First school

Experiment 5 – Does the ice float or sink?

The density of a material is what determines whether or not it floats, but pay attention: it’s not only the material’s density, but also the fluid where the object will float or sink.

Try the following experiment.

Material:

• An ice cube
• two glasses
• 250ml of alcohol
• 250ml water
• Food coloring

Procedure:

1. Fill one glass with water without reaching the edge and one with alcohol.
2. Take an ice cube and throw it in the glass of water. See if it floats or not.
3. Now remove it from the glass and throw it in the glass of alcohol. Observe what happens.
4. Once you’ve practiced, you can present it in public, preparing 4 cups, two with different color and two colorless.
5. Ask the public if it floats or not. Once you have responded, making an ice and put it in the glass with alcohol and without food coloring.
6. Once the public is skeptical, show them you can make the same ice cube float; distract them and swap the glass of alcohol by the glass of water. Put the ice cube in the glass of water. It will float.
7. Then show them the experiment with the glasses having colorant, an alcohol and one with water.

Have fun with your presentation.

Questions:
Why does ice float in water and not in alcohol?
Does the oil float on water? Does it float in alcohol?
What is lighter, water or alcohol?

Experiment 4 – Mysterious Shower

Material:

• A plastic bottle no longer be used.
• A small nail or pin.
• Forceps

Procedure:

1. With forceps and the nail (or pin) make a dozen very small holes in the bottom of the bottle.
2. Fill the bottle with water and cover it quickly, before all the liquid escapes through the small holes.
3. Let take a few seconds after closing the bottle and watch the water as it stops coming out through the holes.
4. Re-open the bottle and observe what happens.
5. Have fun with your little shower on your house plants.

Questions:

Why leave out the water when the bottle cap?
Why does the water back out when you uncover the bottle again?
What if the holes made to the bottle were too big?
How do you think you could use this system?

Experiment 3 – The Power of Pressure

Everyday we carry a column of air of about 8km high and we don’t even notice it. Said air weighs several tons, but we are not aware of the pressure put on us because the air itself helps us to carry it. Sometimes we’re aided by this pressure when we lift water columns, for example, when we drink something with a straw.

In this experiment we will show another way in which the water is pushed upward by air pressure.

Note: You will need the aid of an adult, because fire is handled in this experiment.

Material:

• dish
• glass
• piece of cork
• matches or a small candle (the size of the piece of cork)

Procedure:

1. In a shallow dish pour a little water until it covers the bottom few millimeters.
2. Insert the match into the cork and put it above the water, or, put the candle in place.
3. Turn on the match (or candle), so it’s like a small boat floating with its little light in the water.
4. Hold the glass and cover.

Questions:

What do you think will happen?
What do you notice?
Explain the physical phenomenon occurred.
Design another experiment based on this physical phenomenon.

Experiment 2 – I can hear bells…

Sound travels faster through solids. This means that when you stick an ear to the railroad tracks (like in the Wild West movies) you can hear better if the train is coming or not. With this experiment, you can hear the bells of a church when no one else does.

Material:

• Sewing thread or yarn
• Scissors
• Two tablespoons (the experiment is better if they are made of silver).

Procedure:

1. First, make sure that sound is heard better when traveling through a solid than when it does through the air: Stick your ear to a desk and knock on it a little.
2. Cut a 80cm strip along the thread or yarn.
3. Fold the yarn in half and tie it tightly to the spoon handle, just where the fold is. It must be very tight.
4. Roll up each of the ends of yarn on each of your index fingers.
5. Stick your fingers with the yarn into your ears and drop the spoon so that the yarn tightens (so it looks like doctors’ stethoscopes).
6. Have someone gently tap your spoon with another spoon.
7. Have fun with your church bell.

Questions:

What do you hear?
Do you think that all materials will be produce the same sound?
What other objects could be used for this experiment?

Experiment 1 – Bat Ears

This experiment, despite being designed for elementary school students, may be useful for older people. What we do is a better hearing aid at a distance, we might even calle them “binauriculars”, for they are like binoculars for the ears. They turn to be very useful at concerts or to spy on the neighbor.

Material:

•  aluminum foil
•  a pair of glasses or just the frame
•  instant glue for plastic and metal

Procedure:

1. Cut two pieces of foil into a 30x30cm² square shape.
2. Fold the foil into 4 as shown in Figure 1.
3. Bend the corners as also shown in Figure 1.
4. When you’ve done that, mold the octagon to form a “parabolic”, which is like a satellite dish (see Figure 2).
5. Finally, attach the aluminum frame lenses (as in Figure 3) and our “binauricular” will be ready.

Once the “binauricular” is ready, have fun! Hear conversations that are far away, try it at concerts, listen animals from afar.

Questions:

Can you hear what is behind you? What do you hear better, what’s ahead or what’s behind?

Find out how bats hunt and explain what is the relationship between bats and “binauriculars”

Why can you hear conversations at a distance better than those near you?

How would you improve this experiment?