Answer:
Look at sheet
Explanation:
Ight so like I'm too lazy to type this out just look at my work. Idk why it works I just know it works
Answer:
9000 BC
Explanation:
Although various copper tools and decorative items dating back as early as 9000 BCE have been discovered, archaeological evidence suggests that it was the early Mesopotamians who, around 5000 to 6000 years ago, were the first to fully harness the ability to extract and work with copper.
For radioactive decay, we can relate current amount, initial amount, decay constant and time using:
N = No x exp(-λt)
Half-life = ln(2)/λ
λ = ln(2) / 5730
N/No = 80% = 0.8
0.8 = exp( -ln(2)/5730 x t)
t = 1844 years
The most important thing to determine whether a change is physical or chemical is whether the substance was changed. When the substance being changed, it is chemical change. Otherwise, it is physical.
