Ch. 2: Matter & Energy

1. Ch. 2: Matter & Energy Chem. 20 El Camino College

2. Classification of Matter • Matter occupies space and has mass • Is water matter? • Is air matter?

3. Classification of Matter • Pure substances: fixed composition. element, compound • Mixtures. Homogeneous mixture, heterogeneous mixture

4. Physical properties of Matter • Physical properties can be observed without affecting the identity of the substance

5. Chemical properties of Matter • Chemical properties can be observed only when the identity of the substance changes

6. States of Matter • 3 states of matter: solid, liquid, gas. • Water can be in the solid form (ice), liquid form, or gas

8. Solids • Have definite shape and volume • The particles are close together • The particles are attracted to each other • Solid particles move slowly.

10. Liquids • Take the shape of a container bottom • Have definite volume • The particles are close together • The particles are attracted to each other • Liquid particles move at a moderate rate.

12. Gases • Take the shape of a closed container • Take the volume of a closed container • The particles are far apart • The particles are not attracted to each other • Gas particles move at a rapid rate.

13. liquid solid solid • Solid, liquid, or gas? • gasoline • paper • plastic • nitrogen • snow • Which state of matter has the particles far apart? gas solid gas

16. Change of State • Solid to liquid is melting • When heat is applied to a solid, it melts • Liquid to solid is freezing • When something freezes, it releases energy • The melting point (mp) is the same temp. as the freezing point (fp).

18. Change of State • Liquid to gas is vaporization • When heat is applied to a liquid, it vaporizes (boils or evaporates) • Gas to liquid is condensation • When something condenses, it releases energy.

22. Change of State • Solid to gas is sublimation • When heat is applied to some solids, they sublime.

23. To boil water, do you add heat to the water, or is heat removed? add heat • When water vapor in the air hits a cold soda can, it turns to liquid. Is energy added or removed in this process? removed • Which is lower, the mp of H2O or the bp of H2O? • Which is higher, the mp of H2O or the fp of H2O? the mp they’re the same

24. Energy • Energy is defined as the ability to do work. • SI unit of energy is joule (J) • calorie is defined as exactly 4.184 J It is equal to amount of energy needed to raise the temperature of one gram of water by 1 0C

25. Temperature • There are three temperature scales: Fahrenheit (oF), Celsius (oC) and Kelvin (K) • Freezing pt of water at 1 atm • 0oC, 273K, 32oF • Boiling pt of water at 1 atm • 100oC, 373K, 212oF

27. Temperature • Memorize the formulas. Always show units after the answer • Always isolate the desired variable before plugging in numbers oF - 32 = 1.8 * oC K = oC + 273

28. oF - 32 1.8 oC = If oC is Wanted oF - 32 = 1.8 * oC First do the subtraction, then do the division Always show units in your answer.

29. oF = (1.8 * oC) + 32 If oF is Wanted oF - 32 = 1.8 * oC First do the multiplication, then do the addition Always show units in your answer.

30. 69.00 - 32 1.8 oF - 32 1.8 = oC = 37.00 1.8 = 20.56 oC = Solved Example • Convert 69.00 oF to oC. oF - 32 = 1.8 * oC

31. 98.6 - 32 1.8 oF - 32 1.8 = oC = 66.6 1.8 = 37.0 oC = • Convert 98.6 oF to oC. oF - 32 = 1.8 * oC • Convert 37.0 oC to K. K = oC + 273 = 310.0 K

32. = 59 oF oF = (1.8 * oC) + 32 -40.0 - 32 1.8 oF - 32 1.8 = oC = -72.0 1.8 = -40.0 oC = • Convert -40.0 oF to oC. oF - 32 = 1.8 * oC • Convert 15 oC to oF. oF - 32 = 1.8 * oC

34. Elements • You’ll be responsible for memorizing the names and symbols for the common elements on the handout. Spelling counts! • The symbols have either one capital letter, or one capital and one lower-case letter. Bad (not acceptable) Good N nitrogen Na sodium na nA NA

35. Fig. 5-8, p.128