How Do Leaves Get Water from Roots?

Plants need water, carbon dioxide and nutrients to live. Water and nutrients come to the plant from the ground, whereas the carbon dioxide comes from the air. The roots of the plant, which are under the ground, absorb water and nutrients for the whole plant above the ground. Have you ever wondered how water reaches the leaves of tall plants, especially the ones at the top? Water has to climb several hundred feet before it can reach the leaves of the top-most branches in some trees like oaks, pines or eucalyptus.

Capillary action and leaf pressure are two important factors that help move water in plants. Capillary action can simply be termed as the automatic movement of water through extremely narrow tubes known as capillaries (hair-thin in some cases) present inside the plant stem. In plants these tubes are called xylem. Capillary action helps plants in getting water to such heights against the downward force of gravity.

Leaf pressure is a property whereby the leaf is able to convey a message to the roots that the pressure of water is low in the leaf and hence it needs more water.

So what is it that helps the water drops stay together and climb up through the minute vessels in the plant body by capillary action? A physical property called surface tension helps water molecules stay together. Surface tension can be termed as the amount of force holding two molecules of the same kind together.

This property is quite high for water than many other liquids. Any impurities like dirt or salt in water tend to lower its surface tension. Because the surface tension for pure water is fairly high, when the water drops are absorbed by the tips of the plant vessels subsequent water drops cling on to the initial ones rising in the plant vessels and begin a journey to the top.

The high surface tension of water is also a reason why rain drops tend to be spherical. For more information on capillary action, read the article at http://en.wikipedia.org/wiki/Capillary_action.

Little Lion Experiment 1:

Items Needed:

• A small glass of bottled water
• A few leaves with waxy surfaces
• A candle
• Some flat cardboard pieces

You can apply wax to a cardboard piece by rubbing a candle lengthwise on the cardboard for a few minutes. This experiment is to show that surface tension is lowered due to addition of impurities.

1. Place a drop of water on the leaf or the waxes cardboard using an ink dropper.
2. Observe what happens to the water drop.
3. If the drop is still on the wax surface, try adding a few salt particles to the water drop.
4. Observe what happens.
5. If the drop of pure water had rolled off then mix one teaspoon salt to the water.
6. Add a drop of the salted water to the leaf/waxed cardboard.

Little Lion Experiment 2:

Items Needed:

• A tall juice glass
• A small thin cardboard piece
• A small needle or thumb tack to make holes
• Cotton thread (white thread works best)
• Scissors
• A small bowl of sugar (crystal sugar preferred)

This experiment will aim to demonstrate the movement of nutrients through capillaries.

1. Cut the cardboard piece to a size slightly larger than the juice glass opening.
2. Make several small holes in the cardboard piece using the needle or thumb tack (be careful).
3. Cut the thread into several pieces as tall as the glass.
4. Now push one thread piece through each hole such that the thread reaches at least below the half way mark in the glass. Keep the cardboard piece with the threads aside.
5. Now fill the glass halfway with water, add a spoon of sugar to it and mix till all the sugar dissolves.
6. Place the cardboard lid on top so that the threads all touch the water at least a little.
7. Leave the glass undisturbed for 2-3 hours.
8. Now carefully lift the lid off along with the threads and pour away all the water in the glass.
9. Let the thread dry over a few hours.
10. Observe what has happened on the thread. What do you see?

You should see some sugar crystals or at least some powdery white substance on the dry threads.

For more information on growing sugar crystals you can see http://www.crystalgrowing.com/recipes/sugar/sugar.htm or http://www.teachnet.com/lesson/science/crystals040999.html

Why Can't Oil and Water Mix?

Have you ever wondered why oil and water do not mix? Chemistry gives us a clue, saying that liquids which are made of similar molecules tend to mix with each other easily. Molecules are some of the fundamental building blocks of matter.

Oil and water are made of different kinds of molecules which interact differently with each other so they do not tend to mix. The molecules of water, for instance has a more "electronic interaction" whereas oil has "non-electronic interactions."

Further, a drop of oil is usually lighter than an equally sized drop of water, so usually oil floats on top of water when the two are present in the same place. In other words, water is more dense than oil. You might have seen this when you place a drop of butter on top of a hot soup. Soup is mostly water and butter has a lot of oil in it, so as the butter melts it floats as a thin layer on the soup.

This is the same thing that happens when an oil spill occurs if a ship carrying petroleum (crude oil) breaks while on the sea. The oil spills and floats on top of the sea water causing lot of pollution and problems to aquatic life. Of course, oil spills occur very rarely and the more common reason for oil in the ocean water is from cleaning and rinsing of ships.

Just like cleaning oil spills can be a problem for environmental scientists, removing grease from clothes is a problem for all of us. Fortunately, although oil and water do not mix, there are chemicals like detergents which are attracted to both oil and water and can aid in their mixing.

When a detergent is added and mixed up between the oil and the water, it holds hands with oil and water molecules and helps in getting the oil rinsed off with excess water. Such a mixture where oil and water can finally be together with the help of another substance is called emulsion.

Some emulsions which are actually edible happen to be milk, butter, mayonnaise, etc. Of course these are not made with detergents! In summary, oil and water will not mix by themselves because of many different properties, but they can be made to mix with the help of things like detergents or emulsifiers. Since oil floats on water, a lot of fun (but messy) experiments can be done using oil and water.

For fun experiments about oil and water, see http://www.epa.gov/nps/kids/SHAKE.HTM.

Little Lion Experiment:

We will learn how oil and water interact . Caution: These experiments can all get pretty messy, so do NOT attempt them on carpeted floors at all. Also, it is advised to not do it on a wooden floor either, as any spill can be slippery and dangerous. These are best done on a garage floors, preferably with a lot of paper towels around and a small box of sand nearby.

You will need:

• Water
• Vegetable oil
• Glass jar or clear drinking glass (an old pasta sauce bottle will do the job)
• Food coloring (optional)
• Salt
• Detergent powder or dishwashing liquid.
• A wide glass bowl.

Steps: Experiment 1:

1. Pour water halfway into the glass jar.
2. Pour quarter cup oil on top of the water.
3. Let the liquids settle and observe what happened, which layer is on top, etc.
4. If you have food coloring add a drop or two to the top surface and wait and see what happens.
5. Another thing you can do is, sprinkle some salt to the top of the oil and see what happens.
6. You can also now try pouring a small amount of water using a table spoon to the top of the oil layer and see what happens to this new water.
7. Add some detergent powder or a few drops of dishwash liquid and mix things up with a spoon. Allow mixture to settle and see what it looks like now. Do you still see two clear layers?

Steps: Experiment 2:

1. Pour water halfway into the glass bowl.
2. Take a table spoon of oil and try to form a small region of oil film on the water.
3. Try to see if you can break the oil film into several small regions with your spoon.
4. Then try putting them back together into one film.
5. Sprinkle some detergent on top of the oil and mix it up.
6. Now see what has happened to the shiny oil film.

How Do Plants And Water Break Rocks?

You have probably seen people use big hammers to break rocks (in movies) or bulldozers to knock down large buildings. Did you know that plants too can break rocks? Have you seen tiny plants come out of cracks in the road or a concrete sidewalk? It is amazing to see a tiny plant break apart a big rock as it grows in a crack in the rock.

Plants exert a large amount of force on everything around them. All this hidden strength in plants and seeds come from the process of imbibition. Imbibition simply means taking up or absorbing water. This process can be understood by knowing what plants are made of.

Plants are made up of millions of little cells. Cells are the building blocks of living organisms. In plants, the cells are close together but are still set apart by a large number of pores, empty spaces between cells in plants.

Each cell in a plant has a flexible outer covering called cell wall. When the plants or seeds are near water, they absorb the water into their pores and also into the cells. Since the cell wall is flexible, it allows the cell to expand in size and yet not break.

The expansion of all cells is what causes a seed to enlarge so much or wood to swell. Did you know that long, long ago (several thousand years ago) the people who built pyramids in Egypt and temples in India used the power of the swelling in wood to break large rocks?

They used to place wooden wedges in cracks of large rocks, pour some water, and wait. In a few days the wood would swell up and slowly crack the rock open. Then the broken rocks were used to build pyramids and stones. The ancients even used the swelling to wood to lift the rocks, but that story is difficult to explain here!

Other fun experiments on plants are at: http://mgonline.com/experimentsforkids.html. It is going to be spring time so growing plants is the fun thing to do! For information on pyramids and temples visit: http://www.historyforkids.org/learn/egypt/architecture/egyptarchit.htm and http://www.templenet.com/tamilnadu.html.

Little Lion Experiment:

The great strength of wood-based materials when they expand due to water absorption can be easily shown at home. Seeds and beans (whole dry beans) are similar to woody matter and swell if soaked in water over a few hours. The interesting thing with soaking beans or seeds in water is that you will end up getting sprouted beans after a couple of days.

This experiment can be set up in few minutes, but will show results only after few hours, so some patience will be needed. You will need these materials:

• dry beans (green mung beans, or red kidney beans or garbanzo beans - you have to use dry beans)
• a small plastic container with a lid (yogurt containers with clear lids work best)
• water
• a large plastic bowl or plate

Steps:

1. Fill the container with dry beans leaving small amount of room at the top.
2. Set this container into the large bowl or plate.
3. Add water slowly to the beans until you see water reach the top.
4. Place the lid on the small container and close it firmly. If you use plastic wrap, you can clasp it tightly to cover the top and then put a rubber band around the container wall.
5. Write down the time, and check the container at intervals of 1 hour.