Acid and Base Yeast Lab

How does yeast react with acids and bases?

The hypothesis was that the yeast would be most active in the acidic solution. To test the lab, we added yeast to an acid, neutral, and a base. The yeast was made in a solution so it could be added as a liquid. The air pressure inside of the test tube was taken for each substance once the yeast was added.

For the acid test, the pressure climbed rapidly. At about 130 kPa, the stopper popped, and the pressure plunged. The pressure topped out 132.63 kPa.

In the neutral test, the pressure climbed to 177.18 kPa, and then, again, the stopper popped and the pressure plunged rapidly. The pressure never came back to what it was before the pop.

In the base test, the pressure climbed rapidly. At 164.70 kPa, the stopper popped and the pressure dropped lower than the start and the other two tests.

In all of the tests, the stopper popped. The pressure would have been much higher if the stopper hadn't popped. It is hard to determine which one had the most pressure build-up, because the one that had the "highest" pressure was the one that held out the longest. There is no ability to say which one would have  had the highest pressure. 

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In which mixture was the yeast activity greatest?

The yeast activity was greatest in the neutral mixture. This may have been because it held out longest against the pressure, making it to 177 kPa before the stopper popped. It did get more foamy and frothy than the other ones, so it may have had the highest pressure if none of them popped. This could be because yeast neutralizes hydrogen peroxide, which was in all of the test tubes, and the water just diluted it, it didn't add any other chemicals.

In which mixture was the yeast activity the least?

The yeast activity was least in the acidic mixture. The acidic mixture was also the earliest one to pop, popping at 130 kPa. It was not rising as fast as the others in the beginning, so it would have probably been the lowest pressure no matter what. 

What can you conclude from your results?

From my results, I can conclude several things. One is that the pressure accumulated in the beaker was so great that the stopper actually popped out of it. Another thing is that yeast does not have a major reaction with the acids and bases. I think that a large influence of the pressure came from the yeast neutralizing the hydrogen peroxide. 

Conservation of Mass Investigation

Background Information:

Pop rocks are made of sugar, lactose, corn syrup, and flavoring. When they reach their boiling point, the are combined with carbon-dioxide gas under high pressure. This causes little carbon dioxide bubbles to form. When the candy is put in your mouth, the little gas bubbles are released, causing the popping sensation. 

When baking soda and vinegar are combined, it causes a chemical reaction. The products release carbon dioxide, a formerly unfound element in the two substances. 

Lab Investigation:

We did a lab comparing the reaction between pop rocks and soda blowing up a balloon, and baking soda and vinegar blowing up a balloon. In the pop rocks test, there were quite a few obstacles. The balloons were very small, making it hard to get the pop rocks in, and making it difficult to get it around the balloon. Once the pop rocks were dumped into the balloon, not much of a reaction occurred. The balloon inflated very slightly. The balloon could also take some fault for this, because it was very small and not stretchy, and it wasn't easy to blow up. 

The combination of pop rocks and soda is a physical reaction. Because both ingredients already contained trapped carbon dioxide. When they were combined, they just released that carbon dioxide that was trapped, not created a new product. 

In the baking soda and vinegar test, the results were much better. The balloon problem was still apparent, but it didn't seem to make as much of a problem. The first balloon we tried to put on the bottle broke, and the second one also broke, but still worked. Once the baking soda was added, the reaction was quick. It blew up the ballon within a couple of seconds. The balloon grew to a much greater size than the pop rocks and soda test.

Variables:

There were several variables in this experiment that may have varied the results. The first variable that may have affected the experiment is the balloon. It is possible that the balloon pushed the air back down when it couldn't inflate anymore, and the reaction wasn't violent enough to inflate the stiff balloon. Another variable may have been the soda. Different types of soda may have made a difference to what the reaction was because of the different ingredients. 

Chemical Reactions and Heat Lab Investigation

"In order for a chemical reaction to occur, the particles, atoms or ions which are reactants, must physically come into contact with one another. Anything that increases the frequency of these encounters will increase the rate at which products are formed.
The rate of a chemical reaction can be increased by increasing the temperature of the reaction" -Lab Sheet

How does temperature affect chemical reactions?

The lab was conducted in three tests, one heated, one at room temperature, and one cold. An alka-seltzer tablet was dropped into each one, and temperature, time, and reaction was recorded.

In the heat test, the water was 24˚C to begin. It was heated to 50˚ C, and then taken off the hot plate. At about 45˚C the water began to bubble. The alka-seltzer tablet was the added, and reacted and fizzled for 39.18 seconds. The temperature fluctuated almost 5˚C while the reaction was taking place.

In the room temperature test, the water was 23.6˚C. After sitting for a minute, it rose to 23.8˚C. The tablet was then added, and it reacted for 41.49 seconds. It took longer at room temperature to dissolve the tablet. The temperature dropped .7˚C during the reaction.

In the cold water test, the water was 12.5˚C when the ice was first added. After a minute of stirring, it dropped to 2.8˚C and most of the ice had completely dissolved. The reaction lasted for 1 minute 55.23 seconds. The tablet jumped around in the bottom of the beaker. It took almost triple the length of the hot reaction. When the temperature probe was near the dissolving tablet, the temperature went up. Overall the temperature change was 1.9˚C.

The tablet was releasing energy in the reaction, because whenever the probe was close to it, more heat was recorded. Also, the hotter the water, the more energy. So when the most energy was combined, it produced the fastest reaction.

Chemical Reactions: Chem Think

C H E M I C A L R E A C T I O NS T U T O R I A L Q U EST I O NS :

1. Starting materials in a chemical reaction are called: reactants

2. The ending materials in a chemical reaction are called: products

3. The arrow indicates a: chemical change

4. All reactions have one thing in common: there is a rearrangement of the bonds

5. Chemical reactions always involve: breaking bonds, forming bonds, or both.

6. In all reactions we still have all of the same atoms at the end that we had at the start.
7. In every reaction there can never be any  missing   atoms or new atoms.
8. Chemical reactions only rearrange in the atoms that are already there.

9. Let’s represent a reaction on paper. For example, hydrogen gas (H2) reacts with oxygen gas (O2) to form water
(H2O): H2 + O2H2O
If we use only the atoms shown, we’d have 2 atoms of H and 2 atoms of O as reactants. This would  make 1 molecule of H2O, but we’d have 1 atom of O leftover. However, this reaction only makes H2O.

10. So to make H2O from oxygen gas and hydrogen gas, the balanced equation would be:

__1__ H2 + ___2__ O2 _____ H2O Which is the same as:

# of atoms in reactants	Element	# of atoms in product
4	H	4
2	O	2

11. This idea is called the__Law of Conservation of Mass________
12. There must be the same__mass_____and the same number of_atoms___before the reaction (in the reactants) and after the reaction (in the products).
13. What is the balanced equation for this reaction? _2___ Cu+___2__ O2 --> __2__ CuO
14. In the unbalanced equation there are:

Reactants	Products
Cu Atoms: 1	Cu Atoms: 1
O Atoms: 2	O atoms: 1

15. To balance this equation, we have to add __CuO____ molecules to the products, because this reaction doesn’t make lone __O___ atoms.
16. When we added a molecule of CuO, now the number of __O___ atoms is balanced but the number of _Cu___ atoms don’t match. Now we have to add more __Cu___ atoms to the reactants.
17. The balanced equation for this reaction is __2__ Cu
+ __2__ O2 = __2_ CuO
This is the same thing as saying:

Reactants:	Products:
Cu atoms: 2	Cu atoms: 2
O atoms: 2	O atoms: 2

18. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) _1____ CH4 + _2____ O2 ___2__ H2O + __1___ CO2

# of atoms is Reactants	Element	# of atoms in product
1	C	1
4	H	2
2	O	3

19. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) ___1__ N2 + __3___ H2 = __2___ NH3

# of atoms is reactants	Element	# of atoms in produc
2	N	1
2	H	3

20. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) __2___ KClO3 __2___ KCl + __3___ O2

# of atoms in reactants	Element	# of atoms in products
1	K	1
1	Cl	1
3	O	2

21. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) ___4__ Al + __3___ O2 = __2___ Al2O3

# of atoms in reactants	Element	# of atoms in products
1	Al	2
2	O	3

SUMMARY

1.) Chemical reactions always involve: They always involve making or breaking bonds, or bothe making and breaking bonds.
2.) The Law of Conservation of Mass says that the same atoms must be: There must be the same number of atoms before and after the reactions.
3.) To balance a chemical equation, you change the _coefficiants__ in front of each substance until there are the same number of each type of __atoms____ in both reactants and products