Chemistry and materials

30 to explore

• Watch Try it What If? Lab What if a balloon floated very high? As a balloon floats higher, the air around it gets thinner and pushes on it less, so the gas inside spreads out and the balloon swells. In our model, a perfectly stretchy balloon launched at sea level is about 14 times its starting size by the time it reaches 20 kilometers.
• Watch What If? Lab What if apples never turned brown? When an apple is cut, a natural chemical in it mixes with oxygen from the air, and the fruit turns brown. Lemon juice and the fridge slow it down, and some apples are now grown to brown less. Imagine apples that never browned and follow what might change.
• Watch What If? Lab What if bubbles could last forever? A soap bubble's skin is a thin sandwich of soap and water, and it pops when the water drains or dries away. Scientists in France made a bubble that lasted 465 days. Imagine bubbles that lasted forever and follow the clues: thin films, drying out and frozen bubbles.
• Watch What If? Lab What if cakes had no baking powder? Look closely at a slice of cake and you'll see it is full of tiny holes. Baking powder makes bubbles of a gas called carbon dioxide, and those bubbles puff up the batter as it bakes. Imagine baking with no baking powder and follow what might happen.
• Watch What If? Lab What if colors never faded? Leave a bright poster in a sunny window and, over weeks, its colors grow pale. Light slowly changes the colored molecules in dyes and inks. Imagine a world where colors never faded, and follow the clues: sunlight, paints and blocking ultraviolet.
• Watch What If? Lab What if concrete could heal its own cracks? Concrete is strong, but it cracks, and water creeping into the cracks can rust the steel inside. Scientists are testing concrete that seals its own cracks, using sleeping bacteria or special lumps of lime. Follow the clues to see what self-healing concrete might change.
• Watch Try it What If? Lab What if concrete had no steel inside? Concrete is very good at being squashed but bad at being stretched, and a bent beam is stretched along its bottom. In our model, a 20-meter beam of plain concrete with no steel inside cracks under a 20-tonne truck, and it cannot even hold up its own weight.
• Watch What If? Lab What if everything were made of wood? Wood is strong, it grows on trees, and builders already frame most American homes with it. Today engineers even build towers from thick layered timber. Imagine a world where everything is wood, and find out what would work well, what would need care, and why.
• Watch What If? Lab What if fire had no oxygen? Every fire needs three things: fuel, heat and oxygen. Take away any one and the fire goes out. Follow what happens when the oxygen is taken away, from a candle under a jar in a science class to the way firefighters, fire extinguishers and smoke alarms keep people safe.
• Watch What If? Lab What if glass were bendy? Glass is made by melting sand and cooling it quickly. When it's cool, it's hard and brittle, so it cracks instead of bending. But hot glass is soft, and glass thinner than paper can bend. Imagine glass that was bendy and follow what might change.
• Watch What If? Lab What if glue stuck to everything? Glue and tape stick by spreading into tiny bumps on a surface and holding on with weak pulls between molecules. They stick well to some things and badly to others. Imagine a glue that stuck to everything, and follow the clues: how glue holds on, sticky notes and gecko feet.
• Watch What If? Lab What if gold were as common as sand? Gold makes up only a few parts in every billion of Earth's crust, while silicon, the main element in sand, makes up more than a quarter. Gold never rusts, so tiny amounts of it help our phones work. Imagine gold as common as sand and follow what might change.
• Watch What If? Lab What if ice cream never melted? Ice cream is a frozen foam of tiny ice crystals, air bubbles and fat, held together by a sugary syrup that never quite freezes. Imagine ice cream that never melted, and follow the clues: melting, fat and air bubbles, and how ice cream is kept cold on its way to you.
• Watch Try it What If? Lab What if ice were heavier than water? Ice floats because it is about 9 percent less dense than liquid water, which is unusual: most solids sink in their own liquid. Make a block of pretend ice heavier than water in our model, watch it sink, and find out why floating ice matters for life in lakes.
• Watch What If? Lab What if metal melted in your hand? Every metal melts at its own temperature. Iron needs more than 1,500 °C, but a metal called gallium melts at just under 30 °C, cooler than your body. Imagine if all metals melted that easily and follow what might change.
• Watch What If? Lab What if metal never rusted? Rust forms when iron and steel react with oxygen and water. It slowly eats away bikes, gates and even giant bridges, so people fight it with paint, zinc and special steels. Imagine a world where metal never rusted and follow what might change.
• Watch What If? Lab What if milk never turned into cheese? Cheese starts as milk. Helpful bacteria turn milk sugar into acid, and an enzyme called rennet makes milk proteins clump into curds, leaving a watery liquid called whey. Imagine milk that never turned into cheese, and follow the clues: bacteria and enzymes, curds and whey, and yogurt.
• Watch What If? Lab What if oil and water mixed? Oil and water won't stay mixed because water molecules cling to each other much more strongly than they cling to oil. But helpers like egg yolk and soap can hold tiny oil drops in water. Imagine oil and water that mixed easily and follow what might change.
• Watch What If? Lab What if paper were waterproof? Paper is a mat of tiny plant fibers that water loves to cling to. Water creeps into the spaces between them and loosens the bonds that hold them together, so wet paper goes soft. Coatings can keep water out. Imagine paper that was always waterproof and follow what might change.
• Watch What If? Lab What if pencil lead were diamond? The gray core of a pencil is graphite, a form of carbon. A diamond is carbon too. The difference is how the carbon atoms hold on to each other: in sheets that slide in graphite, in a tight 3D net in diamond. Imagine a pencil with a diamond core and follow what might change.
• Watch What If? Lab What if popcorn did not pop? A popcorn kernel holds a tiny drop of water inside a hard shell. When it is heated, the water turns to steam, the pressure builds, and the shell bursts. Imagine popcorn that didn't pop, and follow the clues: the water inside, the steam pressure and other grains that pop.
• Watch What If? Lab What if rubber were not stretchy? Rubber stretches because its molecules are long, tangled chains. Pull, and they straighten out. Let go, and they curl back into a tangle. Imagine rubber that would not stretch and follow what might change for tires, balloons and rubber bands.
• Watch What If? Lab What if salt did not melt ice? Salt water freezes at a lower temperature than plain water. That's why salt melts icy roads and why salty ice can freeze ice cream. Imagine salt that did nothing to ice and follow what might change.
• Watch What If? Lab What if soap did not exist? Water on its own slides right off greasy hands. Soap is different: each soap molecule has one end that holds on to grease and another end that holds on to water, so the grease, dirt and germs rinse away. Imagine a world without soap and follow what might change.
• Watch What If? Lab What if sugar would not dissolve? When sugar dissolves, it doesn't disappear. Its tiny molecules spread out among the water molecules, so you can't see them anymore. Warm water holds more sugar, and the sugar can even grow back into crystals. Imagine sugar that would not dissolve and follow what might change.
• Watch What If? Lab What if there were no acids? Acids are everywhere: in lemons and vinegar, in rain, and even in your stomach. Scientists measure how acidic something is with the pH scale. Imagine a world with no acids at all and follow the clues to see how much would change.
• Watch What If? Lab What if there were no plastic? Plastic is light, cheap and lasts a long time, so it is everywhere: in toys, bottles, phones, cars and hospitals. Those same things make it hard to clean up when it ends up in the ocean. Imagine a world without plastic, then meet the older materials and the new plant-based plastics people are designing.
• Watch Try it What If? Lab What if windows were made of diamond? Light bends when it passes from air into a window. Swap the glass for diamond in our model and the same beam bends far more, and much more of it bounces back. That strong bending is part of why a cut diamond sparkles.
• Watch Try it What If? Lab What if you boiled water on a high mountain? Water does not always boil at 100 °C. Climb a mountain and the air pressure drops, so water boils at a lower temperature. In our model of the atmosphere, water 5 kilometers up boils at about 83 °C, which is why food cooked in boiling water takes longer high up.
• Watch Try it What If? Lab What if your cocoa went in a flask? A mug of hot cocoa cools fast: in our model it drops from 80 °C to 60 °C in under 12 minutes. Pour the same cocoa into a vacuum flask and it takes about 100 minutes. Find out how a flask blocks the three ways heat escapes.