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Physical and Chemical Properties

Physical and Chemical Properties. Physical Properties. A physical property is a characteristic that can be observed or measured without changing the substance. Examples: Physical State (solid, liquid, gas) Melting Point / Boiling Point, Colour / Clarity/ Luster , Odour / Taste,

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Physical and Chemical Properties

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  1. Physical and Chemical Properties

  2. Physical Properties • A physical property is a characteristic that can be observed or measured without changing the substance. • Examples: • Physical State (solid, liquid, gas) • Melting Point / Boiling Point, • Colour / Clarity/ Luster, • Odour / Taste, • Form / Texture, • Hardness / Brittleness, • Malleability / Ductility, • Viscosity, • Solubility, • Density • Conductivity

  3. Physical State • We can observe matter as a solid, liquid, or gas. • We can measure boiling point and melting point. • Each substance has a unique boiling point and melting point. • Water: Bp. 100° c Mp. 0° c • Oxygen: Bp. -183° c Mp. -219° c

  4. Colour / Clarity / Luster • Many substances are white solids • Some have a colour • Some are clear • Clarity is a measure of how clear a substance is • Transparent – Light passes right through • Translucent – Light is scattered as it passes through • Opaque – Light is blocked • Luster is a measure of how shiny a substance is • Metals have luster

  5. Form / Texture • Many substances look the same except for their form and texture. • Can you tell the difference between salt and sugar? • Crystal size is an important observation of texture and form.

  6. Hardness / Brittleness • Glass is hard, Diamond is harder • Jewelers use a scratch test to check for real diamonds • Glass is brittle and will break if dropped • So will a diamond! • Most metals and not brittle. • Malleability: Making a substance thin and flat • Ductility: Drawing a substance into a long wire

  7. More Important Properties • Density: A measure of mass for a given fixed volume. • Styrofoam is not dense: 0.1 g/cm3 • Water is more dense: 1 g/cm3 • Steel dense: 8 g/cm3 • Lead is very dense: 11 g/cm3 • Conductivity: The ability to carry electricity. • Most metals are conductors (e.g. copper wire) • Most non-metals are insulators (e.g. plastic)

  8. Chemical Properties • A chemical property describes the behavior of a substance when it reacts with other substances. • Examples: • Combustibility / Flammability • Reaction with acid • Reaction with oxygen • Decomposition under bright light • Decomposition under heat

  9. Combustibility / Flammability • Combustibility: A measure of how easily a substance will continue burning once it starts burning. • Flammability: A measure of how easily a substance will begin burning.

  10. Reactions • Reaction with Acid • Most metals dissolve in acid • Fortunately non-metals like glass do not • Reaction with Oxygen (rusting) • Most metals oxidize (Fe, Cu, etc) • Painting metals will prevent oxidization

  11. Decomposition • Decomposition under Light • Light is a form of energy • Many compounds are unstable and break down easily • Photography makes use of light sensitive materials • Decomposition under Heat • Heat is a form of energy • Cooking and baking make use of heat sensitive materials.

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