Chapter 1 Elements and Measurements You are responsible for all sections in this chapter

Chemistry and the Elements

Periods: 7 horizontal rows. Groups: 18 vertical columns. International standard: 1-18 US system: 1A-8A, 1B-8B

Elements and the Periodic Table

Some Chemical Properties of the Elements 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.

The Metric System (SI) The metric system or SI (international system) is a decimal system based on 10. used in most of the world. used everywhere by scientists. 6

Experimentation and Measurement All other units are derived from these fundamental units Système Internationale d´Unités

Measuring 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 Temperature T F = 1.8 T C + 32 T C = (T F – 32) 1.8 K = °C

Scientific Notation is used to write very large or very small numbers. for the width of a human hair of m is written 8 x m. of a large number such as s is written 4.5 x 10 6 s. 11

Accuracy, Precision, and Significant 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 Significant Figures length = 1.74 cm cm 1.7 cm < length < 1.8 cm

Accuracy, Precision, and Significant Figures Rules for counting significant figures (left-to-right): 1.Zeros in the middle of a number are like any other digit; they are always significant cm 4 sf 2.Rules for counting significant figures (left-to- right): Zero at the beginning of a number are not significant (placeholders) g 3 sfor 6.61 x g

Accuracy, Precision, and Significant Figures Rules for counting significant figures (left-to-right): 3.Zeros at the end of a number and after the decimal point are always significant K 5 sf 4.Zeros at the end of a number and after the decimal point may or may not be significant. 34,2000 ? SF

Rounding Numbers If the first digit you remove is 5 and there are more nonzero digits following, round up = If the digit you remove is a 5 with nothing following, round down =

Multiplication and Division When multiplying or dividing the final answer must have the same number of significant figures as the measurement with the fewest significant figures. Example: x = = 5.3 (rounded) 4 SF 2 SF calculator 2 SF 17

Addition and Subtraction When adding or subtracting the final answer must have the same number of decimal places as the measurement with the fewest decimal places one decimal place two decimal places 26.54calculated answer 26.5 final answer with one decimal place 18

Calculations: Converting from One 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

Conversion Factors A conversion factor is obtained from an equality. Equality: 1 in. = 2.54 cm written as a fraction (ratio) with a numerator and denominator. inverted to give two conversion factors for every equality. 1 in. and 2.54 cm 2.54 cm 1 in. 20

Conversion Factors in a Problem A conversion factor may be obtained from information in a word problem. is written for that problem only. Example : The cost of one gallon (1 gal) of gas is $ gallon of gasand $4.29 $4.291 gallon of gas 21

Example: How many ounces are in 1.0 kg? How many in 3 in 1.5 m 3 22

Examples If your pace on a treadmill is 65 meters per minute, how many minutes will it take for you to walk a distance of 7500 feet?

Derived Units: Measuring Density density = volume mass solids- cm 3 liquids- mL gases- L Typical volume units

Examples Osmium is a very dense metal. What is its density in g/cm 3 if 0.11 lb of osmium has a volume of 2.22 ml? The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane?