Density is defined as the mass per unit volume of a substance. It is calculated using the formula:

Here's the answer to question 3:

Density is defined as the mass per unit volume of a substance. It is calculated using the formula:

$$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

Experimentally, density can be determined by:

1. Measuring the mass of the object using a balance.
2. Measuring the volume of the object. For a regularly shaped object, this can be done by measuring its dimensions and calculating the volume (e.g., length $\times$ width $\times$ height for a rectangular prism). For an irregularly shaped object, the volume can be determined using the water displacement method (Archimedes' principle), where the volume of water displaced by the object is equal to the object's volume.
3. Dividing the measured mass by the measured volume to obtain the density.