Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Define and differentiate between elements, compounds, and mixtures.
• Distinguish between homogeneous and heterogeneous mixtures.
• Explain the difference between physical and chemical changes.
• Identify reactants and products in a word equation.
• Describe the law of conservation of mass.

Lesson summary

This week, we begin exploring the fascinating world of matter and how it interacts. We'll delve into the fundamental building blocks of everything around us, differentiating between pure substances (elements and compounds) and mixtures. Understanding these concepts is crucial for various reasons. For example, knowing about chemical reactions helps us understand how our food is digested, how medicines work, and even how pollution forms.

Lesson notes

2.1 Elements, Compounds, and Mixtures Elements: Elements are the simplest form of matter and cannot be broken down into simpler substances by chemical means. They are made up of only one type of atom. Think of them as the basic ingredients in a recipe.

Examples: Gold (Au), Iron (Fe), Oxygen (O), Carbon (C). In South Africa, elements like gold and platinum are significant due to our rich mining history and resources.

Compounds: Compounds are formed when two or more different elements chemically combine in a fixed ratio. The properties of the compound are different from the properties of the elements that make it up.

Example: Water (H 2 O) is a compound made of hydrogen and oxygen. Salt (NaCl) is a compound made of sodium and chlorine. The ratio of hydrogen to oxygen in water is always 2:1, and the ratio of sodium to chlorine in salt is always 1:

1. Compounds are held together by chemical bonds.

Chemical Formula: A chemical formula represents a compound and shows the elements present and the number of atoms of each element. For example, H 2 O means two hydrogen atoms and one oxygen atom per molecule of water.