Water is a pretty magical and awesome compound and it’s so important for so many things that our body is made up of 70%-ish water, the planet is covered in it and the compound basically makes it possible for many chemical reactions to take place. Children are enthralled by water; they love splashing in it or blowing bubbles with it and parents love that it tires them out, but why is water so special?
It’s special because it is something called polar. Water is a compound which means it’s made of two hydrogen atoms and one oxygen atom. A compound has two or more elements in defined proportions so that’s where we get H2O (the two is usually written as a subscript). The way they are bonded together is through the attraction of electrons which are the negatively charged particles of the atom. If you don’t remember atoms are usually made of three components: protons, neutrons, and electrons. Hydrogen doesn’t have any neutrons so it’s basically just a proton and an electron. Oxygen has all three. When elements meet up that can either swap or share electrons they make bonds. Oxygen shares one electron with each hydrogen and each hydrogen share their electron with oxygen but it’s not a fair arrangement. In the case of water, it’s polar because they are having a tug of war and oxygen is winning which means the electrons are mostly hanging around oxygen giving it a slightly negative charge (since electrons are negative, often written as e-) and hydrogen a slightly positive charge.
What do we know about opposites? They attract! The negative of one water molecule is attracted to the positive of another water which results in water being “sticky” with others that have charges. Water using this polarity to stick to other water molecules is called cohesion and to stick to other substances is called adhesion. This is the basis for all the awesome things water can do; it allows bubbles to form, water droplets to be created on leaves and water to run down the shower door.
This is what helps create the “skin” on the surface of water that bugs can walk across. Water is sticky! It’s like a magnet with opposite ends that are attracted to each other. If you try to push the two negatives towards each other they resist but the negative and positive snap right together. If you wear contacts and you’re having a hard time getting your contact into your eye, a drop of solution in the contact causes it to practically jump into your eye because the water in the solution is attracted to the water in your eye. This is also why a leaky faucet can keep you awake going drip. drip. drip.
There are a couple simple questions and experiments you can try with your child(ren) to test these magical properties of water:
How many drops can fit on a penny? All you need is a penny, some rubbing alcohol, a pipette (a fancy name for eye dropper), and some paper towels. Clean the penny with rubbing alcohol first and then ask your child(ren) how many drops of water do they think can fit on the penny? Write down their guess and then start dropping. You want to try and do calm controlled drops so if you need a few practice rounds that’s fine. The Munchkin guessed 10 and we made it to 42 before the water bubble broke on the penny.
For older kids or ones who can sit still longer you can do multiple trials (it’s always important for scientists to repeat experiments) or you can use different solutions. How does water compare to vinegar? Or filtered water? Or salt water? What about the head of the penny versus the tail? How about compared to other types of change? There are any number of variations you can do with this one just by looking around your kitchen.
Who can make the best bubbles? Another easy experiment to talk about water’s magic is bubbles and kids, at least mine, loves bubbles. All you really need is some sort of liquid dish soap and water. You could even make this a contest at a party for the kids to try their hands at different recipes and see what they come up with. You could have a goal of biggest bubble or bubble that lasts the longest or my personal favorite, the longest bubble snake:
You can have kids put in different amounts of soap and water or you can get creative and ask them to add other things such as salt, glycerin, corn syrup or any other liquid-y substance you may have on hand to see what happens.
The bubble on the penny and when you blow bubbles rely on cohesion and adhesion working together to make surface tension (the skin on water). The surface tension holds the bubble together. When we’re making a water droplet on the penny it’s just using the penny as a base but when you’re blowing a bubble you want the surface tension to expand enough to allow the air in but not too much that it pops right away and can’t hold onto the bubble shape.
Always ask kids what they expect will happen before they conduct their experiment; this is the foundation for making a hypothesis. If they are able to think through what will happen, even if that’s not what REALLY happens, it gets them thinking about cause and effect and that’s a huge player in critical thinking skills. And if (or especially for most younger kids when) the experiment doesn’t go according to plan talk about why that might have happened and remember failure is a hallmark of good science. If we always got it right the first time it wouldn’t be nearly as interesting!
Allowing children to play with ordinary household substances they can still discover so much about chemistry and the natural world. Look through your cabinets, turn on the taps and get to exploring!