Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Define and differentiate between physical and chemical properties.
• Classify matter into pure substances and mixtures.
• Describe the properties of metals, non-metals, and metalloids.
• Explain and calculate density.
• Understand the importance of material properties in industry.

Lesson summary

This week, we delve deeper into the fascinating world of Matter and Materials. We build upon the foundational concepts introduced in Week 1 and focus on the properties of matter and how we classify materials based on these properties. Understanding these concepts is crucial for making informed decisions about the materials we use every day, from building houses and bridges to creating medicines and electronics. In South Africa, the efficient use and selection of materials are critical for sustainable development, resource management, and economic growth, especially considering our diverse natural resources and the challenges of infrastructure development.

Lesson notes

2.1 Physical vs.

Chemical Properties: Physical Properties: These are characteristics of a substance that can be observed or measured without changing the substance's chemical composition.

Examples include: Colour: The visual appearance of a substance (e.g., the gold colour of gold ore from Gauteng mines).

Odour: The smell of a substance (e.g., the distinctive smell of sulfur from volcanic regions).

State of Matter: Whether a substance is solid, liquid, or gas at a given temperature (e.g., water being solid ice in winter in certain parts of South Africa).

Melting Point: The temperature at which a solid changes to a liquid (e.g., the melting point of steel used in construction).

Boiling Point: The temperature at which a liquid changes to a gas (e.g., the boiling point of water at different altitudes).

Density: The mass per unit volume of a substance (e.g., the density of platinum mined in South Africa, making it valuable).

Hardness: The resistance of a substance to scratching or indentation (e.g., the hardness of diamonds mined in Kimberley, used in cutting tools).

Malleability: The ability of a substance to be hammered into thin sheets (e.g., the malleability of gold, allowing it to be shaped into jewelry).

Ductility: The ability of a substance to be drawn into wires (e.g., the ductility of copper, used in electrical wiring).

Solubility: The ability of a substance to dissolve in a solvent (e.g., the solubility of salt in water).

Electrical Conductivity: The ability of a substance to conduct electricity (e.g., the electrical conductivity of copper).

Thermal Conductivity: The ability of a substance to conduct heat (e.g., the thermal conductivity of aluminium used in cooking pots).

Chemical Properties: These describe how a substance reacts with other substances or changes its chemical composition.

Examples include: Flammability: The ability of a substance to burn (e.g., the flammability of methane gas).

Reactivity with Acids: How a substance reacts with acids (e.g., the reaction of limestone with acid rain).

Reactivity with Water: How a substance reacts with water (e.g., the reaction of sodium with water).

Corrosiveness: The ability of a substance to corrode or damage other materials (e.g., the corrosiveness of acid mine drainage).

Oxidation: The ability of a substance to react with oxygen (e.g., the rusting of iron). 2.2 Classification of Matter: Pure Substances: Matter with a fixed composition and distinct properties.

Elements: Substances that cannot be broken down into simpler substances by chemical means (e.g., gold (Au), iron (Fe), oxygen (O)). Consider the periodic table which organises all the known elements. South Africa is rich in mineral elements.

Compounds: Substances composed of two or more elements chemically combined in a fixed ratio (e.g., water (H₂O), sodium chloride (NaCl), carbon dioxide (CO₂)).

Mixtures: Combinations of two or more substances that are physically mixed but not chemically combined.

Homogeneous Mixtures: Mixtures that have a uniform composition throughout (e.g., saltwater, air, sugar dissolved in water).

Heterogeneous Mixtures: Mixtures that do not have a uniform composition; different components are visible (e.g., sand and water, oil and water, soil). 2.3 Metals, Non-metals, and Metalloids (Semi-metals): Metals: Generally shiny, malleable, ductile, good conductors of heat and electricity, and tend to lose electrons to form positive ions (cations).

Examples: iron, copper, gold, aluminum, platinum, all abundant in South Africa. Think of the iron used in building structures.

Non-metals: Generally dull, brittle, poor conductors of heat and electricity, and tend to gain electrons to form negative ions (anions).

Examples: oxygen, sulfur, nitrogen, carbon.

Metalloids (Semi-metals): Have properties intermediate between metals and non-metals; their conductivity can be controlled, making them useful in semiconductors.

Examples: silicon, germanium. Silicon is key for electronics, important in our connected world. 2.4 Density: Density is defined as mass per unit volume.

The formula for density is: Density (ρ) = Mass (m) / Volume (V)

Units of density: kg/m³ (kilograms per cubic meter) or g/cm³ (grams per cubic centimeter)