The main variables in a science experiment are the independent variable, the dependent variable and the control variables.
The Independent Variable is what we change or control in the experiment.
The Dependent Variable is what we are testing and will be measured in the experiment.
The Control Variables are what we keep the same during the experiment to make sure it’s a fair test.
In this experiment the:
Remember - these variables are controlled (or kept the same) because to make it a fair test, only 1 variable can be changed, which in this case is the volume of the object.
As the volume of the material increases, the mass will also increase.
Justification for the prediction
The greater the volume of the object the greater the number of atoms present.
This will result in the object having greater mass.
Six regular objects of the same material but different volumes, a half-metre rule, a top pan balance.
|Mass/g||Length/cm (1)||Length/cm (2)||Average length/cm||Breadth/cm (1)||Breadth/cm (2)||Average breadth/cm||Height/cm (1)||Height/cm (2)||Average height/cm||Volume/cm3|
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 = = density
Calculate the gradient of the graph and hence the density of the object.
We can see from the graph that as the volume of the object increases its mass also increases.
This agrees with our prediction.
In fact, since the line of best fit is a straight line through the origin, we can be even more precise.
We can say that the volume of the object is directly proportional to its mass.
As the volume increases the mass of the object increases in direct proportion.
The gradient of the graph equals the density of the material.
Cause of error
The main cause of error in this experiment is the measurement of length, breadth and height.
This can be kept to a minimum by repeating each measurement and calculating the average.
A measuring cylinder, a top pan balance, tap water.
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.
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.