Demo Ideas

All these experiments came from this website;
http://www.theteachersguide.com/Sciencedemos1.htm

Some offered sources, some didn't, and some information is slightly different but the concepts and experiments are straight forward. It did not offer any idea of how long each experiment would take to prep and perform but I think most of them are pretty cut and dry while the scientific method experiment might take a bit longer.


1.
Subject Area: Physics Concepts
-Volume
-Change of State
-Volume of Gases
-Atmospheric Pressure

Grade: Middle-High School

Title: THE COLLAPSING CAN

Materials:
One empty aluminum can (354 ml)
A Hot plate or burner
Large bowl of water
Tongs to hold pop can

Procedure:
Put about 5 ml of water in the pop can (just enough to cover the bottom).
Heat the can over the hot plate or burner.
Let the water boil vigorously.
In a single motion, remove the pop can from the burner and INVERT it in the bowl of water.
Submerge the opening to the pop can in to the water. The can will IMPLODE instantly.

Questions:
What was in the can besides water?
What happens when water is boiled?
What do you think will happen if the can is inverted in the bowl of water?
What happens to the air in the can as water vapor is formed?
What force is working on the outside of the can?

Rationale:
Before heating, the can was filled with water and air. By boiling the water, it changes states, from liquid to gas (water vapor). The water vapor (steam) pushes the air that was inside, out of the can. By inverting the can in water, we are cooling the vapor very quickly and constraining the potential for rapid flow of air back into the can. The cooling condenses the water vapor back to water. All of the vapor which took up the interior space of the can before is now turned into a few drops of water, which take up much less space. This causes the pressure to drop and the atmospheric pressure is therefore pushing on the can and crushing it.
The total force working on the outside of the can is the total of the can's surface area in cm. multiplied by 1 kg.

Application:
Production of vacuum containers
Home canning


2.
Subject Area: General Science

Grade: Middle School

Title:MAGIC LID

Objective: To show students that atmospheric pressure is not just a downward force, but is a force acting in all directions.

Materials:
1-one gallon jar
1-glass dish large enough to cover mouth of jar
Procedure: Fill jar completly full, so the meiniscus stands high. Place glass plate on top of the jar. making sure that no air is trapped between jar and glass plate. Then quickly turn the jar upside down. It may take a couple of times to get this right, so this should be done over a sink area.

Questions:
What will happen to the plate? Will it fall or stay in place?
What causes the plate to stick to the jar?
What conclusions can one draw from this?
Is atmospheric pressure greater than water pressure?
How tall would a cup have to be in order for the water pressure inside to overcome the atmospheric pressure outside?

Rationale: This is an application of atmospheric pressure. Most students think that atmospheric pressure and the force of gravity have only a downward effect, the latter is true, but atmospheric pressure exerts force in all directions. This is what allows the plate to stay attached to the jar.

3.
Title: B Squared (Burning Balloons)

Source: Robert Ruisinger

Grade: 7-12 (chemistry)

Materials: One balloon filled with water, one balloon filled with air to an equal volume, and matches.

Procedure: Hold the lit match to the balloon filled with air and it will pop immediately. Next, hold the lit match to the water balloon and notice that it will not pop. It is advisable not to hold the match in one place for too long, because it may eventually pop! You may want to one before the other one, depending on your application.

Concept: The air balloon explodes immediately because the heat from the lit match quickly burns through the rubber wall. The water balloon, does not explode because the water inside absorbs the heat and disperses it throughout the volume of water. It does not let the rubber wall get to it's melting point. You can tie this demo into a lesson on heat capacities, melting points, heat absorption, conduction, etc. . Credits: South Windsor High School, South Windsor, CT 06074

4.
Source:Toni Orso

Subject Area: General Science
Grade:(7-12)

Concepts Covered by Demonstration: Scientific Method

Title: The Black Whole

Materials:
A coffee can which is specially constructed (a slanted metal piece attached on the inside to keep water in.
A glass of water

Procedure:
Hold the coffee can above the observers to ensure that they can not view what is inside.
Pour a glass of water directly into the coffee can. Note: do not let observers see inside to coffee can.
Tip the can over on the side which will allow no water to spill out of the coffee can.

Questions:
Describe exactly what you observed.
Based on your observations, describe or draw what might be in the coffee can.
Are you making an educated guess about what occurred?
What is the scientific word for making and educated guess?
How might you collect further information to support your educated guess?
Write down some examples in which scientist have made educated guess about natural events that occur to try to explain what is happening in the world.

Rationale: This demonstration is an excellent way to introduce the Scientific Method because it deals with observing and recording those observations. Furthermore, the students can make an educated guess (hypothesis) about what might be occurring.
Students can also be introduced to the idea that in science there are many wonders that scientist can not fully explain. Scientist can only make observations and try to collect as much information as possible and based on the knowledge they gain from these observations they can hypothesize about what is happening. For example, scientist did not actually see the dinosaurs that lived during the Triassic Period; However, they can predict because of the evidence that was left behind in the fossil record.
It is important to inform the students that even though their educated guess about what was inside the coffee can was correct, that they would have to do millions of test to state that it was because in order for a hypothesis to become a fact or theory an enormous amount of data must be collected to support the hypothesis and millions of tests must have taken place.