How Much Salt is in Ocean Water?

1
How Much Salt is in Ocean Water?
2
Purpose

• To determine how many mL of salt there is in
  200mL of ocean water.

3
Hypothesis

• I think that there will be 6mL of salt in the
  200mL of ocean water. I tried a taste test before
  the mixtures went into the freezer.

4
Materials

• A sample of ocean water
• Small plastic cups/marker
• Measuring cup
• Table salt
• Thermometer
• Freezer
• Teaspoon
• Tap water
• Syringe (to measure salt)

5
Procedure

1. Get a sample of ocean water, and a sample of tap
   water.
2. Allow water to stand for 24 hours to achieve room
   temperature.
3. Number eight plastic cups and label the salt
   content as 0, 2, 4, 6, 8, 10, 12, and ocean
   water.
4. Then measure out the amounts of salt and put the
   correct amount in each cup.
5. Pour 200mL of tap water into cups 1-7. Put 200mL
   of ocean water in cup 8.
6. Now, place the cups in a row in the same section
   of the freezer, and make sure there arent other
   items around them.
7. Every 10 minutes, check the mixtures to see if
   there are any signs of freezing, and when there
   is, check the mixtures every 5 minutes until the
   tops of the mixtures are frozen.
8. Repeat steps 4-7 two more times.

6
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7
Variables

• Manipulated Variable the amount of salt in each
  cup.
• Responding Variable the time it takes for the
  mixtures to freeze.
• Control Variables
• The temperature of the freezer (-18 C)
• Initial temperature of the mixtures (18 C)
• The type of cups used in the experiment.
• Type of salt (table salt)
• The placement of the cups in the freezer. (Placed
  in a row in the very back of the freezer)
• Amount of water in each cup.

8
Observations

• The 12mL of salt mixture and the ocean water look
  almost identical when starting to freeze.
• The cups with salt in them crystallize before
  they freeze.
• After the mixtures crystallize, they turn slushy,
  and then slowly harden.

9
Results Trial 1
Cup Amount Of Salt 10 mins. 20 mins. 30 mins. 40 mins. 45 mins. 50 mins.
1 None Nothing Frost on the cup Starting to Freeze In process of freezing Frozen -
2 2mL Nothing Frost on the cup Starting to Freeze In process of freezing Frozen -
3 4mL Nothing Frost on the cup Starting to Freeze In process of freezing Freezing In process of freezing
4 6mL Nothing Frost on the cup Nothing Nothing Starting to Freeze In process of freezing
5 8mL Nothing Frost on the cup Nothing Nothing Starting to Freeze Crystals and slushy
6 10mL Nothing Frost on the cup Nothing Crystals and slushy Crystals and slushy Crystals and slushy
7 12mL Nothing Frost on the cup Nothing Nothing Nothing Nothing
8 Ocean Water Nothing Frost on the cup Nothing Nothing Nothing Starting to Freeze
10
Results Trial 1 (continued)
Cup Amount of Salt 55 mins. 60 mins. 65 mins. 70 mins. 75 mins. 80mins.
1 None - - - - - -
2 2mL - - - - - -
3 4mL Close to frozen Frozen - - - -
4 6mL Close to frozen Close to frozen and slushy Slush is hardening Almost frozen Frozen -
5 8mL Slushy Slushy Slush is hardening Close to Frozen Close to Frozen Frozen
6 10mL Slushy Slushy Slush is hardening Close to Frozen Close to Frozen Close to Frozen
7 12mL Slushy Slushy Slush is hardening Close to Frozen Slushy Close to Frozen
8 Ocean Water Crystals and slush slushy Slush is hardening Close to Frozen A little Slushy Close to Frozen
11
Results Trial 1 (continued)
Cup Amount Of Salt 85 mins. 90 mins.
1 None - -
2 2mL - -
3 4mL - -
4 6mL - -
5 8mL - -
6 10mL Frozen -
7 12mL Not quite Frozen Frozen
8 Ocean Water Frozen -
12
Results Trial 2
Cup Amount Of Salt 10 mins. 20 mins. 30 mins. 35 mins. 40 mins. 45 mins.
1 None Nothing Nothing Nothing Starting to Freeze In process of freezing Frozen
2 2mL Nothing Nothing Starting to Freeze Starting to Freeze Frozen -
3 4mL Nothing Nothing Nothing Starting to Freeze Starting to Freeze In process of Freezing
4 6mL Nothing Nothing Nothing Starting to Freeze Starting to Freeze In process of Freezing
5 8mL Nothing Nothing Nothing Nothing Starting to Freeze In process of Freezing
6 10mL Nothing Nothing Nothing Starting to Freeze Nothing In process of Freezing
7 12mL Nothing Nothing Nothing Nothing Nothing Nothing
8 Ocean Water Nothing Nothing Nothing Starting to Freeze Starting to Freeze In process of Freezing
13
Results Trial 2 (continued)
Cup Amount of Salt 55 mins. 60 mins. 65 mins. 70 mins. 75 mins. 80mins.
1 None - - - - - -
2 2mL - - - - - -
3 4mL In process of Freezing Frozen - - - -
4 6mL In process of Freezing Slushy Slushy Frozen - -
5 8mL In process of Freezing Slushy Slushy Slushy Frozen -
6 10mL In process of Freezing Slushy Slushy Slushy Slushy Slushy
7 12mL Nothing Slushy Slushy Slushy Slushy Slushy
8 Ocean Water Slushy Slushy Slushy Slushy Hardening slush Slushy
14
Results Trial 2 (continued)
Cup Amount Of Salt 85 mins. 90 mins. 95 mins. 100 mins.
1 None - - - -
2 2mL - - - -
3 4mL - - - -
4 6mL - - - -
5 8mL - - - -
6 10mL Frozen - - -
7 12mL Slushy Slushy Slushy Frozen
8 Ocean Water Frozen - - -
15
Results Trial 3
Cup Amount of Salt 10 mins. 20 mins. 30 mins. 35 mins. 40 mins. 45 mins.
1 None Nothing Frost on Cup Nothing Starting to Freeze Starting to Freeze In process of Freezing
2 2mL Nothing Frost on Cup Nothing Starting to Freeze Starting to Freeze In process of Freezing
3 4mL Nothing Frost on Cup Starting to Freeze Starting to Freeze Starting to Freeze In process of Freezing
4 6mL Nothing Frost on Cup Nothing Nothing Starting to Freeze Starting to Freeze
5 8mL Nothing Frost on Cup Nothing Nothing Nothing Nothing
6 10mL Nothing Frost on Cup Nothing Starting to Freeze Starting to Freeze In process of Freezing
7 12mL Nothing Frost on Cup Nothing Nothing Nothing Nothing
8 Ocean Water Nothing Frost on Cup Nothing Nothing Nothing Nothing
16
Results Trial 3 (continued)
Cup Amount of Salt 50 mins. 55 mins. 60 mins. 65 mins. 70 mins. 75 mins.
1 None In process of Freezing Nothing Frozen - - -
2 2mL In process of Freezing Frozen - - - -
3 4mL In process of Freezing Frozen - - - -
4 6mL In process of Freezing Nothing Slushy Nothing Slushy Frozen
5 8mL In process of Freezing Nothing Slushy Nothing Slushy Frozen
6 10mL In process of Freezing Nothing Slushy Nothing Slushy Slushy
7 12mL Nothing Nothing Slushy Nothing Slushy Slushy
8 Ocean Water In process of Freezing Nothing Slushy Nothing Slushy Slushy
17
Results Trial 3 (continued)
Cup 80 mins. 85 mins. 90 mins.
1 - - -
2 - - -
3 - - -
4 - - -
5 - - -
6 Frozen - -
7 Slushy Slush is Starting to harden Frozen
8 Slushy Slush is starting to harden Frozen
18
Time for Samples to Freeze
Trial 1-None 2-2mL 3-4mL 4-6mL 5-8mL 6-10mL 7-12mL 8-Ocean Water
1 45 mins. 45 mins. 60 mins. 75 mins. 80 mins. 85 mins. 90 mins. 85 mins.
2 45 mins. 40 mins. 60 mins. 70 mins. 75 mins. 85 mins. 100 mins. 85 mins.
3 60 mins. 55 mins. 55 mins. 75 mins. 75 mins. 80 mins. 90 mins. 90 mins.
19
Analysis
20
Conclusion

• After gathering my information, it seems that in
  200mL of ocean water, there is about 10-12mL of
  salt. My hypothesis was wrong. While I was doing
  my trials, I noticed that the ocean water mostly
  froze at the same time as the 10mL or the 12mL
  salt mixture. Therefore, I conclude that there is
  between 10 and 12mL of salt in 200mL of ocean
  water. To be more accurate I would have to
  conduct more trials using 1mL increments of salt.

21
Sources of Error

• Where I placed the cups in the freezer was a big
  factor on how the mixtures froze, because it was
  colder in the back of the freezer rather than the
  front (I learned this the hard way and had to
  redo the whole trial)
• It was tricky to measure the salt and the water,
  so it might not be exactly right.
• How warm or cold the mixtures are. (I left the
  mixtures on the counter for 24 hours before doing
  my experiments)
• Any chemicals in the tap water could have
  affected the results in freezing.
• The temperature of the freezer each time I used
  it.
• If the salt was not completely dissolved and
  stirred throughout, there may have been surface
  freezing of plain water.
• Amount of time the freezer door was open while I
  collected my data.

22
Ways to Improve

1. Try the experiment again, except this time
   instead of going up in increments of 2mL, for the
   amounts of salt, go up by 1mL each time.
2. Try boiling amounts of ocean water and collecting
   the residue of salt. Measure the amount of salt
   remaining.
3. Try using rock salt instead of table salt.