General Chemistry Lecture Week One
General Chemistry Lecture Week One CHEM103090
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This 6 page Class Notes was uploaded by Nina Drachman on Tuesday September 15, 2015. The Class Notes belongs to CHEM103090 at University of Delaware taught by Graves PhD,Kimberly Susan in Fall 2015. Since its upload, it has received 103 views. For similar materials see General Chemistry in Health and Human Services at University of Delaware.
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Date Created: 09/15/15
Question Chemistry Lecture Sep 1 Is it safe to drink the water How do we solve problems Problem PACER Paraphrase the question of problem 0 Ex How can we tell if the water is safe Analyze the question and the given information 0 O 0 Ex What information do we need to answer this ques on Identify key concepts and skills required to solve problem and assemble information needed What information do we have the algae is causing the water to become unsafe What information do we need what kind of algae is it what is the risk what caused the algae to grow what is the level of algae in the water at what level is the water safe What is the major toxin being produced by the algae microcystinLR Why can t we boil molecule with smaller atoms are easier to boil microcystinLR has too many atoms in it What are the acceptable levels of microcystinLR in drinking water only a very very small amount one microgram What levels of microcystinLR were present in drinking water 25 x lOquot3 ppm parts per million Connect your given to your goal 0 O 0 Evaluate information and relationships or connections sometimes units will help identify steps needed to solve the problem We know the limit that s allowed is one microgram per liter and we have 25 x lOquot3 1 ppm 1 mgl L x water Execute your plan 0 25 x lOquot3 ppm 25 x lOquot3 mgl L x water o 25 x 10quot3 mg 0025 o 0025 mg 25 microgram 1 mg 1000 O microgram Answer 25 micrograml L x water Reality check 0 O O 0 Is the answer reasonable Are the units correct The limit 1 microgramL we found 25 microgramsL Value isn t negative Same order of magnitude as known value Chem Lecture Sep 3 Chapter 1 Seashore mallow have potential to generate biofuels Jack Gallagher at UD Lewes campus is investigating Harvesting challenging with Raps weed seeds Focus question How can we separate these harvests Properties of Matter Physical property 0 Property of a substance that can be observed without changing it into another substance 0 Ex luster hardness color etc Chemical property 0 A property of a substance that can be observed only by reacting it to form another substance 0 Ex ammability lntensive does not depend on the amount Extensive does depend on amount Classes of Matter Types of matter 0 Pure substance Same physical and chemical properties throughout Cannot be separated into simpler substance by a physical process 0 Mixture Combination of two or more pure substances Can be separated by physical processes Pure Substances Can be either an element or a compound Compounds follow the Law of Constant Composition 0 All samples of a particular compount contain the same elements combined in the same proportions 0 Water H20 Consists of two units of hydrogen H combined with one unit of oxygen 0 Elements and proportions are represented by chemical formulas Not a mixture Chemical Formulas 0 Chemical bonds link atoms together to make molecules 0 Arrangement of atoms can be represented in four ways Chemical Reactions 0 Separation of a pure substance requires a chemical reaction The transformation of a one or more pure substances into difference substances 0 Chemical equation Use chemical formulas to express the identities of substance involved in a reaction Use coef cients to indicate quantities of substance involved in a reaction Separating Pure Substances o For water apply electrolysis 0 Both H2 and 02 are gases g 0 Compound water H20 a liquid Mixtures Homogenous 0 Components are distributed uniformly throughout the sample and have no visible boundaries or regions 0 Ex a solution dissolving something into water can t see a difference tea Heterogeneous 0 Components are not distributed uniformly and may have distinct regions of different composition 0 Ex mixing water and oil Separating Mixtures Constituents in a mixture can be isolated by physical means no chemical reactions needed 0 Filtration process for separating particles from a liquid or gas by passing the mixture through a medium that retains the particles How can we separate seashore mallow and raps Use the density physical property to separate How much quotstuffquot we have in the volume How closely packed inside Intensive property no matter how much we have we ll still have the same density Density of water is 10 gmL Density ratio of mass of an objectsubstance to the volume of the objectsubstance Density massvolume Common units of density gmL gcmquot3 kgL 1 cmquot3 1 mL Making Measurements Measurements 0 Essential for characterizing physical and chemical properties of matter 0 Two parts of every measurement number and unit Changing Units Conversion Factors Unit conversion factor 0 Fraction in which numerator and denominator represent equivalent quantities but are expressed in dif units 0 1 km 06214 mi 1km06214 mi or 06214 mi1 km 0 Converting a value from one unit to another initial units x desired unitsinitial units desired units Uncertainty in Measurements All measurements contain uncertainty 0 Depends on instruments used to make measurement 0 A digit that must be estimated is called uncertain last recorded digit Signi cant Figures Includes all digits known with certainty plus one digit that is uncertain Rules for counting sig gs 0 All nonzero integers are signi cant 0 Zeros depends on location Trailing zeros Captive zeros o Exact numbers 0 Ex 004550 signi cant General Rules for Sig Figs Rounding off 0 Drop insigni cant digits 0 Only at the end of calculations quotWeakest linkquot principle 0 The number of sig gs in the nal results cannot be greater than the quotweakest linkquot used in the calculation Practice Using Density Density of Ti is 45 gcmquot3 What is the volume of 720 g of Ti in cmquot3 Put both the seeds in water the mallow will sink because of different densities raps will oat
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