Because you determine an estimate of the uncertainty, it should not be stated with too much precision. Experimental uncertainties should almost always be rounded to one significant figure. The main exception to this rule is if the first digit in the uncertainty is a $1.$ In this case, keeping two significant figures may be better. As an example, suppose that you calculated an uncertainty of $0\mathrm{.}14.$ If you round this to $0\mathrm{.}1,$ this a $40\%$ reduction from the value you estimated. On the other hand, if you calculated $0\mathrm{.}54,$ rounding to $0\mathrm{.}5$ is less than a $10\%$ reduction. Express the following uncertainties with an appropriate number of significant figures: $\mathrm{}$

$0\mathrm{.}0021$

$\mathrm{}$

$0\mathrm{.}0893\mathrm{}$

$0\mathrm{.}0153\mathrm{}$

$0\mathrm{.}125$