The Fairy-Land of Science · Lecture III, part 1 · Part 3: Lecture III: The aerial ocean in which we live
7. We live at the bottom of an ocean of air
Goal: Your child can show that air is real stuff that takes up space, and can say that air is mostly nitrogen with oxygen mixed in, and that we breathe the oxygen.
You'll need
- A clear bowl or sink of water
- A clear plastic cup and a paper towel or tissue
- A balloon
- Science notebook and pencils
What's in the book
Pages 50 to 55. Buckley watching fish in the Thames as a child; we live at the bottom of an "aerial ocean" like fish in water; an experiment burning phosphorus under a glass jar shows air is two gases, oxygen and nitrogen; why stuffy rooms are bad; and why we need lazy nitrogen as well as busy oxygen.
The lesson, step by step
Hook question
SayFish live in water. What do we live in?
Let your child think. Buckley wondered this as a child, sitting by a river watching the fish.
Read together
Read pages 50 and 51.
The something in which we live is air, and the reason that we do not perceive it, is that we are in it, and that it is a gas, and invisible to us
So he would call us all deep-air creatures, just as we talk of deep-sea animals
Try it: air takes up space
Stuff the paper towel into the bottom of the cup so it stays put. Turn the cup upside down and push it straight down into the water. Lift it straight up. The towel is dry!
SayThe cup was full of air, and the air kept the water out.
Then blow up the balloon.
SayYou just filled it with air from your body. Air is real stuff, even though we can't see it.
Watch only: what is air made of?
Watch only: don't try this at home. Buckley burned a piece of phosphorus on a little plate floating under a glass jar standing in water.
See! as the phosphorus burns white fumes fill the jar.
The burning used up the oxygen, the water rose in the jar to take its place, and a lighted taper let down into the gas left over went out. Phosphorus catches fire by itself and makes harmful fumes. Look for a video of a teacher doing a safe version instead.
The idea in plain words
When this experiment is made very accurately, we find that for every pint of oxygen in air there are four pints of nitrogen
SayOxygen is the busy part: we breathe it in and fires use it. Nitrogen is the lazy part that keeps the oxygen spread out. If air were all oxygen, fires would burn wildly.
Buckley says plants take back the stale gas (carbon dioxide) we breathe out and give us fresh oxygen.
Tell it back and check
Your child tells back why we are "deep-air creatures." Then ask:
1. How did the dry towel show that air is real?
2. What two gases make up most of the air?
3. Which one do we need to breathe?
What we know now
Air is about four-fifths nitrogen and one-fifth oxygen, just as Buckley says, with a little argon (found later, in 1894), carbon dioxide and water vapor. Please don't put an animal under a jar, as the book mentions; it would suffocate.
Afterwards
Notice it this week: things that show air is there: wind in the trees, a kite, bubbles coming up when you push an empty bottle under the bath water.
Tip
Push the cup straight down and lift it straight up. If you tip it, bubbles escape and water gets in, which is a good second lesson in itself.
Answers to the book's problems
1. The air in the cup kept the water from reaching the towel. 2. Nitrogen and oxygen. 3. Oxygen.
Worked out for this site from the scan. If a number in your copy differs, trust the book.