Lesson 1 – SI Units and Dimensional Analysis MATH and Methods Lesson 1 – SI Units and Dimensional Analysis

Introduction to Chemistry (not in notes) Chemistry: The Central Science Chemistry is the science that investigates and explains the structure and properties of matter. Seeks to explain the submicroscopic events that lead to macroscopic observations

Branches of Chemistry (not in notes) Area of Emphasis Examples Organic chemistry most carbon-containing chemicals pharmaceuticals, plastics Inorganic chemistry (this class) in general, matter that does not contain carbon minerals, metals and nonmetals, semi-conductors Physical chemistry the behavior and changes of matter and the related energy changes reaction rates, reaction mechanisms Analytical chemistry components and composition of substances food nutrients, quality control Biochemistry matter and processes of living organisms metabolism, fermentation

SI Units (Le Systéme Internationale) Units of measurement SI Units (Le Systéme Internationale) Scientists need to report data that can be reproduced by other scientists. They need standard units of measurement. Standard Units A standard unit is a defined unit in a system of measurement There are seven standard units in SI. Le 4

SI Units Official definitions of the seven base units http://www.unc.edu/~rowlett/units/sifundam.html 5

Derived units of measurement A derived unit is any unit based off one or more SI units In other words: a derived unit is a created unit as opposed to a natural occurrence The main derived units used in this class are volume and density.

Volume Volume = the amount of space occupied by a substance Volume can be found mathematically (Vrect. prism= L*W*H) Volume can also be measured by water displacement By definition 1 cm3 = 1 mL

Density Density = amount of mass per unit of volume D=m/v Units for mass are grams Units for volume can either be mL or cm3 Remember 1ml = 1 cm3 Many known densities are listed in your reference packet, these will be useful throughout the semester.

BASE UNIT (gram, liter, meter) Prefix Symbol Factor Scientific Notation giga G 1 000 000 000 109 mega M 1 000 000 106 kilo k 1000 103 hecto h 100 102 deka da 10 101 NO prefix, use BASE UNIT (gram, liter, meter) 1 deci d 1/10 10-1 centi c 1/100 10-2 milli m 1/1 000 10-3 micro μ 1/1 000 000 10-6 nano n 1/1 000 000 000 10-9 pico p 1/1 000 000 000 000 10-12

Why do we use the metric system? Advantages Simple to use Easy to convert from one unit to another Dimensional Analysis (coming soon!) Universal – used worldwide By all scientists to communicate By all industrialized nations Except United States

Unit Equalities – Some examples 1 meter = 1000 mm 1L = 1000 mL 1 km = 1000 m 1 mole = 6.022 x 10²³ particles (e.g. atoms, molecules, ions, etc.) 1 kg = 1000 g 1 day = 24 hours All unit equalities can be turned into conversion factors.

Dimensional Analysis Process for converting between units. The Unit Equality (1 km = 1000 m) becomes the Conversion Factor: 1 km or 1000 m 1000 m 1 km This is a technique for converting units. 95% of all your problems in this class will be of this type.

Using Dimensional Analysis Multiply the starting unit by the conversion factor. Example: Convert 4.6 m to km 4.6 m x 1 km = 0.0046 km 1000 m If you use your conversion factors properly, the units you started with should cancel

Examples Convert between the following measurements using dimensional analysis (show your conversion factors): 1.) 2.34 mg x ___________ = g 2.) .98 mol x ________________= atoms 3.) 1,098 mL x _________ = L 4.) 5 km x _______ x ________ = cm 1 g 0.00234 1000 mg 6.022 x 1023 atoms 5.9 x 1023 1 mol 1 L 1.098 1000 mL 1000 m 100 cm 500,000 1 km 1 m

Multiple Unit Dimensional Analysis Convert 455 km/hr to m/s Convert 6.67 g/mL to mg/L Convert 45.0 m/s to mm/hr 455 km/hr x 1000 m/1 km x 1 hr/60 min x 1 min/60 s = 126 m/s 6.67 g/mL x 1000 mg/1 g x 1000 mL/1 L = 6,670,000 mg/L 45.0 m/s x 1000 mm/1 m x 60 s/1 min x 60 min/1 hr = 162,000,000 mm/hr

(Honors) Converting Cubed Units Express 4563 mm³ in m³ Express 35.6 mol/m³ in atoms/cm³ 4563 mm3 x (1m/1000 mm)3 = 4.563 x 10-6 m3 35.6 mol/m3 x 6.022 x 1023 atoms/mol x (1m/100 cm)3 = 2.14 x 1019 atoms/cm3