1. Introduction To Chemistry
Unit 2
Introduction To Chemistry

2. Topic Units Of Measurements

3. Measurements Measurements are quantitative information.
Measurement = a number + a unit

4. The Metric System Also Known As… Le Systeme International d’Unites
The SI system
The decimal system
The scientific community’s agreed upon single measurement system.
Based multiples of 10’s
Seven base SI units
Length, mass, time, temperature, amount of substance, electric current and luminous intensity.

5. QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION
LENGTH
MASS
TIME
TEMPERATURE
AMOUNT OF SUBSTANCE

6. l QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION LENGTH meter m MASS TIME
TEMPERATURE
AMOUNT OF SUBSTANCE

7. l QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION LENGTH meter m MASS
kilogram kg
TIME
TEMPERATURE
AMOUNT OF SUBSTANCE

8. l QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION LENGTH meter m MASS
kilogram kg
TIME t
second
sec
TEMPERATURE
AMOUNT OF SUBSTANCE

9. l QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION LENGTH meter m MASS
kilogram kg
TIME t
second
sec
TEMPERATURE T
degree Celsius
kelvin ºC K
AMOUNT OF SUBSTANCE

10. l QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION LENGTH meter m MASS
kilogram kg
TIME t
second
sec
TEMPERATURE T
degree Celsius
kelvin ºC K
AMOUNT OF SUBSTANCE n
mole
mol

11. Mass vs. Weight Mass is a measure of matter, measured by a balance.
Weight is a measure of gravitational pull, measured by a scale.
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On Earth, mass equals weight.

12. SI PREFIXES`
Prefix
Unit Abbreviation
Exponential Factor
Meaning
Tera T
1012
Giga G
109
Mega M
106
Kilo k
103
1000
Hecto h
102
100
Deka da
101 10
Base Unit
(g, L, m)  1
Deci d
10-1
1/10
Centi c
10-2
1/100
Milli m
10-3
1/1000
Micro μ
10-6 1/
Nano n
10-9 1/
Pico p
10-12 1/

13. QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION
Volume
(SI)
(Common)
Density

14. QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION
Volume
(SI) V
cubic meter m3
(Common)
Density

15. QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION
Volume
(SI) V
cubic meter m3
(Common)
liter L
Density

16. kilogram per cubic meter
QUANTITY
SYMBOL
BASE NAME
UNIT ABBREVIATION
Volume
(SI) V
cubic meter m3
(Common)
liter L
Density D
kilogram per cubic meter
kg/m3

17. QUANTITY SYMBOL BASE NAME UNIT ABBREVIATION
Volume
(SI) V
cubic meter m3
(Common)
liter L
Density D
kilogram per cubic meter
kg/m3
grams per cubic centimeter
grams per milliliter
g/cm3
g/mL

18. Remembering the Important Ones
King Henry Died By Drinking Chocolate Milk
Kilo-, Hecto-, Deka-, BASE, Deci-, Centi-, Milli-

19. Conversions
Converting a measurement from one unit to another unit.

20. Metric-Metric Measurement Conversions
Slide The Decimal Method
Slide the decimal the number of steps there are between the given and desired unit.
Remember that meters, liters, and grams are base units.
When you move from large to smaller units (), move the decimal to the right.
When you move from small to larger units (), move the decimal to the left.
Example Problems

21. English-Metric & Metric-English Measurement Conversions
Factor Label Method (Fence Post)
Identify the needed conversion factor for the given units and desired units.
A conversion factor is a ratio that relates two measurements.
Set up your problem according to the factor label method.
Make sure the conversion factor is set up to cancel out given units.
Multiple across and divide below to solve the problem.

22. Temperature
Measures the amount of kinetic energy associated with the motion of atoms or molecules
Quantitative observation
Physical property
Measured with a thermometer

23. Temperature Scale
Fahrenheit (°F) is only used by the public in the U.S.
Celsius (°C) is used by the public in the rest of the world and in most scientific experiments
Kelvin (K) is used in scientific experiments involving gases
Each temperature scale is defined by its boiling point of water, its freezing of water and its lowest possible temperature.

24. Temperature Scales

25. Temperature Conversions
°C = (°F – 32) × (5/9) °F = (°C × (9/5) K = °C – 273 °C = K - 273

26. Density The ratio of mass to volume
Mathematically, density = mass ÷ volume
Physical property – unique to each pure substance
Quantitative observation
Value (g/cm3)
Qualitative observation
Sink or float

27. Water Displacement

28. Solving Density Problems
Familiar Units
g/mL
g/cm3

29. Solving Density Problems
Identify given and unknown variables
Decide what equation is needed
Plug in given quantities
Solve equation

30. Using Scientific Measurement

31. Uncertainty Of Measurements
Due to
1. Human Error – Skill and carefulness
2. Limitation of measuring device.
Example – use of metric ruler.
To measure the length of book – YES
To measure the thickness of a page – NO

32. Accuracy how close a measurement is to the accepted value
accuracy is measured with percent error
accurate = correct

33. Precision how close a series of measurements are to each other
precision is measured with significant digits
precise = consistent

34. High Precision High Precision Low Precision
High Accuracy Low Accuracy Low Accuracy

35. Percent Error Measurement
Measurement of the accuracy of an experimental value compared to an accepted value.
Percent error value under 5% is considered acceptable
Percent Error = Accepted – Experimental X Accepted
Experimental  calculated, measured or found value
Accepted  correct, known, actual or given value

36. Significant Figures (AKA…Sig Fig)
A measurement consisting of all the digits known with certainty plus one final digit, which is somewhat uncertain or estimated.
An answer can never be any better than the least accurate piece of data.

37. Rules For Significant Figures
Rule 1 - All nonzero numbers are significant Rule 2 - All zeros between non-zero digits are significant Rule 3 - Leading zeros are never significant Rule 4 - Trailing zeros with a decimal are significant

38. Examples:
     760. 

39. Why Bother With Significant Figures?
Sig figs help us determine how many places your answer needs.
Answers cannot have more sig figs than the measurement with the least number of sig figs.

40. Multiplication/Division
The answer can have no more significant figures than are in the measurement with the fewest number of significant figures.

41. Practice Problems:
4.3 × 5.09 = 562 ÷ 8.7 = 1.05 × 321 = 43.2 ÷ 7.55 = × 0.75 = ÷ =