All of these experiments/lessons can be adapted for many different ages. Depending on the age, you could go into more depth with explaining the science behind the experiments. For younger children, I would explain the basic concept; but for older children, I would discuss more of the science or chemistry behind the activity.
1. Cloud Experiment: This activity helps children understand the concept of weather and rain. You simply fill a cup with water and put shaving cream on top. Then explain that when clouds get heavy with water (blue food coloring), it rains. http://pinterest.com/pin/182958803581783619/
2. Cartesian Diver: Children can make an object sink or float by a squeeze of the hand. The air in the straw in the bottle reacts when the bottle is squeezed and results in it sinking. This experiment symbolizes how fish are able to sink or float by squeezing their muscles around a small air sac. This is a great lesson to use to discuss why things float or sink. http://momfilter.com/kid-diy/cartesian-diver
3. "Dinosaur" Excavation: This is a great activity to do as a review after you have been studying archeology. To build background knowledge, you could read books on archeological digs and paleontologists such as Digging Up Dinosaurs by Aliki. Students can then practice being paleontologist by searching through this container of sand for dinosaur bones.http://www.motherhoodonadime.com/kids/dinosaur-excavation-for-kids/
4. Balloon Reaction: Can you really blow up a balloon with just a chemical reaction? Prove to children that you can by doing this experiment. Place a small amount of baking soda in the ballon and fill up bottle with vinegar. Then lift the balloon so the baking soda combines with the vinegar. The chemical reaction will blow up the balloon. This lesson is great to teach children about chemistry and chemical reactions. http://notjustcute.com/2011/07/22/reactions-fun-science-activities-that-fizz-foam-and-pop/
5. Viscosity Race: Conduct a race to see which fluid will make it to the finish line first! For this experiment you could use ketchup, chocolate syrup, cooking oil, orange juice, and milk. Next, students can time the fluids to see how long each one takes to get to the end of the table/poster. Children can then make a table displaying all of the data they have found. This experiment can be used to introduce the topic of viscosity. http://www.science-sparks.com/2012/04/23/viscosity-races-investigating-the-flow-of-liquids/
6. Flower Science: This is a great lesson to do with children who are learning about plants. This experiment shows children that flowers absorb nutrients like water through their stems. In this experiment, you will need white carnations, water, and food coloring. Put the carnations in the colored water and watch the flowers change color. The students can then look at the stems with magnifying glasses to demonstrate that flowers absorb water.
http://www.education.com/activity/article/teach_science_second/
7.Homemade Lava Lamps: In this experiment, you will need oil, water, food coloring, a water bottle and Alka Seltzer tablets. Simply fill up a recycled water bottle two thirds full of oil then fill the rest of the bottle with water. Next, add food coloring and half of the Alka Seltzer tablet and watch the reaction! This is another great activity to do with children to demonstrate a chemical reaction.
http://www.cometogetherkids.com/2011/07/make-your-own-lava-lamp.html
8. The Leak-Proof Bag: Can you spear a plastic bag full of water without it leaking? The answer is surprisingly yes! For this experiment, fill a Ziploc plastic bag with water. Then take sharpened pencils and pierce the bag with the pencils (making sure not to push the pencil the entire way through the bag). Children will be amazed that the water doesn't leak out of the bag. Then discuss the science behind why it doesn't leak. Because the plastic bag is made of long chains of molecules called polymers, the polymers can seal back up around the pencil preventing leaks.
http://www.stevespanglerscience.com/experiment/leak-proof-bag
9. Making Colorful Crystals with Coal: For this experiment you will need to combine liquid blueing, laundry detergent, salt, and ammonia together. Next place the pieces of charcoal in a pie pan and put a few drops of food coloring on the charcoal. Then add the mixture previously described to the piece of charcoal and watch the crystals form.
http://www.education.com/activity/article/Colorful_Crystals_Coal/
10. Mystery Markers: For this experiment, you will need different colored markers, water, and paper towels. Then draw a wavy line an inch above the end of the paper towel and submerge the towel in the water. Make sure you submerge just the end of the paper towel and not the line of ink. Then watch as the paper towel absorbs the water. As the water reaches the ink, the ink will spread revealing all the colors used to make that ink.
http://www.parents.com/kids/education/math-and-science/everyday-science-experiments/?sssdmh=dm17.545672&esrc=nwpmmdailytip083011&email=1833431252