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# Chapter 1: Chemistry: The Study of Change ## 1.1 Chemistry: A Science for the 21st Century ### Chemistry: - Is the study of matter and the changes it undergoes. - Is central to our understanding of many fields. - Has impact on: - Health care - Preservation of the environment - Daily livin...

# Chapter 1: Chemistry: The Study of Change ## 1.1 Chemistry: A Science for the 21st Century ### Chemistry: - Is the study of matter and the changes it undergoes. - Is central to our understanding of many fields. - Has impact on: - Health care - Preservation of the environment - Daily living ### Chemistry deals with: - The composition - Structure - Properties - Reactions of matter ### Experimenting - Is a key component ## 1.2 The Scientific Method ### The Scientific Method: - Is a systematic approach to research. ### Steps in the Scientific Method 1. Define the problem 2. Performing experiments, making observations, recording data. 3. Formulating a hypothesis. - A hypothesis is a tentative explanation for a set of observations. 4. Testing the hypothesis. - After sufficient amount of data, hypothesis becomes a theory. - A theory is a unifying principle that explains a body of facts and/or those laws that are based on them. ## 1.3 Classifications of Matter ### Matter - Is anything that occupies space and has mass. ### States of Matter 1. Solid - Fixed shape and volume. - Particles close together and locked in place. 2. Liquid - Fixed volume, takes shape of container. - Particles close together but not locked in place. 3. Gas - No fixed volume or shape. - Particles are far apart and move randomly. ### Substances and Mixtures #### Substance - Is a form of matter that has a definite composition and distinct properties. - Examples: Gold, Water #### Mixture - Is a combination of two or more substances in which the substances retain their distinct identities. - Examples: Air, Soda ### Types of Mixtures 1. Homogenous mixture - Composition of the mixture is the same throughout. - Example: Soda 2. Heterogeneous mixture - Composition is not uniform. - Example: Cement, Iron filling in sand. ### 1.4 Elements and Compounds #### Element - Is a substance that cannot be separated into simpler substances by chemical means. - Examples: Gold, Aluminum, Oxygen #### Compound - Is a substance composed of two or more elements chemically united in fixed proportions. - Examples: Water ($H_2O$), Methane ($CH_4$), Table Salt (NaCl) ### Separation of Mixtures - Filtration: - Separates solid from liquid. - Example: coffee filter - Distillation: - Separates substances based on boiling points - Example: water from solution - Magnet - Separate magnetic substances from nonmagnetic - Example: Removal of Iron from sand. ## 1.5 Physical and Chemical Properties of Matter ### Physical Property - Can be measured and observed without changing the composition or identity of a substance. - Examples: Melting point, boiling point, color. ### Chemical Property - To observe, must carry out a chemical change/reaction. - Examples: flammability, reactivity ### Types of Changes #### Physical Change - Changes physical properties. - No change in composition. - Examples: Melting, Freezing #### Chemical Change - Changes chemical properties. - Change in composition. - Examples: Combustion, Oxidation, Decomposition ## 1.6 Measurement ### SI Units - Système International d’Unités - A complete system of units #### Base SI Units | Quantity | Unit | Symbol | | :-------------------- | :--------- | :------ | | Length | meter | m | | Mass | kilogram | kg | | Time | second | s | | Electric Current | ampere | A | | Temperature | kelvin | K | | Amount of Substance | mole | mol | | Luminous intensity | candela | cd | #### Prefixes Used with SI Units | Prefix | Symbol | Meaning | Example | | :---------- | :----- | :----------------- | :--------------------------------------- | | Pico | p | $10^{-12}$ | 1 picometer (pm) = $1 x 10^{-12}$ m | | Nano | n | $10^{-9}$ | 1 nanometer (nm) = $1 x 10^{-9}$ m | | Micro | $\mu$ | $10^{-6}$ | 1 micrometer ($\mu$m) = $1 x 10^{-6}$ m | | Milli | m | $10^{-3}$ | 1 millimeter (mm) = $1 x 10^{-3}$ m | | Centi | c | $10^{-2}$ | 1 centimeter (cm) = $1 x 10^{-2}$ m | | Deci | d | $10^{-1}$ | 1 decimeter (dm) = $1 x 10^{-1}$ m | | Kilo | k | $10^{3}$ | 1 kilometer (km) = 1 x $10^{3}$ m | | Mega | M | $10^{6}$ | 1 megameter (Mm) = 1 x $10^{6}$ m | | Giga | G | $10^{9}$ | 1 gigameter (Gm) = 1 x $10^{9}$ m | | Tera | T | $10^{12}$ | 1 terameter (Tm) = 1 x $10^{12}$ m | ### Mass and Weight - Mass is a measure of the amount of matter in an object. - Weight is the force that gravity exerts on an object. ### Volume - SI derived unit for volume is cubic meter ($m^3$) - Commonly use liters (L) and milliliters (mL) - 1 mL = 1 $cm^3$ - 1 L = 1000 mL = 1000 $cm^3$ = 1 $dm^3$ ### Density - Is the ratio of mass to volume - density = $\frac{mass}{volume}$ - $d = \frac{m}{V}$ - SI derived unit is kg/$m^3$ - Commonly use g/mL or g/$cm^3$ ## 1.7 Handling Numbers ### Scientific Notation - Is used to express very large and very small numbers. - $N x 10^n$, where N is a number between 1 and 10 and n is an integer. - Example: 568.762 = $5.68762 x 10^2$ - Example: 0.00000772 = $7.72 x 10^{-6}$ ### Significant Figures - Any digit that is not zero is significant. - 1.234 kg – 4 significant figures - Zeros between non-zero digits are significant. - 606 m – 3 significant figures - Zeros to the left of the first non-zero digit are not significant. - 0.08 L – 1 significant figure - If a number is greater than one, then all zeros to the right of the decimal point are significant. - 2.0 mg – 2 significant figures - If a number is less than one, then only the zeros at the end of the number and between non-zero digits are significant. - 0.00420 g – 3 significant figures ### Significant Figures in Calculations #### Addition or Subtraction - The answer cannot have more digits to the right of the decimal point than either of the original numbers. #### Multiplication or Division - The number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures. ### Accuracy and Precision #### Accuracy - How close a measurement is to the true value. #### Precision - How close a set of measurements are to one another. ## 1.8 Dimensional Analysis in Solving Problems ### Dimensional Analysis - Is a method of problem solving in which carried along throughout the entire calculation. - Conversion factor is a fraction in which the numerator and denominator are the same quantity expressed in different units. Diagram showing the problem solving steps. 1. Given/Known 2. Conversion Factors 3. Desired/Unknown