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CHANGES

Explore physical and chemical properties, reactions, and examples like rust, fire, and weathering. Learn about endothermic and exothermic reactions and the energy involved in chemical bonding.

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CHANGES

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  1. CHANGES

  2. PHYSICAL PROPERTIES • Physical property- characteristics of a material that can be observed without changing the identity of the substances in the material. • These include color, shape, size, density, melting point, and boiling point

  3. Appearance- Physical description of a substance. (color, shape, size, density) • Behavior- How a substance acts. (magnetism, viscosity, ductility) • Observations- Start and end with the same substance

  4. PHYSICAL CHANGE • Physical change- Change in a substance’s size, shape, or state of matter. • Substances do not change identity when it undergoes a physical change.

  5. PHYSICAL CHANGESEXAMPLES Biting Melting cutting

  6. More Examples breaking a glass haircut adding chocolate syrup to ice cream squeezing a wet sponge

  7. CHEMICAL PROPERTIES • Chemical property- characteristic of a substance indicating that it can change chemically. (flammability, light sensitivity)

  8. Chemical Change • Chemical Change- When one substance changes to another substance a chemical change has occurred. • Some indicated by temperature change, color change, noticeable smell, gas production or formation of a precipitate • Others occur slowly. – rust

  9. CHEMICAL CHANGES EXAMPLES • SALIVA, STOMACH ACID, ENZYMES (chemicals which speed up reactions) • Rust/Tarnishing • FIRE-burning

  10. EVIDENCE OF CHEMICAL CHANGES

  11. WEATHERING • Weathering- involves both chemical and physical changes. • Physical- ex: big rocks split into smaller ones, streams carry rocks from one place to another • Chemical- • ex: occur in rocks when calcium carbonate in limestone changes to calcium hydrogen carbonate due to acid rain

  12. Energy in Reactions

  13. Bonding and Energy • Energy is required to break chemical bonds. • Energy is released when chemical bonds are formed.

  14. Chemical reactions can also be categorized into two types Endothermic Reactions Exothermic Reactions

  15. Endothermic Reactions

  16. Sucks in the heat Turns cold Absorbs energy - heat

  17. Endothermic(in-heat) • Reactions absorb heat by absorbing energy • Sometimes called endergonic

  18. Endothermic • Temperature of the products may be less than temperature of reactants • This type of reaction produces a decrease in temperature

  19. Endothermic • Examples : • Baking soda and vinegar • Instant cold packs

  20. Exothermic Reactions

  21. Releases energy - heat

  22. Exothermic(out-heat) • Reactions that produce heat by releasing energy • Sometimes called exergonic

  23. Exothermic • Temperature of products is usually greater than temperature of reactants • This type of reaction produces an increase in temperature

  24. Exothermic • Examples : • Hot hands • Bunsen Burner-lit • Candle • Combustion in car engine

  25. Why isn’t freezing water an endothermic reaction?

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