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Ch. 2: Matter & Energy

Chem. 20

El Camino College

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Classification of Matter

Matter occupies space and has mass Is water matter? Is air matter?

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Classification of Matter

Pure substances: fixed composition. element, compound

Mixtures. Homogeneous mixture, heterogeneous mixture

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Physical properties of Matter

Physical properties can be observed without affecting the identity of the substance

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Chemical properties of Matter

Chemical properties can be observed only when the identity of the substance changes

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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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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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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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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.

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

apart?

liquid

solid

solid

solid

gas

gas

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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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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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Change of State

Solid to gas is sublimation When heat is applied to some solids, they

sublime.

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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 H2O or the bp of H2O?

Which is higher, the mp of H2O or the fp of H2O?

add heat

removed

the mp

they’re the same

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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

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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

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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

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If oC is WantedoF - 32 = 1.8 * oC

oC =oF - 32

1.8

First do the subtraction,then do the divisionAlways show units in your answer.

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If oF is Wanted

oF - 32 = 1.8 * oC

First do the multiplication,then do the additionAlways show units in your answer.

oF = (1.8 * oC) + 32

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Solved Example

Convert 69.00 oF to oC.oF - 32 = 1.8 * oC

oC =oF - 32

1.8= 69.00 - 32

1.8

= 37.001.8

= 20.56 oC

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Convert 98.6 oF to oC.oF - 32 = 1.8 * oC

oC =oF - 32

1.8= 98.6 - 32

1.8

= 66.61.8

= 37.0 oC

Convert 37.0 oC to K.

K = oC + 273 = 310.0 K

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Convert 15 oC to oF.oF - 32 = 1.8 * oC

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

oF - 32 = 1.8 * oC

oC =oF - 32

1.8= -40.0 - 32

1.8

= -72.01.8

= -40.0 oC

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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.

GoodBad

(not acceptable)N nitrogenNa sodium NAna nA

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Fig. 5-8, p.128