The due date is not the start date!

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1 element song wskfbpo&feature=related January 9 th, Chem 1A S Chem 1A S014 What do we say in chem. 1A? The due date is not the start date! If you have not taken and passed the chemistry 1A diagnostic placement exam, it is too late to do so. We will only add students that have passing diagnostic scores from F1 or S Chem 1A F Chem 1A S

2 Next week in disc: Monday / Tuesday Nomenclature Handout There will be an online Mastering Chemistry assignment this week for discussion covering dimensional Analysis & nomenclature Next week in Lab: Wednesday / Thursday Experiment 1 Practice Proficiency quiz Lab begins this week! Got goggles? No toes! Got lab coat? Got Gloves? Got pre lab? No pre lab, no lab! Chem 1A S Chem 1A S014 8 Chapter 1: Key Topics It s time to play Reading: Ch I will only cover a few examples of calculations l using unit conversions. lead (II) sulfide PbS Chapter : Key Topics Reading: Ch I will cover a few examples of calculations with isotopes and mole/mass concepts Chem 1A S014 9 potassium permanganate KMnO 4 ammonium nitrite NH 4 NO HC H O (aq) acetic acid BCl boron trichloride Chem 1A S014 10

3 Problem Solving in Chemistry: Chapter 1 Matter, Measurement, and Problem Solving Many of the problems you will solve in chemistry involves a technique called Dimensional Analysis. (Ch.1) Dimensional analysis converts one unit to another by using conversion factors. unit (1) conversion factor = unit () The resulting quantity is equivalent to the original quantity, it differs only by the units Chem 1A S Chem 1A S Problem Solving in Chemistry: When submitting written work in this class: Labs Quizzes Exams All work must be accompanied by units. The work given must show a logical progression towards the answer given. The answer must have units itself that match the work. There will be severe grading penalties if this is not the case! Example problem: A certain automobile has a fuel economy of miles/gallon. What is the same fuel economy in km/l? How do you start this problem? Ask what you need! What is given? How do these quantities relate? new distance and volume units miles and gallons miles can be converted to km gallons can be converted to L Now you are ready to set up the problem using dimensional analysis! Chem 1A S Chem 1A S014 16

4 Example problem: A certain automobile has a fuel economy of miles/gallon. What is the same fuel economy in km/l? The Plan: convert miles to km then gal to L miles ft in cm m km then gal L you should know these cf s look this up! miles 580ft 1in.54cm 1m 1km 1gal = km/l 1 gal 1mile 1ft 1in 10 cm 10 m.79l round to sig figs: 14 km/l Chem 1A S Problem solving in chemistry: You need to be systematic in your approach. You can t memorize every type of problem. Here is how you should approach solving problems: 1. Put your calculator l down.. Read the problem.. Read it again! 4. Identify the units needed. 5. Identify the units given. 6. Set up a conceptual plan for the solution. 7. Write down any conversion factors you might need. 8. Set up a conversion from the starting units to the needed units using dimensional analysis. 9. Now use your calculator! 10. Check for sig figs, order of magnitude and units Chem 1A S What the solution to a problem should look like! Examples of the wrong way to solve a problem: a plan in outlined sf s The correct sig figs are expressed in the answer: Notice that all units are written: Conversion factors cancel out the units! You also expect a large number! Chem 1A S014 0 No plan! No Units! Wrong cf s! No Partial Credit!?????? Chem 1A S

5 Examples of the wrong way to solve a problem: Examples of the wrong way to solve a problem: No credit! butt! No Credit! There is no credit for magically pulling an answer out of your Not E W ven rong Work does not match! See me in my office ASAP... Dr. Mack Correct answer Chem 1A S Chem 1A S014 Example problem: The aluminum in a package containing 75ft of foil weighs 1 oz. If the density of aluminum is.70 g/cm, what is the thickness of the foil in mm? How do you start this problem? Ask what you need! What is given? How do these quantitiesrelate? mass and density give volume The thickness of the foil. area, mass and density volume and area give thickness! Now you are ready to set up the problem using dimensional analysis! Chem 1A S014 4 Example problem: The aluminum in a package containing 75ft of foil weighs 1 oz. If the density of aluminum is.70 g/cm, what is the thickness of the foil in mm? you may need to look up some First find the total volume of the foil: conversion factors! 8.4 g cm 1 oz = 16 cm 1 oz.70 g Next find thickness from volume and area: volume 16 cm 10 mm area 1 in.54 cm 1 cm Keep the extra sig figs and round at the end. thickness = = = mm 75 ft 1ft 1 in Chem 1A S

6 It s time to play What is the area of a circle? What is the volume of a cylinder? What is the volume of a sphere? How many feet are in a mile? A = πr V = L πr 4 V = r π 580 ft = 1 mile You should know these and many other general knowledge facts from your K 1 education! Chem 1A S014 8 I will place another dimensional analysis problem in the notes that is not covered in class Chem 1A S014 9 Example problem: A certain wire alloy has a density of 7.65 g/cm. What length (m) of wire corresponds to 5.0 lbs of the wire if the radius is 0.55 mm? First one must realize that the wire is cylindrical in shape. Example problem: A certain wire alloy has a density of 7.65 g/cm. What length (m) of wire corresponds to 5.0 lbs of the wire if the radius is 0.55 mm? Conceptual Plan: use density as a conversion factor radius mass volume length (knowing the radius) length Chem 1A S014 0 You should know this from high school Chem 1A S014 6

To find the length of the wire, begin with volume: mass is related to volume by density: solving for volume: V= L π r m d = V m V = d m setting the two equal: L π r = d solving for L: mass L = d πr A

7 To find the length of the wire, begin with volume: mass is related to volume by density: solving for volume: V= L π r m d = V m V = d m setting the two equal: L π r = d solving for L: mass L = d πr A certain wire alloy has a density of 7.65 g/cm. What length (m) of wire corresponds to 5.0 lbs of the wire if the radius is 0.55 mm? Plugging in the values... L = 5.0 lb 1kg.05 lb L = mass Watch your units, d πr conversion factors are needed! 10 g 1kg g (1cm) 7.65 π (0 (0.55mm) cm (10 mm) 1m 10 cm = m or m ( sig. fig.) Chem 1A S Chem 1A S014 5 Chemical Symbols: What we observe To what we can t see! Chapter Atoms and Elements Chemical symbols (H O) allow us to connect Chem 1A S Chem 1A S

Where do we begin The Periodic Table Why do we call it the Periodic Table?

modern organization of the periodic table came about as a result of the work of Dimitri Mendeleyev The Periodic Table:

similar properties in the same column Periodic Law when the elements are arranged in order of increasing i atomic mass,

8 Where do we begin The Periodic Table Why do we call it the Periodic Table? Because, periodically, we use it in chemistry Chem 1A S Chem 1A S014 9 The Modern Periodic Table The modern organization of the periodic table came about as a result of the work of Dimitri Mendeleyev The Periodic Table: Metals and Nonmetals Characteristics: Ordered elements by atomic mass Repeating pattern of properties Elements with similar properties in the same column Periodic Law when the elements are arranged in order of increasing i atomic mass, certain ti sets of properties recur periodically. Patterns used to predict properties of undiscovered elements Chem 1A S Metals Chem 1A S

The Periodic Table: Metaloids The modern periodic table is defined by: Groups

4 1-9-14 Chem 1A S014 4 Chemical Symbols and Formula: Tin is in group 4A (14) in the 5

Elements: H = hydrogen O = oxygen C = carbon Molecules: H = hydrogen some of the names

9 The Periodic Table: Metaloids The modern periodic table is defined by: Groups (families) (columns down) Periods (rows across) aka: Semiconductors Chem 1A S Chem 1A S014 4 Chemical Symbols and Formula: Tin is in group 4A (14) in the 5 th period. Elements: H = hydrogen O = oxygen C = carbon Molecules: H = hydrogen some of the names are not systematic! O = O H O = CH 4 = oxygen water methane Uh Oh! this is confusing Yes it is Get over it and get used to it! Chem 1A S Chem 1A S

10 To pass this class: You are required to develop a working knowledge of Chemical Nomenclature Chem 1A S How do I remember all of these things: 1: Memorize the common elements and their symbols: How many? As many as possible! : Complete the worksheets provided on the web site. Do extra homework problems. : Make up flash cards and practice with your classmates, friends or family. Practice Chemistry is really: Practice Chem is try Practice Chem 1A S

10. How many significant figures in the measurement g? a. 2 b. 3 c. 4 d. 5 e. 6

10. How many significant figures in the measurement g? a. 2 b. 3 c. 4 d. 5 e. 6 Summer Practice Test Ch 1 (va pg 1 of 5) Matter and Measurement Name Per You should NOT use a calculator except for #0. This practice test should be in your 3 ring notebook on the first day of school.