Don’t let elementary school teachers have all the fun! Get a little wacky with your own sciences experiments.
To illustrate some basic principles in science, you don’t need much except some household products and a sense of adventure.  Here are some easy projects that inspire curiosity and fun.
1. It’s slime time!  What is the difference between a liquid and a solid? Well, here’s a way to discover the answer.  By taking liquid starch, Elmer’s white glue and some food color, you can combine ingredients into elastic, slime. This recipe is so easy that kids old enough to hold a pitcher can do it themselves.  Make sure you get the measurements right so the food color is fully integrated. Here’s a quick video that tells you how to do it:
2. How do clouds work?  Take a clear plastic container, fill up two thirds with water and coat the surface with shaving cream.  Then give the kids some food-coloring droppers that then can sprinkle into the “clouds”.  In the same way real clouds become full of moisture, these shaving cream clouds will start to “rain” the
food color.  
3. Crystalize.  With just sugar and water, kids can learn about how crystals form, and get a little treat at the same time.  Take a tall glass of water and bring it to a boil on the stove. Slowly add in 2/3 cup of sugar until all of it is dissolved in the water.  Let the mixture cool, and then pour it into a tall, clear glass.  Take a wooden chopstick and suspend it straight up and down in the glass using a clothespin, making sure it is not touching the sides of the glass. Set the glass aside in an out-of-the-way place for 3-7 days.  The sugar will form beautiful crystals on the submerged part of the chopstick. Helpful hint: you can put some dark colored food coloring in the mixture; the crystals will absorb the color!
4. Make a Hovercraft.  Materials: balloon, a snap top from a water bottle (the kind that you push down on to close, a glue gun and an old CD.  Take the top from the water bottle and affix it to the CD using the glue gun (the tricky part is that it needs to be sealed, so you may need to make more than one pass). When the glue is dry, blow up the balloon and fit the mouth of it over the plastic top.  When the balloon is on securely, snap the top open and place the CD on a level surface.  The pressure of the air escaping will make your little craft hover!  For more complete instructions, check out this pdf from Science Bob:
5. Invisible Ink!  This one really blows kids away, and it’s so simple, they can do it anytime.  Take a ¼ of baking soda and mix it with a ¼ cup of water. Using a q-tip or paintbrush, write a message on a regular piece of paper.  After it is dry, go over the paper with grape juice (careful, grape juice stains!) The acid in the grape juice reacts with the backing soda, and the message becomes visible.  
6. How did you get that egg into a bottle?  This one is really fun because there is something totally electrifying about the egg getting sucked into the bottle. Hard boil an egg and find a glass bottle that has a mouth slightly smaller that the egg.  Peel the shell and set the egg down on the mouth of the bottle soeveryone can see that it doesn’t fit.  Using a match, light a small piece of newspaper that has been folded several times and fits through the hole.  As soon as the newspaper is lit, drop it in the bottle and put the egg on top, creating a vacuum.  The egg will slowly get sucked into the bottle, making a satisfying thunk sound. A tip: rub some oil around the edge of the glass so the egg doesn’t break apart when it gets sucked in.  

These little projects don’t require much in the way of preparation or materials, and they provide a great teachable moment as well as some entertainment.  Have the conversation with your little inventors about safety when it comes to home experiments and discover something new together.