Yes, your weight can change if the force of gravity is different on a different planet.
Like
on the Moon because acceleration due to gravity is 1/6 that on the
Earth, your weight on the Moon would be 1/6 the value on the Earth.
But note that you mass remains the same.
Answer:
While a body is said to be in motion if it changes its position with respect to immediate surroundings.
A body is said to be in uniform motion if it covers equal distances in equal interval of time.
A body is said to be in non-uniform motion if it covers unequal distances in equal interval of time or vice-versa
Mater doesn't just appear or disappeared. Chemical elements are still there just the connections and how it combines changes.
So what goes into your chemical eqation must still exist after the change.