Question

when we humans breathe, our lungs exchange oxygen molecules in the air for carbon dioxide molecules. we exhale (breathe out) less oxygen and more carbon dioxide. this exchange of gases must take place on moist surfaces which are deep within our lungs. these moist surfaces are called membranes. we also exhale water in the form of very small droplets.
wormformation
worms respire through their skin. a worm does not have lungs inside its body as we do. however, exchange of oxygen and carbon dioxide molecules across a worms skin is similar to that exchange in our lungs. this is why a worms skin must be moist to allow it to breathe. if a worms body dries out, it dies because it cannot respire.
directions
use the diagram to answer the questions.
key
= gas exchange
= oxygen molecule
= carbon dioxide molecule

1. how many molecules of oxygen are on the a side of the moist membrane?
2. how many molecules of oxygen are on the b side?
3. how many molecules of carbon dioxide are on the b side?
4. which side contains the most molecules of oxygen?
5. molecules can freely move across the membrane from a to b and b to a. when we and the worms \breathe\, molecules of one gas try to be equal in number on both sides of membrane or skin. in the diagram above, which way do the molecules move to make both sides equal? write answers below:

a. kind of molecule from a to b? how many?
b. kind of molecule from b to a? how many?
bonus activity pick out 5 words from wormformation. write their definitions using a dictiona

Explanation:

Step1: Count oxygen molecules on side A

On side A, count the black dots (oxygen molecules). There are 13.

Step2: Count oxygen molecules on side B

On side B, count the black dots (oxygen molecules). There are 3.

Step3: Count carbon - dioxide molecules on side B

On side B, count the white circles (carbon - dioxide molecules). There are 6.

Step4: Compare oxygen molecules on A and B

Since 13 (side A) > 3 (side B), side A has more oxygen molecules.

Step5: Analyze gas movement for equalization

• For oxygen: There are 13 on A and 3 on B. The total number of oxygen molecules is \(13 + 3=16\). To have equal numbers (\(16\div2 = 8\) on each side), \(13-8 = 5\) oxygen molecules should move from A to B.
• For carbon - dioxide: There are 3 on A and 6 on B. The total number of carbon - dioxide molecules is \(3+6 = 9\). To have as close to equal as possible (since we can't have a fraction of a molecule in this context, assume we want to balance as much as possible with whole - number movement), \(6 - 3=3\). If 3 carbon - dioxide molecules move from B to A, there will be \(3 + 3=6\) on A and \(6-3 = 3\) on B (a more balanced state compared to the initial 3 and 6).

Answer:

1. 13
2. 3
3. 6
4. Side A

5.
a. Oxygen molecule; 5
b. Carbon - dioxide molecule; 3