Conversation with children -10

This conversation between Socratic-minded parents and children was reported in The Science Creative Quarterly.


OLDER CHILD: Remember that car we saw when we were walking to school, with the vapor coming out of its tailpipe?

YOUNGER CHILD: I made vapor come out of my mouth, too. It was cold.

FATHER: What do you suppose that vapor was that came out of the tailpipe?

OLDER CHILD: Was it steam?

MOTHER: Sounds good to me.

YOUNGER CHILD: Why was there steam coming out of its tailpipe?

FATHER: What is steam?

OLDER CHILD: Gaseous water.

MOTHER: So why would a car have gaseous water coming out of its tailpipe?

OLDER CHILD: Maybe there was water in the fuel tank?

FATHER: Can you think of any other reason?

MOTHER: What’s the fuel people usually put in the fuel tanks of their cars?

YOUNGER CHILD: Gasoline!

FATHER: That’s right.

OLDER CHILD: But how does gasoline end up making steam come out the tailpipe?

MOTHER: Do you know what the car has to do with the gasoline to get the energy out of it?

YOUNGER CHILD: No.

MOTHER: It has to burn the gasoline.

YOUNGER CHILD: Like a fire?

FATHER: Yep. And do you remember what a fire needs to burn?

OLDER CHILD: Oxygen!

MOTHER: That’s right.

FATHER: So, do you remember what happens when we light candles and then let them burn all the way down?

YOUNGER CHILD: They melt!

MOTHER: 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.

OLDER CHILD: What happens to the wax?

YOUNGER CHILD: Yeah, where does it go?

FATHER: 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?

OLDER CHILD: The flame will go out!

YOUNGER CHILD: (As the flame does go out) It ran out of oxygen!

MOTHER: That’s right. So that must mean that the oxygen gets used up when something is burning.

FATHER: (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 CHILD: Is that wax?

MOTHER: Soot?

OLDER CHILD: Steam! It’s steam!

FATHER: That’s right. So, burning uses up oxygen …

OLDER CHILD: And makes water!

MOTHER: Do you know what else is produced when you burn something?

OLDER CHILD: Carbon dioxide.

YOUNGER CHILD: How do you know that?

OLDER CHILD: I don’t remember. I must’ve heard it somewhere.

FATHER: 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?

MOTHER: (After some blank looks) What is carbon dioxide made of?

YOUNGER CHILD: Carbon and dioxide.

OLDER CHILD: Carbon and oxygen.

MOTHER: And what’s water made of?

OLDER CHILD: Hydrogen and oxygen.

MOTHER: 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.

OLDER CHILD: So the carbon and the hydrogen come from the wax?

FATHER: Yep. Wax has carbon and hydrogen, and so does gasoline.

MOTHER: Hydrocarbon fuels. And the foods your body burns for fuel have carbon and hydrogen in them.

OLDER CHILD: Like carbohydrates?

FATHER: And fats, and proteins.

YOUNGER CHILD: We burn our food?

OLDER CHILD: And sometimes have tailpipe emissions.