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How to Determine the Density of Water

Density is a measure of mass concentration, the weight of a material contained in a standard unit of volume. In scientific terms density is defined as "mass per unit volume" and expressed by the equation D = M/V. The numerical value of density depends on the measurement units used for mass and volume. For example, a density value expressed in grams per liter is different from the value in pounds per cubic foot. Incompressible substances such as water have a fixed density at every temperature. Water does vary significantly in density across its liquid temperature range of 32 to 212 degrees Fahrenheit, and has maximum density 1.000 gm per ml at 39 degrees Fahrenheit.

Graduated measuring cylinder, capacity 100 ml
Isopropyl alcohol
Facial tissue
Plastic disposable pipette
Room or laboratory thermometer
Container of tap water at room temperature
Electronic weight scale

Instructions

- 1
  
  Graduated cylinder
  
  Add about 25 ml of alcohol to the cylinder. Stop-up the top with a thumb and shake for about a minute. Empty the cylinder, and suspend it upside down for several
  
  minutes until you are sure it is dry and there is no smell. This will remove any dirt or contamination that could cause an error in volume measurement.
- 2
  
  Electronic weight scale
  
  Place the empty cylinder in the center of the scale pan and weigh it to highest accuracy. Remove the cylinder and record the value. Do not turn off, move or adjust the scale in any way.
- 3
  Fill the cylinder with water to just below the 100 ml mark, taking care not to wet the outer surface of the cylinder. Use a tissue to thoroughly remove any exterior water.
- 4
  
  Disposable pipette
  
  Raise the cylinder to bring the 100 ml mark directly in front of your best-trained eye. Add water dropwise using the pipette until the curved surface of the water, known as the "meniscus," appears to merge with the 100 ml mark.
- 5
  Place the cylinder on the scale pan and record the weight.
- 6
  Record the room temperature.
- 7
  Subtract the weight of the cylinder from the weight of water plus cylinder to obtain the weight of 100 ml of water. Record the result
- 8
  Divide the weight by 100. The result is the density of water expressed in gm/ml at room temperature.

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