Chem with Cagg TR (12:30-1:45)
Chem with Cagg TR (12:30-1:45) CHEM 1030-004
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This 4 page Class Notes was uploaded by Tristen Strength on Friday August 19, 2016. The Class Notes belongs to CHEM 1030-004 at Auburn University taught by Brett Cagg in Fall 2016. Since its upload, it has received 10 views.
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Date Created: 08/19/16
CHEM SI Session Mondays and Wednesdays 4-5:30 Haley 2224 Chapter 1 - The Study of Chemistry - Chemistry is the study of matter and the changes (physical or chemical) that matter undergoes - Matter is anything that has mass and occupies space - Scientist follow a set of guidelines known as the scientific method - gather data via observations and experiments - identify patterns or trends in the collected data - summarize their findings with a law - formulate a hypothesis - with time a hypothesis may evolve into a theory - Classification of Matter - Chemists classify matter as either a substance or a mixture of substances - a substance is a form of matter that has definite composition and distinct properties - (Example: salt (sodium chloride), iron, water, mercury, carbon dioxide, and oxygen) - Substances differ from one another in composition and may be identified by appearance, smell, taste, and other properties - A mixture is a physical combination of two or more substances - A homogeneous mixture is uniform throughout - also called a solute - A heterogeneous mixture is not uniform throughout - Solids - Liquids - Gases - All substances can, in principle, exist as a solid, liquid, or gas - We can convert a substance from one state to another without changing the identity of the substance - A mixture can be separated by physical means into its components without changing the identities of the components - There are two general types of properties of matter - 1 Quantitative properties are measured and expressed with a number - 2 Qualitative properties do not require measurement and are usually based on observation - A physical property is one that can be observed and measured without changing the identity of the substance - Example: color, melting point, Physical process CHEM - Mixtures are separated, but the identities of the matter does not change - A chemical property is one a substance exhibits as it interacts with another substance - Examples: flammability, corrosiveness - A chemical change is one that results in change - Extensive property depends on the amount matter - Examples: mass, volume - An intensive property does not depend on the amount of matter - Examples: temperature - Properties that can be measured are called quantitative properties - A measured quantity must always include a unit - The English system has units such as the foot, gallon, pound, etc. - The metric system includes units such as the meter, liter, kilogram - We have units so we can agree on it - SI base units - The revised metric is called the international system of units and was designed for universal use by scientist - There are seven SI units - Meter, gram, seconds, ampere, kelvin, mole, candela (not used) - The magnitude of a unit may be tailored to a particular application using prefixes - Pico to Tera - MEMORIZE THE PERIODIC TABLE - Mass is a measure of the amount of matter in an object or sample - Because gravity varies from location to location the weight of an object varies depending on where it is measured. But mass doesn’t change - The SI base unit of mass is the kilogram, but in chemistry the smaller gram (G) is ofter used - 1kg = 1000 g - Atomic mass unit - Temperature - There are two temperature scales used in chemistry: - the Celsius scale (C) - Freezing point (water) = 0 - Boiling point (water) = 100 - The kelvin scale - The absolute scale - Lowerst possible temperature is 0 K - K=C + 273.5 - The Fahrenheit scale is common in the US - Freezing Point (water) = 32 - Boiling point (water) = 212 - Temp in F = (9/5 x Temp in C) + 32 - Derived Units: Volume and Density CHEM - There are many units (such as volume) that require units not uncluded in the base SI units - The derived SI unit for volume is the meter cubed (m^3) - A more practical unit for volume is the liter (L) - The density of a substance is the ratio of mass to volume - D= Density - M= Mass - V= Volume - d=m/v - SI- derived unit: kilogram per cubic meter (kg/m^2) - Common units based on state of matter - There are two types of numbers used in chemistry - 1) Exact numbers - are those have defined values - are those determined by counting - 2) Inexact numbers - measured by any method other than counting - Uncertainty in measurement - An inexact number must be reported so as to indicate its uncertainty - Sig Figs are the meaningful digits in a reported number - The last digit in a measured number is referred to as the uncertain digit - The number of sig figs can be determined using the following guidelines - 1) any non-zero digit is significant - 112.1 (4 sig figs) - 2) Zeros between non zero digits are significant - 305 (3 Sig figs) - 50.08 (4 sig figs) - 3) Zeros to the left of the first nonzero digits are not significant - .0029 (2 Sig Figs) - 4) Zeros to the right of the last nonzero digit are significant if a decimal is present - 1.200 (4 sig figs) - Zeros to the right of the last nonzero digit in a number that does not contain a decimal point may or may not be significant - 100 (1,2, or 3 – ambiguous) - Calculation with measured numbers - In addition and subtraction, the answer cannot have more digits to the right of the decimal point than any of the original numbers - In multiplication and division, the number of sig figs in the final product or quotient is determined by the original number that has the smallest number of sig figs - Calculations with measured numbers - Exact numbers can be considered to have an infinite number of sig figs and do not limit the number of sig figs in a result - In calculations with multiple steps, round at the end of the calculation to reduce any rounding errors CHEM - If the 1 digit to be dropped is less than 5, round down st - If the 1 digit to be dropped is more than 5, round up (add 1) - Accuracy and Precision - Accuracy tells us how close a measurement is to the true value - Precision tells us how close a series of replicate measurements are to one another - Conversion factor is a fraction in which the same quantity is expressed one way in the numerator and another way in the denominator - -
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