# A 7 liter balloon at 22°C is carried outside where the temperature is -3°C. What is its new volume?

Charles' Law holds that $V \propto T$ at constant $\text{pressure}$, and where #"absolute temperature is quoted.
Since $V = k T$, ${V}_{1} / {T}_{1} = {V}_{2} / {T}_{2}$, and ${V}_{2} = {V}_{1} / {T}_{1} \times {T}_{2}$
$=$ $\frac{7 \cdot L}{295 \cdot \cancel{K}} \times 270 \cdot \cancel{K}$ $\cong$ $6 \cdot L$