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Have you ever thought much about soil? If you went on the critter crawl several weekends ago, you might have dug around in soil looking for soil creatures. Did you pay attention to the soil? Soil is a wonderful thing, which deserves further study.

Take your children out to a place they can examine some soil. Start by simply sitting on a patch of soil. Ask your children what they think soil is. Is it alive? (Yes, components of soil are alive.) What does it consist of? Are all soils alike? Smell your patch of soil, what do you smell? Touch the soil. What does it feel like? Is it wet or dry?

If you have time, bring a small bag of sand and a bit of clay with you. Have the children look at the sand, clay and a small sample of your soil. How are they similar? How are they different?

Soil is made up of a lot of different things. The most obvious will be the particles of rocks and minerals. The particles will be of different sizes. Soil scientists name the particles according to their size. The largest particles are sand grains, the middle-sized are called silt and the very finest particles make up clay.

Another important component of the soil is water. As you might guess, water moves through the different-sized particles at different rates. An easy demonstration is to fill three plastic cups, one with dry sand, one with dry potting soil and one with clay. Have the children pour in some water and watch what happens. Older children can time how long the water takes to reach the bottom of the cup with a stopwatch. Usually the water goes through the sand rapidly, and sometimes does not move through densely packed clay at all.

With a group of children, or even children and adults, you can make this even clearer. Tie a bit of blue cloth to one child volunteer, who will represent the water. The rest of children (or children and adults) can be soil particles. First have the soil particles hold out their arms and form a cluster. They are now big sand grains taking up big space. Let the water child try to move through. It should be easy. Then have the soil particles put their hands on their hips and move closer together. Now they are middle-sized silt particles. The water child should still be able to move through, but it will be more difficult. Finally, have the children put their arms tight to their sides and pack together. They are now clay particles. The water child will have a lot of trouble getting through now. If she or he does manage to get in, point out that it is hard to get out again too. Clay holds water tightly once it gets in.

Brainstorm about what else is in soil. Be a soil detective and carefully pick apart a soil sample. You should find some bits of twigs, leaves, plant roots, and other decaying plant parts. This is what is called the organic or humus part. In this case organic does not mean the same as in the grocery store. Organic here means coming from living things, containing carbon.

Another part of soil is air. We often forget that plants need air in the soil as well as water to grow properly.

Did you find any soil critters? Many organisms are found in the soil, such as earthworms, mites, nematodes, fungi and bacteria. They have big roles helping break down the plant matter, adding oxygen to the soil and sometimes increasing the nutrient content, depending on the type.

Time to run out and check out the soil. And when you get back inside, you might want to wash your hands and celebrate by making a dirt cake as a snack. Enjoy!

And if you have time, read some books about life in the soil.

Alvin and Virginia Silverstein have written quite a number of nonfiction and science books. All that we have read have been full of well-researched and interesting information. Life in a Bucket of Soil is another fine example.

With the summer months upon us, it is time to think of swimming pools, sprinklers and beaches. Let's celebrate by doing science experiments with water.

Water truly is a wondrous substance. You could spend months, even years, studying water and its special properties. Although it is easy to take it for granted because it flows out of the tap, water is important to life and precious, too.

Physics Experiments
1. Friction
All you'll need for the first experiment is a surface that can get wet, such as floor, patio or counter top, and a few wooden blocks or flat bottomed toys. Slide the blocks over the dry surface first. Ask your children to think about how it feels. Is it hard or easy? What happens when you push the blocks quickly back and forth? Do they get warmer on the bottom?

Once the children have gotten a feel for blocks on a dry surface, pour on some water. Is it easier or harder to push the blocks around? Do the bottoms of the blocks get warmer or do they stay cool?

If your children seem interested still, you can ramp it up a bit (sorry, pun intended) by building what is called an inclined plane and allowing the blocks to slide down. A child’s slide would work great for this. You can even race blocks on a dry surface versus blocks on a wet surface. Have fun!

2. Floating and sinking
A classic water experiment is to examine what floats and what sinks. Fill the bathtub, a bucket, kiddie pool, or plastic bin with a few inches of water. Provide your children with age-appropriate objects to test, such as wooden blocks, coins, lumps of clay, and strips of aluminum foil. Believe it or not, what seems mundane to adults may fascinate a child, so be open to revisit this experiment and to test many different objects. Ask them to predict what will happen before the object goes into the water. Older children may be ready to learn about terms such as density and buoyancy.

Note: For safety, always empty the water out of the container after play and always watch children around water.

Chemistry

States of Matter
Water exhibits all three states of matter (solid, liquid, gas) at relatively normal temperatures and thus is ideal for studying these properties.

Solid:
Put some water in different-shaped containers (margarine bowls, food molds) and freeze it. Allow the children to help pick containers and fill them. For added enjoyment, add a few drops of food coloring to the water. Or you can add bits of edible flowers such as roses, or leaves of herbs as decorations

On a warm day, take the ice outside and use it to build ice sculptures. Remove the ice from the containers by briefly immersing in water if it won't just slip out. If you don't have time to make special shapes, simple ice cubes can work great for this, too. I have been told you can use salt to melt two pieces together, but I've never had much success with doing that. Pile the ice into buildings, animals or abstract forms. You can lightly mist the finished products with water containing food coloring. Then watch the sculptures melt. Predict how long it will take.

Older children can design inventions to protect the ice from melting, and then build and test their invention by seeing how long it takes for the ice to melt inside the device versus unprotected.
Enjoy the cool.

Liquid
You can perform many fun experiments with liquid water, such as seeing how many drops of water will fit on a penny. Dissolve salts or sugar into water. See how oil and water don't mix. You can study the movement of water in a straw, the possibilities are endless. Try this page for detailed instructions about testing oil and water.

Gas
To study water in the gas form, you will need water, paint brushes and a sidewalk or driveway on a hot day. If you must stay indoors, a chalkboard will work too. Simply paint the water onto a flat surface and then time how long it takes to evaporate. Explain that the liquid water is turning into a gas as it disappears and is rising up into the air.

To show the gas water turning back into liquid, set out a glass full of ice water on a warm day. The gas should condense into liquid around the outside of the glass after a few minutes.

Biology
Water is essential for life on our planet. We all know we must water plants for them to grow. But what are plants doing with that water?

To test this question, on a warm sunny day, slip a plastic bag around the end of a leafy branch of a tree and tie it tightly to the branch, effectively bagging the end to the tree branch. Visit the tree in fifteen minutes and then again in a half hour. What is happening inside the bag?

You should see the bag start to fill with condensing water. Trees release a lot of water on a hot day through a process known as transpiration. You are capturing the water that is being released.

You may also want to visit a pond, lake or ocean and observe all the living creatures that use water for a home. And hopefully you can do some wading or swimming to test the water yourself.

For recent weekend science fun posts we have had a couple of walks: a spring flower walk and a flowering tree walk. Now it is time for a change of pace and do a critter crawl.

Have you ever dug through a pile of leaf litter or looked under a log? How about sifted through a compost heap? Take some time to find a quiet, preferably moist, spot where pieces of dead plants are piled and spend a while getting to know the small, but important animals that live there. Prepare to be amazed at how many different tiny creatures dwell in this often-ignored part of our world.

Before you get started, you might want to gather up a few items:

  • A magnifying lens can help you see more details
  • Tweezers, forceps or a small stick to gently move leaves or bark
  • Small paintbrush to remove dirt and move tiny creatures
  • Paper and pencil to make drawings and record results
  • Gloves (optional but helpful)
  • Identification guides, or take a look at descriptions of compost critters like this one at the Junior Master Gardener website

Locate a compost heap, pile of leaves or logs where you have permission to explore. First survey the area. Make sure you and your family are familiar with common poisonous creatures such as snakes or scorpions that might also be found hiding under leaves, rocks or logs in your community. Bees and wasps sometimes nest in the ground too, so exercise caution.

Gently begin to turn over leaves or peel off loose bark. Pay close attention. What kinds of things might you see?

Expect:

  • Insects such as beetles, crickets, cockroaches, ants or earwigs
  • Snails, slugs
  • Spiders, mites
  • Millipedes, centipedes
  • Worms

If you are lucky you might find a few creatures that are children's favorites, the rolypolies or sowbugs (also called potato bugs, wood lice and various other names). Depending on the type, rolypolies and sowbugs are 1/4- to 1/2-inch-long, gray and relatively hard shelled.

If you find some, gently pick one up. How does it react to being picked up? Does it roll into a tight ball? If so, then it is a rolypoly.
rolypoly

Does it simply try to scamper away? Then it is likely to be a sowbug. Sowbugs look similar to rolypolies, but lack the ability to curl up tightly.

sowbug

The rolypolies and sowbugs belong to a group of animals called the Isopoda. "Iso" means same, and "poda" means foot. Carefully tip yours over and see if this name fits. Does all its feet look the same? How many legs does it have? Insects have six legs and spiders have eight legs, do you think it is either of those?

upside down rolypoly

Does the isopod have eyes? Does it have antennae? What are those small spikes sticking out from the rear part?

When scientists carefully examined isopods, and then compared the isopod appendages and other characteristics to those of other groups of animals, they figured out that isopods are closely related to crabs, shrimp and lobsters. They are crustaceans. Tiny crustaceans in your garden or compost heap, isn't that cool?

What happens when you set your isopod back down? Does it run towards the light or away from the light? Does it try to hide or does it curl up? Try thinking up some more questions to ask.

Keep looking through the litter. You will probably encounter a few things less familiar than the rolypolies, but no less interesting. Have a lot of fun while you observe and learn about this hidden world.

If you can't get outside this weekend, then pick up a few books, like the ones suggested below. After reading them, crawl around the house pretending to be earthworms, crickets and isopods.

Rolypolyology (Backyard Buddies)
by Michael Elsohn Ross, Published by Carolrhoda Books, Inc. Minneapolis, 1995. ISBN 0876149018 contains detailed information and ideas for experiment with isopods.

Compost Critters
by Bianca Lavies, Published by Dutton, 1993. ISBN 0525447636 has absolutely stunning photographs of the inhabitants of a compost heap. Amazing!