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Section 3.4—Changes in Matter

Section 3.4—Changes in Matter. What type of changes can produce a gas for an airbag?. Definition. Physical Change – chemical structure remains the same. NO NEW substance forms!. breaking, dissolving, distilling, cutting, etc. Changes in state are physical changes (boiling, condensing,

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Section 3.4—Changes in Matter

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  1. Section 3.4—Changes in Matter What type of changes can produce a gas for an airbag?

  2. Definition Physical Change–chemical structure remains the same. NO NEW substance forms! • breaking, dissolving, distilling, cutting, etc. • Changes in state are physical changes (boiling, condensing, • melting and freezing) Chemical Change-chemical structures of the substances have changed. NEW Substances form! • rusting, burning, metabolizing food, oxidation or reduction, reacting with oxygen, etc.

  3. Possible Signs of Chemical Changes • Gas production (bubbling) • Energy change (getting hot or cold) • Color change • Light given off • Formation of a precipitate (making an insoluble substance from two soluble substances)

  4. Sometimes these “signs” accompany physical changes as well! • Gas production (bubbling).Bubbles are formed during boiling (a physical change) • Energy change (getting hot or cold).Energy changes accompany changes in state (physical changes) • Color change.Color change can occur due to dissolving a substance (a physical change)

  5. How do you know for sure? • Measure and observe chemical and physical properties before the change in question. • Measure and observe the properties after the change. • If the properties are the same, then it was a physical change!

  6. Physical & Chemical Changes Also…if a change can be un-done by a physical change, then the original change was physical as well. • If salt is dissolved in water, it seems to disappear… • But if the water is evaporated (a physical change), the salt is left in the container. • Since the original change was un-done with a physical change, then the original change (the dissolving) was a physical change as well.

  7. Using Changing Words Properly Sometimes, students misuse the words that appear below: Definition Term Type of Change Changes a solid into a liquid Melting Physical Reacting with oxygen to produce CO2 and H2O Burning Chemical Adding one substance to another to form a homogeneous mixture Dissolving Physical Heating a sample to evaporate the water Drying Physical

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