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

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

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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.

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

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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).

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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.

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

23 When water vapor in the air hits a cold soda can, it turns to liquid. Is energy added or removed in this process? To boil water, do you add heat to the water, or is heat removed? Which is lower, the mp of H 2 O or the bp of H 2 O? Which is higher, the mp of H 2 O or the fp of H 2 O? add heat removed 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 J It is equal to amount of energy needed to raise the temperature of one gram of water by 1 0 C

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

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

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

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

30 Solved Example Convert o F to o C. o F - 32 = 1.8 * o C o C = o F = = = o C

31 Convert 98.6 o F to o C. o F - 32 = 1.8 * o C o C = o F = = = 37.0 o C Convert 37.0 o C to K. K = o C = K

32 Convert 15 o C to o F. o F - 32 = 1.8 * o C o F =(1.8 * o C) + 32 = 59 o F Convert o F to o C. o F - 32 = 1.8 * o C o C = o F = = = o C

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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. Good Bad (not acceptable) N nitrogen Na sodium NANA nana nAnA

35 Fig. 5-8, p.128