"Yeast Beasts In Action" Investigation

Problem: How do certain compounds (a compound that is primarly acidic, a compound that is primarily basic, and a compound that is primarily neutral) affect the pressure of yeast activity?

Hypothesis: The pressure will die down when exposed to the diet coke, since acidic compounds normally hinder "life" and growth, both of which are yeast's primary function. The yeast will be the most active when exposed to the peroxide, as previously proved in the Elephant Toothpaste/Monster Foam experiment. It will have a normal amount of pressure when exposed to the skim milk-- the neutral liquid.

Results: To summarize it simply, we put three different liquids-- Diet Coke, skim milk, and hydrogen peroxide-- in three different test tubes. We mixed yeast with water and then put a few drops of the solution into the Coke's test tube. We then capped the test tube with a rubber stopper that connected directly to a pressure sensor, which in turn was linked to the Logger Lite data collection program. We then recorded the data, and repeated the experiment with the skim milk, and then the hydrogen peroxide when we were finished with the skim milk.

The above images show our results for the second Coke experiment-- we had to redo it, since the cap popped completely off the first time due to pressure, causing a large "dent" in the graph. (This makes it obvious that my hypothesis was unsupported.) It popped somewhat off the second time, leaving a slightly smaller "dent" in the graph.

The next ones show the hydrogen peroxide's pressure over the course of two minutes. Contrary to my original prediction, hardly anything happened. The only possibility was that the yeast was mixed with water-- a single chemical added or subtracted can change a chemical reaction drastically!

These images show the skim milk, which unexpectedly rose more than the others.

So, the highest pressure, lowest pressure, and pressure raise (from beginning to highest point) for each substance was:

Coke: 110.07 and 98.81 kPa, with 11.26 kPa being its highest pressure raise (considering it only got a chance to raise 7.1 kPa again after the cap popped.)

Peroxide: 105.89 and 98.90 kPa, with 6.99 kPa being its entire pressure raise.

Skim milk: 118.34 and 98.73 kPa, with 19.61 being its entire pressure raise.

Conclusion: My hypothesis was completely unsupported. I expected the hydrogen peroxide to have the most pressure because yeast creates an "exploding" foam substance when exposed to it, but the water mixed in with the yeast may have stopped this reaction. As a result, the hydrogen peroxide had the lowest pressure raise (6.99), and the lowest high pressure point (105.89). I expected Coke-- with all of its acids-- to make the pressure die down, but its pressure did increase-- it was neither the highest of lowest of the three, with 11.26kPa, and with 110.07. (This was probably due to all of the sugar in the Coke.) Had the cap not popped, the pressure would probably have increased a bit higher, and probably would be around the same amount as the skim milk by the time the data had stopped collecting. The skim milk, which I expected to be neither the lowest or highest in increase and highest pressure point, ended up having both the highest pressure point and highest increase. The results would have been much different if our lab group had held the cap down more tightly during the Coke's data collection-- that is something we would definitely do different next time.

Conservation of Mass Lab Investigation

Which will release more gas... soda pop and pop rocks, or vinegar and baking soda?

Hypothesis: The soda pop and pop rocks will release more gas because both are filled with CO2.

The combination of pop rocks and coke did release enough CO2 to fill the balloon, but it wasn't filling very much (compared to other groups). Our group suspected that this was because our balloon wasn't completely attached to the top of the soda bottle.

The combination of vinegar and baking soda filled the balloon quite a lot, though-- more than three times as much as the poprocks and soda did, probably.

(The poprocks and soda mixture is on the left, obviously, while the vinegar and baking soda mix is on the right.)

Pop rocks are made with Co2, as is soda, (and we were using a whole bottle of soda) so I expected there would be more of a chemical reaction for that mixture than for the other one, but I was wrong.

Conclusion: The hypothesis was unsupported. I assumed the soda and poprocks would make more Co2 simply because of the high amounts of CO2. One thing we might have done wrong in this experiment was not tighten the balloon on the soda correctly, since it didn't fill up as much as other groups' did. This is a problem that can be easily avoided next time. One thing I learned in this experiment was that some food has more chemicals in it than we expect. I knew that the soda had CO2, but I wasn't aware that the pop rocks had any.

Chemical Reactions & Heat Investigation

Problem: How does temperature affect the speed of chemical reactions?

Hypothesis: If we make the water colder, the alka seltzer will dissolve slower-- likewise, if we make the water hotter, it will dissolve faster. This is because the molecules in a hot object move faster than the molecules in a cold object.

Results:

As expected, the dissolving time went up as the water temperature went down. This graph will give a somewhat better idea of it.

It's also important to note that the alka seltzer tablets floated at the top when dissolving in the hot water, while they stayed on the bottom when dissolving in the room temperature and cold water. The alka seltzer tablets themselves had generally the same reaction-- excluding the time it took for the reaction to happen-- they fizzed and bubbled, and covered the entire glass with bubbles, as seen in the picture above.

Conclusion: Our hypothesis was supported. The seltzer tablet dissolved in 21 seconds in the hot water, 40 in the room temperature water, and 121 in the cold water. In this experiment, I learned that it's important to stay focused and be precise. If we had (accidentally) let the water heat up any longer, the alka seltzer would have dissolved faster than it was supposed to. Staying focused and being precise applies to any real life situation- school especially. However, since we did stay focused and we were precise, no problems or errors occured.

ChemThink: Chemical Reactions

The materials left at the end of a reaction are called products.

Let's take a look at these reactions. What do all three of the products have in common?
Their bonds are being rearranged. Rearranging bonds is necessary for a chemical reaction.

Generally, we don't draw pictures when showing reactions. We use chemical symbols.

The first reaction is the bonding of Fe and S-- Fe + S-- which results in FeS.
The second reaction is the splitting of CaCO3, which results in CaO + CO2.
The third reaction is the splitting of H2 and Cl2 along with the joining of Mg and Cl. This goes from 2 HCl + Mg to H2 + MgCl2.

In every chemical reaction, the chemicals at the end are the exact same ones as the ones at the beginning. No chemicals are ever removed or added in a chemical reaction, since chemical reactions are just rearrangements of the bonds between atoms.

This is not the correct way to make water, since there is an extra oxygen molecule. To fix this, we must add two more hydrogen molecules.

Now, that's water!

Each atom on the reactant side must also be on the product side. This idea is the Law of Conservation of Mass. There must be all of the same atoms before and after every reaction.

This is not a balanced equation because there are two oxygen atoms on one side but only one on the other. To represent the chemical reaction, we need to add another CuO.

Uh oh! Now the Cu atoms are unbalanced! We have to use two Cu atoms to interact with each O2 molecule, so if we use these two reactants it will produce two molecules of CuO.

Now it's balanced!

Let's try balancing this one using only these molecules.

There! Let's try a more difficult one.

Solved. Now let's try one without the scale.

And another...

Good! These are the sheer basics of chemical reactions, but it's easy to make more complex reactions if you know the basics!

Polymer Lab- Changing Variables

For our latest polymer lab, we had to change certain variables in the experiment to see if the results changed. So, for our variable change, we decided to do two experiments- one with wood glue instead of school glue, and one with wood glue and more borax- about twice as much- as our original experiment. So our question would be "how will the polymer change if we change its variables?"
The wood glue polymer was very similar to the original- bouncy, stretchy, and squishy, but it had a few distinct differences as well. It was a different color-- pale yellow rather than white-- and it was stickier than the other polymer. In addition, it was much stretchier- it stretched nearly seven feet before breaking! It had a 4.5cm rebound average after four trials, making it significantly less bouncy than its school glue counterpart. Upon freezing it-- even though the wood glue said "do not freeze"-- it became less stretchy, harder, and, obviously, colder. Its differences from the original polymer made it more interesting.
Our second polymer wasn't quite as successful. We used four teaspoons of borax instead of the original two, in addition to using wood glue. Though we expected it to be exactly like the wood glue polymer because it looked exactly like it, it never ended up hardening after we mixed it. It was a soggy, goopy mess, and we couldn't do anything with it!
The answer to our question is simple. One polymer will be stickier, stretchier, and less bouncy if we use wood glue. The other polymer will be a mess that can't solidify if we use wood glue and excess borax. The moral of the story is don't use too much borax!

Pictured below is the result of our second experiment.

Polymer Lab Investigation

Our initial hypothesis was "If we mix the given materials, then a rubbery substance will form, because sodium silicate is similar to glue."

But that was completely wrong.

After running through the experiment, we found that the polymer made today was very different from the wet, rubbery polymer made on Tuesday. But before explaining the results, let's talk about the observations made during the experiment.

"The Sodium Silicate Solution is similar to glue. It closely resembles the glue from a hot glue gun especially. When poured into a smaller beaker, ethanol is milky, though in its larger container it looked clear. The polymer of the two is hard, crumbly, and smells like nail polish remover. It has the consistency of sand. However, it starts to stick together when exposed to a little water, and then has the consistency of a citrus altoid. (One of these!) When rolled into a ball, it bounces higher than the polymer made Tuesday.

Our polymer-- we'll call him Richard-- was tested to see just how high it could bounce. At normal temperature, Richard bounced an average of twenty-one centimeters, while Richard bounced an average of 18.75 centimeters when chilled for about ten minutes.

Our hypothesis ended up being rejected, seeing as Richard was actually very hard as opposed to being wet, sticky, and moldable. Since sodium silicate is similar to glue, it would probably have turned rubbery had we mixed it with the borax we used on Tuesday.

Here is the polymer when being mixed. It almost looked like a mixture of liquid and plastic. By then, we could tell that a chemical reaction had taken place.

Here is the result, Richard. It was the complete opposite of what the lab group had expected. In the beginning, ethanol could be squeezed out of it.

The polymer made on Tuesday...

• Had a rubbery consistency.
• Molded easily.
• Dried when played with.
• Stuck to different surfaces.
• Bounced higher when chilled.

The polymer made today...

• Had a hard, plastic-like consistency, but could probably break apart with enough pressure.
• Could be molded into a ball, but probably nothing else.
• Dried before it was even touched.
• Didn't stick to anything.
• Didn't bounce as high as chilled.

Both polymers...

• Had a whitish color.
• Were able to bounce.
• Had some sort of molding capability.
• Dried out the hands.

Our polymer was pretty much the same as every other group's, which was a bit of a pain when trying to find individual polymers.

Most commercial polymers were carbon-based, though this one was silicon based. Silicon and carbon are very similar, so both will easily polymerize. The silicone polymer is exactly like any plastic polymer, but made with... well... silicone!

To sum this experiment up, I'd say it was rather interesting to see just how polymers are formed. It's easy enough to do at home!