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Physical versus Chemical Properties

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

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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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