1. Chemistry! 9/22/09 Properties of Matter

2. Measuring matter Mass: amount of matter. (kg, g, lbs) Volume: Space taken up in 3D (m 3, mL, cm 3, Liters)

3. Types of properties Extensive: length, mass, volume, weight. (change with amount of substance) Intensive: density, reactivity, hardness, viscosity.

4. Changes in matter Physical change: change in extensive properties. Examples: cutting, expanding, deforming Chemical change: change in intensive properties Examples: mixing baking soda and vinegar, burning gasoline.

5. Signs of chemical change Exothermic (reaction gives off heat) Endothermic (reaction needs heat around it to happen) Color change

6. Physical or chemical change?

11. Volume Readings Read the meniscus at eye level

12. Reading the meniscus WATER prefers to adhere to the glass walls. Hg prefers to COHERE (sticks to itself). Cohesion vs. adhesion: a meniscus may be either concave or convex, depending on fluid.

13. Measuring Volume with water displacement

14. Phase Changes Solid: Crystal structure, Molecules held in place. Liquid: molecules “slide” past each other Gas: molecules repel away from each other, spread out.

15. Phase Changes Solid: Definite shape, definite volume. Liquid: takes container shape, definite volume. Gas: takes container shape and volume.

16. Temperature Scales: Farenheit Water boils/condenses: Water freezes/thaws: Absolute zero: 212° 32° -459.67°

17. Temperature Scales: Celsius Water boils/condenses: Water freezes/thaws: Absolute zero: 100° 0° -273.15°

18. Temperature Scales: Kelvin Water boils/condenses: Water freezes/thaws: Absolute zero: 373.15 K 273.15 K 0 K

19. Temperature Scales: Celsius 1° F is “narrower” than 1° C. Converting between Farenheit and Celsius: Scales start in different places. An increase of 1° C = 9/5° F F = 9/5C + 32 At 0° C : F = C + 32

20. Temperature Scales: Kelvin Kelvin: “width” of 1 K same as 1° C. 0 K is absolute zero.

21. Significant Figures How do I round this answer? Significant figures: rules for rounding answers, writing measurements.

22. Significant Figures 300.123 g : very precise. Precise measurements: more sig. figs. 300 g : not as precise. 6 s.f. 1 s.f. Converted to pounds: 0.136136 lbs 0.1 lbs

23. Significant Figures: my mass 1 s.f.: 60 kg, 60000 g, 0.06 Mg, 0.00006 Gg, 6 x 10 -8 Tg All the same thing! Go back and measure more carefully: 2 s.f.: 63 kg, 63000 g, 0.063 Mg, 0.000063 Gg6.3x 10 -8 Tg Rough measurement: 60 kg 3 s.f.: 63.2 kg, 63200 g, 0.0632 Mg, 0.0000632 Gg6.32x 10 -8 Tg

24. Significant Figures: my mass 5 s.f.: 63.205 kg, 63205 g, 0.063205 Mg, 0.000063205 Gg, 6.3205 x 10 -8 Tg 4 s.f.: 63.20 kg, 63200 g, 0.06320 Mg, 0.00006320 Gg6.320x 10 -8 Tg

25. Significant Figures: the rules Always count nonzero digits. Count zeroes only when:  They come between non-zero digits (502 g)  If after decimal, they don’t change the value of the number if removed (e.g. 63.0 mL)