How do we know that the ocean water contains salt? #1
Materials:
Salt, Teaspoon, Goggles, 2 pans, Distilled water, Measuring cup, Potholder, 1 Hot plate
Directions:
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1. Pour about 1/2 cup (120 ml) of distilled water into one pan. Mix in 2 teaspoons (10 grams) of salt.
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2. Pour the same amount of distilled water into the other pan.
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3. Heat each pan on the hot plate until all the water evaporates. CAUTION: WEAR GOGGLES; if the salt gets too hot, it may splatter.Also use caution when using the hot plate.
4. Make observations and fill in the experiment form.
Follow up:
See follow up for option #2.
OR #2
Materials:
Pie pan, 2 Cups ocean or water from the Sound (Or to make your own salt water, mix 2 tsp. of salt with 2 C water)
Directions:
1. Pour the 2 cups of water into the pan.
2. Place the pan in a warm, dry place.
3. Allow the water to evaporate over the next few days.
4. Make observations. Fill in the Experiment Form.
Follow Up :
Have a class discussion by sharing the answers on the experiment form or by asking questions. When you finished your experiment was there anything left in the pans? What do you think it is? Do you think the method you used would be a good one for separating any other minerals from the ocean (or the Long Island Sound) water? Why or why not?
[TEACHER NOTE: When water evaporates, salt is left in the pans.]
What causes tides?
Tides are the regular rise and fall of the waters of the ocean. Tides are caused by many forces, but the most important is the gravitational attraction of the moon. The next important force is the gravitational attraction of the sun.
As the earth rotates, one of two bulges of water forms in the ocean on the part of the earth facing toward the moon. This tide is caused by the gravitational pull of the moon. This bulge moves westward around the earth as the earth rotates. At the same time, another bulge forms in the ocean on the part of the earth facing away from the moon. This other tide is caused by the weakness of the gravitational force that the moon exerts of that part of the earth. On the part of the earth away from the moon, the earth itself is pulled toward the moon more than the water is pulled (centrifugal force). This greater attraction on the solid part of the earth tends to create a bulge of water (a tide) on the side of the earth opposite the moon.
From the highest point on each of the two bulges, the water level slopes down ward to low points halfway between the two highest points. The low points result from the water being pulled away from those areas between the part of the earth facing the moon and the part facing away from the moon. The high points are high tides, while the low points are low tides.
