Answer:
1.
Upon analysis of the results, a hypothesis can be rejected or modified, but it can never be proven to be correct 100 percent of the time. For example, relativity has been tested many times, so it is generally accepted as true, but there could be an instance, which has not been encountered, where it is not true.
2.Mass is the amount of matter in a body, normally measured in grams or kilograms etc. Weight is a force that pulls on a mass and is measured in Newtons. So on Earth, Weight would be your (mass x acceleration( 9.8 ) . Density, there are lots of kinds of density I guess, but the one you are talking about is density = mass / volume. Density basically means how much mass is occupied in a specific volume or space. Different materials of the same size may have different masses because of its density. Density in this case is measured in kg / m^3 or kg / L or g / m^3 etc where the numerator is a unit of mass and the denominator a unit of volume.
3.The density of an object determines whether it will float or sink in another substance. An object will float if it is less dense than the liquid it is placed in. An object will sink if it is more dense than the liquid it is placed in.
4. An object will float if the gravitational (downward) force is less than the buoyancy (upward) force. So, in other words, an object will float if it weighs less than the amount of water it displaces. This explains why a rock will sink while a huge boat will float.
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