Candles burn carbon using oxygen
You can do experiments to show that you need oxygen for a fire to burn. Light a candle, and when it is burning well, put a glass jar (like a jelly jar) over the candle. It will go out in a short time, because the flame has used all of the oxygen in the jar and it can’t get any more. Without oxygen, there’s no way to convert the hydrocarbon molecules in the candle into energy (heat and light).
You can also watch oxygen combining with iron to make rust. First put a nail in a little vinegar for a day (to eat away the protective coating) and then put it in a jar of water and come back in a few days to see the rust. Just like with the candle, this change also lets off some loose electrons in the form of heat (but not as much as the candle).
Oxygen also combines with iron in food to make rust. Cut an apple into slices. Put one of the slices in a plastic bag and seal it tightly to keep out the oxygen. Leave the other slice on the table. In just a few minutes, the slice on the table turns brown – that’s rust too.
The apple turns brown
All animals (including people) also breathe in oxygen and breathe out carbon dioxide. Plants, on the other hand, breathe in carbon dioxide and breathe out oxygen. You can see this by putting your glass jar over a plant and waiting a few days. Then (leaving the glass jar on the plant) take a large plastic soda-pop bottle and cut a hole in the bottom. Light two candles on the table. Quickly remove the glass jar from the plant and place it over one of the candles. Put your plastic bottle over the other candle and breathe out into the top of the bottle a few times. The candle inside the plant jar should burn better than usual, because it gets more oxygen. The candle inside the jar you blew into should burn worse than usual, because it gets more carbon dioxide.
More about oxygen
More about fire
Bibliography and further reading about oxygen and atoms:
Have you ever wondered, do white candles burn faster than colored candles? It seems that just about every element of a candle can affect how fast they burn, so it's no wonder that people are curious about the addition of candle dyes and colorants.
Reasoning Behind the Theory
Most people seem to think that plain white candles will burn faster than those with added dyes. The reasoning behind this theory is that the plain wax is more pure, and will give a faster burn than candles with additives.
There's nothing wrong with this line of thought, but when put to the test, do white candles burn faster than colored candles?
Color Makes Little Difference
In reality, color makes little to no difference in how fast a candle burns. In fact, candle dyes can make a candle burn hotter in some cases, causing the colored candles to burn faster. This is especially true for richly colored candles with a lot of added dye.
Overall, there is so little dye used in candle making that it doesn't affect the burn time much at all. Only a small amount of colorant is needed to turn pure white wax into bright, vivid colors.
Do White Candles Burn Faster than Colored Candles - The Proof
The topic of white candles versus colored candles is a popular subject for school children's science fair projects. Almost all of these begin with a hypothesis that the white candle will burn fastest, but that is never the case. Here are some links to show the results of such experiments:
- Poster.4teachers - This is an illustration of the actual project with results, in which the student found that red candles burned fastest.
- All-Science-Fair-Projects - Here's a very well planned and executed experiment using five different colors of candles. This student discovered that her yellow candles burned the fastest.
The Main Factors in Candle Burning Speed
As you can see, color doesn't play much of a factor in how long a candle burns. There are many other elements of candle making that will speed up or slow down the length of time that a candle takes to burn down.
The most important consideration in burn time is the candle wick. Wider or thicker wicks will burn much faster than thin ones, and the material the wick is made with can also make an impact.
That said, it's important to choose the right wick for your candle project. Large candles with very thin wicks will burn unevenly and you risk the flame being drowned out by pooling wax.
Different types of candle wax burn at different temperatures. Generally speaking, the harder the wax, the longer the burn time. Soy wax, for example, is a softer base for candle making, and these candles will burn more quickly than those made of beeswax or paraffin.
Other elements that can affect how long a candle burns include:
- Additives, such as wax hardeners
- Burning the candle in drafty spaces
- The age of the candle, as older candles tend to dry out
When you consider all the other factors that determine how long a candle burns, you might be tempted to discount the science experiments listed above. Since everything from the wick to the candle wax contributes to burn time, perhaps these experiments should have taken all of these into consideration.
In fact, the kids doing the experiments used the same brand and size of candles for their tests. It would stand to reason that a candle manufacturer would use standard materials to make these candles, with the only difference between them being the added dyes. Therefore, the experiments are likely correct.
Try It Yourself
If you want to test the theory for yourself, or have your children give it a go as a fun afternoon science project, it's easy to set up and execute. There are full instructions, including materials needed, at LearnerScience.com. If you really want to have control over the materials, you can even make the candles yourself, ensuring that the only difference between them is the added color.