Introduction to Gases

Barbara Pawela Retired


5-6th grades

1. To demonstrate that gases are a state of matter.
2. To generate a number of gases.
3. To discover some properties of gases.
4. To compare some of the properties of different gases.
5. To relate the Kinetic Molecular Theory to the change of state
of matter.

Materials: Activity 1 Activity 2 Activity 3 Activity 4 balloons balloons dry yeast 1/2 t. powdered sulfur plastic bags vinegar hydrogen peroxide 1/2 t. iron filings clay baking soda large test tube crucible transparent small bottles balloon hot plate pan or bowl egg shells wooden splint candle wooden splint matches matches matches Activity 5 (optional) Activity 6 a few iodine crystals shoe box sealed flask small light-weight spheres 5 mL hydrochloric acid a few zinc chips large test tube Strategy:

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 lab safety rules.

Activity 1 Begin the presentation by asking the students what they see in front of their nose. Let students respond. Tell the students to wave their hand in front of their face. Discuss and conclude that although they could not see the air in front of their face, they could feel it as a breeze against their skin. Spray a little room deodorant or perfume. Ask the students to raise their hand when they smell something. The smell will diffuse and, depending on the distance away from the source, the students will raise their hands at intervals. Have some of the students blow air into balloons, and some students blow air into plastic bags. Discuss and conclude that air takes up space. Wave a sound tube or use something to make a sound. Discuss and conclude that the sound vibrations are being transmitted through the air. These three demonstrations help to show that: although the air cannot be seen, it can be felt; an odor can be diffused through it; and sound vibrations can be transmitted through it, air is matter and does exist and take up space. Discuss and conclude that air is a mixture of gases. Stick clay pieces on the base of a candle and on the opposite sides of the rim of a tall glass. Stand the candle in a transparent container. Pour water into the container 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 will rise. Discuss with the students and conclude that the candle burned until it used up all the oxygen, which is one of gases in air. The water rises about one-fifth of the way up the glass because oxygen, which is necessary 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 some other gases. Activity 2
Teacher holds an open bottle of ammonia and lets the students take a waft.
Explain that the pungent odor is ammonia gas that is escaping from the water
in which it is dissolved.
To generate carbon dioxide put about one tablespoon vinegar into a empty
small pop a bottle. Put about three tablespoons baking soda inside a balloon.
Place the open end of the balloon over the top of the bottle. Hold the
balloon so that the baking soda will fall into the bottle. The reaction will
release carbon dioxide gas and the balloon will expand. Discuss with the
students what they observed and conclude that a gas was released and that a
gas takes up space.

Activity 3 Place 1/2 teaspoon into a large test tube. Add about 10 mL of hydrogen peroxide. Immediately place the open end of the 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 and tie the open end of the balloon to keep the gas in the balloon. 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. Activity 4 Put 1/2 teaspoon powdered sulfur into a crucible. Add 1/2 teaspoon iron filings. Heat the crucible. Make sure that there is good ventilation, because an acrid gas will be released in the reaction. Activity 5 (Optional teacher demonstration )
To make an iodine gas tube place a few iodine crystals into a flask and seal
it with a stopper. Gently heat the flask for about 10 seconds. The crystals
will sublimate and a purplish gas will be visible in the flask. CAUTION:
Iodine gas is poisonous.
To generate hydrogen gas: Place a few zinc chips in the test tube. Add about
5 mL of dilute hydrochloric acid. CAUTION: HYDROCHLORIC ACID IS VERY CAUSTIC.
Cover the test tube to prevent the gas from escaping. Light a match and bring
it close to the test tube's mouth: uncover the test tube. Hydrogen gas was
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.

Activity 6 Take a shoe box and make cuts in the box to make flaps which can be opened. Fill the shoe box with small light-weight plastic or styrofoam balls. Use this to model the Kinetic Molecular Theory. Have the shoe box filled about three-fourths full with the balls. With the cover off, gently shake the box. Explain that the although the balls can move, they are restricted. This is a model of the way the molecules are arranged in a solid. Shake the box harder, so that the balls will have more motion. Explain that this models the way the molecules behave in a liquid. Finally open the flaps in the box and shake the box vigorously. The "molecules" should come out of the box and spread out. Explain that this models the way gas molecules behave. Performance Assessment:

Students' responses during the activities and follow-up discussions will be
used as the performance assessment.

Return to Chemistry Index