Water that you find in nature is not necessarily clean or pure; you would not want to drink pond water, for example. There are ways to clean water, though, and you can try this experiment at home!
First, take a clean jar with a lid and fill it with water from a lake, pond, stream, or any other source of water outside your home. Put the lid on until it is time for the next step. What do you notice about the water?
To clean the water, you will need something called alum. Alum is a hydrated double sulfate of aluminum and potassium, used in dyeing and tanning. If you don’t have this at home, it can be found in the spice aisle in the grocery store.
Put 2 tablespoons of alum in your water, close the lid tightly, and shake it up. Then let the water sit for a few hours.
When you look at your jar again, what do you see?
You may notice that the dirt gets pulled to the bottom. In a real water treatment plant, the added alum forms clumps with the dirt and pulls it down to the bottom of the basin.
To learn more about water and water pollution, check out one of these books.
Eggs are an incredible adaptation that allow birds to stay light and able to fly while their babies are growing. Bird eggs are covered in a shell with lots of tiny holes. These allow air and moisture to pass through. Eggs are also covered in a coating that keeps out bacteria and dust.
Place the egg in your hand (take off any rings first). Squeeze the egg with even pressure. Does it break?
Now (over the sink or outdoors) squeeze the egg with just two fingers. Did it break?
What will happen:
The shape of an egg makes it very strong to even pressure. Even an adult squeezing it can’t break the shell.
When uneven pressure is put on the thin shell, the egg cracks easily.
When a bird sits on an egg to incubate it, the pressure is evenly distributed on the shell and the egg can easily support the bird. When a chick is ready to hatch, it pushes on just a small part of the shell with its egg tooth and the shell will crack to allow the bird to hatch.
A drinking glass
Place the egg in a glass and cover with household vinegar. Wait about 24 hours, pour the vinegar out and replace with fresh vinegar. Wait a full week and then take the egg out.
What will happen:
The shell is made of calcium carbonate, which dissolves in acetic acid. The vinegar will dissolve the shell, leaving the semipermeable membrane intact. The yolk and white will still be contained in the soft membrane, so it will look like an egg, but will be squishy when touched.
Are you a fan of Dog Man and Cat Kid? Dav Pilkey, the author and illustrator of these series, is presenting the virtual program, Flipgrid Virtual Field Trip: Cat Kid Comic Club is In Session: Create Comics with Dav Pilkey!, on Monday, March 22, 2021 from 12-12:30 p.m.