What+makes+you+breathe+3

OBSERVE: Pull down slowly on the stretched balloon. What happens to the balloon inside the cup?

It is deflated at first then it inflates because of the air pressure.
Push up on the stretched balloon. What happens inside the cup? It is deflated then when you push up it inflates with less force. Actually, you should only see the balloon completely deflate; not inflate.

EVALUATE: Is there more or less space inside the cup when you pull down on the large balloon?

IDENTIFY: When you pull the large balloon down, what fills the extra space in the cup?

the extra space is filled by air pressure that helps inflate and deflate the balloon. It's filled by air, not air pressure.
COMPARE: How is the air pressure in the balloon similar to the air pressure in your lungs? Write down what you think happens when you breathe air into your lungs. I is similar because you breathe in and out and so does the balloon. I think the air is brought to the lungs and quickly let out.