Candle Lab

Candle Labs

Burning Candle: 

Observations:

• 3 parts of flame

            -yellow at the top of the flame

            -darker cone in the lower middle part of flame

            -blue at the very bottom of the flame by the wick

Parts of a flame diagram.

• Wax melts

            -some of the wax melts down the side of the candle

            -remaining wax rises up the wick just as water will do when you dip a string into the water, the wax will then vaporize, and the wax vapor (which is very flammable) will burn

• The candle needs oxygen to burn

             -we placed an Erlenmeyer Flask over a candle allowing no substances to escape or enter and the flame slowly went out (this is because as the candle burns, the reaction turns the oxygen and the wick into CO2 and water vapor, after all the oxygen is replaced the flame has no oxidizer and goes out)

What is going on when a candle burns?

When a candle is burning only a small portion of the flame is from the wick itself, the remaining portion of the flame is from the candle wax vapor burning. A candle is a combustion reaction (a reaction in which there is  fuel + oxygen producing CO2 + H2O). When a candle is lit, the wick burns for a short time and the heat from this reaction melts the wax. The melted wax then rises up the wick just as water rises up a string when dipped into water. When the melted wax is closer to the flame, the heat vaporizes the wax and the now vaporized wax is what the majority of the flame is from.

Mass of a candle:

• As the candle burns, the mass of the candle falls

            -we put a burning candle on a masser
                 -after 75 seconds the mass fell by .05 grams from 10.31 grams to 10.26 grams
                 -this is due to the reaction with oxygen and the candle wick: the reaction changes the  wick  and the oxygen to CO2 and water vapor. Also, the wax melts and eventually evaporates from the candle. As the amount of matter lessens, the mass of the candle falls.

            -furthermore, we placed a beaker on top of the candle on the masser and observed

                 -the candle only burned for a short time (10 seconds) as expected due to the lack of oxygen, but during this time the mass fell by only .01 grams, there was such a small change due to the fact that all the matter was contained and none could enter or exit, the change in mass was either due to the change in air pressure around the beaker (movement could cause this) or from the melted and vaporized wax which is less dense then the solid form.

Erlenmeyer Flask and Candle:

Procedure:

1. Place a sheet pan on a flat surface.
2. Pour hot candle wax onto pan and secure candle the to the pan.
3. Pour enough water to cover that pan completely with approximately 1 centimeter of water.
4. Light the candle and place an Erlenmeyer flask completely covering the candle.
5. Observe.
6. When the water has stopped rising, quickly take off the Erlenmeyer Flask and pour 10 mL of bromo blue (be careful not to get any bromo blue on your skin) into the flask. 

A video of the experiment

Observations:

            -Notice after the candle is lit, it burns briefly and then goes out. This is due to the fact that there is a limited amount of Oxygen in the flask and once all the oxygen has reacted with the wick and wax vapor, there is none left for further reactions causing the flame to go out.

             -The water level rose up the Erlenmeyer Flask. The water level in the flask rises because when you put the flask on, the candle is lit causing the air to have a higher temperature. When the air has a higher temperature, it expands and takes up greater volume. As the candle burns, the oxygen in the flask is converted to CO2. The lack of oxygen causes the flame to go out. While the flame is out, the air temperature inside the flask cools back to room temperature. As the temperature in the flask drops, the air pressure falls because the cooler air takes up less volume than the warm air previously inside the Erlenmeyer Flask. This imbalance of pressure forces the water to rise up the flask.
           
            -When the water stops rising, and the bromo blue is poured into the Erlenmeyer Flask and the flask is swirled, the bromo blue turns green. The color change happens because the bromo blue reacts with the CO2 from the burning candle changing the color of the liquid. This is evidence that CO2 is a product of combustion reactions

            -A real world example of something similar to this experiment is when you submerge a drinking straw into a liquid, place your finger on the top hole and pull out the straw. The liquid then fills the straw to how far it was submerged. This happens because there is a very small, limited amount of matter in between your finger and the liquid and if the liquid was to fall out, there would be a small amount of matter in a now larger portion of the straw creating a difference in pressure from the outside world. This difference in pressure is what creates the suction keeping the liquid from falling out the bottom of the straw.

Candle Relighting:

Procedure:

1. Light two candles (make sure they are fairly large with a place to hold them).
2. Let the candles burn for about 30 seconds.
3. Blow out one candle and immediately put the lit candle directly above the blown out candle (place the flame of the lit candle where the vapor of the unlit candle is).
4. Observe.

Observations:

            -When the flame of the lit candle is placed in the remaining vapor of the extinguished flame, the candle relights. The candle relights because the wax of a candle is highly flammable while in a gas form. The vapor rising from the extinguished flame is a mixture of CO2 and the candle wax (C20H42). While the candle is still burning, all the vaporized wax is being burnt along with the wick, but when the flame is put out, the heat from the flame is gone (the heat is needed to get the reaction going) and the wax vapor doesn't burn, but floats into the atmosphere. When you then take the lit candle and put it next to the vapor, the reaction starts again, producing heat igniting further reactions down the trail of smoke back to the wick, which by the heat is re-lit.

Candle Wax Reaction:

2 C20H42 + 61 O2 = 40 CO2 + 42 H20

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

This reaction is a combustion reaction.

Molar Mass:

1 mole is equal to 6.02X10^23 molecules

            -One mole of C20H42= 282.54748 grams

            -One mole of O2= 31.9988 grams

            -One mole of CO2= 44.0095 grams

            -One mole of H2O= 18.01528 grams

Reactants: 2517.02176 grams

Products:  2517.02176 grams

Physical Changes of a Burning Candle:

            -Wax melting and eventually vaportizing

            -Water created by the combustion reaction vaporizing

Chemical Changes:

            -Wick burning (combustion reaction)

            -Candle wax vapor burning (combustion reaction)

            -Bromo blue reacting with CO2 turning it a green hue