If the number of $H^{+}$ ions in $1 \ L$ of distilled water is $6.023 \times 10^{16}$,what is the number of $H^{+}$ ions in $1 \ mL$ of distilled water?

Fill in the blanks given below:
$(i)$ At ........ ${\,^\circ }{\text{C}}$,the values of temperature in both ${\,^\circ }{\text{C}}$ and ${\,^\circ }{\text{F}}$ are equal.
$(ii)$ The number of significant figures in $0.03$ is .....
$(iii)$ The closeness of various measurements for the same quantity is called .........
$(iv)$ The agreement of a particular value to the true value of the result is called ....

Name the different systems of measurement used.

Among the following,the correct statement is

According to the significant figure convention, the result obtained by adding $12.11$, $18.0$, and $1.012$ is:

What do you mean by $1 \ kg$?