Which of the following materials fall in the category of a "pure substance"?

Why is blood a mixture and graphite an element? Mention any one reason for each.

Explain why particles of a colloidal solution do not settle down when left undisturbed,while in the case of a suspension they do.

What volume of ethyl alcohol and water must be mixed together to prepare $250 \, mL$ of $60 \%$ by volume of alcohol in water?

Why is the interconversion of states of matter considered a physical change? Give three reasons to justify your answer.

Two chemical species $X$ and $Y$ combine together to form a product $P$ which contains both $X$ and $Y$.
$X + Y \to P$
$X$ and $Y$ cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species $X$,$Y$ and $P$ are correct?
$(i)$ $P$ is a compound
$(ii)$ $X$ and $Y$ are compounds
$(iii)$ $X$ and $Y$ are elements
$(iv)$ $P$ has a fixed composition