1. Introduction to Chemistry
Chapter 1
Introduction to Chemistry

2. What is Science?
“Natural abilities are like natural plants; they need pruning by study.” – Sir Francis Bacon ( )

3. The Nature of Science and Chemistry
Definitions
Science: knowledge
Sir Francis Bacon: “And thus knowledge itself is power”
Modern science, the acquisition of knowledge, is acquired by experience (experiment)
Chemistry: the study of matter and its interactions with other matter and with energy.

4. Chemistry and the Natural Sciences

5. The Scientific Method
Scientific method: investigations that are guided by theory and earlier experiments.
Hypothesis: a possible explanation for an event.
Law: a statement that summarizes a large number of observations.
Theory: an explanation of the laws of nature.

6. Matter Matter: anything that has mass and occupies space.
Mass: the quantity of matter in an object.
Weight: the force of attraction between an object and other objects.

7. Mass and Weight Mass on moon and earth is the same.
Weight on moon and earth is the different.

8. Properties of Matter
Property: anything observed or measured about a sample of matter.
Extensive property: depends on the size of the sample.
mass, volume
Intensive property: independent of sample size.
density, color, melting or boiling point

9. Physical Properties and Changes
Physical properties: can be measured without changing the composition of the sample.
mass, density, color, melting point
Physical change: a change that occurs without changing the composition of the material.
freezing, melting

10. Chemical Properties
Chemical properties: describe the reactivity of a material.
Natural gas burns in air; iron rusts.
Chemical change: at least part of the material is changed into a different kind of matter.
The digestion of sugar is a chemical change.

11. Practice
State if the underlined property or changes is intensive or extensive and chemical or physical.
The color of mercury is silvery.
The sample of iron rusts by reaction with oxygen.
The heat released by burning coal can power a city.
Water boils at 100°C.
A new pencil is 10 inches long.

12. Classification of Matter
Substances - a material that is chemically the same throughout.
Two types of substances
Elements cannot be broken into simpler substances.
Compounds can be broken down into elements.

13. Substances
Substance: cannot be separated into component parts by physical methods.
Compound: a substance which can be separated into simpler substances by chemical methods.
Element: a substance which cannot be separated into simpler substances by chemical methods.

14. Mixtures
Mixture: matter that can be separated into simpler materials by physical methods.
Heterogeneous mixture: composition of the mixture changes from one part to another.
Homogeneous mixture or solution: composition of the mixture is uniform throughout.
Alloy: a solution of a metal and another material (usually another metal).

15. Classification of Matter

16. Practice
Identify the following types of matter as elements, compounds, heterogeneous mixtures, or homogeneous mixtures.
Sodium chloride
Stainless steel
Chlorine
soil

17. Measurement Most modern science depends on measurements
Parts of a measurement
The object of the measurement
The value of the measurement
The units of the measurement
The reliability of the measurement
Example “The mass of iron was grams
All parts MUST be present in an answer for complete credit!!

18. Accuracy and Precision
Modern chemistry is largely based on experimental measurements. The confidence in measurements involves:
Accuracy: agreement of a measurement with the true value.
Precision: agreement among repeated measurements of the same quantity.

19. Accuracy and Precision
accurate and precise
accurate but not precise
precise but not accurate
neither accurate nor precise

20. Accuracy and Precision

21. Significant Figures
The number of significant figures is the number of digits from the first non-zero digit through the last reported digit.
The uncertainty is at least ±1 unit in the last reported digit.
Leading zeros – zeros preceding the first non-zero digit are NEVER significant.
Trailing zeros – a decimal point is the key.
No decimal – trailing zeros are NOT significant
Decimal – trailing zeros ARE significant

22. Significant Figures
Quantities that are not limited by significant figures:
counted numbers or tallies.
defined numbers.
the power of ten in exponential notation.

23. Significant Figures
How many significant figures are present in each of the measured quantities?

24. Significant Figures
Since trailing zeros in numbers without a decimal points may be confusing for significant figures use scientific notation.
100 1? Or should there have been a decimal? 1 x x x 102 3

25. Practice Determine the number of significant figures:
, ,904, x x

26. Uncertainty in Addition and Subtraction
The absolute uncertainty can be no smaller than the least accurate number.
1.6
The answer should have no more decimal places than the least accurate number.

27. Uncertainty in Multiplication and Division
Answers should have no more significant figures than the least accurate number.
3121 x 12 = = 3.7 x 104 # sig. digits x = =
NOT 37!!!!!!
37000 is questionable 2 2 2

28. Mixed Operations
Determine accuracy in the same order as the mathematical operations, # of significant digits are in red.
density = 3.7 g/mL
Be mindful of what your calculator gives you!! 3
2.79 g
8.34 mL mL v m
0.76mL = 3 2 2

29. Rounding Be cautious about rounding during multiple steps.
Keep more significant figures than you need in intermediate steps.
Ex:
2.5 x 4.50 x = ?

30. Practice
Evaluate each expression to the correct number of significant figures. (a) x x ( ) (b) (c)
x 100%
8.925
9.6 x
8.321

31. Practice
Calculate each to the correct number of significant figures . a) b) 8.27 x ( ) c) d) 4
(4 is exact)
x 100%
9.025

32. Base Units in the SI Quantity Unit Abbreviation Length meter m
Mass kilogram kg
Time second s
Temperature kelvin K
Amount mole mol
Electric current ampere A
Luminous intensity candela cd

33. Common Prefixes Used With SI Units
Prefix Abbreviation Meaning
mega- M 106
kilo- k 103
centi- c 10-2
milli- m 10-3
micro- m 10-6
nano- n 10-9
pico- p

34. Prefixes Used With SI Units
1 kilogram is equal to g.

35. Unit Conversion Factors
Unit conversion factor: a fraction in which the numerator is a quantity equal or equivalent to the quantity in the denominator, but expressed in different units
The relationship 1 kg = 1000 g
Generates two unit conversion factors:

36. Unit Conversions Lets convert 5.73 g to kg.
Start with what you know!!!
Add conversion factors to cancel units
Units must be same on top & bottom to cancel kg
grams on top
grams on bottom

37. Practice
Convert the following:
17.43 km to cm
165 μg to kg

38. Conversion Among Derived Units
Volume is the product of three lengths.
The standard unit of volume is the cubic meter (m3). 100 cm = 1 m (100 cm)3 = (1 m) cm3 = 1 m3
Two important non-SI units of volume are the liter and milliliter. 1 liter (L) = 1000 mL = 1000 cm3 1 mL = 1 cm3

39. Volume
Volumes can be expressed in different units depending on the size of the object.
1 m3 contains
1000 L
1 L contains
1000 mL

40. Using Unit Conversions
Express a volume of L in mL, cm3, and m3

41. Density Density: mass per unit volume
Density, in SI base units, is kg/m3 (kg m-3).
Most commonly used density units are g/cm3 (g cm-3 or g/mL) for solids and liquids, and g/L for gases.

42. Conversions Between Equivalent Units
The density of Ti is 4.50 g/cm3 or g = 1 cm3.
Calculate the volume of 7.20 g Ti.
Units cancel
What we know
Answer:
√ number
√ units
√ object
√ sig figs

43. English System

44. Practice Express 323 milliliters in gallons.
Express 3.61 cubic feet in cubic centimeters.

45. Temperature Conversion Factors
For water
0 Kelvin o Celsius 0o 100o -460o Fahrenheit 32o 212o

46. Practice
Express 17.5°C in °F and in K.

47. Practice
It has been estimated that 1.0 g of seawater contains 4.0 pg of Au. The total mass of seawater in the oceans is 1.6x1012 Tg, If all of the gold in the oceans were extracted and spread evenly across the state of Georgia, which has a land area of 58,910 mile2, how tall, in feet, would the pile of Au be?
Density of Au is 19.3 g/cm Tg = 1012g.

48. Practice
One metal object is a cube with edges of 3.00 cm and a mass of g. A second metal object is a sphere with radius 1.42 cm and a mass of 61.6 g. Are these objects made of the same or different metals? Assume the calculated densities are accurate to 1.00%.

49. Practice
A 40-lb container of peat moss measures 14 x 20 x 30 in. A 40-lb container of topsoil has a volume fo 1.9 gal.
Calculate the density of both the peat moss and the topsoil.
How many bags of peat moss are needed to cover an area measuring 10 ft x 20 ft x 2 in?

50. Practice
On a typical day, a hurricane expends the energy equivalent to the explosion of two thermonuclear weapons. A thermonuclear weapon has the explosive power of 1.0 Mton of nitroglycerin. Nitroglycerin generates 7.3 kJ of explosive power per gram of nitroglycerin. The hurricane’s energy comes from the evaporation of water that requires 2.3 kJ per gram of water evaporated. How many gallons of water does a hurricane evaporate per day?

51. THINK!! Homework: OWL: All of the required assignments
book: All questions from the end of the chapter are recommended as practice.