Both Free-Ride offspring are charter members of the Order of the Science Scouts Special Children’s Auxiliary. They have not, as yet, built their own fire, either in a fire pit or a laboratory. However, a discussion this week about the strange vapor seen emanating from a car’s tailpipe one morning moves them further in the direction of being O.O.T.S.S.O.E.R.A.A.A.P. fire-certified.
Elder offspring: Remember that car we saw when we were walking to school, with the vapor coming out of its tailpipe?
Younger offspring: I made vapor come out of my mouth, too. It was cold.
Dr. Free-Ride’s better half: What do you suppose that vapor was that came out of the tailpipe?
Elder offspring: Was it steam?
Dr. Free-Ride: Sounds good to me.
Younger offspring: Why was there steam coming out of its tailpipe?
Dr. Free-Ride’s better half: What is steam?
Elder offspring: Gaseous water.
Dr. Free-Ride: So why would a car have gaseous water coming out of its tailpipe?
Elder offspring: Maybe there was water in the fuel tank?
Dr. Free-Ride’s better half: Can you think of any other reason?
Dr. Free-Ride: What’s the fuel people usually put in the fuel tanks of their cars?
Younger offspring: Gasoline!
Dr. Free-Ride’s better half: That’s right.
Elder offspring: But how does gasoline end up making steam come out the tailpipe?
Dr. Free-Ride: Do you know what the car has to do with the gasoline to get the energy out of it?
Younger offspring: No.
Dr. Free-Ride: It has to burn the gasoline.
Younger offspring: Like a fire?
Dr. Free-Ride’s better half: Yep. And do you remember what a fire needs to burn?
Elder offspring: Oxygen!
Dr. Free-Ride: That’s right.
Dr. Free-Ride’s better half: So, do you remember what happens when we light candles and then let them burn all the way down?
Younger offspring: They melt!
Dr. Free-Ride: But if they just melted, all the wax that started out in the candles would end up dripping onto the table. We get a few drips, but not whole candles’ worth of drips.
Elder offspring: What happens to the wax?
Younger offspring: Yeah, where does it go?
Dr. Free-Ride’s better half: Let’s see if we can figure that out. (Grabs a tealight candle, a 4 ounce canning jar, and a lighter.) OK, I’m lighting the candle. What will happen if I lower the jar over the candle?
Elder offspring: The flame will go out!
Younger offspring: (As the flame does go out) It ran out of oxygen!
Dr. Free-Ride: That’s right. So that must mean that the oxygen gets used up when something is burning.
Dr. Free-Ride’s better half: (Relighting the candle) What if I lower the jar more slowly so the oxygen doesn’t run out so quickly? Can you see something forming on the inside of the jar?
Younger offspring: Is that wax?
Dr. Free-Ride: Soot?
Elder offspring: Steam! It’s steam!
Dr. Free-Ride’s better half: That’s right. So, burning uses up oxygen …
Elder offspring: And makes water!
Dr. Free-Ride: Do you know what else is produced when you burn something?
Elder offspring: Carbon dioxide.
Younger offspring: How do you know that?
Elder offspring: I don’t remember. I must’ve heard it somewhere.
Dr. Free-Ride’s better half: So, if burning the wax uses up oxygen and makes carbon dioxide and water, what can you say about what the wax is made of?
Dr. Free-Ride: (After some blank looks) What is carbon dioxide made of?
Younger offspring: Carbon and dioxide.
Elder offspring: Carbon and oxygen.
Dr. Free-Ride: And what’s water made of?
Elder offspring: Hydrogen and oxygen.
Dr. Free-Ride: And you know that oxygen is getting used up when you burn the candle — the oxygen that goes to make the water and carbon dioxide.
Elder offspring: So the carbon and the hydrogen come from the wax?
Dr. Free-Ride’s better half: Yep. Wax has carbon and hydrogen, and so does gasoline.
Dr. Free-Ride: Hydrocarbon fuels. And the foods your body burns for fuel have carbon and hydrogen in them.
Elder offspring: Like carbohydrates?
Dr. Free-Ride’s better half: And fats, and proteins.
Younger offspring: We burn our food?
Elder offspring: And sometimes have tailpipe emissions.