Intro to Chemisty
Intro to Chemisty CH1213
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This 4 page Class Notes was uploaded by alb1081 on Wednesday August 31, 2016. The Class Notes belongs to CH1213 at Mississippi State University taught by Dr. Xiu Xu in Fall 2016. Since its upload, it has received 165 views. For similar materials see Chemistry 1 in Chemistry at Mississippi State University.
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Date Created: 08/31/16
I. Essential Ideas A. The Study of Chemistry 1. Chemistry is the study of matter and the changes that matter undergoes 2. Matter is anything that has mass and occupies space a) Energy, thoughts, etc. is NOT matter 3. Scientists follow guidelines known as the scientific method a) Gather data via observations and experiments b) Identify patterns c) Summarize findings with a law d) Formulate hypothesis (1) With time, a hypothesis may evolve into a theory B. Classification of Matter 1. All substances in principle exist as a solid, liquid, or gas. 2. Particles packed closer together are solids C. Types of Matter 1. Mixtures – variable compositions a) Heterogeneous – not uniform, wet sand b) Homogenous – uniform, tea with sugar 2. Pure Substance a) Element – Helium, etc. b) Compound – separable into simpler substances, pure water D. Atoms/Molecules 1. An atom is the smallest indivisible unit for an element 2. Molecules consist of two or more atoms joined together by chemical bonds a) A chemical compound always contains the same elements in the same proportions by mass E. Properties of Matter 1. Two general types: a) Quantitative – expressed by a number (1) Measurements, etc. b) Qualitative – based on observations (1) Colors, shapes, etc. 2. Physical property – can be observed and measured without changing identity of substance 3. Physical change – state of matter changes but identity of matter does not 4. Chemical property – property a substance exhibits as it interacts with another substance 5. Chemical change – results in a change of composition; original substance no longer exists 6. Extensive property – depends on the amount of matter a) Mass, volume, etc. 7. Intensive property – does not depend on amount of matter a) Boiling point, melting point, etc. F. Scientific Measurement 1. Properties can be measured and are called quatitative properties 2. Must always include a unit 3. English system has units such as foot, gallon, pound, etc. 4. Metric system has units such as meter, liter, kilogram, etc. G. SI Units 1. International System of Units (SI Units) 2. Universal use (except U. S.) a) Length – meter b) Mass – kilogram c) Time – second d) Temperature – Kelvin H. Mass 1. Mass is a measured amount of matter in an object or sample a) Weight changes by location; mass DOES NOT 2. Atomic Mass Unit (atm) a) Used to express the masses of atoms and other similar sized objects b) 1 atm = 1.6605378x10^-24 g I. Temperature 1. Two scales used: a) Celsius b) Kelvin (1) Absolute scale (2) Lowest possible temperature is 0 K J. Derived Units: Volume and Density 1. Volume a) The derived SI unit for volume is the cubic meter b) The more practical unit is liter c) 1dm^3 = 1L d) 1cm^3 = 1mL 2. Density a) The density of a substance is ratio of mass to volume b) D = m/v c) Derived SI unit = kg/m^3 K. Uncertainty in Measurement 1. Two types of numbers in chemistry a) Exact numbers (1) Have defined values (2) 1 kg = 1000g b) Inexact numbers (1) Measured by any method other than counting (2) Length, etc. (3) Uncertain digits are any last digits L. Significant Figures 1. Significant figures are meaningful digits in reported numbers 2. Sig figs are non-place holding digits a) Any nonzero digit is significant (1) Ex. 4, 2, 15 b) Zeroes between nonzero digits are significant (1) Ex. 101, 2049, 10000001 c) Zeroes to the left of the first nonzero digit are not significant (1) Ex. 0.1, 01, 0.0001 d) Zeroes to the right of the last nonzero digit are significant if a decimal is present (1) Ex. 9.0, 10.0, 1.150 e) Zeroes to the right of the last nonzero digit in a number without a decimal may or may not be significant (1) Ex. 1000, 1050, 60 f) Exact numbers have an unlimited number of sig figs (1) Ex. 1 meter, 15 pennies, 100 cm 3. Calculations with sig figs a) Adding and subtracting: (1) Line up the decimal places and the number of sig figs is the number with the least amount of numbers after the decimal b) Multiplying and Dividing: (1) The amount of sig figs is the smallest amount of numbers c) DO NOT ROUND UNTIL THE VERY END OF A MULTISTEP PROBLEM. KEEP TRACK OF SIG FIGS THROUGHOUT. M. Accuracy and Precision 1. Accuracy – how close a measurement is to the true value a) Hitting bullseye, or the center of a target 2. Precision – how close results are to each other a) Grouping together, not scattered, not close to true value
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