My nieces are seven years old and into science. The experiments were easy and straightforward - easily read and done by the kids but adult supervision is probably a good idea. Mind blowing? Not so sure about that but very cool for the budding scientist. Perfect kit to start with. I think it's a cool way to encourage girls to love science and math. Boys will love it too - an exploding volcano! - so it really is great for the whole family. Younger kids could definitely participate with the aforementioned supervision. We LOVED it!

You could even step into the living room to have more scientific fun. Learn about static electricity with some tiny scraps of paper and a balloon. Blow up the balloon and tie it closed. Make a small pile of paper scraps on the floor, and rub the balloon back and forth several times on your hair or on a sweater. Immediately move the balloon to the paper and watch as the paper scraps cling to the balloon. Rub the balloon on your head or sweater again and then place it against the wall to see it stick there. This surprising sticking happens because you have moved electrons around and the balloon now has more of a negative charge, while the paper or the wall has more of a positive charge. Putting the two surfaces together makes the opposite charges stick to each other.
Like the popular baking soda and vinegar experiments, this film canister rocket literally takes it to the next level by using that creation of gas and energy to jet off into the sky. If your explorer has seen videos of mountain tops getting blown off during a volcanic eruption, this science project is pretty much any space lover’s version. Get the building instructions over at kids science activity blog The Science Kiddo.
If you do this sidewalk constellation craft, you’ll be able to see the Big Dipper and Orion’s Belt in the daylight. On the sidewalk, have kids draw the lines of constellations (using constellation diagrams for guidance) and place stones where the stars are. You can then look at astronomy charts to see where the constellations they drew will be in the sky.
With just some basic materials you can create your own musical instrument to teach kids about sound waves. In this water xylophone experiment, you’ll fill glass jars with varying levels of water. Once they’re all lined up, kids can hit the sides with wooden sticks and see how the itch differs depending on how much water is in the jar (more water=lower pitch, less water=higher pitch). This is because sound waves travel differently depending on how full the jars are with water.
3. Now remove about an inch of the plastic coating from both ends of the wire and attach the one wire to one end of a battery and the other wire to the other end of the battery. (It is best to tape the wires to the battery – be careful though, the wire could get very hot!) Now you can experiment by picking up paper clips and small non-aluminum objects. 

Be careful: The water only has the power to make the sugar crystals “invisible” when it’s piping hot. After the water cools down and evaporates, the sugar turns back into a solid. And with a little help of your sugar-soaked string, the crystals will find a home to grow upon and become rock candy. Learn how to make your smart sweets with these instructions from the Exploratorium. 
Kids this age will probably enjoy a whole range of different science kits. It’s good to look for something which will help with what they are learning about at school. Pre-teens are becoming more and more independent, so it might be worth looking for an experiment kit which is simple enough for them to do alone, but still hard enough to keep them entertained and learning.
Scientific Explorer My First Mind Blowing Science Kit is your junior chemist’s introduction to the world of scientific exploration. Learn the basics of science from chemical reactions to the use of science tools. With mind blowing experiments such as creating a sunset in a test tube and making a color-changing volcano, children will love learning fascinating facts about their natural world and this kit will keep them engrossed with interactive experiments. Includes Red cabbage powder, citric acid, baking soda, 3 color tablets, crosslinked polyacrylate copolymer, vegetable oil, corn starch, 2 cotton swabs, 3 test tubes with stand, 3 plastic cups, pipette, 2 sticks, 2 measuring scoops and activity guide. Recommended for children 6 years of age and older with adult supervision.
We have categorized by age to make things really easy when deciding which type of experiment kit to go for and start experimenting with. There is everything from geology rock experiments, ocean discovery kits, volcano boxed experiments, butterfly and insect garden kits, robotics activities and kits, human biology box sets and chemistry sets that bring the obscure into light making learning loads of fun and super exciting for everyone involved.  These mentioned are only in the 3 years old and over a section, but we also have a 6 years old and above, because we understand the capabilities of children. The section for 8 years old and above come under one section to help make a clear distinction.
This grow-your-own experiment that lets you grow crystals inside an egg shell. Be sure to get alum powder that contains potassium, or else you won't get any crystal growth. Adding drops of food dye to the growing solution yields some super cool crystals. A perfectly formed geode takes about 12-15 hours to grow, making this a great weekend project. Check out more of Art and Soul's gorgeous eggs over at their blog!
Find out how plants “drink” water with some food coloring. Use carnations, roses, or stalks of celery submerged in the colored water and watch the liquid slowly seep through the plant’s “veins” and towards the leaves. Keep an eye out -- you could have a very colorful bouquet just after the first day. Get the rundown by Dad’s Book of Awesome Science Experiments over here.
There is a clear line between experimenting with a homemade science kit and one that is paid for. I like both, but it is easier for children to use and be left to their own devices with the kits that come boxed up. These have all the equipment needed, usually labeled and comes with clear, distinctive and easy to use manuals for conducting the experiment.
This Rainbow Skittles science experiment can be done in seconds, making it a great way to try science at home even with the most easily distracted of toddler-sized assistant. All you’ll need to do is arrange Skittles in a circle on a plate and fill the middle with warm water. Then sit back and watch as the colours drain and mix with the water, creating a cool rainbow pattern in front of your eyes. Plus, any bonus Skittles = a tasty treat for you.
If your kids are curious about how animals like polar bears and seals stay warm in polar climates, you can go beyond just explaining it to them; you can actually have them make some of their own blubber and test it out. After you’ve filled up a large bowl with ice water and let it sit for a few minutes to get really cold, have your kids dip a bare hand in and see how many seconds they can last before their hand gets too cold. Next, coat one of their fingers in shortening and repeat the experiment. Your child will notice that, with the shortening acting like a protective layer of blubber, they don’t feel the cold water nearly as much.
Learn interesting science and technology facts by experimenting with different materials that react in surprising ways. You'll find a lot of experiments can be done using simple ingredients found around your house (with adult supervision of course). Basic materials can help you perform experiments that are simple, safe and perfect for kids. Enjoy our fun science experiments, make cool projects with easy ideas for children, show friends & family what you've discovered and most importantly, have fun!
Kids will love shooting pom poms out of these homemade popsicle stick catapults. After assembling the catapults out of popsicle sticks, rubber bands, and plastic spoons, they’re ready to launch pom poms or other lightweight objects. To teach kids about simple machines, you can ask them about how they think the catapults work, what they should do to make the pom poms go a farther/shorter distance, and how the catapult could be made more powerful. 

With just a package of Starbursts and a few other materials, you can create models of each of the three rock types: igneous, sedimentary, and metamorphic. Sedimentary “rocks” will be created by pressing thin layers of Starbursts together, metamorphic by heating and pressing Starbursts, and igneous by applying high levels of heat to the Starbursts. Kids will learn how different types of rocks are forms and how the three rock types look different from each other.

This kit also teaches your kids about the influential scientists who paved the way in the field, such as Francis Crick, James Watson, and Gregor Mendel. From genes, heredity, traits, and inheritance, to reproduction, cellular components, DNA sequencing, and genetic engineering—this kit will teach it all in a fun and educational way that your kids are sure to love.
The "volcano" was basically a miniature mound that fizzled. Could get a bigger reaction from dropping an Alka Seltzer in water or mixing baking soda with a little vinegar. The "giant crystals" only grew a couple of centimeters. All the experiments are on such a miniature scale it doesn't have any of the wow factor we were looking for. I will go back to googling fun experiments to do with my son.
This solar energy science experiment will teach kids about solar energy and how different colors absorb different amounts of energy. In a sunny spot outside, place six colored pieces of paper next to each other, and place an ice cube in the middle of each paper. Then, observe how quickly each of the ice cubes melt. The ice cube on the black piece of paper will melt fastest since black absorbs the most light (all the light ray colors), while the ice cube on the white paper will melt slowest since white absorbs the least light (it instead reflects light). You can then explain why certain colors look the way they do. (Colors besides black and white absorb all light except for the one ray color they reflect; this is the color they appear to us.)
Invisible inks either react with another chemical to become visible or else weaken the structure of the paper so the message appears if you hold it over a heat source. But we're not talking about fire here. The heat of a normal light bulb is all that's required to darken the lettering. This baking soda recipe is nice because if you don't want to use a light bulb to reveal the message, you can just swab the paper with grape juice instead.

You’ve probably tried a salt crystal growing kit at some point in your life (5th grade Science Fair perhaps?) but Schooling a Monkey takes the idea to a new level with these Salt Crystal Feathers. This awe-inspiring project is deceptively simple and inexpensive to achieve, and requires just a wee bit of patience to see the results—kids will love checking in on the progress. Visit Schooling a Monkey now to get started.

Put the pencil across the top of a jar so that the string hangs down the middle of the jar. If it hangs down too far, roll the string around the pencil until the string is not touching the sides or bottom of the jar. The string will act as a seed for the crystal. Any type of jar will do, but canning jars are best since they can endure the hot temperatures. Tall skinny olive jars are also nice because they don’t use up so much of the liquid.