Lecture Notes on Chemistry

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ShawnPacinocal,United States,Researcher
Published Date:09-07-2017
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The Role of Chemistry as a Prerequisite Course Key facts and results: Fact: The problem solving skills routinely utilized in the ‘high IQ’ and related professions (such as nursing, business management, accounting, etc.) are introduced, learnt and mastered during physical science courses. Result: Professional programs and subsequent employers insist that their candidates have a background in one of the physical sciences – both for specific (allied health, engineering) and general (your family room carpet) reasons. Fact: Study within any of the ‘high IQ fields’ will increase cognitive skills, but only the physical sciences do so via the study of fundamental, everyday phenomena so are of broad relevance and interest (we all interact with and benefit from the manipulation of matter on a daily basis after all). Result: Chemistry (and physics) may be considered to be the ‘gatekeepers’ of cognitive learning – chemistry in particular introduces, develops and subsequently equips students with cognitive skills necessary to succeed in their chosen careers Take home message: While the direct relevance of chemistry to your chosen course of study may at times seem tenuous, remember that the cognitive skills developed during such programs of study are of significant importance to your professional development and employability. In essence, this is why you are here. 5 How Chemistry is Perceived & Skills Needed to Succeed in Chemistry How Chemistry is Perceived: Discussion: How did your friends and family respond when you told them you were taking a chemistry course this semester?? “Frank” slide Study Skills Needed to Succeed in Chemistry: Fact: As discussed above, chemistry is all about the student developing and learning to apply problem solving skills - your study habits should reflect this. Do NOT fall in to the trap of believing you can learn chemistry simply by memorizing the information from your text – you must practice applying this information, not just be familiar with it. Result: Successful chemistry students typically spend most of their independent study time working assigned problems, not just reading about them. To learn chemistry you must do chemistry is a truism worth remembering. An analogy would be this: you read all the books out there on the subject of golf, but don’t get round to swinging a club – what do you think happens when you tee off for the first time? Fact: Chemistry relies on a cumulative method of learning, i.e. theories learnt from week 1 onwards will be repeatedly applied all the way through the course. Thus, it is important that the student does not let any ‘gaps’ in their knowledge develop. This fact exemplifies the differences in philosophy between the sciences and arts, as art courses are often more modular in nature. Example: I overhead a student tell another: “Yeah, I blew off reading the first book in my English class, but read the second one and got a ‘B’”. This method of study is not recommended in chemistry 6 Analogy: Building a tower Result: Successful chemistry students typically have exemplary attendance records. In some cases they may not be the ‘best’ students, but guarantee themselves a better grade than more capable students, who in turn typically may miss as few as one or two lecture sessions (this is especially true with regard to 3 hr. class sessions). Pictorial analogy of attendance vs cumulative knowledge ‘I missed a lab’ ‘I missed a lecture’ ‘I missed a couple of lectures’ Don’t ‘Swiss cheese’ or ‘torpedo’ your chances of passing the course because of missed work Take home message: Simply by attending class regularly and completing the HWK assignments you essentially guarantee yourself a passing grade for the course, while, due to the nature of the material, deviating from this approach may ensure the opposite 7 Chemistry in action: Explaining what happens on your BBQ grill. The burning of a charcoal brick on your backyard grill (MACRO) explained in terms of a balanced chemical equation (MICRO) ANY large (MACRO) scale chemical process can be described using a MICRO scale chemical equation featuring individual atoms and/or molecules A cartoon representation of the reaction of the pertinent atoms and molecules; along with the Chemists’ description – a balanced chemical equation illustrating a single microscopic event. Cartoon Balanced Equation This process is repeated many billions of times (MICRO) for the burning of a charcoal briquette (MACRO) 12 The Components of Matter Reading: Ch 1 sections 1 - 5 Homework: Chapter 1: 37, 39, 41, 43, 45, 47, 49 = ‘important’ homework question Review: What is matter? Recall: “Chemistry is the study of matter and its properties, the changes matter undergoes and the energy associated with those changes” Recap: There are 3 stable states of matter – solid (s), liquid (l) and gas (g). 13 Specific macro- and microscopic physical properties define the three states of matter State of Matter Macroscopic Description Microscopic Description (observation) (chemical model) Solid Liquid Gas The state matter is in depends on the strength of the forces (chemical bonds) between the individual microscopic particles within the matter Task: Rank the intermolecular forces present in steam, ice and water in order of increasing strength. Use the included figures as a guide. Ranking 14 Changing between the 3 states of matter Describe the relationship between the mpt. and bpt. of matter, with regard to microscopic processes, occurring at these specific temperatures Example: The boiling of water to make steam ( H O →( H O ) 2 (l) 2 (g) 15 Physical and Chemical Properties – what’s the difference? Analogy: We all posses ‘as is’ physical properties, or characteristics, that define us. For example, Dr. Mills is 5’11” and has green eyes. As with people, each chemical also possesses a unique set of ‘as is’ physical properties that define it. For example, water is a clear, colorless, tasteless o o molecular material that has a fpt. of 0 C and a bpt. of 100 C. Chemical Properties, in contrast, are a function of change (usually associated with a chemical reaction). For example, Iron (Fe) reacts with oxygen gas to form rust: 4 Fe (s) + 3 O (g) → 2 Fe O (s) 2 2 3 Task: Identify the flowing as either chemical or physical properties Property Chemical or Physical Diamond is the hardest known substance. Charcoal burns to make CO (g) 2 The statue of liberty turned ‘green’ Copper is a good conductor of electricity Sugar dissolves in water Melting of ice Think up two more chemical properties of your own 16 Elements and Compounds – the further classification of pure matter Task: State which of the following are elements, and which are compounds. When done, try to come up with a definition of what elements and compounds are. Material Chemical Formula Element or Compound? Water H O (l) 2 Oxygen gas O (g) 2 Pure silver coin Ag (s) Sugar crystals C H O (s) 6 12 6 Carbon dioxide gas CO (g) 2 Elements: Compounds: 17 Compounds and elements can have either ‘giant’ or molecular structures: ‘Giant’: Repeating lattice of particles – usually strongly bound (high mpt.) solids. Examples: sand (SiO ), diamond (C), table salt 2 (NaCl) Molecular: a collection of independent molecular units (molecules will be discussed in more detail later). Usually (low mpt) liquids or gasses at room temp. Definition: Molecule – a small, independent particle of matter made up from 2 or more atoms Examples: water (H O), carbon dioxide (CO ), 2 2 Nitrogen gas (N ) 2 Think of molecules like cars on the expressway – each car (molecule) is a separate, independent unit that contains a number of passengers (atoms). The cars (molecules) are free to move while the people (atoms) stay fixed inside. ‘Giant’ materials are like people (atoms) ‘locked’ in place at a very crowded concert, the DMV waiting room etc…… 18 Review: A microscopic scale view of several materials is presented below. Label each using elemental or compound and molecular or ‘giant’ tags Water (H O (l)) Silicon (Si (s)) 2 Steam (H O (g)) Sodium Chloride (NaCl) 2 Details: Ice is a solid (crystalline) form of water (a molecular compound). How would you describe the structure of ice? Can you think of other similar examples? More Details: Allotropes of an Element Example: Carbon C C C (diamond) (graphite) 60 19 Pure Matter v Mixtures Recap: Pure matter is classed as either an ELEMENT or a COMPOUND. Elements can have either Molecular or ‘giant’ structures. Examples: N (g) (Nitrogen gas, molecular), Pb(s) (metallic 2 lead, a ‘giant’ structure) Compounds can also have either Molecular or ‘giant’ structures. Examples: H O(l) (water, molecular), Fe O (s) 2 2 3 (‘rust’ (iron oxide), a ‘giant’ structure) Recall: A molecule is an independent unit containing two or more atoms. Remember the car / passenger analogy. Molecules can exist as either elements or compounds Mixtures ANY combination of different types of pure matter ‘placed together’ is defined as a mixture (eg. air, milk, pepsi). Mixtures are NOT pure materials. eg. Pure gold (Au) vs ‘white’ gold (Au+ Ag), or water (H O) vs pepsi (H O + 2 2 sugar….) Discussion: Air contains a number of different components – what are they? How would you describe what air is made up from using words like element, compound, gas, molecular etc.? 20 Task: Assign generic labels that describe to microscopic scale matter shown on the slide (e.g. ‘gaseous atomic element’ etc.) Mixture Types As viewed from a macroscopic perspective, mixtures are classified as either HOMOGENEOUS or HETEROGENEOUS HOMOGENEOUS MIXTURES: Examples: HETEROGENEOUS MIXTURES: Examples: 21 Discussion: Can you think of something that is both a homogeneous mixture and a solid? A Bronze statue of Caesar Augustus Examples of Alloys: Classification of Matter Flowchart (Dr. Mills really likes this slide – why? Hint: Recall the fundamental job of a chemist) 22 Task: Use the ‘Classification of Matter’ flowchart (above) to classify the following: 1. The compressed gasses in a deep sea diver’s gas bottle (He(g) and O (g)) 2 2. A ham and cheese omelet 3. An ice cube (made from pure water) 3+ 4. A ruby (Al O (s) with Cr impurities) 2 3 Extra Credit: Ask me about the separation of mixtures assignment (based on background reading) 23 Units of Measurement Reading: Ch. 1 sections 6 & 7 Homework: Chapter 1: 51, 55, 57, 59, 61, 65, 67, 69, 71, 75, 77, 81, 83 = ‘important’ homework question Common Units Discussion: List some common units of measurement we use on a daily basis. How did these units originate? Quantity measured Familiar Unit Mass Question: What are the ‘metric’ (S.I.) versions of the everyday units listed above? Quantity measured Fundamental S.I. Symbol Unit (base unit) Notes: SI base units are used to determine derived S.I. units, as discussed below. Some S.I. base units feature a decimal prefix – which one(s)? 25 Derived S.I. Units Insert appropriate S.I. base units into an equation that defines the respective derived S.I. unit desired. Example: 2 Area = length x length = m x m = m 2  the derived S.I. unit for area is m Determine derived S.I. units for the following quantities Quantity measured Math involving S.I. base units Derived S.I. unit Volume Velocity (speed) Density Force Energy These are harder examples. To solve them start by inserting appropriate S.I. base units into an equation that defines the quantity sought. Discussion: Why do scientists prefer the S.I. system? 26 Questions: 3 Is the S.I. unit of volume (m ) reasonable for everyday applications? Why? What unit of volume do chemists prefer? Why? 3 1 dm = 1 L More detail on the chemist’s volume unit 27 Scientific Notation and S.I. Prefixes Large Quantities Fact: Chemical problem solving most often involves using either very large or very small numbers (e.g. counting the number of molecules in a drop of water, or quoting the mass of the water drop in kilograms) Recall: How many individual H O (l) molecules are there 2 in a drop of water. Write this amount as a regular number: Number H O (l) molecules in 1 drop water = _____________________________ 2 Problem: How do we represent and manipulate such quantities in an ‘easier’ way? Answer: Overview Example: Consider the statement “eight million people live in London”. How can this quantity be best expressed numerically? ‘Everyday’: ‘Better’: 28