Pressure, Atmospheric Pressure
8th grade Physical Science
Density and Buoyancy
- All objects experience a buoyant force when immersed in a fluid. As a basis for understanding this concept:
- Students know how to predict whether an object will float or sink.
Investigation and Experimentation
- Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
f. Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed=distance/time, density= mass/volume, force = pressure × area, volume = area × height)
Prior knowledge & experience:
Predict what will happen when the glass tube in the flask is turned upside down and placed in the yellow water in the beaker.
Why does the water go back up into the flask?
The cooling gases in the flask create lower pressure in the flask and there is higher pressure outside the flask. The water moves to the lower pressure area.
500 mL flask tongs (curved at the top) safety goggles
1000 mL beaker 1 holed rubber stopper with 20 cm glass tube hot plate
- Fill the flask with 350 mL of water. Put several drops of blue food coloring into the water. Securely fit the rubber stopper with the glass tubing into the flask.
- Fill the beaker with 500 mL of water. Put several drops of yellow food coloring into the water.
- Put on the safety goggles.
- Heat the flask on the hot plate until it is boiling rapidly and steam is rushing out through the glass tubing.
- Turn off the hot plate.
- Using the tongs grasp the flask under the lip at the top and tip the glass tube into the yellow water in the beaker.
- Hold the flask in this position until the blue water from the flask rushes into the yellow water. Continue holding the flask and the gases in the flask will cool. (I usually count slowly to 5 during this time). Suddenly the water will rush back up into the flask creating a fountain.
Photographs and Movies