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Solution Preparation
Background Information:
 
 
Example:
 
To prepare 100.0 grams of 1.0% salt water you would add 1.0 gram of salt to just 99.0 grams of water. Remember that the total mass of the solution must be 100.0 grams.
 
x = 1.0 gram of salt
 
Procedure:
 
During this experiment you will need to prepare 5 different solutions. You might try making up 0%, 1.0%, 2.0%, 3.0%, and 4.0% salt water. Use food coloring to tint each solution a different color.
 
Once the solutions have been made, "stack" two different colored solutions in the glass rod. If it doesn't work and the solutions mix, try reversing the order. Investigate until you have a solid understanding of how the % of salt is related to the density of the solution. Make sure you are able to stack all 5 layers in the glass rod.
 
Practice Problem:
 
A sample of water was obtained from the Atlantic Ocean. Determine the density of the ocean water. Justify your position using experimental evidence. You should be able to include ocean water in the stack you assemble in the glass rod. Show your teacher when you have accomplished this.
 
 
Analysis Questions:
 
  1. If you have ever ordered a soft drink at a fast food restaurant, you may have played with the idea of picking liquid up with the straw. By placing your finger over the end of the straw, you can lift some of the drink up in the straw. As long as your finger remains on the straw, the liquid doesn't fall out. Why is this?

  2. In your experiment, what happens when a dense liquid is placed above a less dense liquid? Explain.

  3. What happened when a less dense liquid is stacked above a liquid with greater density?

  4. With care, you can "stack" all five solutions in the glass rod.  Assuming you could maintain the seal, would the 5 layers stay separated forever or would they eventually mix to create a uniform distribution? When explaining this, be sure to recall that molecules are in constant motion.

  5. Draw a diagram showing the sequence of the five solutions, from least to most dense, stacked in the glass rod. Label the % salt in each layer.

  6. Make a graph of mass of salt (x-axis) versus % salt (y-axis). Draw the line of best fit. On the graph, indicate the region of the line corresponding to the ocean water you analyzed.
 
BONUS:
 
People find that swimming in the Dead Sea is difficult because they tend to "bob" at the surface like corks. Do an internet search. What is the % of salt in the Dead Sea? Why are people more buoyant in the Dead Sea than in the Atlantic Ocean?



E Saylor

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