Determining the volume of a plastic cup is a simple and fundamental scientific endeavour. Volume measurement is three dimensional and can be approximated with mathematics, or determined more precisely with actual volume measurements, or weight measurements using water and a scientific balance. Using all three methods will give students an idea of how precise or accurate each method is, and provide a basis for understanding scientific measurements.

Approximate the volume using mathematics. Use the equation for a cylinder to estimate the volume. The volume of a cylinder is pi times radius squared times the height of the cylinder. Use an average of the radius at the top and bottom of the cup for estimation.

Measure the volume with a graduated cylinder. Fill the cup to the top with water.

Pour the contents of the cup into a graduated cylinder. Measure the volume to the smallest increment possible on the graduated cylinder. Dump out the water and repeat to determine how accurate this method is.

Measure the weight of water in the cup. Place the cup on a scientific balance and zero the balance.

Fill the cup with distilled water near to the top. Continue adding water with an eyedropper or syringe until it is completely full. Record the weight in grams.

Determine the volume. Distilled water weighs exactly 1 gram per millilitre. Millilitres is a volume measurement. Convert grams to millilitres 1:1 and you have the volume of the plastic cup. Compare the results from the three different methods to determine which is the most accurate.

### Things you need

- Plastic cup
- Distilled water
- Scientific balance
- Eye dropper
- Graduated cylinder

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