LAPORAN PELANCARAN BULAN SAINS DAN MATEMATIK 2013 2

EKSPERIMEN

1.   

DRY ICE FOG

Difficulty: Easy

Time Required: Instantaneous

Here's How:

1.     This is so easy! Add chunks of dry ice (solid carbon dioxide) to hot water in a styrofoam or other insulated container.

2.    The fog will sink to the ground. You may use a fan on a low setting to move your 'smoke'.

3.   The water will cool, so you will need to refresh the hot water to maintain the effect.

4.   Room temperature matters - you will get the most fog in a cool room. Have fun!

Tips:

1.     Dry ice is cold enough to give frostbite. Wear protective gloves when handling it.

2.    Larger chunks of dry ice will last longer than smaller ones.

3.   Be aware that extra carbon dioxide is being added to the air. Under some circumstances, this can present an asphyxiation hazard.

4.   Sometimes inexpensive dry ice machines are available, otherwise check party supply stores and shipping companies for availability.

5.   Keep dry ice away from children, pets, and fools! Adult supervision is required.

What You Need

• Dry Ice (Carbon Dioxide)
• Hot Water
• Insulated Container

2.   SMOKE BOMB

The smoke bomb you would purchase from a fireworks store usually is made from potassium chlorate (KClO3 - oxidizer), sugar (sucrose or dextrin - fuel), sodium bicarbonate (otherwise known as baking soda - to moderate the rate of the reaction and keep it from getting too hot), and a powdered organic dye (for colored smoke). When a commercial smoke bomb is burned, the reaction makes white smoke and the heat evaporates the organic dye. Commercial smoke bombs have small holes through which the smoke and dye are ejected, to create a jet of finely dispersed particles. Crafting this type of smoke bomb is beyond most of us, but you can make an effective smoke bomb quite easily. There are even colorants you can add if you want to make coloured smoke. In fact, this type of smoke bomb was used to craft the world’s biggest smoke bomb! Let's start out with instructions for the easiest/safest type of smoke bomb you can make:

Smoke Bomb Materials

·       sugar (sucrose or table sugar)

·       potassium nitrate, KNO3, also known as saltpeter (buy it online or you can find this at some garden supply stores in the fertilizer section, some pharmacies carry it too)

·       skillet or pan

·       aluminum foil

      How to Make a Smoke Bomb

1.      Pour about 3 parts potassium nitrate to 2 parts sugar into the skillet (5:3 ratio is also good). Measurements don't need to be exact, but you want more KNO3 than sugar. For example, you can use 1-1/2 cups KNO3 and 1 cup sugar. If you use equal amounts of KNO3 and sugar, your smoke bomb will be harder to light and will burn more slowly. As you approach the 5:3 KNO3:sugar ratio, you get a smoke bomb that burns more quickly.

2.     Apply low heat to the pan. Stir the mixture with a spoon using long strokes. If you see the grains of sugar starting to melt along the edges where you are stirring, remove the pan from the heat and reduce the temperature before continuing.

3.     Basically you are carmelizing sugar. The mixture will melt and become a caramel or chocolate color. Continue heating/stirring until the ingredients are liquefied. Remove from heat.

4.     Pour the liquid onto a piece of foil. You can pour a smaller amount onto a separate piece, to test the batch. You can pour the smoke bomb into any shape, onto an object, or into a mold. The shape and size will affect the burning pattern.

5.     If you aren't going to clean your skillet immediately, pour hot water into the pan to dissolve the sugar (or else it will be harder to clean). Clean up any residue you may have spilled out of the pan, unless you want mini-smoke bombs on your stovetop.

6.     Allow the smoke bomb to cool, then you can peel it off the foil.

Now that you've made your smoke bomb, it's time to light it...

3.   ELEPHANT TOOTHPASTE

The elephant toothpaste chemistry demonstration is a dramatic demo which produces copious amounts of steaming foam that sort of looks like the toothpaste an elephant might use. Here's how to set up this demonstration and a look at the reaction behind it.

Elephant Toothpaste Materials

• 50-100 ml of 30% hydrogen peroxide (H₂O₂) solution
• saturated potassium iodide (KI) solution
• liquid dishwashing detergent
• food colouring
• 500 mL graduated cylinder
• splint (optional)

Safety

Wear disposable gloves and safety glasses. Oxygen is evolved in this reaction, so do not perform this demonstration near an open flame. Also, the reaction is exothermic, producing a fair amount of heat, so do not lean over the graduated cylinder when the solutions are mixed. Leave your gloves on following the demonstration to aid with cleanup. The solution and foam may be rinsed down the drain with water.

Procedure

1.     Put on gloves and safety glasses. The iodine from the reaction may stain surfaces so you might want to cover your workspace with an open garbage bag or a layer of paper towels.

2.    Pour ~50 mL of 30% hydrogen peroxide solution into the graduated cylinder.

3.   Squirt in a little dishwashing detergent and swirl it around.

4.   You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam resemble striped toothpaste.

5.   Add ~10 mL of potassium iodide solution. Do not lean over the cylinder when you do this, as the reaction is very vigorous and you may get splashed or possibly burned by steam.

6.   You may touch a glowing splint to the foam to to relight it, indicating the presence of oxygen.

Variations of the Elephant Toothpaste Demonstration

• You can add 5 grams of starch to the hydrogen peroxide. When the potassium iodide is added, the resulting foam will have light and dark patches from the reaction of some of the starch to form triiodide.
• You can use yeast instead of potassium iodide. Foam is produced more slowly, but you can add a fluorescent dye to this reaction to produce elephant toothpaste that will glow very brightly under a black light.
• You can colour the demonstration and make it into an Elephant Toothpaste Christmas Tree for the holidays.
• There is also a kid-friendly version of the elephant toothpaste demo that is safe for hands.

Elephant Toothpaste Chemistry

The overall equation for this reaction is:

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)

However, the decomposition of the hydrogen peroxide into water and oxygen is catalzyed by the iodide ion.

H₂O₂(aq) + I^-(aq) → OI^-(aq) + H₂O(l)

H₂O₂(aq) + OI^-(aq) → I^-(aq) + H₂O(l) + O₂(g)

The dishwashing detergent captures the oxygen as bubbles. Food colouring can colour the foam. The heat from this exothermic reaction is such that the foam may steam. If the demonstration is performed using a plastic bottle, you can expect slight distortion of the bottle from the heat.