Changes_in_Matter_Revised.ppt
- 1. Physical and Chemical Changes of Matter
- 2. What is “Change”? It is the act of altering a substance. An event, NOT a trait. Before condition After condition. Can be PHYSICAL or CHEMICAL.
- 3. Physical Change Does not alter the chemical composition or identity of the substance, only the form. Melting ice (change in state or phase) Freezing Kool-aid Tearing paper Boiling water (change in state or phase) Stretching silly putty Making a mixture (ex. Sugar water) Unmixing a mixture (ex. sorting)
- 4. Chemical Changes Does alter the chemical composition or identity of a substance and makes new substances. Burning paper Digesting food Rotting Iron reacting with oxygen gas A chemical change is also called a chemical reaction.
- 5. Is it Physical or Chemical? Change Physical Chemical Melting cheese Burning wood Milk souring Wadding up paper Bicycle rusting
- 6. All Changes of Matter Involve Energy being Tranfered and Transformed Energy always moves between the system and the surroundings during changes of matter. System = the chemicals of interest Surroundings = everything else (including the beaker and thermometer) Energy cannot be created or destroyed, it can only be transferred from place to place and transformed from type to type (Law of Conservation of Energy).
- 7. Exothermic change - heat moves out the the system into the surroundings. The surroundings get hotter. System Surroundings System System System
- 8. Endothermic change – Heat moves into the system from the surroundings, so the surroundings gets colder! System Surroundings System Surroundings System System Surroundings Surroundings Surroundings
- 9. Changes of Matter Demos Magnesium + oxygen gas Ammonium nitrate + water
- 11. Law of Conservation of Mass (1789) Matter is never created or destroyed in chemical reactions. Mass of reactants = Mass of products Why??? Because atoms are simply rearranged in new ways in chemical reactions. (LEGO analogy)
- 12. Parts of a Chemical Reaction Reactants Products Reactants: Substances that are broken down by the chemical change. Products: Substances created by the chemical change. Means “Yields”
- 13. Evidence for Chemical Reaction 1) Evolution of light.
- 14. Evidence for Chemical Reaction 2) Temperature Change.
- 15. Evidence for Chemical Reaction 3) Formation of a new Gas/Bubbles.
- 16. Evidence for Chemical Reaction 4) Color Changes.
- 17. Evidence for Chemical Reaction 5) Formation of a solid precipitate.
- 18. Chemical Reactions Produce New Substance with New Properties Ex. Iron Plus Oxygen Yields Rust 4 Fe (s) + 3O2 (g) 2 Fe2O3 (s) Iron Oxygen Rust Physical Properties Chemical Properties Mass 226 g 93 g 319 g
- 20. States of Matter The 3 main states of matter: solid, liquid, gas. Changes in state are physical changes (no change in composition). Temperature is caused by the vibrational (kinetic) energy of atoms or molecules. As temperature increases, 1) solids turn to liquids, and 2) liquids turn to gases.
- 21. States of Matter for H2O
- 22. Kinetic Molecular Theory of Matter A theory that describes the differences between the states of matter in terms of particle behavior 1) all matter is made of tiny particles (atoms, molecules) 2) particles in matter are constantly moving (vibrating) , except at absolute zero 3) The volume that matter occupies is mainly due to the space between particles rather than the particles themselves; the particles are very small
- 23. Kinetic Molecular Theory - Continued 4) In a solid, attractive forces hold the particles close together, although they still vibrate in positions. 5) In a liquid, the particles may move past one another, particles motions are slightly more random, and particles are spread out slightly more than in the solid. Attractions between particles are still important. 6) In a gas, particles are very spread out. They move in straight line, random paths until they collide elastically with each other or the walls of the container. Attractive forces between particles are negligible.
- 24. Definite Shape? Definite Volume? Compressible? GAS N N Y LIQUID N Y N SOLID Y Y N
- 25. CHANGES OF STATE
- 26. THE 3 TEMPERATURE SCALES Symbol Reference Points Celsius C Water freezes at 0C; Water boils at 100C. Fahrenheit F Water freezes at 32F. Body temp. = 98.6F. Kelvin K Atoms and molecules stop vibrating at 0 K (absolute zero).
- 27. THE 3 TEMPERATURE SCALES
- 28. THE 3 TEMPERATURE SCALES Tc = (Tf - 32) / 1.8 Tf = (1.8)*Tc + 32 Tk = Tc + 273.15 Tc = Tk – 273.15