Janice VanCleave’s Crazy, Kooky, and Quirky Chemistry Experiments
expando Purpose To observe the effects of expanding gas Materials empty 2-liter plastic soda bottle timer ½ cup 125 ml tap water 1 tablespoon 15 ml dishwashing liquid saucer NOTE This experiment requires a freezer Procedure 1 Place the empty soda bottle in a freezer for two minutes or more 2 While you are waiting mix the water and dishwashing liquid together in the saucer 3 Remove the soda bottle from the freezer and dip its open end in the soapy water 4 Stand the bottle on a table and observe what happens NOTE If a soap bubble does not form over the mouth dip the bottle in the soapy water again Results A soap bubble forms over the mouth of the bottle Why As the temperature of molecules decreases molecular motion decreases and the cohesive force increases pulling the molecules closer together Cooling caused the air molecules inside the bottle to move closer together removed from the freezer the cold air inside it heated up 8 Janice VanCleave’s Crazy Kooky and Quirky Chemistry Experiments
and the air molecules moved farther apart Some of the air was forced out of the bottle and pushed on the soap film across the mouth of the bottle making a soap bubble 9 Expando
Foamy Purpose To show how pressure affects dissolved gases Materials plastic cereal bowl 16-ounce 480 ml glass soda bottle ¼ cup 63 ml tap water two effervescent antacid tablets Procedure 1 Set the bowl on a table and stand the soda bottle in it 2 Pour the water into the bottle 3 Break the antacid tablets in half 4 Quickly drop the broken tablets into the bottle of water and immediately cover the mouth of the bottle with the palm of your hand 5 Observe the contents of the bottle 6 When it becomes difficult for you to keep your hand over the bottle because of the pressure against your palm quickly lift your hand and observe what happens to the bottle’s contents Results The antacid tablets mix with the water producing bubbles When the bottle is covered bubbles are seen in the water and a small amount of foam forms on the surface of the water Uncovering the bottle produces a bubbly foam that rises within the bottle Why When the antacid tablets are combined with water carbon dioxide gas is produced Covering the opening of the bottle prevents the 10 Janice VanCleave’s Crazy Kooky and Quirky Chemistry Experiments
gas from escaping As more gas is produced the pressure inside the bottle increases Increasing the pressure on any mixture of liquid and gas results in more gas dissolving in the liquid and a reduction in the size of the gas bubbles Raising your hand allows the excess gas above the water to escape which quickly reduces the pressure pushing down on the surface of the water At this lower pressure many gas bubbles move upward and break through the surface of the liquid Each bubble rises rapidly expands and pushes some of the liquid upward resulting in the rising foam 11 Foamy
