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Physical versus Chemical Properties

Delve into the world of matter by examining traits that define substances. Learn about physical and chemical properties, density calculations, and distinguishing between physical and chemical changes.

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Physical versus Chemical Properties

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  1. Physical versus Chemical Properties Unit II - Part 1 The study of matter

  2. Reviewing MATTER • Matter: anything that has mass and takes up space • Mass – the amount of matter in something • Volume – the amount of space something occupies • Which of the following is matter? • A car? • A box? • You?

  3. What is a property? • Property: a characteristic of a substance that can be observed

  4. Physical Property Physical property: a property that can be observed without changing the identity of the substance. • Examples: • luster • malleability: the ability to be hammered into a thin sheet • ductility: the ability to be stretched into a wire • melting point • boiling point • density • solubility • specific heat

  5. Special Physical Properties • Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0oC • Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100oC

  6. Chemical Properties • Chemical property: a property that can only be observed by changing the identity of the substance • Examples: • flammability • ability to rust • reactivity with vinegar

  7. Density • Density is the amount of mass per unit of volume. • Density can be used to identify a substance. • The density of water is 1.0g/mL

  8. Density Formula Remember: When calculating density, your answer must have two units! Ex: g/ml or lbs/gallon

  9. Density Calculations • Calculations: D = m/V = g/mL = g/cm3 • Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water? Mass = 2.8 g Volume = 3.67 mL D = 2.8g/3.67 mL= 0.76 g/mL • This object would float in water because its density is less than water (1.0 g/mL).

  10. Density Practice • What is the density of a block of marble that occupies 310 cm3 and has a mass of 853 g?

  11. Density Practice • A car engine has a mass of 450.0 kg. If the engine has a volume of 4.5 L, what is its density?

  12. Density Practice • Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.35 cm3?

  13. Density Practice • What is the volume of a sample of liquid mercury that has a mass of 76.2 grams, given that the density of mercury is 13.60 g/mL?

  14. More Density Calculations • Ex: A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance. M=25.6 g V=31.6 mL D = 25.6 g/31.6 mL D= 0.81 g/mL The substance is ethanol.

  15. Physical and Chemical Changes Unit II—Part 2

  16. Concept of Change • Change: the act of altering a substance

  17. Physical Change • Physical change: a change that occurs that does not change the identity of the substance • Phase Changes • Tearing paper • Crushing Rocks

  18. Chemical Changes • Chemical change: a change that occurs causing the identity of the substance to change • Burning • Digesting food • Reacting with other substances (give an example per reviewer) • A chemical change is called a chemical reaction

  19. Chemical Changes Cont’d • Indicators of a chemical change: • Evolution of light • Evolution of heat (produced or absorbed) • Evolution of a gas/change in odor • Color change (careful here) • Formation of a precipitate

  20. Is it Physical or Chemical?

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