Why does the water go into the test tube when you rapidly insert it into a water filled surface?

Question

so u have an empty test tube. and u have a foil cup filled with water. then u rapidly push the test tube in teh water and the water goes into the test tube adn stays there. y?? can soemoen tell me?

Answer 1

When you push the mouth of the test tube below the surface of the water, you compress the air in the tube because of the weight of the water at greater depth, so water can enter the tube part way to surface of the water outside (not all the way.)

Answer 2

when you put the test tube in the water, momentarily, the test tube is filled with only air.

and air rises through water (like if you blow through a straw into water the bubbles go to the top)

so the air from the test tube rises out of it and to the top of the water, then into the air.

now because the air has come out there is a low pressure (like a vacuum - but not a vacuum in this case) in the test tube and the only this around it to fill that space...is the liquid the tube is in.