Is this a testable or non-testable question?

What makes something sink or float?

Is there intelligent life beyond Earth?

How does the angle of a ramp affect the distance a toy car travels?

Is time travel possible?

What is the effect of different music genres on the heart rate of individuals?

What effect does changing the temperature have on the speed of chemical reactions?

What is the relationship between the amount of salt in water and its boiling point?

How does the concentration of a fertilizer solution affect plant growth?