Salinity- Density experiment data table



Salinity Density Lab

Testable Questions:

How does salinity affect the density of water?

Hypothesis: ________________________________________________________________________

________________________________________________________________________

Objective

-PART 1: The students will experiment in order to explain what factors affect the density of ocean waters.

Materials

100ml graduated cylinder 30 ml medicine cup paper towels

Goggles Stopwatch cold tap water

Saltwater A (blue) Saltwater B (green) Saltwater C (red)

Part 1: Density Variations with Solutions

Procedures (Read twice before acting, and check off steps as you go)

____ 1. Fill the graduated cylinder provided with cool tap water up to 90ml.

____ 2. Fill the beaker with about 10ml (saltwater A) and pour it slowly into the cylinder, being careful to not dump it in, but rather pour it along the side of the cylinder. Observe and describe what happens. Record the time it takes for the solution to reach the bottom. START the stopwatch when pouring begins and STOP watch when the colored liquid first hits the bottom.

____ 3. Repeat steps 1 and 2 three additional times and measure the time required for the front edge of the saltwater to travel from the surface of the water to the bottom of the cylinder. Record the time for each test in the data table. Make certain that you drain the cylinder after each trial and refill it with fresh water and use the same amount of solution with each trial.

_____ 4. Determine the travel time 3 times for saltwater B, and saltwater C exactly as you did with solution A and enter your measurements in Table 9.1.

Table 9.1

|Solution |Trial 1 |Trial 2 |Trial 3 |Average Time |

|A | | | | |

|B | | | | |

|C | | | | |

Questions

1. Since the solution that traveled fastest has the greatest density, solution (A, B, C) is most dense. Circle your answer.

2. Write a brief summary of the results of your salinity-density experiment.

3. Use your results to identify the percentages of each saltwater solution as 1%, 7 %, and 20%:

Solution A (blue) __________

Solution B (green)___________

Solution C (red) _____________

4. What is density (include units)?

Part 2 (Day 2) Creating Salt Solution

Objective:

-PART 2: The students will experiment in order to explain the role that evaporation plays in the density of ocean waters.

Materials

100ml graduated cylinder 50ml beaker 10 ml graduated cylinder

Tongs Hot Plate Goggles

Apron Stopwatch Electronic Balance

Cold tap water Salt Filter paper

Each group will be given the task of creating a different salt solution.

Circle the salt solution your group was given. 5% 25%

CALCULATIONS: PERCENT COMPOSITION – You will be working with amounts other than 100 milliliters, so this is taken into account by the formula below

PERCENT = PART x 100

                    WHOLE

Example: Percent: Mass in a total volume (m/v) Most frequently used form of %.

    A 5% solution means 5 grams in 100 mL volume. Or 2.5 grams in 50 mL volume.

    A 5mg % solution means 5 mg in 100 mL volume. Same as 5 mg/dL. (dL = 100 mL)

If you have a 100ml solution, how much salt is needed to create your solution?

______________ml of water

______________g of Salt

Totaling _________________ml of saltwater solution

Get Teacher Verification initials before proceeding_____________.

Directions for student verification

Procedure for making “SEA WATER”- Trial run

_____ 1. Weigh the small beaker_______________(g)

_____ 2. Add 10ml of the salt solution to the small beaker.

_____ 3. Weight of small beaker and salt solution_______________(g)

_____ 4. Determine the weight of ONLY salt solution____________(g) subtract

_____ 5. Evaporate the solution by heating it at level 5/6 on the hotplate for 5-10 minutes. Be sure not to let the beaker over-heat. Watch it carefully. Take the beaker of immediately after all the water has evaporated.

_____ 6. Allow it to cool for a minute or two. Using the tongs reweigh the beaker with the residue___________________(g)

PART 2B—

______7. Subtract the weight of the empty beaker from the current weight to get weight of just the residue_______________(g)

______ 8. Calculate the percentage of salt. Divide the weight of the solution (step 4) into the weight of the residue(step 7). Multiply the answer by 100. ___________% salt

______9. Place all of your materials in the trays. Wipe down your station. Discard any trash in the proper place.

Questions (Continued):

4. What are two factors that control the density of salts in seawater?

5. Refer to the factors listed in question 4 as well as your lab, and the diagram below. What is the cause of the difference in surface water salinity between equatorial and subtropical regions in the Atlantic Ocean?

5. Based on the diagram below, of the two oceans, the (Atlantic, Pacific) Ocean has higher average surface salinities. Circle your answer.

[pic]

6. Using the diagram above, at which latitudes are the highest surface salinities located? Use what you know about currents and the water cycle to provide a reason this might be true.

7. How is density and salinity of ocean water related?

Calculate the following salinities. Refer to part B of your lab.

8. If the mass of a sample of water 1000ml contains 200 g of salt, what is the salinity?

9. If a mass of a sample of water 650ml contains 75 g of salt, what is the salinity?

Conclusion:

Write a conclusion for the lab which includes the following parts:

• Restate the purpose for doing the experiment.

• Restate your hypothesis and whether it was correct or incorrect.

• Summarize and analyze your data. Discuss trends and reasons for the trends. Be sure to cite your data.

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