/v

This process of using the pycnometer is quite lengthy and as a result mistakes can easily be made.

For the liquid method i chose hydrometer method ad again she wants errors and accuaracy of method??

Hydrometer method -The relative density of a liquid can be measured using a hydrometer. This consists of a bulb attached to a tube. Fill the hydrometer with the liquid of your choice. Then hydrometer is floated in water and the the level of the liquid on the tube is marked. The liquid can be anything, however it is usually water The hydrometer is then floated in a liquid of unknown density. The change in displacement water level is noted. The application of simple physical principles allows the relative density of the unknown liquid to be calculated from the change in displacement.

This process is relatively easy if the guidelines of the process are followed with accuracy and precision

Can anyone help me out as well as naming a different method used for determining the density of a solid material

thanks,
Aaron