If a Submarine Starts to Sink Will It Continue

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a "control." A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral "reference point" for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a "controlled experiment."

Experiment 1: Make Your Own Submarine

Build your own submarine. Discover the principle of buoyancy in your kitchen sink or bathtub!

All you need is:

• a plastic soda or water bottle with cap (any 16 oz, 20 oz or 2L bottle will do)
• a flexible straw
• modeling clay
• adhesive tape (PVC electrical tape)
• 7 quarters
• 2 rubber bands
• bathroom tub, kitchen sink or large bucket filled with water
• aluminum foil

Here's what you do:

Empty the bottle and make a hole in the cap large enough for the straw to fit through (This is easiest to do with a hammer and large nail, so ask an adult to help). Now make two holes in line with each other along one side of the bottle. Tape the quarters together in one group of three and one group of four. Using rubberbands, secure the 4-quarter group below the hole nearest the bottle's bottom and secure the 3-quarter group underneath the uppermost hole. Fit the shorter end of the straw through the hole in the bottle's cap and seal with modeling clay. Put the cap back on the bottle.

Now, fill up the bathroom tub, kitchen sink or large bucket with water. Hold your "submarine" underwater so that it fills with water and sinks (be sure to keep the open end of the straw out of the water). Now, blow into the straw and watch what happens.

Here's how it works:

The submarine filled with water has negative buoyancy and is denser than the surrounding water, so it sinks. As air is blown into the submarine, it gains positive buoyancy and is less dense than the surrounding water, so it rises.

Experiment pictures:

In this bottle submarine the air hole is made on the side, not on the cap. This will make it easier to control the submarine and allow it to go up and down horizontally.

A soft plastic tube about 3 feet long is inserted into the hole.

Some chewed bubble gum is used to seal the hole around the plastic tube.

PVC tape also known as electrical tape is used around the neck of the bottle to hold the tube in place.

I attached a heavy piece of lead on the other side of the bottle (opposite the tube hole) and secured it there with some more PVC tape. I used the lead rod because I had it available. You may use any other heavy metal instead. A long metal piece will help to maintain the balance; otherwise, one end of the submarine may be heavier than the other side.

Lead is a soft metal; so I simply bent it to the size of the bottle.
Two other small holes are made at the bottom of the submarine for entering and exiting water. I made one hole close the front and one hole close to the back.

When I placed the submarine in water, the lead piece automatically moved down and water started to enter the submarine from the bottom. As the water was entering the bottle, air was exiting from the tube. I could use my finger to close the end of the plastic tube to stop the air and water flow would stop as well.

In a few seconds enough water entered the submarine and made it sink.

I could bring it up again by blowing into the tube.

---

Experiment 2: How Does a Submarine Dive?

Can you make a submarine dive?

Navy sailors do it everyday. Here is an experiment that demonstrates the principle that allow a submarine to dive. All you need is:

• a tall, narrow jar (like an olive jar),
• a rubber sheet (it would also work to cut the end off a rubber balloon,
• a medicine dropper, and
• water

Procedure:

1. Fill the jar almost to the top with water.
2. Put the medicine dropper in and squeeze the bulb just a bit. Allow only enough water into the dropper so that it is just floating at the top.
3. Now, put the rubber sheet or balloon over the mouth of the jar. Stretch it as far as you can and use the strong rubber band to hold it.
4. Press down on the sheet with your hand. What happens? Now, remove your hand. What happens? Why?

Here's how it works:

When you press on the rubber sheet, the air has less space in the jar and so it pushes down on the water more. This increases the water pressure and adds more water to the dropper. The added water causes the dropper to sink. When the pressure on the sheet is released, the air resumes its normal space and exerts less pressure on the water. The extra water pushed into the dropper is released, and the dropper rises to the top.

Whether a submarine is floating or sinking depends on the ship's buoyancy. Buoyancy is controlled by the ballast tanks, which are found between the submarine's inner and outer hulls. A submarine resting on the surface has positive buoyancy, which means it is less dense than the water around it and will float. At this time, the ballast tanks are mainly full of air. To submerge, the submarine must have negative buoyancy. Vents on top of the ballast tanks are opened. Seawater coming in through the flood ports forces air out the vents, and the submarine begins to sink. The submarine, ballast tanks now filled with seawater, is denser than the surrounding water. The exact depth can be controlled by adjusting the water to air ratio in the ballast tanks. Submerged, the submarine can obtain neutral buoyancy. That means the weight of the submarine equals the amount of water it displaces. The submarine will neither rise nor sink in this state. To make the submarine rise again, compressed air is simply blown into the tanks forcing the seawater out. The submarine gains positive buoyancy, becomes less dense than the water and rises.

---

Experiment 3: Make Marbles Float

Have you ever wondered how heavy objects can float? A ship made of heavy steel carries thousands of heavy cars and it can still remain floating on water. This experiment shows how heavy objects can float.

Materials:

• a tub filled with water
• marbles (rocks work too!)
• a jar with lid (the only requirement is it be small enough to fit inside the tub)

Procedure:

1. Gently drop the marbles one by one into the tub. Do they float or sink?
2. Close the jar lid tight and place into the tub. Does it float or sink? (Hint: If the jar sinks, get a new jar!)
3. Now, take the marbles and jar out of the water. Add one marble to the jar, replace the lid and place it into the water. Does it still float?
4. Add another marble, replace the lid and put it back in the water. Does it float now?
5. Keep adding marbles until the jar sinks.
6. Why does the jar still float when it has a couple of marbles inside when all the marbles sink if they are not in the jar?

Here's how it works:

The marbles are denser than the surrounding water, so they sink. This is the basic principle behind Archimedes' Principle. The closed jar filled with air is less dense than the surrounding water. It has positive buoyancy. Adding marbles to the jar affects its weight and thus its density. If enough marbles are added, the jar will sink because it is negatively buoyant.

---

Experiment 4: Make Your Own Periscope

Introduction: Submarines use a device known as periscope to see above the water. Periscope in submarine is a vertical retractable telescopic pipe with mirrors and lenses. The upper end of the periscope will come out of the water so the underwater staff can see what is happening above the water and be aware of the nearby land and other vessels.

Construction of a periscope is a valuable addition to a submarine project.

How can I use a periscope?

Have you ever wanted to be able to see what's on top of the refrigerator or around the corner? Now, you can, using the same method Submariners use to see above the water's surface while they are submerged.

Materials:

• a long narrow box
• 2 small square mirrors
• scissors

Procedure:

Start with the long narrow box and make the viewholes. Do this by cutting two rectangular holes in the box: one at the top and the other at the bottom on the opposite side.

Next, you need to insert the mirrors. These should be set at 45-degree angles opposite each hole. You can cut slits in the sides to insert the mirrors and use tape to hold them in place.

Now, you can spy on your siblings around corners or see if the grass really is greener on the other side of that tall fence!

Here's how it works:

Images in front of the top hole are reflected from the top mirror into the bottom mirror where they can be seen through the bottom hole. Submarine periscopes operate very much the same way except on a bigger scale and with magnifiers to help Submariners view distant objects clearly.

---

Experiment 5: How does the size (Volume) of a submarine affect the force needed to sink it.

Introduction: Submarines need to get very heavy in order to go under water. In other words the only force that can pull a submarine down is its own weight. The weight of a submarine comes from the weight of its structure, equipment and load (passengers). Are these enough to sink a submarine? How much force (weight) is needed to sink submarines with different sizes?

Materials:

• a tub filled with water
• marbles (rocks work too!)
• Three different size jars with lid

Procedure:

1. Measure and record the volume of each jar.
2. Get the smallest jar, place one marble in it, close the lid and place it in the tub. Does it sink or float? If it floats, add one more marble and try it again. Continue this until the jar sinks. Record the size of the jar and the number of marbles it took to sink.
3. Repeat this with the two other jars and find out how many marbles it take to sink each jar.

Your results table may look like this:

Volume of the jar	Number of marbles to sink the jar
200 cc
400 cc
600 cc

Notes:

• cc is the abbreviation of cubic centimeter.
• Instead of the number of marbles, you may record the total weight of the jar with its contents. This is especially good if you don't have marbles and you want to use sand or small rocks instead. We recommend to measure and record the weights using a gram scale (metric system); however, it is acceptable to measure the weight in ounces as well.

Make a graph:

Make a bar graph to visually demonstrate your results. Make three vertical bars; one bar for each of the jars you test. Under each bar write the size of the jar. The height of the bar will represent the number of marbles or the total weight that made a jar to sink.

---

Experiment 6: Make a Chemical Submarine

Introduction:

These submarines are operate by a chemical reaction inside the submarine. Some submarines use Alka-Seltzer while others use baking soda and vinegar.

How does it work?

The Chemical submarines use the concept of density to float and sink. When baking soda and Alka-Seltzer meet vinegar and water, respectively, they bubble up and either displace water or expand the sub. This decreases the mass or increases the volume, decreasing the density (mass over volume) enough to make it float. After the reaction calms, the sub regains its previous state (more mass or less volume) causing it to sink again.

Purpose: The purpose of this experiment is to build a submarine that will change density in a tank of water enough to allow it to rise and sink repeatedly.

Materials:

• Small container
• Alka-Seltzer
• Weight
• Masking tape
• Plastic wrap

Procedure:

1. Tape the weights to the bottom of the container.
2. Cut a hole in the side of the container, close to the bottom.
3. Wrap the Alka-Seltzer in a small piece of plastic wrap and hang it inside the container, as close as possible to the top.
4. Cut about 5 holes in the plastic wrap.
5. Fill up the container up to about 3/4th.
6. Hold the hole with your finger so the water does not drain and then close the cap.
7. Drop the bottle in water, and watch.

What will happen?
Initially the water has no contact with Alka-Seltzer and the bottle sinks because of the heavy weight. At the bottom of the tank the bottle falls on its side. That is when the Alka-Seltzer gets wet and produce gas. The pressure of gas will push some water out of the hole, reducing the total mass of the bottle. The bottle will rise at this time and come to the top.

What happens next?

After a while the produced gases may dissolve in water and cause a vacuum that will suck in some more water and make the bottle heavy again. If this happens, the cycle will repeat.

In good conditions this cycle may repeat a few times.

What can I use as heavy weight?

Lead and bismuth are heavy metals used as weight for fishing. You can use some PVC tape and attach a few pellets on the side of the bottle.

Iron pieces, bolts, nuts and coins are good too; however, you need much more of them. Before you hang the Alka-Seltzer bag, do a test to make sure that your bottle can sink slowly. If it floats, you need more weight or more water.

grosswantooke1972.blogspot.com

Source: https://www.scienceprojects.org/submarine-how-to-sink-how-to-float/

Share this post