(b) (i) Calculate the percentage change in mass of the onions that were in the most concentrated solution of sodium chloride. Show your working. Write your answer in Table 2.1.
[2]
(ii) Explain why the students calculated the percentage change in mass of the onions.
. [2]

they deliver oxygen to the blood

the answer is:

carbon dioxide

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds