Liquids
Apparatus
A measuring cylinder, a top pan balance, tap water.
Method
This experiment is very similar to the one for regular solids but there is a different way of measuring the mass and volume of the water.
- Place an empty, dry measuring cylinder on the top pan balance. Read the mass and record in a suitable table in g.
- Remove the cylinder from the top pan balance. Pour 50cm3 of water into it and place it on the balance again. Read the mass and record in the table.
- To calculate the mass of the water, subtract the mass of the empty cylinder from the mass of the cylinder plus water. Record the mass in the table.
- Read the volume of water from the measuring cylinder. Record the volume of water in cm3.
- Repeat the procedure adding 50cm3 each time up to 300cm3 for 6 results.
Safety
Water should not be poured into the measuring cylinder when it is on the top pan balance.
Water spilled on the electric balance could cause electric shock.
Always remove the measuring cylinder from the balance before adding water.
Results
| Mass of empty measuring cylinder in g | Mass of measuring cylinder + water in g | Mass of water in g | Volume of water in cm3 | ||||
| Mass of empty measuring cylinder in g | |
|---|---|
| Mass of measuring cylinder + water in g | |
| Mass of water in g | |
| Volume of water in cm3 | |
| Mass of empty measuring cylinder in g | |
|---|---|
| Mass of measuring cylinder + water in g | |
| Mass of water in g | |
| Volume of water in cm3 | |
| Mass of empty measuring cylinder in g | |
|---|---|
| Mass of measuring cylinder + water in g | |
| Mass of water in g | |
| Volume of water in cm3 | |
| Mass of empty measuring cylinder in g | |
|---|---|
| Mass of measuring cylinder + water in g | |
| Mass of water in g | |
| Volume of water in cm3 | |
Graph
Plot a graph of mass in g on the y-axis against volume in cm3 on the x-axis.
Draw a line of best fit through the points.
The gradient of the graph = \(\frac{mass}{volume}\) = density of water.
Calculate the gradient of the graph and hence the density of water.
Conclusion
As for the previous experiment, the line of best fit is a straight line through the origin.
We can say that the volume of water is directly proportional to its mass.
As the volume of water increases its mass increases in direct proportion.
The gradient of the graph equals the density of water.
Error
The main cause of error in this experiment is reading the volume of water.
Care should be taken to read the volume at eye level, with the measuring cylinder placed on the bench.
The density of water changes with temperature so care must also be taken to keep the water at a constant temperature throughout the experiment.