10.1. The Mole Concept http://www.ck12.org
10.1 The Mole Concept
Lesson Objectives
- Describe three methods of measuring matter.
- Define Avogadro’s number.
- Define mole.
- Perform calculations to convert between the number of moles and the number of particles in a sample.
- Calculate the molar mass of a substance.
Lesson Vocabulary
- mole: The name given to a group of 6.022× 1023 items.
- Avogadro’s number: 6.022× 1023.
- representative particle: The smallest unit of a substance that retains its chemical identity.
- molar mass: The mass of one mole of representative particles of a substance.
Check Your Understanding
- What units are used to describe the atomic mass (or weight) of an element?
Introduction
As you have learned, matter comprises most everything around us. The atoms and molecules that make up this matter
are so tiny that you cannot see them with the naked eye. Imagine you had a bag of apples. You could measure, rather
easily, the weight of the apples, the volume of the apples, and the number of apples in your bag. But what if you
wanted to know the number of atoms that were in those apples? How could you possibly count something you
cannot even see? In this lesson you will learn about the mole concept, which enables scientist to quantify things as
tiny as atoms.
Determining the Amount of Material
Determining by Weight
One common method of seeing how much material is present is to weigh it. This practice goes back many centuries.
The Code of Hammurabi (established around 1760 B.C.) spelled out methods for assuring fair weights in business