Chemistry Chapter 2

1. Chemistry Chapter 2 Changes in Matter Physical and Chemical Changes

2. Types of changes in matter: Physical Change Chemical • Physical change alters the form of a substance but does not change it to another substance. The substance has the same properties as the starting material • Tearing paper, bending a nail, spinning wool into yarn • When a substance undergoes a chemical change, it is changed into a different substance with different properties • Burning wood turns it into carbon dioxide and ash Both changes involve energy!!

3. Changes in matter involve energy: Every substance contains energy from the movement of its particles called THERMAL ENERGY The higher the temperature of a substance, the greater its thermal energy. Another form of energy comes from the chemical bonds within matter : CHEMICAL ENGERY Matter changes whenever energy is added or taken away! The LAW OF CONSERVATION OF ENERGY states that in every physical change and chemical change the total amount of energy stays the same.

4. Melting • Change in state from a solid to a liquid • Ice cube melting – energy to melt comes from the air in room. Added thermal energy makes the water molecules vibrate faster, which raises their temperature. Eventually water molecules vibrate so fast they break free from their position in ice crystals. Click for melting chocolate video Click for melting gold video

5. Freezing • Change in state from a liquid to a solid • Water turns to ice – when water is placed in the freezer the water loses energy to the cold air in the freezer. Water molecules move more slowly. When the temperature reaches 0°C, the molecules are moving so slowly that they form regular patterns which form ice. Water freezing video (click ice cube tray) Click for video

6. Condensation • Change in state from a gas to a liquid • Occurs when a gas loses enough thermal energy to become a liquid • Clouds, breath on a mirror, fog, steam Condensation video (click on glass) Condensation on window Condensation on soda can Condensation on mirror

7. Vaporization –change in state from a liquid to a gasOccurs when a liquid gains enough energy to become a gas Evaporation Boiling • When vaporization takes place only at the surface of the liquid • A puddle drying up after a rainstorm • Beads of sweat evaporate off your skin • When vaporization takes place inside the liquid as well as at the surface • Water boiling on stove Click for video Click for video

8. Sublimation • Change in state from a solid to a gas • Occurs when a solid gains enough energy to become a gas. Particles DO NOT pass through the liquid state at all. • Dry ice, moth balls, snow on a cold day Sublimation of Dry ice (click to watch video)

9. Changes in state http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html

10. Changes of State http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html

11. Chemical Changes (Chemical Reaction) • One substance breaks down into two or more other substances or • Two or more substances combine forming one or more new substances. • NEW SUBSTANCES ARE PRODUCED

12. Signs of a chemcial reaction • Signs of chemical reactions • Bubbles (gas produced) • Light produced • Color change • Solid (precipitate) formed • Odor change • Heat

13. Examples of Chemical Reactions • Mentos and diet coke • http://www.youtube.com/watch?v=LjbJELjLgZg&feature=related • Baking soda and vinegar • http://www.youtube.com/watch?v=nrTpubja0z8 • Sodium Chloride • http://www.youtube.com/watch?v=Ftw7a5ccubs&feature=related

14. The end of changes…….

16. Non-Newtonian Fluids • Has properties of both solid and liquid • Examples: Oobleck, PVA slime, and silly putty Click for video