Hot Pack (Hands-on)
Produce a hot pack by mixing a solid with water.
Reference: “Chemical Demonstrations, Volume 1,” by Lee R. Summerlin and James L, Ealy, Jr., Second Edition, American Chemical Society: Washington, 1988; p. 67.
Add 100 ml of water to a Ziploc bag.
Quickly add 10-15 grams of anhydrous calcium chloride.
Pass the bag around so the students can feel the heat of reaction.
Explanation: The calcium chloride is dissolving into the water to form ions of calcium and chloride. Heat is given off as a result.
Tips:
Produce a cold pack by mixing a solid with water.
Reference: “Chemical Demonstrations, Volume 1,” by Lee R. Summerlin and James L, Ealy, Jr., Second Edition, American Chemical Society: Washington, 1988; p. 65.
Add 100 ml of water to a Ziploc bag.
Quickly add 10-15 grams of ammonium nitrate.
Pass the bag around so the students can feel the heat of reaction.
Explanation: The ammonium nitrate is dissolving into the water to form ions of ammonium and nitrate. Heat is absorbed as a result.
Tips:
Grain Elevator Explosions (Demo)
A lid is blown off a container by using a flammable solid.
Reference: “Chemical Demonstrations, Volume 1,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1983; p. 103.
First assemble an explosion can. See illustration.
It should be about a 2 gallon can with a tight fitting lid.
Pour lycopodium powder into the crucible or funnel.
Insert lit candle and put the lid on the can.
Squeeze the bulb fully and firmly.
Explanation: The finely divided solid reacts with oxygen in the container when it hits the flame. This produces much heat and the products of the reaction are gases. Gases take up much more volume than solids and the increase in pressure blows off the lid.
Tips:
Volcanoes (Demo)
A pile of solid forms a volcano.
Reference: “Chemical Demonstrations, Volume 1,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1983; p. 81.
In a very large beaker or clear glass container, pour a pile of ammonium dichromate in the center of the bottom. A funnel may be helpful.
The size of the pile should be dependent on the size of the container used.
Break a match in half and bury the part that contains the head in the center of the pile so the head is just below the surface.
Light another match and ignite the buried match head.
Observe what happens to the pile.
Explanation: Ammonium dichromate decomposes upon heating to produce nitrogen gas, water and chromium(III) oxide. The nitrogen and water causes the current upward lifting the chromium oxide which is very light.
Tips:
The Black Tower (Demo)
A black tower rises out of a beaker.
Reference: “Chemical Demonstrations, Volume 1,” by Bassam Z. Shakhashiri, University of Wisconsin Press: Madison, 1983; p. 77.
“Chemical Magic from the Grocery Store,” by Andy S. W. Sae, Kendall/Hunt: Dubuque, 1996; p. 69.
This demonstration should be done in a hood or well-ventilated area.
Put about a quarter cup of sugar in a 250-ml beaker.
Pour over the sugar a quarter cup of concentrated sulfuric acid.
After a few moments, the sugar starts to bubble and blow steam and a black column begins to rise.
Steady the tower with a pair of tongs so it does not fall over.
Explanation: Sulfuric acid is a powerful dehydrating agent. The sugar is being dehydrated leaving carbon behind. The heat of the reaction is enough to boil the water that is formed.
Tips:
Ignition of a gas creates a sound like a dog.
Reference: “Chemical Demonstrations, Volume 1,” by Lee R. Summerlin and James L, Ealy, Jr., Second Edition, American Chemical Society: Washington, 1988; p. 16.
Add 300 ml of water to a 2 liter graduated cylinder.
Add 1.5 grams of calcium carbide.
Quickly light a match and drop it into the cylinder.
Keep lighting matches and dropping them cylinder until no more noise is produced.
Explanation: The calcium carbide reacts with water to produce acetylene gas which bubbles out of the water. The match ignites the gas which reacts with oxygen in the air and a loud noise is produced. The flame goes out when the acetylene gas is consumed. The loudest noise should be the first one since there is the most oxygen present in the cylinder.
Tips: Doubling the amount of calcium carbide in this demonstration made the experiment work better. Also, this experiment will produce unpleasant fumes, so it may be best to do the demonstration outside.