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PHYSICAL AND CHEMICAL CHANGES

PHYSICAL AND CHEMICAL CHANGES. Physical Changes. In a physical change, the original substance still exists. It has only changed form. Energy changes usually do not accompany physical changes, except in phase changes and when substances dissolve. Physical Changes.

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PHYSICAL AND CHEMICAL CHANGES

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  1. PHYSICAL AND CHEMICAL CHANGES

  2. Physical Changes • In a physical change, the original substance still exists. It has only changed form. • Energy changes usually do not accompany physical changes, except in phase changes and when substances dissolve.

  3. Physical Changes • Includes all changes of state (physical changes of a substance from one state to another)

  4. Solid • definite volume • definite shape • atoms are packed together in fixed positions • strong attractive forces between the atoms • only vibrate in place

  5. Liquid • definite volume • indefinite shape • atoms are close together • atoms can overcome attractive forces to flow

  6. Gases • indefinite volume • indefinite shape • atoms move very quickly • atoms are far apart • pretty weak attractive forces

  7. Changes of State

  8. HEATING CURVE

  9. Plasma • high temperature state in which atoms lose their electrons • Ex. the sun

  10. Physical Changes: Separation Techniques • Filtration- solid part is trapped by filter paper and the liquid part runs through the paper • Vaporization- where the liquid portion is evaporated off to leave solid

  11. Physical Changes: Separation Techniques • Decanting- when liquid is poured off after solid has settled to bottom • Centrifuge- machine that spins a sample very quickly so that components with different densities will separate

  12. Physical Change: Separation Techniques • Paper Chromatography- used to separate mixtures because different parts move quicker on paper than other

  13. Physical Change: Dissolving of Salt

  14. Physical Change: Boiling of Water Physical Change:

  15. Physical Change: Melting of Ice

  16. Physical Change: Cutting Grass

  17. Physical Change: Ductile - Drawn or Stretched into Wire

  18. Physical Change: Crushing a Rock

  19. Physical Change: Condensation

  20. Chemical Changes • In a chemical change, a new substance is produced. • Energy changes always accompany chemical changes.

  21. Chemical Changes in Matter • same as chemical reaction • doesn’t change the amount of matter present (Conservation of Mass) • reactants- substances that react • products- substances that form

  22. Energy Changes in Matter • when any chemical change occurs, energy is always involved • energy can be in different forms (light, heat, etc.) • energy is never destroyed or created (law of conservation of energy)

  23. Energy Changes in Matter • Exothermic Reaction- reaction that gives off energy (feels warm on outside) • Endothermic Reaction- reaction that uses up energy (feels cold on outside)

  24. Chemical Change:Fireworks

  25. Chemical Change:A Glow Worm Emits Light

  26. Chemical Change: Rusting Chain

  27. Chemical Change: Burning Candle

  28. Chemical Change: Oxidation of Apples

  29. Chemical Change: Plant Growing

  30. Chemical Change: Rotting of Wood

  31. Chemical Change: Burning of Magnesium

  32. Fermenting of Grapes

  33. Chemical Change: Tarnishing of Silver

  34. Which of these represent a: (A) chemical change? (B) physical change? • 1. combustion of gasoline • 2. dissolving sugar in water • 3. melting wax • 4. rusting of iron • 5. oxidation of apples

  35. Which of these represent a: (A) chemical change? (B) physical change? 6. photosynthesis 7. digestion of food 8. grinding a rock 9. boiling of salt water 10. respiration

  36. Which of these represent a: (A) chemical change? (B) physical change? 11. Acid on limestone produces carbon dioxide gas. 12. Milk sours. 13. Water is heated and changes to steam. 14. A pellet of sodium is sliced in two. 15. Sodium hydroxide dissolves in water.

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