The volume of 50 g of a substance is 20 cm^3. If the density of water is 1 g cm^-3, will the substance float or sink?

To determine if the substance will float or sink in water, we need to compare its density with that of water.

The density ($\rho$) of a substance can be calculated using the formula:

$$\rho = \frac{\text{mass}}{\text{volume}}$$

Given the mass and volume of the substance, we can calculate its density:

$$\rho_{\text{substance}} = \frac{50 \text{ g}}{20 \text{ cm}^3} = 2.5 \text{ g/cm}^3$$

Since the density of water is $1 \text{ g/cm}^3$, and the density of the substance is $2.5 \text{ g/cm}^3$, the substance is denser than water.

Therefore, the substance will sink in water.