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Learning Lesson: Salt 'n Lighter
OBJECTIVE Show that as the salinity increases the density also increases.
OVERVIEW Fresh eggs, which are less dense than saltwater, will float, but will sink in freshwater.
TOTAL TIME 3 minutes as a demonstration, 10 minutes if students perform the demonstration.
SUPPLIES 3 fresh eggs, 3 - 1.5 liter beakers (or quart jars), 6 ounces of salt.
6. Moonlight Serenade
 Background  
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Just as air can have different densities, water can have different densities as well. As the salinity of water increases, the density increases as well.
 Procedure  
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  1. Fill each beaker with one liter of tap water (or each quart jar with one pint of water).
  2. Add 35 grams of salt to one beaker and 290 grams of salt to a second beaker (½ ounce of salt to one quart jar and 4½ ounces of salt to a second jar).
  3. Ask the students to speculate in which water solution will the eggs float.
  4. Place an egg in each solution and observed in which solution it floats.
 Discussion  
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Fresh eggs are more dense than fresh water and therefore will sink. However, as the salt content increases in water, it becomes more dense. The egg will float in the two beakers with the added salt. This happens because the added salt makes the water heavier than the egg causing the egg to float.

The solution with the 35 grams of salt represents the salinity of the oceans. The solution with 290 grams of salt added represents the salinity of the Dead Sea. As the salinity increases, the density increases as well. The egg in the beaker with the most salt should float higher that in the other salty solution.

The increased density of the salty water actually increased the weight of the water. An egg will be bouyant (float) if the weight the egg is less than the weight of the water it displaced. The egg sinks if it weights more than the weight of the water that was displaced.

The size (or weight) of a ship is determined by the weight of water that is displaced when fully loaded (reported in tons). The following are sizes of large ships.

Year Ship Type Owner Length
(Feet)		 Width
(Feet)		 Weight
(Tons)
1912 Titanic Liner White Star Line 883 92 46,328
1934 Queen Mary Liner Cunard 1,019 119 81,237
1939 Bismark Battleship Germany 880 120 50,000
1944 Missouri Battleship United States 887 108 58,000
1962 Enterprise Aircraft Carrier United States 1,101 133 89,600
1976 Jahre Viking Supertanker Jordan Jahre 1,504 226 647,955
2003 Ronald Reagan Aircraft Carrier United States 1,092 134 97,000
2004 Queen Mary 2 Liner Cunard 1,132 148 150,000
2006 Freedom of the Seas Liner Royal Caribbean 1,112 184 160,000
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