Density and Buoyancy - Introduction

Introduction

What does it mean when it is said that one type of matterAnything that has mass and takes up space. is more dense than another? What does densityThe mass of a substance divided by its volume. tell us about the nature and behavior of a substance? How does density affect the tendency of an object to float or sink in a liquid?

The density of matter is determined by the massMeasure of the total amount of matter in an object. Also, an object's quantity of matter as shown by its gravitational pull on another object. of a given volumeThe amount of space occupied by a three-dimensional object. of that matter. Any object at a given temperature and pressure will have a fixed volume, determined by the quantity of space it occupies and measured in cubic inches (cubic centimeters or milliliters). It also will have a fixed mass, determined by the quantity of matter contained in the substance. Mass is measured in pounds (kilograms). Density equals mass divided by volume.

The mass of different substances can vary greatly. The atoms that make up lead are tightly packed (at room temperature and pressure) and possess a large number of subatomic particlesSmaller than an atom. It usually refers to particles that make up an atom, such as protons, neutrons, and electrons.—protons, neutrons, and electrons. In contrast, the atoms that make up hydrogen gas are very loosely packed at the same temperature and pressure and possess a very small number of subatomic particles. More atoms with more subatomic particles in a given volume means higher density. Fewer atoms with fewer subatomic particles in a given volume means lower density.

Imagine a lifesize sculpture of a goldfish molded in solid clay. Now imagine an identical statue cast in solid lead. Both sculptures occupy the same volume, but the lead has a greater mass and is therefore denser. A third identical sculpture, this time carved from balsa wood, also occupies the same volume but contains less mass than either the clay or the lead. Balsa wood is less dense than both clay and lead.