Problem: How do you use a balance to find the mass of a liquid?

Any object that is made of molecules has mass. Mass is defined as the amount of matter in an object. Since liquids are made of molecules, they have mass, but you cannot place a liquid directly on the pan of a balance to get the measurement.

The techniques you will use are similar to how you would find your pet’s mass if he/she won’t stay on the scale. First, you would find your own mass, and then you would pick up your pet and find your combined mass. Then, you would subtract the two to get just the mass of your pet.

Directions: Using the triple beam balance, fill in the chart below and answer the questions. Do not forget to label your answers.

Part 1:

Volume of Water / Mass of Empty G.C. / Mass of G.C. with Water / Mass of Water
(Column 3 – Column2)
4.0 mL
6.0 mL
9.0 mL

If you measured carefully, you should notice that the mass of 1.0 mL of water is about 1.0 g. This is a unique relationship that needs to be understood.

  1. If you filled a graduated cylinder with 5.8 mL of water, what would the mass of the water be? ______
  2. A graduated cylinder has a mass of 28.2 g with 2.1 mL f water in it. What is the mass of the graduated cylinder alone? ______
  3. What is the mass of 1.0 mL of water? ______

Part 2:

Repeat the experiments with salt water.

  1. Do you think that the salt water has the same mass as tap water? ______
  2. Do you think it will have more mass or less mass? ______

Volume of Salt Water / Mass of Empty G.C. / Mass of G.C. with
Salt Water / Mass of Salt Water
(Column 3 – Column2)
4.0 mL
6.0 mL
9.0 mL
  1. For the same volumes, how does the mass of salt water compare to that of
    tap water? ______

Part 3:

Now, repeat the experiment with rubbing alcohol.

  1. Do you think rubbing alcohol has the same mass as tap water? ______
  2. Do you think it will have more mass or less mass? ______

Volume of Rubbing Alcohol / Mass of Empty G.C. / Mass of G.C. with Rubbing Alcohol / Mass of
Rubbing Alcohol
(Column 3 – Column2)
4.0 mL
6.0 mL
9.0 mL
  1. For the same volumes, how does the mass of rubbing alcohol compare to
    that of tap water? ______

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