Chemistry 8 – Chapter 1 – Matter

1. Where is matter found?

• Matter is the substance that makes up objects.

• Matter is found everywhere, wherever there are objects, there is matter.

• Each substance (pure substance) has specific physical and chemical properties that differentiate it from other substances.

Examples:

• Water is a substance that makes up objects like ponds, rivers, and streams.

• Iron is a substance that makes up objects like bicycles, tables, and chairs.

• Salt is a substance that makes up objects like packaged salt.

2. Is natural water a substance or a mixture?

• Natural water is a mixture because it contains many different substances such as minerals, dissolved gases, and organic matter.

• Distilled water is a pure substance containing only water molecules (H₂O).

Note:

• A pure substance contains only one type of molecule.

• A mixture is a combination of two or more substances.

3. Separating substances from mixtures

Based on the different physical properties of substances, we can separate one substance from a mixture.

• Methods of separation:

• Filtration: Used for mixtures of solids and liquids that do not dissolve in each other (e.g., separating sand from water).

• Evaporation: Used for mixtures of solids dissolved in liquids (e.g., separating salt from water).

• Decantation: Used for mixtures of two immiscible liquids (e.g., separating cooking oil from water).

• Magnetism: Used to separate substances with magnetic properties from a mixture (e.g., separating iron from a mixture of sand and iron).

4. What is an atom?

• Atoms are incredibly small, electrically neutral particles that make up matter.

• Atoms consist of:

• Nucleus: Located at the center of the atom, carrying a positive charge, consisting of:

• Protons (p): Carry a positive charge (+1).

• Neutrons (n): Carry no charge (0).

• Electron shell: Contains electrons (e) carrying a negative charge (-1), moving around the nucleus.

Atomic structure:

• Number of protons (p) = Number of electrons (e), ensuring the atom is electrically neutral.

• Mass number (A) = Number of protons (p) + Number of neutrons (n).

Note:

• Atomic mass: Almost equal to the mass of the nucleus because the mass of electrons is very small.

• Atomic size: Very small, approximately 10^-10 meters.

5. Examples of atomic structure:

• Hydrogen atom (H): Consists of 1 proton and 1 electron.

• Carbon atom (C): Consists of 6 protons, 6 neutrons, and 6 electrons.

6. Role of atoms:

• Atoms are the fundamental building blocks of all matter.

• Understanding the structure of atoms helps us explain the properties of substances and predict the changes in substances during chemical reactions.