UNIT 07

GARDEN HOSE SCIENCE

PRESSURE IS DEFINED AS THE AMOUNT OF FORCE EXERTED OVER A DEFINED AREA. If you try to walk across fresh snow in boots, you’ll sink as your weight compresses the snow under your feet. Wearing snowshoes spreads the force of your weight over a larger area, decreasing the pressure you put on the snow and allowing you to walk across the surface like a snowshoe hare.

We live beneath a mass of air that puts constant atmospheric pressure on our bodies and everything surrounding us. If you dive underwater, you add the weight of the water above you to the total pressure you experience.

In this chapter, you’ll learn to do a fun water-pressure experiment by elevating a column of water in a hose high enough to lift you up on a water-filled hot-water bottle or an air mattress.

While you have the hose out, fill up a container and explore buoyancy by engineering foil boats. Make some waves, while you’re at it, and try your hand at starting a siphon to cool off on a hot summer day.

LAB 29

SIPHON ROLLER COASTER

SEND BALLOON FRAGMENTS ON A WATERY RIDE THROUGH LOOPS OF PLASTIC TUBING.

 2 large plastic containers, one of them clear

 1/2 inch to 3/4 inch (1.5 to 2 cm) clear, flexible plastic tubing, 6 to 8 feet (1.8 to 2.4 m) long

 Water

— The upper end of the tube must remain submerged at all times, or the siphon won’t work.

— This is a good experiment for two or more people.

— Balloon fragments pose a chocking hazard to young children.

PROTOCOL

STEP 1: Have a water balloon fight. Collect and keep fragments of the water balloons. (Fig. 1, 2)

Fig. 1: Have a water balloon fight.

Fig. 2: Pick up the balloon fragments.

STEP 2: Place a large, clear container on a ledge or chair and use a garden hose to fill it with water. Place the other container next to it, at ground level. (Fig. 3)

Fig. 3: Fill a large container with water.

STEP 3: Submerge the plastic tubing completely in the water in the upper container so that all air is removed. If there are air bubbles in the tube, move the tubing around underwater until they’re all released. You can also use the water coming out of the hose to remove air bubbles from the tubing.

STEP 4: Have someone hold one end of the plastic tubing underwater in the upper container while a second person seals off the other end of the tube with his or her thumb. Have the second person remove the end of the plastic tube from the upper container and move it to the lower container, making sure the covered opening is held lower than the submerged end of the tube.

STEP 5: Continue to hold the upper end of the tube underwater and release water from the lower end of the tube by removing your thumb.

STEP 6: Water should run through the siphon from the upper container into the lower one.

STEP 7: Twist and turn the lower end of the tube to create a roller coaster.

STEP 8: Put balloon fragments into the upper end of the tube and watch them travel through the twisted tube. (Fig. 4, 5)

Fig. 4: When the siphon is running, feed the balloon fragments into the upper end of the tubing.

Fig. 5: Watch the balloon fragments travel through the siphon roller coaster.

STEP 9: When you’re done, pull the upper end of the tube out of the water to stop the siphon.

2. What will happen to the rate of water moving through the siphon if you use a longer piece of tube to make the lower column longer?

LAB 30

KIDDIE POOL BOATS

MAKE FOIL BOATS TO TEST HOW SHAPE AFFECTS FLOTATION.

 Three 12 × 12-inch (30.5 × 30.5 cm) sheets of aluminum foil, plus more for additional boats

 Coins

— Coins present a choking hazard to young children.

STEP 2: Crumple up the piece of aluminum foil. Drop it in the water to see whether it floats or sinks. (Fig. 1)

Fig. 1: Crumple up a piece of aluminum foil to see whether it floats or sinks.

STEP 3: Form another piece of foil into a boat to see whether it will float. (Fig. 2)

Fig. 2: Form a piece of foil into a boat.

STEP 4: See how many pennies you can add to the boat before it sinks. (Fig. 3)

Fig. 3: Add coins to the boat.

STEP 5: Redesign your boat with another piece of foil to see whether you can get more coins in before it sinks. (Fig. 4)

Fig. 4: Design more boats and test them in the water.

2. In a big swimming pool, what shapes can you make with your body to help you sink or stay afloat?

3. Compare what happens when you put a water balloon in the pool versus an air-filled balloon the same size. What happens if you fill a balloon with half water, half air?

LAB 31

WAVY SCIENCE

USE WATER AND A ROPE TO OBSERVE ENERGY DISTURBANCES MOVING THROUGH MATTER.

 Water

 Rocks

 2 flat, sturdy objects, such as plasticware lids or cutting boards

 Long, flexible rope

STEP 2: Drop or toss a rock gently into the middle of the water and observe the wave patterns it makes. Now, drop 2 rocks at the same time in opposite sides of the pool to see what happens. (Fig. 1)

Fig. 1: Drop a rock in the water and observe the wave pattern it makes.

STEP 3: Use a flat object to make a wave by placing it in the water and pushing forward. Change the depth and angle of the object to see how it changes the waves it creates.

STEP 4: With two people, start simultaneous, similar waves from opposite sides of the pool to see what happens when they meet in the middle. (Fig. 2)

Fig. 2: See what happens when two waves meet.

STEP 5: Have two people stretch out a rope between them and lay it flat on the ground.

STEP 6: Pick up one end of the rope and rapidly move it up and down to make waves. Try making fast waves and slow waves. Make big waves and small waves. (Fig. 3, 4

Fig. 3: Make a wave travel through a rope.

Fig. 4: Make lots of waves.

STEP 7: Make similar waves from each end at the same time to see what happens when the waves meet. See resources for a link to a video we made of our own waves!

STEP 8: Jump rope, just for fun.

2. Make a kazoo from a comb and a piece of folded tissue paper to hear sound waves produced by vibrations.

LAB 32

WATER ELEVATOR

FEEL THE POWER OF WATER PRESSURE IN THIS UPLIFTING EXPERIMENT.

 2 garden hoses

 Hot water bottle or air mattress

 Stepladder

 Funnel whose end fits in the mouth of the hose

 Rigid, flat object, such as a thick cutting board

— You will need a lot of duct tape for this experiment, to prevent leaks between the hose and the mattress or hot water bottle.

— Remove all air seals from the mouth of the air mattress, so that the water can back up into the hose.

STEP 2: Hook up the other hose to a faucet and attach the free end to the top of a stepladder with duct tape.

STEP 3: Raise the free end of the hose attached to the mattress up the ladder, put a funnel in it, and position it so that water will run from the upper hose into the funnel. Attach it in position using duct tape.

STEP 4: Fix leaks and make adjustments. Start the experiment by turning the faucet on and letting it run to fill your bottle or mattress. (Fig. 1)

Fig. 1: Turn on the faucet to start the experiment.

STEP 5: If using a hot water bottle, put the cutting board on top and stand on it as the bottle fills. It should lift you up. Turn the hose off when the funnel starts to overflow. (Fig. 2)

Fig. 2: Stand on a cutting board on top of a hot water bottle as it fills.

STEP 6: If using an air mattress, be patient because it will take awhile to fill. Lie down on it if you want, and wait for it to lift you off of the ground. (Fig. 3)

Fig. 3: An air mattress will take longer to fill, so relax.

STEP 7: How many people can stand on the water-filled air mattress?