Candle Experiments and Results

Candle Experiments and Results

Our 2nd period Advanced Ninth Grade Science class at Indianola High School has been doing experiments on candles over the last week. This post will be a guide through everything you would ever need or want to know about candles (Scientifically speaking).

Experiment 1

(Mass Changes in Burning)

In this simple experiment we set out to find changes in a candles mass during a typical burning, if any changes at all. Using very simple tests, observations and equipment we looked to see if a candle would lose mass after it had been lit. 

The items used are as follows; Balance, general purpose matches, a small candle and a timer.

The steps preformed are as follows;

1. Use the balance to find the mass of an unlit candle.
2. Light the candle (Previously massed) and set on the balance
3. Begin timer (Decide on intervals to use for your timing, we used 30 second intervals)
4. Watch the mass as the timer runs and the candle burns, write down any changes that take place at each interval of your choosing.
5.  Finally after you think you have gathered enough data, blow out your candle and write down the final mass. 

This should give you an idea on what is happening (Mass wise) as a candle burns.

Here are the results from my experiment;

  0(Seconds)-10.31 g (Mass)

  30-10.31 g

  60-10.3 g

  90-10.29 g

  120- 10.27 g

So from the data collected we gather that candles will drop in mass slightly, but a larger candle would take a long time to melt down completely.

A real world example of this can be found when heating water. When you heat water for a cup of tea in the microwave, and pull it out you will inevitably have less water in your cup compared to how much you had when you put it in. The reason this happens is because the water absorbs the heat that microwave is giving off and absorbing it. When the water absorbs the heat it begins to evaporate into a vapor, leaving you with less water and thus less overall mass. 

We also preformed a second experiment to gather similar data. You use the same items, with the exception of the addition of a small beaker. 

The steps preformed are as follows;

1.   Use the balance to find the mass of an unlit candle. 
2. Find the mass of the beaker of your choice.
3. Light the candle and immediately place the beaker on top. (Beginning the timer at the same time, it helps to have a partner)
4. Observe the mass as the candle burns, stop the timer as soon as the candle is completely out. 
5. Remove the beaker from the balance and compare before and after mass.

Here are the results from my experiment;

  0(Seconds)-59.5 g (Mass with beaker)

  3.3(Wick burnt out)-59.47 g

From this experiment we concluded with the data recorded that the candle lost mass faster with a beaker on top. The candle needs oxygen to burn, and with the beaker on top limited oxygen is available, causing the candle to burn out. when you remove the beaker after it goes out, the carbon dioxide (CO2) created from the burning wick is released into the air. The release of the CO2 into the air causes the mass to drop, because the CO2 had been resting inside the beaker keeping the mass the same. When the candle loses mass without a beaker on top it is because the wax is being heated from the burning wick (Which is releasing small amounts of CO2). The wax goes through a couple different changes of state; Solid-->Liquid-->Gas(Vapor).

The heat from the flame causes the solid wax to melt into a liquid, and with continuing heat, the liquid wax will evaporate into a vapor (Which releases chemicals that we inhale and then reacts with our brain creating smell).

There were a couple different physical and chemical changes taking place during this experiment, here are the ones we observed;

Physical; Wax melting, wax evaporating and colors in the flame changing

Chemical; Wick burning releasing CO2, combustion taking place
(A few things that clue to a chemical change; Smoke, fire/flames, color change, temperature change and odor.)
The wax melting in a candle is an example of an endothermic reaction. The wax is absorbing heat (energy) from the candle. However, the wick burning is an example of exothermic reaction. The flame is releasing heat (energy) into the air around the flame.

We preformed another experiment looking for changes in pressure and the presence of CO2:

Experiment 2



The items used are as follows; Shallow metal baking pan, just enough water to cover the base of the pan, general purpose matches, one slim candle, one large Erlenmeyer Flask and 100 ml of Bromothymol Blue.

The steps are as follows:

1. Light a candle and let it burn until there is a small pool of wax around the base of the flame.
2. Pour the wax from the candle into the center of the pan, then while it's still hot set the candle on top (Cementing the candle to the pan).
3. Pour in just enough water to cover the bottom of the pan.
4. Set the Erlenmeyer on top of the candle (See video).
5. After the candle burns out, quickly remove the flask and pour in your Bromo Blue.
6. Swirl the Bromo Blue around in the bottom until it changes color.

In this experiment we see that the candle needs oxygen to burn, and that in cutting off the oxygen the candle burned out. We also see that with the great heat inside of the flask the temperature becomes higher on the inside than the outside. And when something is heated it expands, thus the oxygen in the flask is being used and heated causing greater pressure inside. When the oxygen starts expanding and it tries to find a place to go, in this case, through the bottom. As air tries to escape, it lets water in.This is an example of how heat (energy) flows from hot to cold. 

A real world example of how this works can be found in a drinking bird.

In another experiment we tried to relight a candle using another candle. It is a very simple experiment. You are looking to find WHY the smoke will relight the candle. To do this experiment here is what you need;

One candle, one lighter. (pretty straight forward) We used two candles, but we ended up dripping wax everywhere, so I would recommend using a lighter.

Experiment 3

After observing this experiment many times and doing it hands on we concluded the reason this happens. A candle flame involves combustion, a chemical reaction that combines vaporized wax with CO2 creating C20H42. When you put out a candle there is vaporized wax in the vapor you see rising from the candle, which you can heat to re-ignite the candle wick. 

this is the candle wax combustion reaction:

2 C20H42 + 61 O2 = 40 CO2 + 42 H20

2 molecules of wax + 61 O2 molecules = 40 CO2 molecules +  42 water molecules

And this is the molar mass: ( =1 mole is equal to 6.02X10^23)

1. 1 mole of C20H42 (Wax); 282.59 grams 
2. 1 mole of O2; 32 grams
3. 1 mole of CO2 (Carbon dioxide); 44.01 grams
4. 1 mole of H2O (Water); 18.02 grams

The reactants/products in this reaction

Reactants- 2517.02 grams

Products- 2517.02 grams