Place the unlit candle on a balance, and record the mass. Then light the candle. Notice how the mass of the candle will change because of the many different things happening while it's burning. Set a timer, or just watch the clock, and record the mass of the lit candle every 15 seconds. Once you have been recording for about 2-3 minutes (whichever you prefer) you can blow out the candle.
As you can see, the mass of the candle will decrease as it's burning. This may be happening because the wick is burning off or the candle melting and evaporating eliminates some of the candles mass.
Some Physical and Chemical changes that can be noticed from this lab are:
Conclusion: We've learned that a candle actually loses mass as it's burning.
Experiment 2:
Place an unlit candle on the balance. Also, place a beaker upside down over the candle. Record the mass of these objects. Next, take off the beaker to light the candle and then put it back down once you have done so. As you can see, the flame goes out very quickly. The flame needs oxygen to remain lit, and because it is trapped in an enclosed beaker, the oxygen runs out faster. No oxygen, equals no flame. If you are able to record the mass of the lit candle with the beaker on it before it goes out, you can compare the two readings. It is very hard to find a second mass since the flame goes out so fast, so if you can't get one then don't worry. This experiment will also have the same physical and chemical changes as pictured above.
The video below will also help explain the lab:
Conclusion: We've learned that a candle need oxygen to remain lit.
Experiment 3:
First, make sure you have a metal pan and a candle available. Light the candle and let it sit for a while to melt the wax. Once there is a decent puddle of wax on top of the candle, pour it into a small pile on the pan. Quickly set the candle on top of the wax puddle to make it stay put. The melted wax acts like a glue so that the candle will not tip over or float during the next steps of the experiment. Next, pour water into the pan so that about about a half inch of the bottom of the candle is covered. The amount of water you pour in will vary depending on how big of a pan you use. Turn an Erlenmeyer Flask upside down and place it over the candle, like you did with the beaker in Experiment 2. As you can see, the water is rising up the flask. This is caused by a change in pressure. Pressure moves from high to low. So as the candle is heating up the inside of the flask, the molecules speed up and cause more collisions, ultimately creating more pressure from all the colliding. From what we learned from the 2nd experiment, candles need oxygen to burn. Eventually the candle burns out from being in an enclosed area. Without the flame, the inside of the flask cools down. When molecules are cooled, they don't collide as much, meaning the pressure is decreased. Since the pressure inside of the flask is now lower, the area on the outside of the flask is higher. Again, pressure moves from high to low, so the water is being forced up the flask to try and create an equilibrium, or an equal pressure between both outside the flask and inside the flask. The water is able to move up the flask because the bottom isn't sealed off.
Throughout this whole part of the experiment where the water rises, fog and moist water droplets have been forming on the top of the flask. These were formed from the vaporization and condensation of the candle burning off carbon dioxide. Once the water stops rising, take the flask off the candle and pour 20 mL of Bromothymol Blue into the flask. Swirl the liquid around and watch as the color changes from blue to green. Bromothymol Blue was made to detect CO2, so through the color changes it is proven that candles give off carbon dioxide as they burn.
(I did have a video of this but it wouldn't upload, so I didn't put it in.)
Another way that you can prove that Bromothymol Blue is made to detect CO2 is by blowing into it with a straw. The human body breathes in Oxygen and releases carbon dioxide. By blowing into the Bromothymol Blue, you are putting carbon dioxide into the liquid, causing it to turn green again.
The video below will show the process of this experiment:
Conclusion: We've learned that candles give off CO2 when burning.
Experiment 4:
In this experiment, our challenge was to light a candle without actually touching its wick to a flame. How to accomplish this was to light both of the candles. Blow one of them out, then quickly try to light its smoke on fire. Follow the line of smoke with the lit candle to try and get a flame. We found out that when lighting a candle, it's actually the vapors that ignite, not just the wick or wax. In this case, the candle's vapors were smoke. The wick is what actually starts the flame, since it is a flammable substance, but the gases produced from vaporization are actually what keep the flame burning and in control.
To see this experiment being done, view the video below: (This experiment does take many tries, so fast forward to 30 seconds to see the best result)
Conclusion: We've learned that a candle's vapors keep the candle burning.
Chemical Formula:
We were given the chemical composition of wax, C20H42, and were asked to find the rest of the chemical formula. The formula consists of 2 products that go to the left of the arrow, and 2 reactants that go to the right of the arrow. Since we know that candles need oxygen to burn, we added O2 as a product. The final formula we came up with was:
C20H42 + O2 --> CO2 + H2O
This formula is not balanced, however. To balance an equation, you have to make sure there are equal amounts of each element on each side. The balanced equation ended up being:
2C20H42 + 61O2 --> 40CO2 + 42H2O
This is a combustion reaction, because there is oxygen and carbon dioxide involved.
Molar Mass:
Molar mass is the mass of a candle's atom. To find molar mass, you need to use the balanced equation from above, 2C20H42 + 61O2 --> 40CO2 + 42H2O. First, find the atomic mass of every element involved: Carbon, Hydrogen, and Oxygen using a periodic table. Carbon's mass is 12, Hydrogen's mass is 1, and Oxygen's mass is 16. Now just substitute in each number where each letter is, sort of like an algebra problem. If there is a subscript, take the number directly in front of it and multiply it by whichever the number is. For example, if you had a subscript 2, multiply by 2. If there are 2 elements right next to each other, like CO2, then multiply the O by 2, (16x2) and add it to C (12). Then finally, if there is a big number in front of the set, such as the 61 in 61O2, then you would first multiply O by 2 (16x2) then multiply that number by 61. Follow the picture below for step by step instructions:
You can also tell that we balanced our formula correctly, because 2,516 is same on both sides. So, 2,516 is the molar mass of a candle's atom.
Real Life Examples:
Many things can be taken away from this lab and be applied to the real world. A couple listed below are:
1. Ears popping on an airplane- this relates to Experiment 3. Your ears pop on a plane because of the change in pressure. As you go up to a higher altitude in the plane, the air pressure decreases, causing your ear to pop. This relates to Experiment 3 because the water being forced up the flask also happened from a change in pressure.
2. The human body- this relates to Experiment 2 and a little of 3. Everyday you breathe in oxygen and breathe out carbon dioxide. This is the same thing with candles, except not breathing. Candles need oxygen to remain lit, or "alive." They also give off carbon dioxide when burning, just like we release it when breathing.
