1 ch. 2: matter & energy chem. 20 el camino college
TRANSCRIPT
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
7
8
Solids
Have definite shape and volume The particles are close together The particles are attracted to each other Solid particles move slowly.
9
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.
11
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
solid
solid
gas
gas
14
15
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).
17
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.
19
20
21
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 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
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
26
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
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.
29
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
30
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
31
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
32
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
33
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.
GoodBad
(not acceptable)N nitrogenNa sodium NAna nA
35
Fig. 5-8, p.128