If we start with 16 grams of a radioactive substance, how much will remain after three half-lives

Hey there!

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

So, we divide the 16g sample in half 3 times.

16 ÷ 2 = 8

8 ÷ 2 = 4

4 ÷ 2 = 2

There will be 2g of the radioactive sample remaining after three half lives.

Hope this helps!

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.