There are many fun kitchen science projects out there that come with their own take-away things to play with. They are safe for your children and teach them chemistry in the process. Here are a few of them.
This is a very cool project and costs so much less than the store counterpsarts, plus, your kids get to make it themselves. To make ordinary sand 'hydrophobic' or afraid of water, simply lay it out on a newspaper and spray with a waterproofing substance like Scotchgard. Allow to dry and then watch the fun. As you pour it into a container of water, it looks like sandcastles being built, then you can reach in and pull dry sand out of the water again. You can use ordinary sand from the beach (spread out and allow to dry thoroughly first) or purchase at a discount store. You can color it with food coloring or purchase colored sand at a craft store. This is good for hours of fun and they can play with it outside or at the table.
AKA Goo, Gak, Flubber, Ooze, etc. This is easily made with only a few ingredients: Water, borax, glue, and coloring and/or glitter. Stir 1 tsp. borax into 1 c. water. Put 4 oz. of blue into a separate bowl with 1/2 c. of water. Stir to mix well and add 2 drops of so of food coloring and sprinkle in glitter if you want it glitzy. Stir well. Add borax water and stir well. Remove and allow to dry for a few minutes. Click on link for the tutorial.
Fill a small plastic bottle 1/3 full with vinegar. Using a dry funnel, fill a balloon 1/2 full with baking soda. Now place the balloon opening over the bottle mouth, letting the balloon droop. Lift the balloon, emptying contents into bottle and watch the balloon inflate.
Mix 1 cup salt, 1 cup flour, and 1/2-3/4 c. water. Add food coloring. Put in little squeeze bottles. Tweak water so that it stands up and is not to runny, but is thin enough to not clog hole in squeeze bottle.
Fill any clear bottle about 2/3 full with vegetable oil. Add water, but leave a little room at the top. Once water settles at bottom of bottle, add a few drops of food coloring and allow it time to settle into the water. Swish gently to color the water. Break up an Alka-Seltzer tablet into pieces. One at a time, drop the pieces into the bottle and watch the reaction. This doesn't really light up like a lava lamp, unless ... you set it on a flashlight!
This is a great object lesson in delayed gratification and patience. It takes 7 days, but is so worth the effort! You will need: lots of sugar, water, food coloring, bamboo skewers, clothespins, glass jars, funnel, and flavoring if you wish. The link gives instructions.
In a bowl, mix 1/2 tsp. borax in 2 tbsp. water. Stir. Add in food coloring. Mix in 1 tbsp. Elmer's glue. Stir. Now in another bowl, add 1/2 tsp. of the colored borax mixture to 1 tbsp. corn starch. DO NOT MIX. Let set for about 15 seconds. Now stir until it becomes too hard to stir. Then QUICKLY form into a ball and bounce.
Please supervise your children and if they are too young, let them be spectators. These are all good clean fun and will break up the monotony of a long hot summer.