Tuesday, 22 October 2013

Air experiments

Materials used for experiment:
  • big box/sink → water container (each container is a station.)
  • water
  • 2 glass jars/2 beakers/2 graduated or measuring cylinders *these will be referred to as jars in the method.
  • 3 balloons
  • Erlenmeyer flask (triangular shaped)
  • graduated cylinder
  • vinegar
  • baking soda
  • scoop
  • newspaper/paper
  • fire source

Experiment 1
  • Read the method and predict what will happen to the jar-water system after the last step.
Method 1
  1. Submerge the jar in the container of water until the jar is full of water.
  2. Rotate the jar so its mouth is facing down.
  3. Slowly lift the jar until its mouth is just below the surface of the water.
  • the water stays in the container

Deductions Summary
  • Air pressure pushes on the water in the container, so that the water does not fall down.

Experiment 2
  • Read the method and predict what will happen to the jar-water system after the last step.
Method 2
  1. Put the jar in the water with the length horizontal until half of it is full of water.
  2. Rotate the jar so its mouth faces down and its length is vertical.
  3. Submerge another jar and fill it with water and turn it so its mouth is facing down.
  4. Pour the air from the first jar into the second jar by holding the mouth of the second jar above the first jar.  Tilt the first jar so that the air escapes and bubbles up into the second jar.
    • air from one container displaces the water in the other container

    Deductions Summary
    air can displace water; displace means it pushes it out.

Method 3
  1. Inflate one of the balloons to a diameter of about 10 cm.  Deflate it.  Do not tie it!
  2. Practice putting the mouth of the balloon over the mouth of the flask.  
  3. Put about 3 scoops of baking soda into the balloon.
  4. Measure 10mL of vinegar using the measuring cyclinder.
  5. Pour the 10mL of vinegar into an Erlenmeyer flask.
  6. Put the balloon over the mouth of the flask.  Empty the baking soda from the balloon into the flask.
  7. Wait and let the balloon fill up with gas.  Shake the flask gently to complete the reaction faster.
  8. Remove the balloon and tie a knot in it.
    • bubbles were produced gas was produced → indicates a chemical reaction
    • balloon moved and it inflated
    Deductions Summary
    • chemical reactions can change matter’s state (liquid reacting with a solid produced a gas (and a liquid))
    • gas can be used to change the shape and move objects

Experiment 3 & 4
Read the method and predict how the gases in the balloon may be different.

Method 4
  1. Inflate a balloon to about the same size as the balloon in Method 2.
  2. Tie a knot in the balloon.
  3. Compare the gas in the first balloon to the second balloon, and write down your observations.
    • baking soda and vinegar balloon fell faster than the air filled balloon (→ indicates that it was heavier)

    Deductions Summary
    • different kinds of gases with different properties:
      • carbon dioxide (CO2)
      • helium (He)
      • hydrogen (H2)
      • Nitrogen (N2) ~80 % of atmosphere
      • Oxygen (O2) ~20 % of atmosphere
      • Methane (CH4)
      • carbon monoxide (CO)

Experiment 5
Predict what will happen with the balloon-hand-water-tank system.

Method 5
  1. Get a big balloon from Mr. Pro.
  2. Inflate the balloon to a size that’s a little wider than the mouth of the jar.
  3. Submerge the balloon into the water and write down your observations.
    • the balloon pushes up on your hand
    • water level in the container rises
    Deductions Summary
    • objects that are less __dense___ will rise in fluids than more ____dense___
    • fluids become displaced when things are put in them.
    • the fluid that is displaced pushes up on objects that are displacing it

Experiment 6
Explain what happened to the balloon.

Method 6
  1. Crumple up half a piece of paper.
  2. Light the paper on fire from the bottom and place it in the jar.
  3. Put the balloon on top of the jar so the mouth is sealed.
  4. Wait until the flame goes out.
  5. Grab and gently pick up the balloon.
    • balloon went in to the jar, (and then it popped)
    • The jar became warmer
    Deductions Summary
    • temperature: the burning increased the temperature in the jar
    • density: when air heats up, it rises because it becomes less dense
    • pressure: when there’s less dense air in the jar, there’s less pressure.  The air outside the jar has more pressure.  The high pressure air flows to low pressure inside the jar.  The balloon is between the airs so the air pushes the balloon into the jar.

Summary: All the above concepts are connected to matter:
  • Fluids take the shape of what they are in.  Fluids flow.  Water and air are both fluids.  
  • Fluids exert pressure on objects in them.  Air pressure pushes on everything in the atmosphere.
  • Fluids will move from places of high pressure to places of low pressure.
  • Air can displace water.  Displace means take the place of.  
  • Matter has a variety of properties.  There are different kinds of gases, each with similar and different properties.
  • Density is mass divided by volume (density = massvolume).
  • Objects that are less dense than the fluids they are in will rise.
  • If the temperature of a gas increases in an open container, the gas will becomes less dense and rise.

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