Part 2: Identifying an Unknown Liquid

How can you identify an unknown liquid based on the way it behaves on different surfaces?

In this activity you will be presented with an unknown, which is one of four known liquids as well as a variety of surfaces and tests to conduct. You will conduct four tests (beading, pull, absorbtion, and evaporation) to identify the unknown. You will realize that by using a combination of results from two or more tests, you can successfully identify the unknown.

View a past student sample of Physical Properties of Liquids.

Materials needed for each group

• • Tap water in cup

  • Isopropyl rubbing alcohol (70%) in cup

  • Detergent solution in cup

  • Salt water in cup

  • 1 Additional unknown liquid in cup

  • 5 Droppers (labeled W, A, S, D, and U)

  • Toothpicks

  • Permanent marker

  • Brown paper towel

  • Wax paper

  • Pencil

  • Safety goggles

Notes about the materials

• • Be sure you wear properly fitting goggles.

  • Beading Test Procedure

    • Use a permanent marker to label five areas on a piece of wax paper (water, alcohol, detergent, salt water, and unknown).

    • Pick up a small amount of water in its labeled dropper.

    • Squeeze 5 drops of water into its labeled area. Watch the liquid bead up for about 1 minute.

    • Record observations and make a labeled diagram in the proper box of the Physical Properties of Liquids assignment sheet.

    • Repeat steps 2-4 with the alcohol, detergent, salt water and unknown liquids.

  • Pull Test Procedure

    • Gently insert a toothpick into the water bead (use the same bead that you made in the beading test) and drag it around a little bit.

    • After dragging it around, try to break the bead into smaller beads.

    • Record observations and make a labeled diagram in the proper box of the Physical Properties of Liquids assignment sheet.

    • Repeat steps 1-3 with the alcohol, detergent, salt water and unknown liquids.

  • Absorbtion Procedure

    • Use a pencil to label five areas on a piece of brown paper towel (water, alcohol, detergent, salt water, and unknown).

    • Pick up a small amount of each liquid in its dropper and keep it in the dropper.

    • At exactly the same time and from the same height, squeeze 3 drops of each liquid into its labeled area. Watch the liquids absorb for about 1 minute.

    • Record observations and make a labeled diagrams in the proper boxes of the Physical Properties of Liquids assignment sheet.

  • Evaporation Procedure

    • Use a pencil to label five areas on a piece of brown paper towel (water, alcohol, detergent, salt water, and unknown).

    • Pick up a small amount of each liquid in its dropper and keep it in the dropper.

    • At exactly the same time and from the same height, squeeze 1 drop of each liquid into its labeled area. Watch the liquids evaporate for about 1 minute.

    • Record observations and make a labeled diagrams in the proper boxes of the Physical Properties of Liquids assignment sheet.

    • Answer the questions at the bottom of part 2 of the Physical Properties of Liquids assignment sheet using and citing evidence from your four tests.

  • Physical Properties of Liquids Part 1

  • Physical Properties of Liquids Part 3-4

From Inquiry In Action