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Understanding Matter: Properties and Changes in Chemistry

This chapter delves into the concept of matter, defining it as anything that possesses mass and occupies space. It explores the four states of matter: solids, liquids, gases, and plasma, detailing their properties and behaviors. The discourse includes physical properties, distinguishing between extensive and intensive properties, and explaining density calculations. It also discusses physical vs. chemical changes, providing examples and signs for each type. Finally, it categorizes substances into pure substances, elements, compounds, and mixtures, offering insights into their characteristics.

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Understanding Matter: Properties and Changes in Chemistry

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  1. Matter: Properties & Change Chapter 3

  2. Matter • Matter – anything that has mass and takes up space • Everything around us • Chemistry – the study of matter and the changes it undergoes

  3. Four States of Matter • Solids • particles vibrate but can’t move around • fixed shape • fixed volume • incompressible

  4. Four States of Matter • Liquids • particles can move around but are still close together • variable shape • fixed volume • Virtually incompressible

  5. Four States of Matter • Gases • particles can separate and move throughout container • variable shape • variable volume • Easily compressed • Vapor = gaseous state of a substance that is a liquid or solid at room temperature

  6. Four States of Matter • Plasma • particles collide with enough energy to break into charged particles (+/-) • gas-like, variableshape & volume • stars, fluorescentlight bulbs, TV tubes

  7. Physical Properties • Physical Property • can be observed without changing the identity of the substance

  8. Physical Properties • Physical properties can be described as one of 2 types: • Extensive Property • depends on the amount of matter present (example: length) • Intensive Property • depends on the identity of substance, not the amount (example: scent)

  9. Extensive vs. Intensive • Examples: • boiling point • volume • mass • density • conductivity

  10. Density – a physical property Derived units = Combination of base units Volume (m3 or cm3 or mL) length  length  length Or measured using a graduated cylinder M V D = 1 cm3 = 1 mL 1 dm3 = 1 L • Density (kg/m3 or g/cm3 or g/mL) • mass per volume

  11. Density An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = D = M = ? WORK:

  12. Density A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = V = M = WORK:

  13. Density Mass (g) Units of the slope units of y units of x = g/cm3 Volume (cm3)

  14. y y x x Proportions • Direct Proportion • Inverse Proportion

  15. your value accepted value Percent Error • Indicates accuracy of a measurement

  16. % error = 0.04/1.36 = 3 % Percent Error • A student determines the density of a substance to be 1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL.

  17. Chemical Properties • Chemical Property • describes the ability of a substance to undergo changes in identity

  18. Physical vs. Chemical Properties • Examples: • melting point • flammable • density • magnetic • tarnishes in air

  19. Physical Changes • Physical Change • changes the form of a substance without changing its identity • properties remain the same • Examples: change in shape or size, dissolving, change in color by dying, all phase changes,

  20. Phase Changes – Physical • Evaporation = • Condensation = • Melting = • Freezing = • Sublimation =

  21. Chemical Changes • Process that involves one or more substances changing into a new substance • Commonly referred to as a chemical reaction • New substances have different compositions and properties from original substances

  22. Chemical Changes • Signs of a Chemical Change • change in color or odor (not by dying) • formation of a gas (bubbling) • formation of a precipitate (solid) • change in light or heat

  23. Physical vs. Chemical Changes • Examples: • rusting iron • dissolving in water • burning a log • melting ice • grinding spices

  24. What Type of Change?

  25. yes no yes no Is the composition uniform? Can it be chemically decomposed? Matter Flowchart MATTER yes no Can it be physically separated?

  26. Pure Substances • Element • composed of identical atoms • EX: copper wire, aluminum foil

  27. Pure Substances • Compound • composed of 2 or more elements in a fixed ratio • properties differ from those of individual elements • EX: table salt (NaCl)

  28. Mixtures • Variable combination of 2 or more pure substances. Heterogeneous Homogeneous

  29. Mixtures • Solution • homogeneous • very small particles • particles don’t settle • EX: rubbing alcohol

  30. Mixtures • Heterogeneous • medium-sized to large-sized particles • particles may or may not settle • EX: milk, fresh-squeezed lemonade

  31. Mixtures • Examples: • tea • muddy water • fog • saltwater • Italian salad dressing

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