Demonstrations of Gas Laws Lab

Introduction:

As long as the amount of a gas remains constant, the pressure, volume, and temperature of a gas are all related by the combined gas law:

If the temperature of a gas is held constant as well as the amount, then the pressure and volume of that gas are related by Boyle’s Law:

At constant temperature, P1V1 = P2V2

When the volume of a gas is decreased at constant temperature, its pressure increases. When a gas’s volume is increased at constant temperature, its pressure decreases.

If the pressure of a gas is held constant, then the temperature and volume are related by Charles’s Law:

At constant pressure,

When the temperature of a gas is increased at constant pressure, its volume increases. If the temperaure is decreased, the volume decreases also.

If the volume of a gas is held constant, then the pressure and temperature are related by Gay-Lussac’s Law:

At constant volume,

When the temperature of a gas is increased at constant volume, the pressure of the gas increases as well. If the temperature of the gas decreases, so does the pressure.

In today’s experiment you will observe several demonstrations of the gas laws and then attempt to explain them using what you have learned about gases.

Materials and Equipment:

beaker tongs

birthday candle

empty plastic bottle with cap

empty soda can

Erlenmeyer flask

food coloring

hot plate

ice

large glass dish

matches

medicine dropper

petroleum jelly

shallow dish

Safety Considerations:

Exercise extreme caution when using the hot plate.

Procedure:

Part One: The Cartesian Diver

  1. You will need a clear plastic bottle with a cap and a medicine dropper.
  2. Fill the bottle to the very brim with water. Drop the medicine dropper into the bottle with the bulb up. The dropper should float in the water.
  3. Close the bottle tightly.
  4. Squeeze the bottle gently. Record your observations in the Data and Observations section.
  5. Stop squeezing the bottle. Record your observations.
  6. Squeeze the bottle again but this time closely watch the water inside the dropper.
  7. Answer the questions in the Conclusions section.
  8. Pour the water out of your bottle. Leave the bottle and dropper for the next lab section.

Part Two: Happy Birthday

  1. You will need a shallow dish, a birthday candle, some petroleum jelly, and Erlenmeyer flask, and possibly some food coloring.
  2. Put a small glob of petroleum jelly in the center of the shallow dish. Stand a birthday candle upright in the petroleum jelly. Don’t use a lot of extra petroleum jelly or the demonstration won’t work properly.
  3. Add 1 – 2 centimeters of water to the dish. You may add one or two drops of food coloring to make the water more visible. It isn’t mandatory that you do so. Don’t get the wick of the candle wet as you pour the water.
  4. Light the birthday candle.
  5. Place the Erlenmeyer flask mouth down over the candle. Stand it up right in the dish over the candle. Refer to the diagram at right.
  6. Observe what happens. Record your observations in the Data and Observations section.
  7. Answer the questions in the Conclusions section.
  8. Pour the water in the sink. Clean the petroleum jelly out of the dish. Leave the candle to dry for the next lab section.

Part Three: The Invisible Giant

  1. You will need a hot plate, an empty aluminum soda can, a pair of beaker tongs, a large glass dish, and some ice.
  2. Add a little bit of water to the empty soda can. Place the soda can on the hot plate and turn on the hot plate.
  3. While the water in the can is heating up, fill the dish about ¾ full of ice water.
  4. When the water in the can has reached a boil, quickly use the beaker tongs to move it from the hot plate and place it mouth down into the ice water.
  5. Record your observations in the Student Data Section.
  6. Answer the questions in the Conclusions section.
  7. Throw the can away. Pour the ice water down the sink. Make sure the hot plate is unplugged.

Name: ______Date: ______Pd: ______

Demonstrations of Gas Laws Lab

Data and Observations:

Observations for Part One: The Cartesian Diver

Observations for Part Two: Happy Birthday

Observations for Part Three: The Invisible Giant

Conclusions:

Part One: The Cartesian Diver

  1. An object floats in water when it is ______dense than the water.
  1. Why does the dropper initially float in the water?
  1. What happens to the volume of the air trapped in the dropper when you squeeze the bottle?
  1. If the air in the dropper contracts, what happens to its density?
  1. Explain why the dropper sinks when you squeeze the bottle. Use terms like pressure, volume, compressible, and density.

Part Two: Happy Birthday

  1. What did you see around the mouth of the flask when you first put it into the water. How can you explain this? Use terms like temperature and volume in your explanation.
  1. What effect did the water have on the gas inside the flask? How do you know?
  1. Many people mistakenly believe that the water rises into the flask because the candle is removing oxygen from the air. This explanation is not correct because the candle replaces oxygen with carbon dioxide. What is the actual explanation for why the water rose up into the flask? Use terms like cool, volume, and pressure in your explanation.

Part Three: The Invisible Giant

  1. Why did the can collapse when it was placed mouth down in the ice water?
  1. Do you think the can would have collapsed if it had been placed in the water mouth up? Why or why not?
  1. If you open a soda bottle then close it and place it in the refrigerator, you’ll often find that the soda bottle partially caves in when you look at it later. How can you account for this phenomenon? How is it related to what you witnessed in this demonstration?

Part 4: Boiling Cold Water (CLASSROOM DEMONSTRATION)

  1. What happened to the water as it was inverted?
  1. Why did the water boil even though it was taken off the hot plate?(Talk about pressure & temperature)
  1. What law did we observe?