Carbon dioxide versus oxygen... how can you tell which is heavier? Today, we will complete an activity to find out!
First, let’s learn a bit about carbon dioxide and oxygen.
Both carbon dioxide and oxygen are gases, and both of them are very close to what scientists call “ideal gases.” What is an ideal gas? An ideal gas has no interactions, are not influenced by outside forces and thus obeys the gas laws exactly (the gas laws basically state that there is a relationship between the pressure, temperature, and volume of any gas). In reality this is impossible, but carbon dioxide and oxygen come close!
Below is a representation of a carbon dioxide molecule:
Below is a representation of an oxygen molecule:
An oxygen molecule has a mass of 15.999, which we can round up to 16.
A carbon molecule has a mass of 12.011, which we can round down to 12.
If oxygen is written as O2, what do you think you do to find the weight?
Do the math!
O = 16
2 x 16
One oxygen molecule has a mass of 32.
How heavy is a molecule of carbon dioxide?
If a molecule of carbon dioxide is written as CO2, what do you do to find the weight?
Well, you know that C = 12
You also know that O = 16
There are two molecules of O in CO2 and 1 molecule of C in CO2.
Do the math!
12 + (2x16)
12 + 32
One carbon dioxide molecule has a mass of 44.
Now, try out this activity to see these equations in action!
Check out this video to see how to complete the experiment:
YOU WILL NEED:
- An adult to help you out!
- Baking soda
- Two empty glasses
- Measuring spoons
HERE’S WHAT TO DO!
1. Ask an adult to light a candle.
2. Measure 1 teaspoon of baking soda and dump it into one of the clear glasses.
3. Measure 1 tablespoon of vinegar and dump it into the glass with the baking soda.
4. Wait just a minute! CO2 gas is being created!
5. Pick up the bubbling glass and “dump” the gas into the second empty glass. Make sure to not actually dump any liquid! If you are confused, watch the video above to see how to do this.
6. Pick up the glass full of CO2 and pour it onto the burning candle.
7. Whoa! You should have seen the candle go out. Why did that happen?!
Take a guess!
The acetic acid in the vinegar reacts with sodium bicarbonate in the baking soda to form carbonic acid. Carbonic acid is unstable in nature, so it breaks down into carbon dioxide (CO2) and water (H2O). This is a decomposition reaction. A decomposition reaction is a chemical reaction in which a compound breaks down into two or more elements or new compounds.
Simply written it can be shown as:
AB ---------> A + B
This works well for splitting a compound into two elements, such as when water splits into hydrogen and oxygen.
H20 ----------> H2 + O2
In this case, though, the decomposition reaction caused the carbonic acid to break down into two compounds (remember, compounds are two or more elements combined).
Here’s a visual of the decomposition reaction we saw today:
The bubbles formed in the glass during the reaction are the carbon dioxide escaping! As you saw, the carbon dioxide gas is what put out the fire. When the glass with escaping carbon dioxide comes near the candle, the fire is extinguished. Since fire needs oxygen to survive, when you poured the carbon dioxide onto the flame, the CO2 displaced the oxygen, thus putting out the flame. This method is actually used in some fire extinguishers (others use nitrogen).
Still want to know more? Here are 10 different ways of explaining why carbon dioxide is heavier than oxygen!