Yeast Beasts in Action Lab Investigation

Today we had a lab that measured the amount of pressure conducted when a yeast and water mixture is poured into an acid mixture, neutral mixture, and a basic mixture. Our hypothesis was the the yeast activity in the acidic mixture will be the greatest because the more acidic something is the greater the reaction. Our problem was how does yeast activity differ in acidic, neutral, and basic mixtures. Some of the materials that we used were a computer, Vernier computer interface, gas pressure sensor, 1 hole stopper assembly, 10 mL graduated cylinder, 3% hydrogen peroxide, yeast suspension, 3 test tubes, test tube rack, dropper, acidic mixture (diet soft drink), neutral mixture (skim milk), and basic mixture (stomach antacid).

First, we had to pour 3 mL of hydrogen peroxide into each test tube and labeled them with a sticky note, A for acid, N for neutral, and B for base. Second, we had to pour 3 mL of each mixture into its designated test tube. Next, we had to make the yeast solution which was 50mL of water and 1/2 tsp of yeast. We poured 1 dropper full into the acid solution, placed the gas pressure sensor into the test tube, and collected the data, we repeated these steps with every single mixture that we did.

Mixture	mL of Hydrogen Peroxide	mL of Mixture
A (acid)	3mL	3mL
N (neutral)	3mL	3mL
B (base)	3mL	3mL

The objectives for this lab were to use a computer and a Gas Pressure Sensor to measure pressure, measure and compare yeast activity in acid, neutral, and basic mixtures, and make a conclusion about yeast activity.

Our hypothesis was not correct, we said that the more acid something is the greater the reaction will so it will have the greatest pressure. This did not happen. The basic mixture had the highest amount of pressure which was 124.04 kPa.

Mixture	Highest Pressure kPa
Acid (diet soft drink)	118. 62 kPa
Neutral (skim milk)	111. 97 kPa
Basic (stomach antacid)	124. 04 kPa

1. In which mixture was the yeast activity greatest? Explain.

The activity was greatest in the basic mixture. I do not know why it was the highest in the basic mixture because I thought that the acidic mixture would be the one which had the largest amount of pressure. Because the mixture contains hydroxide ions in it while the acid had hydrogen atoms. Hydrogen is the lightest element known to man and that lack of mass might have something to do with the amount of pressure. The hydrogen peroxide is made of hydrogen and oxygen atom stuck together and it can create an acid when the oxygen atom is released. I think that the hydrogen peroxide and hydrogen are pretty much the same, except for that extra oxygen atom and that's what makes the difference in the gas pressure.

2. In which mixture was the yeast activity least? Explain.

The neutral mixture had the lowest amount of pressure because neutral is right in the middle and it is neither basic or acidic.

3. What can you conclude from the results of your experiment?

I can conclude that bases cause the most pressure and gas to be produced and neutral mixtures produce the least gas and pressure.

Conservation of Mass Lab Investigation

Our hypothesis for this lab was that the balloon will get filled up with gas, and this will cause it to expand and get larger. We used a filled Mountain Dew bottle and an empty Pepsi bottle, both of these bottles were 20 oz. The pop rocks were poured into the Mountain Dew soda bottle, and the balloon was stretched out and put on the top of the bottle. When the pop rocks were poured into the soda bottle the soda started to fizz up and a chemical reaction was taking place. The soda helped dissolve the sugar coating of the pop rocks, which allowed the carbon dioxide gas to escape. This was a physical change because the state of matter was altered, and there wasn’t a new solution formed. While doing the experiment I noticed that our balloon wasn’t filling up that

much so we decided to shack the bottle.

Doing so made the soda fizz up more and made the pop rocks dissolve more.
In an attempt to make the balloon blow up bigger we took off the balloon and added more pop rocks into the soda, when we tried to but the balloon back on the soda fell over and spilled all over the table, this was a failed attempt. Some possible variables were the types of soda used, the amount of pop rocks, and how stretched out the balloon was.

In the second experiment we used baking soda and vinegar. The reaction was a lot faster then the first one, but the reaction was smaller so less gas was released.

Chemical Reactions and Temperature Lab

My hypothesis was the the warmer the temperature, more of the chemical reaction will take place because there will be more energy stored, when more energy is stored in the water the shorter the reaction time. The problem that we had to answer was does temperature affect chemical reactions? My hypothesis was correct because the heated water had the shortest reaction time and the cold water had the longest reaction time.

Temperatures	Beginning	End	With Tablet	Time
Cold	6.7 C	2.8 C	3.2 C	2 min 30 sec
Room Temperature	22.2 C	23 C	22.5 C	34 sec
Hot	31.6 C	50 C	50 C	21 sec

The colder the water temperature gets the longer it takes for the tablet to dissolve than it does in warmer or hotter water. Different temperatures do affect chemical reactions because they can either speed up or slow down the process.
This graph shows the one with cold water and how the temperature just keeps dropping.



This graph shows the room temperature water and how it stay the same throughout the whole experiment.





This graph shows the heated water and something very interesting about this one is that the temperature kept fluctuating.

Chem Think- Chemical Reactions

Chemical Reactions Tutorial Questions and Answers:

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 has taken place.

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 when the reaction is over that we had in the start

7. In every reaction there can never be any
missing atoms or new atoms when the reaction is over

8. Chemical reactions only
rearrange the bonds in the atom 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 +O2 = H2O

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 left over. However this reaction only makes H2O.

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

2 H2 + 1 O2 = 2 H2O

Which is the same as:

# of atoms in Reactants	Element	# of Atoms in Products
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 and after the reaction.

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 2 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 product atoms is balanced but the number or reactant atoms don’t match. Now we have to add more Cu atoms to the reactants.

17. The balanced equation for this reactions is:

2 Cu + 2 O2 = 2 CuO

This is the same thing as saying:

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

18. What is the balanced equation for this reaction?

1 CH4 + 2 O2 = 2 H2O + 1 CO2

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

19. What is the balanced equation for this reaction?

1 N2 + 3 H2 = 2 NH2

# of atoms in Reactants	Element	# of atoms in Products
2	N	1
2	H	3

20. What is the balanced equation for this reaction?

2 KCIO3 = 2 KCI + 3 O2

# of atoms in Reactant	Element	# of atoms in Products
1	K	1
1	CI	1
3	O	2

21. What is the balanced equation for the reaction?

4 AI + 6 O2 = 2 AI2O3

# of atoms in Reactants	Element	# of atoms in Products
1	AI	2
2	O	3

Summary:

1. Chemical reactions always involve breaking bonds, making bonds, or both.

2. The Law of Conservation of Mass says that the same atoms must be rearranged.

3. To balance a chemical equation, you change the coefficients in front of each substance until there are the same number of each type of atom in both reactants and products.