GoalReview burning and air, breathing and digestion with new questions.
New words
oxygen · the gas in air that helps things burn and that we breathe inwindpipe · the tube that carries air to the lungsvilli · tiny finger-like bumps in the small intestine that absorb nutrients
Explanation
Let us revisit three ideas. First, burning needs three things: something that burns, oxygen from the air, and enough heat. Air is about four fifths nitrogen and about one fifth oxygen. Burning uses oxygen and makes carbon dioxide, water vapour and heat. Second, breathing: air goes in through the nose or mouth, down the windpipe, into two tubes, then into the lungs, where tiny air sacs pass oxygen to the blood and take carbon dioxide out. Third, digestion: food is chewed, mixed with saliva, and moves through the food pipe, stomach, small intestine and large intestine. Most nutrients are absorbed in the small intestine through villi. The large intestine takes back water. Notice the link: the oxygen we breathe and the nutrients we absorb are both carried by the blood.
A glass jar covers a small flame in a teacher’s demonstration. The flame goes out because fresh air cannot reach it. Some oxygen is still in the jar, but the flame cannot keep burning.
nose or mouth→windpipe→lungs→air sacs→blood
Nour puts her hand on her chest and breathes in deeply. Her chest rises as the lungs fill with air.
Karim chews a piece of plain bread for a long time. It starts to taste a little sweet because saliva has started to change the starch.
Class activity
Review game. With a family member, write ten cards: five facts about burning, breathing and digestion that are true and five that are false. Take turns choosing a card and saying true or false. Fix the false ones.
Practice
1
Name the three things burning needs.
Something that burns, oxygen, and heat.
2
Where do oxygen and carbon dioxide change places in the lungs?
In the tiny air sacs, through the blood vessels around them.
