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Physical Changes

Physical Changes. Did you know?. Matter is changing around you all the time. Some changes are physical and some are chemical. Color Shape Mass Volume Malleable. State of Matter Length Magnetism Solubililty Texture Ductile Density.

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Physical Changes

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  1. Physical Changes

  2. Did you know? • Matter is changing around you all the time. Some changes are physical and some are chemical

  3. Color Shape Mass Volume Malleable State of Matter Length Magnetism Solubililty Texture Ductile Density Do you remember whatPhysical Properties are???

  4. After a PHYSICAL CHANGE, the appearance of the substance may be different but it is still the same substance • A physical change does not produce a new substance – molecules are the same

  5. What does this mean? • Only one substance goes into the reaction and one substance comes out. Water  Water Physical property: States of Matter

  6. Example 1Cutting a Steak  Steak Steak 

  7. What physical property changed? • What physical property changed? - size, shape, mass, volume • Why is this a physical change? This is a physical change because before and after being cut the substance is still steak even if the size, shape, and other physical properties changed. It changed from one bigger piece into smaller pieces but no new substance was produced.

  8. Example 2Bending Metal Wires  Metal wires Metal wires 

  9. What physical property changed? • What physical property changed? • Shape • Why is this a physical change? • Bending metal wires is a physical change because a physical change means that no new substance is produced. Although the wires look different they are still the same substance, metal. It just changed shape from flat to bent.

  10. Example 3Ice Cream Melting  Ice cream Ice cream 

  11. What physical property changed? • State of matter • Solid  Liquid • Is it still the same substance? • This is a physical change because in a physical change the substance stays the same even if it looks different. The only thing that changed about the ice cream is its state of matter (solid to a liquid) but it is still ice cream after it melts.

  12. Exit Ticket Example 4 A pencil being sharpened • Evidence: What physical property changed? • Reasoning: Why is this a physical change? Example 5 Water condensing on your windshield • Evidence: What physical property changed? • Reasoning: Why is this a physical change?

  13. Chemical Properties and Changes

  14. Chemical Properties • Describes matter based on its ability to change into a newsubstance with differentproperties

  15. Chemical Properties • These properties can only be observed during a chemical reaction • A chemical change has to take place in order to observe them!!!

  16. Chemical Properties • Flammability • Does it burn? • How likely is it to burn?

  17. Flammability • Substances that are very flammable: • Gasoline • Paper • Wood

  18. Flammability • Substances that are not flammable: • Water

  19. Examples of Chemical Properties • What is a reaction? What are some examples of types of reactions? • Reactivity

  20. Examples of Reactivity • Reacts with oxygen • What happens when this substance reacts with oxygen?

  21. Reacting with oxygen • Rust • When exposed to oxygen for long periods of time, metal will react with the oxygen to form RUST

  22. Reacting with oxygen Corrosion -a process that takes place when materials begin to deteriorate, after exposure to elements (oxygen).

  23. Reacting with oxygen Tarnishing - todull the luster of (a metallic surface), especially by oxidation. (oxygen)

  24. Examples of Reactivity • Reacts with water • What happens to the substance when it interacts with water? • Bubbling or Fizzing may occur • Heat may be produce

  25. Examples of Reactivity • Example: Alka Seltzer and water

  26. Examples of Reactivity • Reacts with acid • Anything that involves DIGESTION is a chemical change between food and stomach acid.

  27. Example #1 • You light a candle. • Flammability or Reactivity? • Flammability • How do you know? • It describes the substance’s ability to burn. A candle can burn easily, therefore it is flammable.

  28. Example #2 • Yeast acts on sugar to form carbon dioxide and ethanol • Flammability or Reactivity? • Reactivity • How do you know? • Yeast is reacting with sugar and forms two new substances, carbon dioxide and ethanol.

  29. Chemical Changes

  30. After a CHEMICAL CHANGE, a NEW substance is produced with NEW properties. These properties are different from the original substance! Law of Conservation of Mass Matter is never destroyed or created in chemical reactions.  The particles of one substance are rearranged to form a new substance. The same number of particles that exist before the reaction exist after the reaction, they are just rearranged. 

  31. Signs that a Chemical Change took place • Production of a gas • Often appearing as bubbles • If it involves FIRE it involves gas (carbon dioxide in the smoke)

  32. Signs that a Chemical Change took place Production of Light Ex: Fireworks and Glow Sticks Glow sticks light up when two liquids inside of the stick are mixed, causing a chemical reaction. This reaction is called chemiluminescence.

  33. Signs that a Chemical Change took place • Change in temperature • Such as the production or loss of heat • Example: Ammonium nitrate and water in ice packs

  34. Signs that a Chemical Change took place • New color or Unexpected color change • A chemical reaction results in a color change • Metal and oxygen react to form RUST • Color changes from silver to brownish red

  35. Signs that a Chemical Change took place • Formation of a precipitate • An insoluble solid that forms out of a water solution • It forms because the solid does not dissolve in water

  36. Signs that a Chemical Change took place A change in Taste Ex: Burnt Toast

  37. Signs that a Chemical Change took place • Change in Odor When you smell an odd order in foods such as chicken, eggs or milk you know that the food has undergone a chemical change. You can use this clue to avoid eating spoiled food and becoming ill.

  38. Example #1: Burning wood

  39. Example #1: Burning wood • What chemical property is present? • Flammability • What is the evidence of a chemical change? • Production of a gas (SMOKE) • Change in temperature • Why is this a chemical change? • Burning wood is a chemical change because wood is no longer the same substance, it turned into ash. The evidence a chemical change took place is that smoke was produced and the temperature changed. Since wood is no longer the same substance and a new substance was produced, burning wood is a chemical change.

  40. Example #2: Rusting of Metal

  41. Example #2: Rusting of Metal • What chemical property is present? • Reactivity • What is the evidence of a chemical change? • Change in color • Silver to reddish brown • Why is this a chemical change? • Rusting of metal is a chemical change because the metal is no longer the same substance after it reacts with oxygen. The evidence of a chemical change is that the color changed from silver to reddish brown. Since the metal reacted with oxygen to form a new substance, it is a chemical change.

  42. Example #3: Digestion of Pizza

  43. Example #3: Digestion of Pizza • What chemical property is present? • Reactivity (with acid) • What is the evidence of a chemical change? • New substances with new properties • Food is broken down by acid • Why is this a chemical change? • Digesting pizza is a chemical change because it is now a new substance with new properties; food is broken down into other substances. In a chemical change new substances are produced with new properties, therefore I know that pizza being digested is a chemical change.

  44. EXTRA SLIDES

  45. Physical or Chemical??? Use the A-F cards to separate the Physical Changes from the Chemical Changes! D. Rubbing alcohol evaporates from your hand E. Hydrogen peroxide bubbles when you put it on a cut on your leg F. Your friend melts some butter for her popcorn A. You cut a sheet of aluminum foil in half B. You leave the milk on the counter all night and discover it has soured in the morning C. Your Mom lights a candle in a dark room

  46. Example • When charcoal burns in a BBQ grill • Reaction between Carbon and Oxygen • Provides heat that cooks the dinner and gives off CO2

  47. Endothermic reaction • A chemical reaction resulting in the loss of heat • Example: Ammonium nitrate and water in ice packs

  48. Exothermic reaction • Exothermic reaction: A chemical reaction resulting in the production of heat

  49. Exothermic reaction Example • Example: Hand warmers • Iron reacts with oxygen to produce heat Iron & Oxygen  heat

  50. Example #2 • Vinegar will react with baking soda. • Flammability or Reactivity? • Reactivity • How do you know? • Vinegar is reacting with baking soda and carbon dioxide is produced. This describes the interaction between two substances.

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