Earth Science Teacher Graded Assignment appreciate any help i can get?

SCI113B: Earth Science | Unit 3 | Lessons 5 and 6: Laboratory: Dissolved Oxygen

Name:

Date:

Lab Report
Answer the questions below. When you are finished, submit this assignment to your teacher by the due date for
full credit.
Record the number of drops of Reagent D needed to turn the solution light blue in each phase of the lab:

Set-Up Observations
Phase

Amount of water
mL or drops

Amount of yeast

1

6 mL

0.25mL

2

6 mL

0.25mL

3

6 mL

0.25mL

(12 points)

1.

Complete the data table.

Score

Experiment Observations
Phase 1

Phase 2

Phase 3

O2 concentration in
ppm (parts per
million) = number of
drops of Reagent D
added to reach blue
color (oxygen
completely depleted)
and observations
(3 points)

2.

Regarding Phases 2 or 3 of the experiment, if more or fewer drops of Reagent D
(sodium hydroxide) were needed to get the same blue color as in Phase 1, what does this
tell us about the quality of the water when yeast was consuming nutrients in the water? Did
something similar to eutrophication occur?

Score

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Page 1 of 3

SCI113B: Earth Science | Unit 3 | Lessons 5 and 6: Laboratory: Dissolved Oxygen

(3 points)

3.

What would happen to the dissolved oxygen in the Missouri River if large amounts of
waste were dumped into it?

Score

(3 points)

4.

Under favorable conditions, bacteria can multiply every 20 minutes. Starting with one
bacteria cell, how many bacteria should you expect after 15 hours? Hint: Under favorable
conditions, if one bacterium becomes 2 in 20 minutes (1 multiplied by 2), those 2 become 4
in the next 20 minutes, and then those 4 become 8 in the next 20 minutes. That means that
8 bacteria resulted in 1 hour. Now calculate the growth of bacteria for 15 hours.

Score

(3 points)

5.

In this lab, you continued to add Reagent D to each solution until it turned blue. The
purpose was to remove the oxygen to measure how much was left. The more drops you had
to add to acquire the blue color, the more oxygen was present in the tube. In which phase(s)
did the solution turn blue before you added Reagent D? What do you think that means?

Score

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Page 2 of 3

SCI113B: Earth Science | Unit 3 | Lessons 5 and 6: Laboratory: Dissolved Oxygen

Further Uses
(3 points)

6.

Now that you?ve seen how decomposition affects the amount of dissolved oxygen,
collect three samples from somewhere in your house or community. You can get water from
a puddle, a drinking fountain, a stagnant bowl of pet water, a stream, a pond, or fresh
rainwater?be creative. Then, see how much dissolved oxygen you find in the sample.

Score

Sample

Location

Signs of
Decomposition
(List any visible
microorganisms that
might indicate
decomposition.)

Prediction for
Dissolved
Oxygen Level

Results for
Dissolved
Oxygen

(Would this
location support
aquatic life?)

1
2
3