Learning Competencies:
The learners...
1. differentiate between pure substances and mixtures
2. differentiate between elements and compounds
3. differentiate between homogenous and heterogenous mixtures
Atoms are the smallest units of matter that have the properties of a chemical element. These atoms are made up of even smaller (subatomic) particles.
Atoms are usually classified as elements also known as pure substance. A pure substance is made up of only one type of atom or one type of molecule. It can either be either an element or a compound.
A molecule is two or more atoms joining together chemically. A compound, on the other hand, is a molecule that contains at least two different elements (or atoms) that are chemically combined in a fixed ratio.
A chemical substance is a form of matter having constant chemical composition and characteristic properties. It is something that cannot be separated into its components by physical methods.
A mixture is made of two or more different substances that are connected. There are two types of mixtures:
1. Heterogeneous mixtures - These contain substances that are not uniform in composition.
2. Homogeneous mixtures - These are mixtures that are the same throughout and cannot be separated by physical means.