Barbara Pawela - Retired
It's a Gas!
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Barbara Pawela Retired
1. To demonstrate that gases are a state of matter.
2. To generate some gases.
3. To investigate some properties of gases.
4. To compare some properties of different gases.
Activity 1 Activity 2 Activity 3 Activity 4
sound maker dry yeast balloons ammonia
spray perfume hydrogen peroxide vinegar 5 ml HCL
plastic bags large test tube baking soda a few zinc
pie pan balloon small pop bottles chips
small candles matches wooden splint large test
piece of clay wooden splint matches tube
Set up stations for the different activities and have the materials
needed for each activity ready. Group the students into teams of four.
Remind the students about science safety rules.
Begin the demonstration by asking the students to put their hands about
12 inches away from their face. Ask them what they see in the space
between their nose and their hands. Tell the students to wave their hands
in front of their face. Discuss and conclude that although they could not
see the air in front of their face, they could feel the breeze against
Spray some perfume. Ask the students to raise their hands when they smell
something. The odor will diffuse and, depending on the distance away from
the source, the students will raise their hands at intervals.
Wave a sound tube or use something else to make a sound. Discuss and
conclude that the odor was being diffused; and the sound vibrations
were being transmitted through the air.
Pass out plastic bags (like the ones from the produce section) to each
group. Tell the students to wave the bag and scoop the air, and then to
close the bag. Discuss and conclude that air takes up space.
These demonstrations help to show that although air cannot be seen, it
can be felt; an odor can be diffused through it; sound vibrations can be
transmitted through it; and it takes up space.
Stick clay pieces on the base of of a candle and on opposite sides of the
rim of a clear tall glass. Stand the candle in the pie pan. Pour water
into the pie pan so that about one third of the candle is in the water.
Light the candle for a few seconds, then place the open end of the glass
over the candle. Observe what happens. In a short while the flame goes
out. The water level in the glass rises. Discuss and conclude that the
candle burned until it used up the oxygen, which is one of the gases in
air. The water rises about one-fifth of the way up the glass because
oxygen, which is necssary for combustion, makes up about one-fifth of the
gases in air. The gases left in the glass are about four-fifths nitrogen,
with trace amounts of other gases.
Place 1/2 teaspoon of dry yeast into a large test tube. Add about 10 ml of
hydrogen peroxide. Immediately place the open end of a balloon over the
open end of the test tube. There will be a reaction in which oxygen gas is
released and the balloon will inflate. Take the balloon off. Take a wooden
splint and light it with a match. Blow out the flame so that the splint is
glowing. Insert the glowing splint into the test tube. The oxygen gas will
reignite the splint. Explain that although oxygen itself will not burn, it
is necessary for combustion.
To generate carbon dioxide gas put about one tablespoon of vinegar into a
small pop bottle. Put about two tablespoons of baking soda inside a
balloon. Place the open end of the balloon over the top of the bottle. The
reaction will release carbon dioxide gas and the balloon will expand.
Repeat the glowing splint test (see Activity 2) by placing the glowing
splint into the pop bottle. The splint goes out and does not burn.
Activity 4 (optional teacher demonstration)
To generate hydrogen gas: Place a few zinc chips in a test tube. Add
5 mL of dilute hydrochloric acid. CAUTION: HYDROCHLORIC ACID IS VERY
CORROSIVE. Cover the test tube to prevent the gas from escaping. Light a
match and bring it close to the mouth of the test tube. Hydrogen gas is
produced in the reaction between the zinc and hydrochloric acid. This gas
is highly flammable and gives off a characteristic small explosion, when
ignited in a test tube.
Teacher holds an open bottle of ammonia and lets the students take a weft.
Explain that the pungent odor is ammonia gas escaping from the water in
which it is dissolved.
Students' responses during the activities and follow-up discussions.