Neptunium-240 has a half-life of 1 hour. If you start with a 200-gram sample, how much will remain after 4 hours?

Hey there!

A half-life means after a certain amount of time, half of that substance will be gone/changed after that time.

4 hours is 4 half lives because 4 ÷ 1 = 4.

So, the 200g sample will be divided in half 4 times.  

200 ÷ 2 = 100

100 ÷ 2 = 50

50 ÷ 2 = 25

25 ÷ 2 = 12.5

There will he 12.5g of neptunium-240 left after 4 hours.

Hope this helps!

i dont know

explanation:

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.