Mechanical Principle

(a) Briefly describe the method to measure the density of wood.

To measure the density of the wood you have to find out the mass and the volume of the wood. This is because density equals mass divided by volume. You first start by working out the volume of the wood this is done by multiplying the length of the wood the width of the wood and the height of the wood together. Once you find out the volume of the wood using the formula you then have to work out the mass of the wood by using a digital scale as it gives you the exact value of the wood in grams. Now that you got the mass and the volume of the wood you then have to find out the density using the mass and volume calculated. This is done by dividing the mass by the volume to find out the density of the wood that you are trying to calculate

(b) Explore another method of measuring the density of solid and compare this with above method described in

(a) Another way in which finding out the density of a solid object can be found is by a pycnometer. This will allow you to find out the value of any solid object. To work out the density of the object using a pycnometer we have to first find out how much is the mass of the pycnometer. Once that is done you then have to then measure the pycnometer with the solid object within it. After that is done we than have to add water to it and determine the weight of the pycnometer now. With the water that is added to the pycnometer we then can find out the volume of the added water using the formula V= m/ρ. The volume of the object will then allow us to find the difference between the volume of the water that fills the empty pycnometer. The volume will then be calculated as the mass of the object subtracted by the mass of water then divided by the density of the water.

Once we have worked this out we can then use the formula density equals mass divided by volume. This is another way in which the density of the water can be found. However, the two methods are different. The fist process allows you to find the density quicker that using a pycnometer. However, it is no precise due to the different scales that can be used to measure the mass. However, the pycnometer give a more reliable to result when finding out the density. In addition, the pycnometer is a longer process to complete when finding out the density

(c) Briefly describe the method to measure the density of water.

To calculate the density of the water you have to determine a volume of water using a graduated cylinder, this cylinder is calibrated in millilitres. The units for this is 1ml is 1cm3. As we are going to measure the mass of the water in the cylinder we have to subtract the mass of the cylinder from the total mass of the water and cylinder. By using a digital scale, it will allow you to make it easier. You have to first set the empty cylinder on the scale. Then once you work out the mass you then subtract that from the volume of the water you measure using the cylinder. Then once you work out the mass of the water and the volume of the water you then have to divide the mass of the water by the volume of the water to get the total density of the water.

(d) Explore another method of measuring the density of liquid and compare this with above method described in

(c) Another way in which finding out the density of liquid is by also using a pycnometer to find out the density of the water. This is an alternative method of finding out the density of water. The first thing is that you first have the pycnometer and you fill it up with water this will give you the volume of the water which is in the pycnometer. However, we have to measure the density of the water the formula for water is V= mH2O / ρH2O. As we know the mass of the water we have to weigh the empty pycnometer and subtract it but the water in the pycnometer. We now know the volume mass and density of the water. This is for measuring the water. Then we repeat the procedure with another liquid where we don’t know the density and you then have to work out the mass of the liquid by again weighing the empty pycnometer and subtracting it by the liquid that is in the pycnometer. However, the volume of the liquid is the same as the volume of the water. The equation for this is V= mL / ρL. Now you have the two equations you can then use the two equations to find the density of the liquids the formula for this is mH2O / ρH2O = mL / ρL. you then rearrange the formula so that it equals to the density this is done by ρL = mL / mH2O x ρH2O. this will then give you the density of the liquid. This method is a longer method that the procedure in c as it includes many equations to work out.