How Is Baking Soda Different From Baking Powder?

It’s all in the chemicals. Baking soda (aka bicarbonate of soda) is a single chemical: pure sodium bicarbonate, whereas baking powder is baking soda combined with one or more acid salts, such as monocalcium phosphate monohydrate, dicalcium phosphate dihydrate, sodium aluminum sulfate, or sodium aluminum phosphate. Now that I’ve warmed the hearts of chemistry fans … Read more

Where Does Corn Syrup Come From and How Is Corn Syrup Made?

I know what you’re thinking. The corn that you bought at the farmers’ market the other day wasn’t really “as sweet as sugar,” as the vendor promised, was it? “Sweet corn” does indeed contain more sugar than “cow corn,” but even in the new sugar enhanced and super sweet varieties it’s precious little compared with … Read more

How Does Two Cups of Sugar Dissolve In One Cup of Water?

Why don’t you try it? Add two cups of sugar to one cup of water in a saucepan and stir while heating slightly. You’ll see that all the sugar will dissolve. One of the reasons is very simple: Sugar molecules can squeeze into empty spaces between the water molecules, so they are not really taking … Read more

What Is Sulphured Molasses and How Is Sulphured Molasses Made?

The “sulphur” in sulphured molasses is a good starting point for understanding several interesting aspects of food chemistry. Sulphur is the old-fashioned spelling for sulfur, a yellow chemical element whose common compounds include sulfur dioxide and sulfites. Sulfur dioxide gas is the choking, acrid odor of burning sulfur and is reputed to pollute the atmosphere … Read more

What Is the Difference Between Cane Sugar and Beet Sugar?

More than half of the sugar produced in the U.S. comes from sugar beets, misshapen, whitish-brown roots that resemble short, fat carrots. Sugar beets grow in temperate climates, such as in Minnesota, North Dakota, and Idaho in the U.S., and in much of Europe, whereas sugar cane is a tropical plant, grown in the U.S. … Read more

What Is the Difference Between Raw Sugar and Refined Sugar?

What health-food stores call raw sugar isn’t raw in the sense that it is completely unrefined. It’s just refined to a lesser degree. From the dawn of history, honey was virtually the only sweetener known to humans. Sugar cane was grown in India some three thousand years ago, but it didn’t find its way to … Read more

What Does Entropy Mean and Where Does Entropy Come From?

There’s no such thing as a stupid question. This is perhaps the most profound question in all of science. Nevertheless, it does have a fairly simple answer ever since a genius by the name of Josiah Willard Gibbs (1839–1903) figured it all out in the late nineteenth century. The answer is that everywhere in Nature … Read more

Why Doesn’t Soap Work In Sea Water or Salt Water?

It’s one of life’s little ironies. Sailors do hard, often dirty work, yet with all that water around they can’t bathe or wash their clothes with soap. Not with ordinary soap, anyway. There is a special soap called “sailors’ soap” that works in salt water. But first let’s see why the ordinary stuff doesn’t. It … Read more

Why Is One Side of Aluminum Foil Shinier Than the Other?

It’s because of a time and space-saving shortcut that’s used in the final stage of the manufacturing process. Aluminum, like all metals, is malleable; that is, it will squish when enough pressure is applied. That’s in distinction to most other solid materials, which will crack under pressure. So metals can be rolled out into extremely … Read more

Why Do Smoke Alarms Contain Radioactive Material: Americium-241?

What you have is an ionization-type smoke detector. It detects smoke by the fact that smoke interferes with air’s ability to conduct a tiny electric current. Under ordinary conditions, air doesn’t conduct electricity at all; it’s an excellent insulator. That’s because the nitrogen and oxygen molecules in the air have no electric charge of their … Read more

Why Does the Two Potato Clock Need Two Potatoes?

For the same reason that your flashlight needs two batteries. A set of zinc and copper metals will move electrons with only so much oomph. That’s because there’s only a certain amount of difference between the electron-holding powers of zinc and copper. But if you need more electron-moving force, to light a bulb, for example, … Read more

How Do Kids Jump Over Things On Their Skateboards?

An ollie, is named after its inventor, Allen Ollie Gelfand. Gelfand was one of a number of southern California surfers in the late 1950s who just couldn’t wait for good surf to come up and decided to surf the sidewalks. That’s what started the skateboard craze. An ollie is a jump into the air without … Read more

Why Are New Tires So Much Noisier Than Old Tires?

One obvious factor is that your old tires may have been pretty smooth, and smoother tires will be quieter. Tire noise depends on the tread pattern, the roughness of the road and the roundness of the tires. Really, tires can be out-of-round, and the high spots will thump on the road during every revolution. But … Read more

Why Does Rubber Stretch?

If there is one statement that will make you a passionate believer in molecules, it’s this: Rubber stretches because it is made of stretchy molecules. A rubber band stretches because each of its molecules, all by itself, is built like a miniature rubber band. Rubber molecules are shaped like long, skinny worms, all coiled and … Read more

How Does an Eraser Erase Pencil Marks?

It doesn’t work like a chalkboard eraser, which wipes an accumulation of chalk off a smooth surface. Paper isn’t that smooth and a pencil mark isn’t all on the surface; most of it is embedded among the paper fibers. If you look at a pencil mark under a microscope, you’ll see that it’s not continuous; … Read more

Why Can You Smell When It’s Going To Rain?

It’s not the rain itself that you smell, but just about everything else. Almost everything smells a little stronger when it’s about to rain. Stormy weather is usually preceded by a drop in atmospheric pressure, or what the TV weather people like to call “barometric pressure.” (Is that what you feel when you’re struck by … Read more

Why Does Warm Air Hold More Moisture Than Cold Air?

It’s usually more humid in the summer because there’s more water vapor available. I don’t mean that the oceans, lakes and rivers somehow expand in the heat. (Well, maybe a tad.) More precipitation? Perhaps. But it’s not the amount of water itself; the humidity can be quite low over the middle of the ocean. What … Read more

Why Does a Hair Dryer Have To Both Heat and Blow?

This is one of those questions that seems so natural that we forget to ask them. But that’s what I’m here for: to make you wonder about things you take for granted, and then to replace your complacency with the smugness of knowing. The water in your hair or clothes must first be converted from … Read more

What Does 100 Percent Humidity Mean and Does It Mean Rain?

Chicken Littles who fear drowning in air are forgetting that “humidity” is purely relative. Everybody goes around talking about “the humidity” as if it’s something absolute, but it’s really the relative humidity that they’re talking about, relative to some maximum, but still small, amount of water vapor in the air. And mind you, that’s vapor, … Read more

Why Does Spilled Coffee On My Kitchen Counter Form a Brown Ring When It Dries?

For years, people have observed this phenomenon without giving it a second, or even a first, thought. Hundreds of less-than-fastidious, coffee sipping scientists have probably glanced at the ring, mumbled something about surface tension and told their lab assistants to clean it up. But it wasn’t until 1997 that six scientists at the University of … Read more

Why Is the Ocean Blue and Is It Just a Reflection of the Sky?

That’s a common belief that just doesn’t hold water, so to speak. First of all, the ocean’s surface isn’t exactly what you’d call a mirror. And second, how come it’s a much darker blue than the sky? No, the world’s oceans really and truly are blue, many different shades of blue (ask any sailor), depending … Read more

What Is Water?

It’s the one substance that is indispensable to all living things. It makes up more than half of our own body weights. It is the most abundant chemical on Earth, with more than a billion billion tons of it covering 71 percent of the planet’s surface and probably another billion tons in those little plastic … Read more

Why Is It So Cold In Space?

It isn’t. Satellites and space shuttles do indeed get cold up there, but it’s not because it’s cold up there. First of all, there’s really no such thing as cold, no matter what the penguins tell you. Cold is a linguistic concept, not a scientific one. Our caveperson ancestors needed a word for “not hot,” … Read more

Does the Moon Ever Really Turn Blue?

Yes, but only once in a great while. There has to be exactly the right kind of smoke or dust in the air. It happened most spectacularly in 1883, when the Indonesian volcano Krakatau blew its top, spewing dust all around the globe. The bluest moon since Krakatau was caused by a series of forest … Read more

Why Are the High Tides Higher When the Moon Is Full?

It’s easy to fool yourself into thinking that the moon is bigger when it’s full, and that it therefore pulls on the oceans more strongly to make higher tides. But the moon is always the same size and distance away as it circles Earth. It is just lit up differently by the sun at different … Read more

How Does the Moon Always Keep the Same Face Toward Earth?

Sounds odd, doesn’t it? Either it’s the most colossal coincidence that ever occurred, or there’s something real fishy going on. Well, even the fishiest-seeming coincidences can have rational explanations. Your first guess might be that the moon isn’t spinning on its axis the way Earth is, and that it just goes around us, maintaining the … Read more

Why Do the Stars Twinkle In the Sky?

The answer that you see everywhere is that the twinkling is caused by turbulence in the atmosphere, which distorts the light coming from the star. But that doesn’t explain why “atmospheric turbulence,” whatever that is, should distort light in the first place, or where the on-and-off blinking effect comes from, or why only stars, but … Read more

What Causes a Sonic Boom and Where Does the Sound Come From?

There’s a lot of nonsense out there about sonic booms. The Columbia Encyclopedia 5th edition (1993) says, “An object such as an airplane generates sound. When the speed of the object reaches or exceeds the speed of sound, the object catches up with its own noise” (I wish some politicians would do that), which causes … Read more

What Would Happen If I Used a Vacuum Cleaner In a Vacuum?

You’d get an exceedingly clean vacuum. But seriously, I don’t know why you’d want to imagine a thing like that, because there is nothing cleaner than a true vacuum; it is the epitome of nothingness. I’ll assume, however, that you ask the question out of scientific curiosity, rather than because it’s funny. What is a … Read more

How Can Radiocarbon Dating Tell Us How Old Anything Is?

Radiocarbon dating won’t help you to determine the age of anything that is still alive, such as a twelve-year-old posing as a twenty-five-year-old in an Internet chat room. It’s is useful for determining the ages of plant or animal matter that died anywhere from around five hundred to fifty thousand years ago. Ever since its … Read more

Why Do Toilets Flush Counterclockwise In the Northern Hemisphere and Clockwise In the Southern Hemisphere?

It’s just another one of those urban legends, probably started by an overenthusiastic physics teacher. But it’s based upon a grain of truth. Moving fluids such as air and water are slightly affected by Earth’s rotation. The phenomenon is called the Coriolis effect, after the French mathematician Gustave Gaspard Coriolis (1792–1843), who first realized that … Read more

If the Whole Earth Is Spinning At 1,000 Miles Per Hour, Why Don’t We Get Dizzy or Feel It?

No, it’s because Earth’s rotation is a uniform, unvarying motion, and we can feel only changes in motion (Techspeak: acceleration). Any time a moving object is diverted from its motion, either by a change in its direction or a change in its speed, we say that it has experienced an acceleration. Acceleration doesn’t just mean … Read more

Which Is Colder, the North Pole Or the South Pole?

The South Pole, where the average temperature is about 56 degrees below zero degrees Fahrenheit (−49 degrees Celsius). At the North Pole the average temperature is a relatively balmy 20 degrees below zero (−29 degrees Celsius). Antarctica is actually a continent, with the ice and snow lying on top of a huge land mass, whereas … Read more

Why Does the Air Keep Getting Colder As We Go Higher In Altitude?

The air does keep getting colder, by an average of about 3.6 degrees Fahrenheit for every thousand feet (6.5 degrees Celsius per kilometer) , up to around 33,000 feet (10,000 meters) above sea level. That’s just a bit higher than the cruising altitude of large commercial jet aircraft. You may have heard the airliner’s captain … Read more

Why Do Mountaintops Stay Covered With Snow All Year Round?

Obviously, because it’s always colder up there. But why is it always colder up in the mountains than down at the seashore? After all, doesn’t hot air rise? Shouldn’t it therefore be hotter up there? There’s certainly plenty of hot air in equatorial Tanzania, but Kilimanjaro, which thrusts its peak 19, 340 feet (5,895 meters) … Read more

Why Does Heat Rise and Do All Forms of Energy Go Up?

People say heat rises because they’re speaking carelessly. The statement is just a lot of hot air, because heat doesn’t rise. What they mean to say is that hot air rises. Heat is one of many forms of energy; it is energy in the form of moving molecules. But it’s meaningless to say that any … Read more

Why Does Gravity Try To Attract All Things To the Center of Earth?

Because the center of the planet is the center of Earth’s gravity: its center of gravity. You’ve heard the expression “center of gravity” before, and now’s your chance to understand what it really means. But first, what is gravity, or, more properly, gravitation? Gravitation is one of the three fundamental forces in Nature. (The other … Read more

How Much Current Does It Take To Electrocute a Person?

Electric current is measured in amperes. An ampere is a huge unit of electric current, equivalent to 6 billion billion (6 followed by 18 zeros) electrons passing by every second. So you often hear talk of milliamperes or milliamps,  thousandths of amperes. One milliamp passing through your body will cause a mild tingling sensation. Ten … Read more

Can Global Warming Be Reversed If Everyone Left Their Refrigerator Doors Open?

Unfortunately, no, for several reasons. First of all, the world’s supply of air conditioners and refrigerators isn’t anywhere near what you might think by looking around your neighborhood. But even if every citizen of the less-developed nations were privileged to enjoy cool bedrooms and frozen pizzas, the amount of available coolth wouldn’t amount to an … Read more

Why Do Flames and Fire Always Go Upward?

Light a match and, while it’s burning, twist it into a variety of positions. The flame keeps pointing unerringly upward, regardless of the orientation of its fuel. How, indeed, does it “know”? You are well aware that hot air rises. A flame, whatever it is, must therefore be carried upward by the rising current of … Read more

Why Are the Freezing and Boiling Temperatures of Water At 32 and 212 Degrees Fahrenheit?

They are indeed strange numbers for such common, everyday goings-on as the freezing and boiling of water. We’re stuck with them because a German glassblower and amateur physicist named Gabriel Fahrenheit (1686–1736) made a couple of bad decisions. Gadgets for measuring temperature had existed since about 1592, even though nobody knew what temperature was, and … Read more

Why Is There a Limit To How Cold Anything Can Get?

Heat is energy. What kind of energy? It’s not electrical energy or nuclear energy or the kind of energy that your car has as you barrel down the highway. It’s the energy that an object contains within itself, because the particles that it’s made of, its atoms and molecules, are actually vibrating and bouncing around … Read more

What Is the Difference Between Heat and Temperature?

If Tucson was twice as hot as Miami, it certainly wouldn’t be 160 degrees Fahrenheit (71 degrees Celsius). But that’s not because 160 degrees is too hot; it’s not hot enough. The temperature that is “twice as hot” as 80 degrees Fahrenheit, believe it or not, is 621 degrees Fahrenheit! Here’s what’s going on. First … Read more

Why Is Heat Known As Wasted Energy and Why is Everything Hot?

Everything is hot. That is, it contains some heat. And as a consequence, it has a temperature. Even an ice cube contains heat. “Hot” is strictly a relative term. Heat is the ultimate form of energy, the form into which all other forms ultimately degenerate. There is energy of motion (Techspeak: kinetic energy), there is … Read more