everyday science
In the kitchen, at a cabin, at a garage sale, in dirty laundry. This is science through humour and examples, not math or quizzes.
The world works in wonderful ways. Appreciating them is what Wonderment is all about. But this isn’t a textbook. There are no calculations or quizzes. No vocabulary lists to memorize. There are episodes of science in the everyday. Stories are familiar and approachable and make big ideas easier to remember.
Heat expands most matter
Lightning Strikes, Wheel Washers, and Cup Cracks
Yard work can be sweaty work, even in autumn. Ajay takes a short break and sits under an apple tree. When warm, we relax. We stretch out. Matter does too. Heat makes matter stretch out as its bits move apart.
Ajay sits in the shade, with an eye on clouds gathering over the horizon. Storm clouds could bring lightning. Rapid heat makes matter expand quickly, and a lightning stroke is both rapid and hot. Hotter than the surface of the sun. A bolt can blow your clothes off—or worse.
Lightning sends a shockwave of thunder as heat expands air around the bolt. Rapidly heated air spreads out as a shockwave that rumbles, echoing off the ground and off clouds.
Lightning striking a tree can travel through the sap, heating and expanding so fast it blows off the bark. People don’t have sap, but we sweat. Doing yard work, Ajay has a layer of moisture over his skin. Lightning can heat and expand sweat like sap, turning it to steam so fast it blows off clothes.
* * *
Let’s leave Ajay under the tree and step inside. Loosening a lid is like a lightning strike, but a lot safer. To loosen a stubborn metal lid, run the jar under hot water. Heat in the water works like lightning, at least in concept. It expands metal in the lid, creating a gap between the jar and the lid stuck on by friction. Increasing the gap decreases friction, so the lid is easier to remove.
Pioneers attached wagon wheels this way, by heating a washer (a metal disc, like a coin). Unlike a coin, a washer has a hole in the centre. When heated, the metal expands and so does the hole.
Picture it. First put the wagon wheel on its axle. Heat the washer to expand the hole. When the hole is wide enough, slide the washer onto the axle. As the washer cools, it contracts snugly onto the axle. No need to run to a hardware store, which were few and far between for pioneers.
* * *
Apart from blowing off Ajay’s clothes, rapid heat expansion can crack cups. Tea cups and coffee cups are made of ceramic. Tea cups are thin; coffee mugs, thick. Let’s borrow Ajay’s thick ceramic mug, the one that says “Hot Stuff.” Heat moves slowing through ceramic. That’s another way of saying ceramic is a poor conductor of heat.
Pouring hot water into “Hot Stuff” is again like lightning. The inside expands rapidly, but the mug conducts poorly and so is slow to warm. That creates stress between the hot interior and still-cool exterior. Under stress, the mug will crack. Under stress, many crack.
Rather than cracking Ajay’s favourite mug, we could use a tea cup. Thinner cups reduce the temperature difference, inside to outside. There is less ceramic in the cup wall, so less difference. Another option is to put a metal spoon in “Hot Stuff” before the hot water. The metal absorbs some of the heat, so there is less to cause stress.
Under the tree, Ajay might wonder whether there is inverse lightning. Would quickly cooling the inside of “Hot Stuff” crack it from the outside-in? Dry ice is almost a hundred degrees below zero. A cool idea to think about on a hot summer’s day.
Faster fluid, lower pressure
Rocking, Rising, and Measure of Pressure
Clay’s mom, Mona, volunteers on the school bus when there is a gymnastics competition. She sits near the middle. On a bumpy ride, the front and back of the bus rock up and down more than the middle.
Rocking rotates the bus about its centre of mass, which is just in front of the middle. The engine weighs down the front, so the back of the bus is lively. Some kids choose the back for this reason. On a bumpy road the bus is like a ship in a choppy sea or airplane in turbulent air.
MONA: “The farther I sit from the centre, the greater the see-saw up and down motion.”
* * *
Other times no bus is available and Mona drives Lacy with a few other gymnasts to the competition. As they accelerate to highway speeds, she asks the girls to roll up the windows.
Open windows cause drag. Running the car’s air conditioner increases fuel consumption, but at highway speeds, open windows create air drag that uses more fuel. Drag could offset any saving from turning off the air conditioner.
On the highway, Mona’s car slightly leans toward a passing truck. Air between them is moving fast and the faster a fluid flows, the lower its pressure. With lower pressure between the car and truck, surrounding pressure pushes the vehicles toward each other.
Wind across the top of the chimney at Ajay’s cabin likewise lowers pressure inside the chimney, creating a better draw from air inside the room. That helps the fire burn, but also draws out warm air from the room.
It wasn’t until they stopped for lunch that Mona made the connection. Lacy, playing with a straw in a glass of lemonade, blew across the top of the straw. The fast air drew lemonade up the straw.
That’s why prairie dogs make mounds around their entrance and exit holes. As air is forced up and over the mound, air pressure over the hole lowers, pulling up air from the tunnel, providing prairie dogs with ventilation.
* * *
After lunch, Mona still has ice in her lemonade. The ice in Lacy’s drink has melted away. That’s because Mona had ice cubes and her daughter had crushed ice in their lemonade drinks.
Crushed ice melts faster than ice cubes since the surface area of crushed ice is greater, which gives more melting surface to the surroundings. It is the same principle as kindling or potato slices.
The glasses were poured to the brim, but neither over-flowed when the ice melted. When ice be melts, the water level is unchanged. The volume of water displaced by the weight of the cubes is the same.
Cloudy ice cubes make a slight sizzling sound as they melt. They release the small pockets of air that make the cubes cloudy. Clear ice cubes can make a cracking sound when placed in liquid.
Cracking occurs by a sudden change in temperature. Water is a poor conductor, so the surface of the cube and its cooler interior are under tension. The cube cracks, similar to Ajay’s “Hot Stuff” mug.
* * *
A woman enters the restaurant and takes off her high heels walking across the restaurant’s wood floor. If worn, her high heels could ruin the floor. Their pressure is in a smaller area than an elephant’s flat foot and so can have more pressure.
When the door opened and the woman entered, the girls caught a whiff of gasoline. In the lot, a car is leaking fuel from its gas cap. A tank filled to the brim can overflow if the car is then parked in direct sun. The gas expands with heat, bursting through the gas cap.
Things wear down unless kept up
Messy Party, Magnetic Slime, and Crumbling Cookies
While making home-made gifts, Lacy discovered that things deteriorate. Batteries run down, unless recharged. Her room gets messier, unless cleaned up. That’s entropy for you: the tendency of things to become more disorganized, less useful.
LACY: “Perhaps entropy is why the classroom becomes chaotic when the teacher leaves the room.”
Entropy is at work at a party. At first, the chairs are all lined up. Gifts, neatly wrapped. Clothing pressed and food ready to serve. As the party wears on, there is more to clean-up, tidy-up tomorrow.
Lacy wants a gift for Alan, ideally one that does not become more disorganized. Perhaps a jig-saw puzzle. Out of the box, the pieces are jumbled up. Putting the picture together, there is less and less chaos.
That is, unless the bigger picture is taken into consideration. The food consumed by those putting it together. The gasoline used to shop for food. Electricity for lighting and energy to make the cardboard.
* * *
Life itself seems to wear down considering the resources needed going from a baby to senior citizen. So when thinking of entropy, Lacy needs to consider all that goes into making and playing the jig-saw puzzle.
Lacy decided to make magnetic slime. She mixed white glue (the kind used in school), water, green food colouring, baking soda, and iron filings. It mixes into a putty that does not appear organized or useful.
Magnetic slime sits there like a snotty blob—until near a magnet. The blob will ooze along to follow the magnet and, if close enough, snap out to catch the magnet like a frog catches a fly. Drop on a refrigerator magnet and the blog wraps around, swallowing up the magnet like a sci-fi creature. In the presence of the magnet, the blob seems to become more organized and capable of movement.
Cleaning up, it occurs to Lacy that the blob is like the jig-saw puzzle, given the effort and resources that go into it. That’s when she bumped her mug of cocoa and the mug shattered on the kitchen’s tile floor.
* * *
Lacy tried putting the pieces back together, like Humpty Dumpty. Forces between molecules hold a cup together, so putting pieces together carefully they should stick by attraction between molecules.
It doesn’t work. To adhere, surfaces must be unimaginably close, about the width of an atom. Solid surfaces are too rough to allow more than a tiny amount of their surface area to be this close.
The liquid glue used to make the magnetic blob worked better. Most adhesives are liquid, at least initially, because of the need for close contact between the glue and the materials being stuck together.
A liquid glue can flow into surface irregularities to provide the needed close contact. Close contact is also prevented by settling dust particles and distortion of the cup during the break.
Unfortunately, white glue does not form strong bonds and Lacy relegated the mug to the trash. She poured a glass of milk and took out a cookie. No hot cocoa, so cookie dunked in milk would do.
Dunking draws the liquid into pores in the cookie and dissolves the sugar structure of the cookie. The cookie falls apart. The longer the cookie is submerged, the weaker it becomes. Structures deteriorate.
