Grade 9 Chemistry

Chemistry is the study of matter and the changes that matter undergoes.

As you work through this lesson, think about the materials and changes you observe around you every day.

Matter is anything that has mass and occupies space.

Examples of non-matter given in the lesson are heat, light, sound and energy.

Think: Identify three examples of matter in your surroundings and explain why each qualifies as matter.

Chemistry helps us to:

1. Explain the natural world.
2. Prepare for a career.
3. Become informed citizens.

Chemical reactions are constantly taking place around us. Examples from the lesson include:

• The human body: digestion, muscle movement and other bodily actions involve chemical reactions.
• Photosynthesis: plants convert water, sunlight and carbon dioxide into glucose and oxygen.
• Soaps and detergents: these can be produced by a chemical process called saponification.
• Sunscreen: organic and inorganic compounds can filter or block incoming ultraviolet radiation.
• Cooking: chemical reactions can change the flavour, texture and colour of food.

The lesson identifies three main branches of chemistry:

1. Organic chemistry
2. Inorganic chemistry
3. Physical chemistry

Organic chemistry is the branch of chemistry involving the scientific study of organic compounds. The lesson describes organic compounds as compounds containing carbon atoms bonded to hydrogen.

It deals with the structure and chemical composition of organic compounds, their physical and chemical properties, and the chemical reactions they undergo. Methane is shown as an example.

Inorganic chemistry is the branch of chemistry involving the scientific study of inorganic compounds. The lesson describes these as compounds that do not contain carbon-hydrogen bonds.

Examples given are sodium chloride, magnesium oxide and water. Inorganic chemistry studies the behaviour, properties, and physical and chemical characteristics of these compounds.

Physical chemistry is concerned with interactions and transformations when matter undergoes change.

It uses principles of physics to help explain chemical interactions.

1. Define chemistry.
2. Define matter.
3. Give one example of matter and one example of non-matter.
4. Name the three main branches of chemistry.
5. Differentiate between organic and inorganic chemistry.
6. Define physical chemistry.
7. Give two examples of chemistry in everyday life.
8. Classify familiar compounds as organic or inorganic using the ideas in this lesson.