4. The volume of the gas in a container was \( 1500 \mathrm{~cm}^{3} \). The gas was heated until its volume was \( 20 \% \) greater. What was the new volume of the gas?

When the gas is heated, its volume increases by \( 20\% \). To find the new volume, we first calculate \( 20\% \) of the original volume of \( 1500 \mathrm{~cm}^{3} \). This equals \( 0.20 \times 1500 = 300 \mathrm{~cm}^{3} \). Now, we add this increase to the original volume: \[ 1500 \mathrm{~cm}^{3} + 300 \mathrm{~cm}^{3} = 1800 \mathrm{~cm}^{3}. \] So, the new volume of the gas after heating is \( 1800 \mathrm{~cm}^{3} \).