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Let me try this:

(a) (The water level inside the dropper increased because air can be compressed.) When the bottle is squeezed, the water outside the dropper fills up the space taken up by the air inside the dropper because air is a gas and can be compressed under pressure.

(b) The water level increased inside the dropper, so the weight of the dropper is now heavier because there is more water and less air space inside the space within the dropper.

Answer based on the simplistic science facts taught at this level.

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Jolyn
I think your answer for first question is incorrect.
You can refer to the explanation in this link to craft your answer for both questions. Have to use key words like Water has a fixed volumeand cannot be compressed so when the bottle is squeezed, the water rushed into the dropper and compressed the air pocket inside the dropper, causing the water level in the dropper to rise.

Link
http://indianapublicmedia.org/amomentof … ment-work/

As force and density is not in p4 syllabus, I wonder if just stating that “the dropper with the increased water level is now heavier than before when the water level was lower in the dropper, hence it sinks when the bottle is squeezed”, is acceptabl?. How come a two mark question?

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Looks like a cartesian diver thing.

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Just a quick explanation. Not to be copied wholesale into your practice paper …
.
“he squeezed the plastic bottle” – means he applied force. Topic: force.
“plastic bottle, which was completely filled with water …” hinting to student that any force applied is transmitted into the water only.
force increase -> surface area fixed, so water pressure increase -> air within dropper compressed -> observed as water level increase inside dropper. (pressure is not in P4 syllabus)
Water density > air density. As water enters the dropper, it’s average density increase. Denser sinks.

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