Alka Seltzer Blast-off 2

This project effectively demonstrates the Newton's Laws of Motion.

First Newton's Law of Motion states that an object either remains at rest or continues to move at a constant velocity unless a force acts on it.

• The rocket is at rest, but when it's acted upon by the chemical reactions of water and the Alka-Seltzer tablets, it has a powerful lift-off. The force of the reaction blows off the film canister lid.

Second Newton's Law of Motion states that Force is equal to mass multiplied by acceleration.

• Force = mass x acceleration
• The force of that lift-off is equal to the mass of the film canister, the water, and the tablet inside multiplied by the acceleration provided by the chemical reaction.

Third Newton's Law of Motion states for every action, there is an equal and opposite re-action.

• As the film canister lifts off, the canister lid, water, gas, and slide experience the downward force of the push. The lid pops off. The water and the gas spread out, but because the slide is secured on the ground, we can't see it move.

The Chemistry behind the project:

1. Alka-Seltzer tablets contain sodium bicarbonate and citric acid.
2. When the Alka-Seltzer tablet piece comes in contact with the water inside the film canister, it begins to dissolve. 
3. This results in sodium citrate, water, and carbon dioxide gas.
4. The carbon dioxide gas builds the pressure inside the film canister.
5. Eventually, the pressure inside will pop the film canister lid off.

H₃C₆H₅O₇ + NaHCO₃  ==========>  NaC₆H₅O₇ + H₂O + CO₂ + Heat

Citric Acid + Sodium Bicarbonate ========> Sodium Citrate + Water + Carbon Dioxide + Heat

Because Heat is released during the process, this chemical reaction is called an 

exothermic reaction.

Second Newton's Laws of Motion states F = ma. So, different amount of water or Alka-Seltzer piece will affect the take-off time and altitude of our rocket.

Also, take-off time is affected by the surface area of Alka-Seltzer exposed to water. Crushing it will reduce the take-off time significantly.

Elephant's Toothpaste

I haven't done many Chemistry experiments in class, because there isn't enough time to clean up the mess before the next class comes in, etc. But I always wanted to try this one (even though there are many variations of this on youtube and elsewhere) because any kind of foaming, explosive reactions I've done before were based on vinegar and baking soda (any this one is based on hydrogen peroxide). And it's always really fun to get your hands dirty.

This is what we're doing today. 

This was the extent of the mess I had to clean up from this experiment, which is less than I expected.

List of supplies:

• Empty plastic bottle
• Baking tray (bigger the better)
• 4 fluid oz of hydrogen peroxide (3% concentration is the one I used. I bought it from a nearby pharmacy)
• Dish washing liquid
• Dry yeast
• Hot water
• Funnel
• A small bowl to mix yeast and hot water
• A measuring spoon set (1 tsp & 1 Tbsp)
• A spoon to stir the yeast and hot water mixture

Measure 4oz of 3% concentration of hydrogen peroxide.

Pour hydrogen peroxide into the empty water bottle along with a couple of drops of food coloring and a couple of drops of dishwashing liquid.

Mix a 1 tsp of yeast with 2 Tbsp of hot water.

Using a funnel, add the yeast and water mixture to the hydrogen peroxide in the bottle.

Too bad I didn't do this experiment a couple of days ago. It has a nice heart shaping going. It's probably more impressive in person than in picture.

Big bubbles on the left outer edges of the foam mixture (bubbles from earlier reactions).

Big bubbles on the left outer edges of the foam mixture (bubbles from earlier reactions).

Smaller bubbles in the closer vicinity of the plastic bottle (bubbles from the later reactions).

SO..., why does this happen? Think about what happens in the bottle.

Science notes:

Well, if hydrogen peroxide is left alone long enough, it'll break down to water and oxygen on its own. BUT, by adding yeast into hydrogen peroxide, we're speeding up the break down process.

1. The hydrogen peroxide locks on to the yeast.
2. The yeast breaks down into oxygen and water.
3. The oxygen released by the yeast mixed with dishwashing liquid creates the bubbles and produces the foam.
4. And this one, you can't tell from looking at the pictures, but when I touched the water bottle, it was warm.
5. Hydrogen peroxide + yeast is an exothermic reaction (heat-producing), and that's why the water bottle was warm to touch.

I liked this experiment a lot because it was simple and even though there was a mess, it was easy to clean up after I was done.

I'd like to do this in class varying the concentration of yeast and water mixture. I'd like the students to figure out the relationship between the yeast concentration and the amount of foam (which probably is hard to measure) or the amount of heat the experiment released (which probably is also hard to measure). Also, I can play around with different concentrations of hydrogen peroxide. Anything over 6% concentration is not recommended online.

Again, for a Chemistry project, this was fun, easy to clean up, and it offered a lot of opportunities to mix it up.

Have fun & have a great day!

NOTE: If you have really little kids around you, please make sure they don't consume the foam.