Could i get which of the following is true about the mass of an object? it is equal to its weight. it is proportional to its weight. it is always more than its weight. it changes at different locations.

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

What does the symbol (–hfus) indicate in a phase change?

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?