Steel Wool Experiment

As Gary Larson once said in his

The Far Side

comic strip, “The sheep that gives us steel wool has no natural enemies”

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Setting up the experiment:

1) Wrap a paper clip around your piece of steel wool so that it makes a hook.

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Setting up the experiment (cont.)

2) Soak the steel wool in vinegar for 30 sec.

3) Rinse the vinegar off of the steel wool with running water for about 10 seconds.

4) Shake off the excess water into the sink.

5) Put the steel wool into a test tube (hook side facing the open end) 6) Push it to the end

Setting up the experiment (cont.)

7) Fill a beaker about half way with water.

8) Invert the test tube with the steel wool in it and place it into the beaker of water.

9) Notice how the water does not enter the test tube when you do this due to the air pressure.

10) Label your set up and place it in the designated location for 24 hrs.

Background Information

What gas do you think we are trying to measure with this experimental set-up?

1) Carbon Dioxide 2) Oxygen 3) Nitrogen 4) Hydrogen 5) Water Vapor

What will happen to allow us to measure the amount of Oxygen in air?

1) The acid from the vinegar will dissolve the steel wool into Oxygen 2) The Oxygen in the air will turn into water when it combines with the hydrogen ions of the vinegar 3) The Oxygen in the air will oxidize the iron in the steel wool forming a solid —rust.

The chemistry…

+  Fe 2 O 3 Iron + Oxygen  Iron Oxide (Rust) (solid) (gas) (solid)

What will be the most visible consequence of the rusting?

1) The water level in the beaker will get much lower 2) The water level in the beaker will get much higher 3) The water level in the test tube will get much lower 4) The water level in the test tube will get much higher

Day 2 Instructions:

• Develop a method to determine the exact percentage of Oxygen in our atmosphere.

• Be sure not to remove your test tube until you have taken the necessary measurements.

•Clean up when you are done by using the hook tool and throw the steel wool in the trash. Put all materials away.

Assignment (also on website):

1) How did the water level in the test tube change over the course of this experiment? WHY did this happen?

2) Use your data to explain your estimate of the percentage of Oxygen in Earth's atmosphere. Clarify why this method is logical and possible sources of error in the experiment.

3) How close is your estimate to what experts say? Calculate your percent error: % error = Absolute value of (your estimate - what experts say) divided by what experts say *100 4) Suppose you went to another planet, performed the same experiment and found the following data: Volume of empty test tube = 38 ml Volume of water in test tube at the end of expt. = 13 ml Volume of steel wool used = 0.5 ml