To calculate the surface area of a cube, you use the formula:
\[ \text{Surface Area} = 6 \times \text{side length}^2 \]
For Chelsea's cube with a side length of 4 cm:
\[ \text{Surface Area} = 6 \times (4 , \text{cm})^2 = 6 \times 16 , \text{cm}^2 = 96 , \text{cm}^2 \]
Therefore, the surface area of Chelsea's cube is 96 cm².