Dissolved In Oxygen Lab Report
Temperature vs. Dissolved Oxygen Lab
Lab A:
Hypothesis:
As the temperature increase, the dissolved oxygen level will decrease because gases
like oxygen are less soluble in water at higher temperatures because the molecules in the
water becomes loosely arranged, which will allow the oxygen to escape.
Equipment List:
Oxygen probe
3 200 mL beakers
Temperature probe
Cold water
Toilet water
Tap water
Procedure:
1. Prepare and make sure the probe is correctly calibrated and ready to use.
2. Get 3 200 mL beakers
3. Collect your water samples from three different places.
4. Measure the temperature and dissolved oxygen level with the probe.
5. Record your results.
Results:
Water Samples
cold water
Toilet water
Tap water
Temperature (degree
Celsius)
16.5
30.6
31.3
Dissolved oxygen
level (mg/L)
0.8
0.9
0.7
Saturation point
0.8
10
7
Analysis:
When people are cleaning the toilet, the soap and detergent that they are using has
chemicals in it because there might be some parts that were left out without be wash off
properly. Chemicals in water might have affected the dissolved oxygen in the sample. To
improve, we can make more controls in order to confirm that only the temperature and
dissolved oxygen is being tested.
The probe might not be as accurate as we want it to be due to calibration. We can
prevent this from happening by making sure that the calibrating machines are accurate
before using it on any of our samples.
Conclusion:
By looking at the results, it can be concluded that as temperature increases the
dissolved oxygen level decreases.
The inverse relationship between temperature and dissolved oxygen is due to the
structure of water molecules. As we know, temperature affects the arrangement in water
molecules because as temperature increases, the water molecules become loosely packed,
which allow more gas to escape from it. How loosely packed the molecules become depend
on how high the temperature is.
Lab B:
Purpose:
The purpose of this experiment is to find the relationship between light intensity and
the amount of oxygen dissolved.
Hypothesis:
As the amount of light intensity increases, the amount of primary productivity
increases, and therefore the amount of oxygen dissolved in water. It’s a directly
proportional. However the relationship between light intensity and the amount of oxygen
productivity won’t exactly be linear since the primary producers will reach a saturation point
as the light intensity increases.
Variables:
Independent: Light Intensity
Dependent: amount of oxygen dissolved in water
Fixed: Temperature, amount (concentration) of primary productors,
Control: No protists (no pond water), No light intensity
Equipment List:
6 bottles with lids
Tissues
Foil
Beaker
Tap water
Pond Water
Spike ( to poke holes)
Tape
Oxygen Probe
Temperature Probe
Procedure:
1. Take 50 mL of tank water , 450 mL of tap water.
2.
3.
4.
5.
Pour both of them into a bottle
Do the same for 5 different bottle.
Measure the temperature and oxygen level for each bottle and record it down
Seal the lid on the bottle and poke small holes on the lid ( bottle cap ) for air
exchange.
6. Make different samples with different amounts of light intensity
7. Use paper towels/tissues to control the light intensity.
8. Keep all the 6 bottles in the same temperature.
9. ----After a few days---10. Measure the final dissolved oxygen concentration in each bottle
11. Record your results,
12. Compare the oxygen level.
Results:
Different types of bottles
Full light
Completely dark
1 layer of tissue wrapped
2 layer of tissue wrapped
3 layer of tissue wrapped
Amount of oxygen dissolved in water
4.7 mg/L
4.1 mg/L
4.5 mg/L
4.4 mg/L
4.3 mg/L
Analysis:
There are holes on the bottle caps. While we are holding the bottles we did not
remember that there were holes on the bottle caps. We might had shaken it a little bit too
much and water started to fall out of those holes. Some bottles contains water with protists
in it which may have also fallen out. To prevent this from happening, we should be much
more careful and aware that there are holes and the water will fall out if we shake it too
much.
Since we are humans, there will be a few human errors that will be made such as
measuring. When we are measuring the amount of water with a graduated cylinder our
measurements may not be perfect. It may not be perfect because it is quite impossible to be
100% since our eyes are all different. Some people may think it is accurate and some may
not.
Conclusion:
By looking at the results, we can conclude that the more light it gets the more
oxygen is available. As we can see the full light bottle is 4.7 mg/L, which is exposed to the
most light and has the highest oxygen level in the water. While the completely dark bottle is
completely dark and had the least oxygen dissolved oxygen level. Bottle 3 had 3 layers of
paper towels wrapped and it had a 4.3 mg/L dissolved oxygen level. Whereas bottle 1 had
only 1 layer of paper towels wrapped and it had a 4.5 g/mL dissolved oxygen level. Through
many different samples, it has been proven that the more sunlight the bottles are exposed
to the higher the dissolved oxygen level it has.
The hypothesis is correct because it stated that as the amount of light intensity
increases the amount of primary productivity increase, and therefore the amount of oxygen
dissolved in water. The results proved that as light intensity increases the level of dissolved
oxygen also increases. The reason might be because the pond water might have living
protists in them and some of them might be alive. As they are exposed to sunlight, they
might be doing photosynthesis and respiration.