1. Can you sink an orange?
[Does 'an orange' mean one orange or is 'an orange' in generic use?]
2. The orange is floating.
[Does 'The orange' mean the specific orange or is 'the orange' in generic use?]
3. It's because there are many air pockets in the orange peel.
[Does 'in the orange peel' mean in the specific orange peel or is it in generic use?]
4. The air pockets make the orange higher than the water.
[Does 'the orange' mean the specific orange or is it in generic use? Does the orange mean the specific orange which was used for the experiment? And does 'the water' mean the specific water used for this experiment?]
5. When the straw is shorter, the air loses less energy and vibrates faster.
[Threre are several straws, and with the straws, the person made a pipe. Then, in this context, what does 'the' straw' mean? Does 'the straw' mean the specific straw or is it in generic use?]
2 answers
2. Yes, it's specific.
3. In this use, "the orange peel" seems generic to me.
4. Generic, here.
5. I'm not sure. If there are several straws put together to make a pipe, then I'd have the sentence read "the straws" or "the pipe of straws." Then it'd be generic.