Out, Out, Brief Candle!

In the last post, you learned how important the wax is to burning a candle. In this experiment, you will discover another requirement for burning - air. Burning wax is an example of a combustion reaction, in which carbon and hydrogen in the fuel (wax) combines with the oxygen in the air to form carbon dioxide and water. The more oxygen, the longer the candle will burn.

What you'll need:

Votive candle

Lighter
Several drinking glasses of different sizes

Watch or other timer

Light one of the candles and cover it by inverting the smallest glass over the flame so that it is covered. See how long it takes for the candle to go out. Re-light the candle, and cover it with the next largest glass. Does the candle stay lit longer? Do the same thing for each size of glass.

You will generally find that, that larger the glass, the longer the candle stays lit. The explanation for this is pretty simple - larger glasses trap larger amounts of air (which contains oxygen), and it takes longer for the oxygen to get used up!

Steel Away!

One of the most common metals used in today's world is steel. Steel is mostly iron, but it also contains other elements. As we've already seen, this kind of metal mixture is called an alloy. Most steel contains carbon in addition to iron. Stainless steel also has some chromium, and it doesn't rust. Other types include elements such as molybdenum, vanadium, tungsten, nickel, silicon, manganese, or boron. Different types of steel are used for different purposes. Some are good at high temperatures; others are hard and good at cutting.

The next time you're in a hardware or home-improvement store, take a look at the tools. How many different kinds of steel can you find?

Fun Facts 11

And finally...

• In the early 1900's, glow-in-the-dark watches were made with paint that contained radium (Ra, #88). Many of the young women who made these watches became very sick because of their exposure to this radioactive element.
• Lutetium (Lu, #71) is probably the most expensive element you've never heard of! It costs more than gold or even platinum!
• Did you know that your pencil doesn't actually contain lead? The stuff you write with is carbon (C, #6) in the form of graphite.
• Humans have been using the metal iron (Fe, #26) for thousands of years. There is a 1500-year old iron pillar in Delhi, India that is still rust-free, probably because it is located in an area with a dry climate.
• The nibs (tips) of very expensive pens may be made with rhodium (Rh, #45) because it does not wear down easily.
• Gas camping lanterns often use a compound of thorium (Th, #90) which glows bright white when heated.
• Rechargeable batteries often contain both nickel and cadmium (Cd, #48). They are called nicad batteries.
• Tin (Sn, #50) slowly disintegrates in temperatures below freezing (32^oF or 0^oC). In the 1700's, organs in unheated churches could be destroyed because their tin-containing pipes would turn brittle and crumble.
• Barium (Ba, #56) X-rays can be used to detect problems in the stomach or digestive tract. Barium sulfate does not let X-rays pass through, so after you drink a barium cocktail, those parts of your body become visible.
• The catalytic converter in your car contains palladium (Pd, #46) which helps to reduce the amount of pollution that comes out of the exhaust pipe.