Science - Understanding the concept of Pressure & Energy Density
Reference: The Text for this section may be found in the print versions of
Sourcebook for Teaching Science 5.1.2, Hands-On Chemistry 2.4.1, Hands-On Physics 4.1.1
VIDEO: Collapsing Cans
VIDEO: Collapsing Tank Car
DIAGRAM: Collapsing Can
The Collapsing Can -- Relative Volumes of Liquids and Gases: Obtain a large beaker or bucket and fill with water. Pour water into an empty aluminum soft drink can to a depth of approximately 1 cm and place it on a hot plate until the water boils. Do not allow the can to boil dry! As soon as the water begins to boil, remove the can from the heat source and hold it in an upright position with its base in the water. Is there any change in the can? Repeat the process, only this time invert the can and submerge the opening in the water as illustrated in Figure D. Is there any change in the can? When one milliliter of water boils (vaporizes) it changes into approximately 1000 milliliters of steam. As water in the can boils, it displaces air which was originally in the can. When the can is sealed and cooled, the steam condenses to liquid water, but now occupies only 1/1000th the volume it occupied as steam! In other words, for every milliliter of water that condenses inside the can, approximately one thousand milliliters of vacuum are left behind. The air pressure outside the can remains the same while the pressure inside drops, creating a difference in pressure that collapses the can.
Hands-On Physics 4.1.1-teacher section page 206; Air Pressure Fountain
VIDEO: Upside down flask
VIDEO: Air Pressure fountain
DIAGRAM: Air Pressure Fountain
The Air Pressure Fountain -- Relative Volumes of Liquids and Gases: Caution: This demonstration should be performed by the teacher only. Fill a 1000 mL beaker with water and add a few drops of food coloring to improve visibility. Place approximately 20 mL of uncolored water in a 500 mL flask and heat uncovered (Figure B). NEVER HEAT A SEALED CONTAINER! The flask fills with water vapor as the water boils.
Allow the water to boil until almost all is gone. This will ensure that the environment inside the flask is almost entirely composed of water vapor. Using heat-resistant gloves, remove the flask from the heat source and immediately place a one-hole stopper, that has been fitted with a hollow glass tube as shown in Figure C, in the mouth of the flask. Quickly invert the flask and support it on a ring stand as illustrated. The glass tubing should extend nearly to the bottom of the 1000 mL beaker. As the flask cools, the water vapor inside condenses and the pressure drops. While the pressure inside (internal pressure) the flask drops, the pressure outside of the flask (atmospheric pressure) remains constant, creating a pressure differential. As a result, water is slowly pushed up the tube into the flask (Figure C). As water enters the partially evacuated flask it absorbs heat and further cools the internal atmosphere. The remaining vapor condenses rapidly, resulting in a dramatic drop in pressure, and a strong jet of water is pushed into the flask to fill the void. Once it has cooled and the water level has stabilized, remove the flask assembly and set it on a table. Mark the height of the base of the stopper on the side of the flask using a grease pencil or tape. Remove the stopper assembly, pour the water into a graduated cylinder, and determine its volume (V1). Now fill the flask to the line previously marked and measure this volume as before. This second volume (V2) represents the volume originally occupied by water vapor. What percent of the original water vapor volume (V2) was lost as gaseous water condensed: (V1/V2) x 100%? This provides a rough estimate of the reduction in volume that accompanies the condensation of gases to liquids.
VIDEO: Boiling by evacuation
VIDEO: Balloon in evacuated chamber
SIMULATION: Phases of matter (PHET)
SIMULATION: Gas Laws - Pressure; gas in a syringe (Edumedia)
Source: Hands-On Physics 4.1.4
DIAGRAM: Candle in Flask
SIMULATION: Phases of matter (PHET)
SIMULATION: Gas Laws (Edumedia)
Part 1: "Suction" from Candles? Light a candle and stand it upright in the middle of a pan, and secure it with melted drippings. Fill the pan half-full with water. While the candle is still burning, place a narrow glass or graduated cylinder over the candle (figure K). Carefully observe the base of the container, the water level in the container, and the flame. Record your observations in the table. When does the water level in the jar rise (figure L)? Why does it rise? Indicate on figure L where the pressure must be higher and where it must be lower to cause the results you observed.
Part 2: "Suction" from Burning Paper? Find a flask or jar that has a mouth slightly smaller than the diameter of an egg. Peel the shell from a hard boiled egg. Crumple a piece of notebook paper and after lighting it on fire, quickly stuff it in the flask. Immediately place the egg over the mouth of the flask and observe, paying particular attention to the egg when it is first placed on the flask (figure M). When does the egg enter the flask or bottle? Why does it enter? To remove the egg from the bottle, invert the bottle so the egg settles in the neck. Gently heat the flask with a candle or alcohol burner until the egg is forced out by expanding air. Light a second piece of paper and place it inside a flask. While holding
the flask with a hot pad, quickly place the egg in the neck and invert the bottle while holding the egg in place. Does the egg rise into the flask against gravity? Explain.
VIDEO: Boiling by cooling
SIMULATION: Phases of matter (PHET)
SIMULATION: Gas Laws (Edumedia)
STUDENT Generated models - sample
CCC-4 - Energy
SIMULATION: Phases of matter (PHET)
SIMULATION: Gas Laws (Edumedia)
Alveoli Anatomy (Biodigital Human)
How many examples of pressure can you think of?
Science
SIMULATION: Phases of matter (PHET)
SIMULATION: Gas Laws (Edumedia)
Mechanics
VIDEO: Hero's Engine
VIDEO: Water Rockets - Slow motion
VIDEO: Space Shuttle Rockets
SIMULATION: Boyle's Law, Charles Law (Explore Learning)
SIMULATION: Steam Engine (Edumedia)
Breathing
VIDEO: Creating a lung model
VIDEO: Breathing Dynamics
SIMULATION: Lungs (Edumedia)
Alveloi Anatomy (Biodigital Human)
SIMULATION: Breathing Dynamics (Biodigital Human)
Weather