Transcript Example

Antoine Lavoisier,
1743-1794
Marie Curie,
1867-1934
Joseph Priestly,
1766-1844
Dmitri Mendeleev,
1834-1907
John Dalton,
1766-1844
What is Matter?
Matter: Anything that occupies space and has mass
Energy: Ability to do work, accomplish a change
Physical States of Matter
Gas: Indefinite volume, indefinite shape,
particles far away from each other
Liquid: Definite volume, indefinite shape,
particles closer together than in gas
Solid: Definite volume, definite shape,
particles close to each other
Properties of Matter
Property: Characteristic of a substance
Each substance has a unique set of properties identifying it from
other substances.
Intensive Properties: Properties that do not depend on quantity
of substance
Examples: boiling point, density
Extensive Properties: Properties that depend on or vary with
the quantity of substance
Examples: mass, volume
Physical Properties: Properties of matter that can be observed
without changing the composition or identity of a substance
Example: Size, physical state
Chemical Properties: Properties that matter demonstrates when
attempts are made to change it into new substances, as a result of
chemical reactions
Example: Burning, rusting
Changes in Matter
Physical Changes: Changes matter undergoes without changing
composition
Example: Melting ice; crushing rock
Chemical Changes: Changes matter undergoes that involve
changes in composition; a conversion of reactants to products
Example: Burning match; fruit ripening
Classifying Matter
Pure substance: Matter that has only 1 component; constant
composition and fixed properties
Example: water, sugar
•Element: Pure substance consisting of only 1 kind of atom
(homoatomic molecule)
Example: O2
•Compound: Pure substance consisting of 2 or more kinds of
atoms (heteroatomic molecules)
Example: CO2
Mixture: A combination of 2 or more pure substances, with each
retaining its own identity; variable composition and variable properties
Example: sugar-water
•Homogenous matter: Matter that has the same properties
throughout the sample
•Heterogenous matter: Matter with properties that differ
throughout the sample
Solution: A homogenous mixture of 2 or more substances (sugarwater, air)
Measurement Systems
Measurement: Determination of dimensions, capacity, quantity or
extent of something; represented by both a number and a unit
Examples: Mass, length, volume, energy, density, specific gravity,
temperature
Mass vs. Weight
Mass: A measurement of the amount of matter in an object
Weight: A measurement of the gravitational force acting on an object
Density: mass divided by volume; d = m/v
Specific gravity: density of a substance relative to the density of water
English System Units: Inch, foot, pound, quart
Metric System: Meter, gram, liter
Unit of Length
Meter = basic unit of length, approximately 1 yard
1 meter = 1.09 yards
Kilometer = 1000 larger than a meter
Centimeter = 1/100 of a meter
100 cm = 1 meter
Millimeter = 1/1000 of a meter
1000 mm = 1 meter
Unit of Mass
Gram: basic unit of mass
454 grams = 1 pound
Kilogram: 1000 times larger than a gram
1 Kg = 2.2 pounds
Milligram: 1/1000 of a gram
Unit of Volume
Liter: basic unit of volume
1 Liter = 1.06 quarts
1 Liter = 10 cm x 10 cm x 10 cm
1 liter = 1000 cm3
1 ml = 1 cm3 (1 cc)
Unit of Energy
Joule: Basic unit of energy
calorie: amount of heat energy needed to increase temperature of 1 g of
water by 1oC
1 cal = 4 joules
Nutritional calorie = 1000 calories = 1 kcal = 1 Calorie
Units of Temperature
Fahrenheit: -459oF (absolute zero) - 212oF (water boils)
Celsius: -273oC (absolute zero) - 100oC (water boils)
Kelvin: 0K (absolute zero) - 373 K (water boils)
Different Temperature Scales
Converting Celsius and Fahrenheit:
oC
= 5/9 (Fo - 32)
oF
= 9/5 (oC) +32
Converting Celsius and Kelvin:
oC
= K - 273
K = oC + 273
Scientific Notation and Significant Figures
Scientific notation: a shorthand way of representing very small
or very large numbers
Examples: 3 x 102, 2.5 x 10-4
The exponent is the number of places the decimal must be
moved from its original position in the number to its position
when the number is written in scientific notation
If the exponent is positive, move the decimal to the right of the
standard position
Example: 4.50 x 102  450
3.72 x 105  372,000
If the exponent is negative, move the decimal to the left of the
standard position
Example: 9.2 x 10-3  .0092
Practice with Scientific Notation
50,000 = 5.0 x 104
300 = 3.00 x 102
.00045 = 4.5 x 10-4
.0005 = 5 x 10-4
Significant Figures
Significant Figures: Numbers in a measurement that reflect the
certainty of the measurement, plus one number representing an estimate
Example: 3.27cm
Rules for Determining Significance:
All nonzero digits are significant
Zeroes between significant digits are significant
Example: 205 has 3 significant digits
1,006 has
4 sig. figs.
10,004 has 5 sig. figs.
Leading zeroes are not significant
Example: 0.025 has 2 significant digits
0.000459 has 3 significant digits
0.0000003645
4 sig. figs.
Trailing zeroes are significant only if there is a decimal point in the
number
Examples: 1.00 has 3 significant figures
2.0 has 2 significant digits
20 has 1 sig. fig.
1500
2 sig. figs.
1.500
4 sig. figs.
Calculations and Significant Figures
Answers obtained by calculations cannot contain more certainty
(significant figures) than the least certain measurement used in
the calculation
Multiplication/Division: The answers from these calculations must
contain the same number of significant figures as the quantity with
the fewest significant figures used in the calculation
Example: 4.95 x 12.10 = 59.895
Round to how many sig. figs.?
Final answer:
59.9
3
Addition/Subtraction: The answers from these calculations must
contain the same number of places to the right of the decimal point
as the quantity in the calculation that has the fewest number of places
to the right of the decimal
Example: 1.9 + 18.65 = 20.55
How many sig. figs.required?
1
Final answer: 20.6
Rounding Off
Rounding off: a way reducing the number of significant digits to
follow the above rules
Rules of Rounding Off:
Determine the appropriate number of significant figures; any and
all digits after this one will be dropped.
If the number to be dropped is 5 or greater, all the nonsignificant
figures are dropped and the last significant figure is increased by 1
If the number to be dropped is less than 5, all nonsignificant
figures are dropped and the last significant figure remains
unchanged
Example: 4.287 (with the appropriate number of sig. figs.
determined to be 2)
4.287 4.3
We only use significant figures when dealing with inexact numbers
Exact (counted) numbers: numbers determined by definition or
counting
Example: 60 minutes per hour, 12 items = 1 dozen
Inexact (measured) numbers: numbers determined by
measurement, by using a measuring device
Example: height = 1.5 meters, time elapsed = 2 minutes
Practice:
Classify each of the following as an exact or a inexact number.
Inexact
A.
A field is 100 meters long.
B.
There are 12 inches in 1 foot.
C.
The current temperature is 20o Celsius.
D.
There are 6 hats in the closet.
Exact
Exact
Inexact
Calculating Percentages
percent = “per hundred”
% = (part/total) x 100
Example: 50 students in a class, 10 are left-handed. What
percentage of students are lefties?
% lefties = (# lefties/total students) x 100
= 10/50 x 100
= .2 x 100
= 20%
Practice Using and Converting Units in Calculations
Sample calculation: Convert 125m to yards.
•Write down the known or given quantity (number and unit)
125 m
• Leave some blank space and set the known quantity equal to the unit of
the unknown quantity
125 m
= yards
• Multiply the known quantity by the factor(s) necessary to cancel
out the units of the known quantity and generate the units of the
unknown quantity
125 m x 1.09 yards/1 m = yards
•Once the desired units have been achieved, do the
necessary arithmetic to produce the final answer
125 x 1.09 yards /1 = 136.25 yards
•Determine appropriate amount of sig. figs. and round
accordingly
Fewest sig. figs. in original problem is 3 (from
125), so final answer is 136 yards
Accuracy vs. Precision
Error: difference between true value and our measurement
Accuracy: degree of agreement between true value and measured value
Uncertainty: degree of doubt in a measurement
Precision: degree of agreement between replicated measurements