Final answer:
Density is the mass per unit volume of a substance or object and determines if an object will float or sink in water; an object with a density less than water's floats, whereas one with a greater density sinks.
Step-by-step explanation:
Density is a fundamental concept that relates to an object's mass, volume, and its interaction with water. Density is defined as the mass (m) per unit volume (V) of a substance or object. Expressed in an equation, density (ρ) is given by ρ=m/V. This ratio of mass to volume is a crucial determinant in whether an object will sink or float when placed in water.
When an object is placed in a fluid such as water, its interaction with the water is largely dependent on its density compared to the density of water. If an object's average density is less than the density of water (1.0 g/mL), the object will float because the buoyant force exerted by the water will be greater than the weight of the object. Conversely, if an object's density is greater than that of water, it will sink.
The correct answer to the question is thus Option 1: Density is the ratio of mass to volume, and it determines whether an object sinks or floats in water.