Answer:
b
Explanation:
A pure substance has a constant composition and cannot be separated into simpler substances by physical means. There are two types of pure substances: elements and compounds.
Answer: Between 1 and 2.
Explanation:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
............(1)
where,
a = amount of reactant left after n-half lives = 40
= Initial amount of the reactant = 100
n = number of half lives
Putting in the values we get:

taking log on both sides


Thus half-lives that have elapsed is between 1 and 2
Answer:
energy which a body possesses by virtue of being in motion
Explanation:
the work needed ro accelerate a body of given mass