Chapter 1

Chapter 1Chapter 1

Elements and MeasurementsElements and Measurements

Chemistry and the Chemistry and the ElementsElements

Elements and the Periodic Elements and the Periodic TableTable

Periods: 7 horizontal rows.

Groups: 18 vertical columns. International standard: 1-18 US system: 1A-8A, 1B-8B

Elements and the Periodic Elements and the Periodic TableTable

Main Groups columns 1A-2A (2 groups) columns 3A-8A (6 groups)

Transition Metals: 3B-2B (8 groups, 10 columns).

Inner Transition Metals: 14 groups between 3B and 4B. lanthanides actinides

Elements and the Periodic Elements and the Periodic TableTable

Metals: Left side of the zigzag line in the periodic table (except for hydrogen).

Nonmetals: Right side of the zigzag line in the periodic table.

Semimetals (metalloids): Tend to lie along the zigzag line in the periodic table.

Elements and the Periodic Elements and the Periodic TableTableAlkali Metals

Elements and the Periodic Elements and the Periodic TableTableAlkaline Earth Metals

Elements and the Periodic Elements and the Periodic TableTable Halogens

Elements and the Periodic Elements and the Periodic TableTable Noble Gases

Some Chemical Properties of the Some Chemical Properties of the ElementsElements

Intensive Properties: Independent of sample size. temperature melting point

Extensive Properties: Dependent on sample size. length volume

Some Chemical Properties of the Some Chemical Properties of the ElementsElements

Physical Properties: Characteristics that do not involve a change in a sample’s chemical makeup.

Chemical Properties: Characteristics that do involve a change in a sample’s chemical makeup.

Experimentation and Experimentation and MeasurementMeasurement

All other units are derived from these fundamental units

Système Internationale d´Unités

Measuring MassMeasuring Mass

Mass: Amount of matter in an object.

Matter: Describes anything with a physical presence—anything you can touch, taste, or smell.

Weight: Measures the force with which gravity pulls on an object.

Measuring TemperatureMeasuring Temperature

K = °C + 273.15

TF = 1.8 TC + 32TC = (TF – 32)

1.8

Derived Units: Measuring Derived Units: Measuring VolumeVolume

Derived Units: Measuring Derived Units: Measuring DensityDensity

density =volumemass

solids- cm3

liquids- mLgases- L

Typical volume units

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

Accuracy: How close to the true value a given measurement is. Single measurement: percent error Series of measurements: average

Precision: How well a number of independent measurements agree with each other. Characterized by the standard deviation.

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

good accuracygood precision

Mass of a Tennis Ball

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

good accuracypoor precision

Mass of a Tennis Ball

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

poor accuracypoor precision

Mass of a Tennis Ball

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

Significant figures: The number of meaningful digits in a measured or calculated quantity. They come from uncertainty in any measurement.

Generally the last digit in a reported measurement is uncertain (estimated).

Exact numbers and relationships (7 days in a week, 30 students in a class, etc.) effectively have an infinite number of significant figures.

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

length = 1.74 cm

0 1 2 43cm

1.7 cm < length < 1.8 cm

Accuracy, Precision, and Accuracy, Precision, and Significant FiguresSignificant Figures

Rules for counting significant figures (left-to-right):

Zeros in the middle of a number are like any other digit; they are always significant.

Zeros at the beginning of a number are not significant (placeholders).

Zeros at the end of a number and after the decimal point are always significant.

Zeros at the end of a number and after the decimal point may or may not be significant.

Use scientific notation

ExamplesExamples 76.600 kg76.600 kg 0.003400 mL0.003400 mL 18 students18 students 72,100 km72,100 km

Rounding NumbersRounding Numbers

Math rules for keeping track of significant figures:

• Multiplication or division: The answer can’t have more significant figures than any of the original numbers.

11.70 gal

278 mi= 23.8 mi/gal

4 SF

3 SF

3 SF

Rounding NumbersRounding Numbers

Multiplication or division: The answer can’t have more significant figures than any of the original numbers.

Addition or subtraction: The answer can’t have more digits to the right of the decimal point than any of the original numbers.

3.19+ 0.01315

3.18 2 decimal places

5 decimal places

2 decimal places

Rounding NumbersRounding Numbers

Rules for rounding off numbers:1. If the first digit you remove is less than

5, round down by dropping it and all following numbers.

5.664 525 = 5.66

Rounding NumbersRounding Numbers

2. If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left.

5.664 525 = 5.7

Rounding NumbersRounding Numbers

3. If the first digit you remove is 5 and there are more nonzero digits following, round up.

5.664 525 = 5.665

Rounding NumbersRounding Numbers

4. If the digit you remove is a 5 with nothing following, round down. 5.664 525 = 5.664 52

Calculations: Converting from Calculations: Converting from One Unit to AnotherOne Unit to Another

Dimensional analysis: A method that uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit.

Conversion factor: States the relationship between two different units.

original quantity x conversion factor = equivalent quantity

Calculations: Converting from Calculations: Converting from One Unit to AnotherOne Unit to Another

1 m = 39.37 in

Conversion factor:

Relationship:

1 m39.37 in

or39.37 in

1 m

convertsm to in

convertsin to m

Calculations: Converting from Calculations: Converting from One Unit to AnotherOne Unit to Another

39.37 in1 m69.5 in = 1.77 mx

equivalent quantitystarting quantity

conversion factor

ExamplesExamples Gemstones are weighed in carats, with Gemstones are weighed in carats, with

1 carat = 200 mg (exactly). What is 1 carat = 200 mg (exactly). What is the mass in gram of the Hope the mass in gram of the Hope Diamond, the world’s largest blue Diamond, the world’s largest blue diamond at 44.4 carats?diamond at 44.4 carats? What is the volume in mmWhat is the volume in mm33 of this of this

diamond if the density is 3.52 g/cmdiamond if the density is 3.52 g/cm33 ? ?