What is water pressure?
Objective:
The students will be able to discuss and to demonstrate water pressure .
Materials:
Experiment #1: 1 Balloon, Water, Large pan
Experiment #2: 2 Milk cartons, Large pan, Ruler, Masking tape, Water, Small Nail
Procedure:
Explain to the students that the first experiment will show the force called water pressure. Hold the balloon over the large pan and fill it with water.Have the students write down their observations. Ask what happened to the balloon? ( It got larger.) Ask why? (The weight of the water acts as a force pushing on the inside of the balloon.)
If the water in the balloon can force out the sides of the balloon, imagine how much the weight of the water on the top of the ocean can push on the things in it. The deeper one goes in the ocean the greater the pressure. People who work or dive deep in the ocean where the pressure is great have to return to the ocean surface slowly. If they do not, the sudden change in the pressure can hurt their body.
In our second experiment, we will find out if we can show that water pressure changes with depth.
Directions:
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1. Using the small nail, make a hole in one side of the milk carton 1 inch (3cm) from the bottom. Make a second hole with the nail 2 inches (5 cm) above the first hole. Make a third hole 2 inches (5cm) above the second hole.
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2. Cover the holes with masking tape.
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3. Place the milk carton in the large pan.
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4. Fill the milk carton with water
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5. Quickly remove the masking tape.
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6. Have the students make observations on the Experiment Form. Have a follow up discussion about the experiment. Include the following questions: How did the water flow from each hole? Were the 3 streams of water alike? Why or why not? Suppose the three nail holes were made at the same level, but on different sides of the milk carton. What would you expect the water flow to be like? Have a student (or yourself) do this as another experiment, using the second milk carton.
Closure:
From what we have observed, what could we define water pressure as? (The force of the water in the ocean, pushing down on what is in the ocean.) Is water pressure near the surface of the ocean greater than or less than water pressure deep in the ocean? (Less than.)
Why and how did people get into diving?
Knowing what the ocean floor looked like was not enough for people who wanted to know more about the oceans. They knew that somehow they had to go down into the ocean. At first people tried diving into the ocean, but they couldn’t go very deep in the water. They could not stay in the water for a very long time, either. This was because they couldn’t breathe under water. Also, the ocean water in most parts of the world is too cold for people.
After a time, some ways were discovered that made it possible to go down into the ocean. By carrying tanks of gas on their backs for breathing under water, and wearing special suits to protect them from the cold, divers could go down over 440 feet. They saw that the ocean was still alive with both plants and animals at that level.
Later, with better suits and helmets that covered their face and head, other divers went even deeper in the ocean. These divers had to wear a suit with a long line fastened to a platform from which air was pumped to them. Even with these improvements, divers were still not able to reach the deepest parts of the oceans.
Thanks to the invention of SCUBA (Self-Contained Underwater Breathing Apparaatus) diving gear by French engineers and perfected by Jacques Cousteau and Emile Gagnan, we humans now have a freedom to scoot through the water in any direction! You can swim to the surface, or dive to the ocean floor without coming to the surface for air.
ACTIVITIES:
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1. What are the people called who live and work under water for weeks at a time? (ANSWER-Aquanauts) How can they live and work in under -water stations placed on the ocean floor as far down as 600 feet (180 meters)? Look in reference books to find out.
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2. Deep sea divers must come up to the surface of the oceans slowly to avoid getting the bends, a crippling pain in their joints. Find out why this happens to divers who rise quickly from deep in the ocean. HINT: look under the heading “Bends” in the reference books.
What substances are in the ocean waters?
Many minerals of great value are found in the ocean waters other than sodium chloride, salt. The most valuable mineral taken today is magnesium. It is used making metal and in photography. It is also used in medicine that helps to settle stomachs and in Epsom Salts (used to soothe swollen or sprained joints).
Another mineral is bromine. This is added to gasoline to help cars’ engines run more smoothly. There are also small amounts of gold and silver.
There are many gases dissolved in the ocean, such as oxygen, carbon dioxide and hydrogen to name a few. Marine animals and plants use oxygen in respiration. Carbon dioxide is used by marine plants in making food.
Materials get into the ocean because large amounts are dumped by the rivers from the continents. The land is worn down by the action of running water and other pro-cesses of erosion. The materials are bought to the ocean dissolved in the water. Other substances have come from rocks in the sea itself.
Along with chemicals in solution in the water, there are many chemicals lying on the sea floors of all the oceans, in lumps. One of these rock-like nodules is manganese. This metal is not the only one occurring in this form. There is also copper, nickel and cobalt.
Also, an important and common resource of the ocean is sand and gravel. Because much of it is found near land, it can be dredged up in huge amounts and used in building roads and buildings.
Why should we protect our oceans?
Just imagine if there were no oceans on Earth. What would life be like?
When you think about a world without oceans, you realize how many things you depend on that come from the ocean—from beneath the waves. As a source of food, the oceans provide us with a variety of plants and animals that form an important part of the daily diets of people in many parts of the world. Shellfish, tuna, shark, swordfish, salmon, and edible seaweed are just a few of these foods.
Oil and gas that come from the oceans give us fuel to drive our cars and heat our homes. Even some of the medicines that help to cure us when we are ill come from marine plants and animals.
Because the ocean is so huge, it has an important effect on the weather of most places on the earth. Without the ocean, the days would be warmer and the nights would be cooler than they are now. In fact, the ocean can even affect the climate, or the kind of weather, a place has over many years.
The rewards we receive from the oceans will no longer be available to us if we neglect our responsibilities to nature. Just as we rely on the ocean to provide us with things that are necessary to our survival, oceans survival depends upon human awareness of, and protection from, pollution and activities that harm valuable, endangered marine life.
