Chemistry I Honors/C101

Unit I: Matter and Scientific Calculations

*The material in Objectives # 1-3 should have been mastered in previous coursework. Demonstrations & Laboratory Exercises will be performed to review the material.

*You should be able to answer the questions listed in Discussion Worksheets 1 & 2. Ask for additional assistance if needed--these types of questions will appear on the unit test.

Objectives #1-6: Matter – Properties and Changes

*Review the list of elements/symbols and polyatomic ion names/formulas

*The list of symbols and names of elements should be memorized for the Unit 1 Test.

*The list of polyatomic ions should be memorized before we begin Unit 5.

Objectives #1-6: Matter – Properties and Changes

Classification of Matter

Matter

Pure Substances

Elements Compounds

Mixtures

Homogenous Heterogeneous

Matter - has mass and volumePure Substances - one type of matter, definite

compositionMixtures - more than one type of matter, no definite

compositionElements - can’t be broken down chemicallyCompounds - can be chemically broken downHomogeneous Mixtures (solutions) - can be

physically separated, uniformHeterogeneous Mixtures - can be physically

separated and not uniform

Objectives #1-5: Classification of Matter

Make any notes that will be helpful!

Demonstrations

Objective #6:Sections of the Periodic Table

The Periodic Table…

Groups: 1-18; Run vertically; similar chemical properties due to electron configurations

Periods: 1-7; Run horizontally; same number of energy levels to hold electrons of elements

Metals: Groups 1-16 (left of the stairstep line)Luster Conducts electricity Malleable Ductile High melting point Generally solids at room temperature

Types & Basic Characteristics of Elements

Nonmetals: Groups 13-18 (right of the stairstep line)Dull

Insulator Brittle Low melting point Exist as solids, liquids & gases at room temperature

Types & Basic Characteristics of Elements

Metalloids: Along the stairstep line, except Aluminum (#13) & Polonium (#84)

Have a somewhat metallic lusterSemi-conductorLess malleable than metals, but not brittleIntermediate melting pointsSolids at room temp

Types & Basic Characteristics of Elements

You should be able to solve the text problems listed below; please come in for help immediately if you need assistance; these types of problems will appear on quizzes and the unit test

P. 40 # 1-3 P. 59 # 7, 16, 19

P. 42 # 1,2,3,5 P. 60 # 43, 44P. 57 # 7, 8

Objectives #7-8:Basic Math Skills

Examples:1. What is the density of a block of marble that occupies

310. cm3 and has a mass of 853 g?

2. Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume .351 cm3?

Objective #9: Calculation of Density

Note that for water,

1 cm3 = 1ml, so these units

are used interchangeably in density calculations!

Refer to Lab 3 : Determining Density for further details on this topic!!

*All measurements contain some error; the quality of measurements can be determined by determining their: Accuracy-closeness of a measurement to the true value Precision- consistency of repeated measurements

*Accuracy can be measured by calculating the percent error

% Error = Observed Value – Actual Value x 100 Actual Value

Objectives #10-13Using Scientific Measurements

500 grams vs. 499 grams:

2 grams vs 1 gram:

Percent Error Examples

%2.100500

500499

grams

grams

%0.50100 2

21

grams

grams

SO…what does this tell us????1 gram difference can result in a large percent error. The purpose of Percent Error is to compare the error of measurement to the standard value so that lab procedures & techniques are modified as needed.

A positive value for percent error indicates that the data is HIGHER than the accepted values…

Possible causes: Impure product, Poor lab technique

How to fix: Clean glassware, follow procedure exactly, allow adequate drying time, preview & practice lab skills before using them during procedure

A negative value for percent error indicates that the data obtained is LESS than the accepted values…

Possible causes: Loss of chemical during transfer,

Poor lab technique, inaccurate measuring How to fix: Take time during procedure to

execute skills well, take average of

multiple measurements

Percent Error…

The goal of the chemist is to

obtain % Error as close to zero

as possible!!Note that 0% Error is rarely

obtained.

Precision can be determined by significant figures

Significant figures are all digits in a measurement known with certainty, plus the last digit that is estimated

In lab calculations, the number of sig figs in the answer must reflect the least precise instrument used

Using Scientific Measurements

Determining significant figures involves a set of rules as summarized on p.47 of text

Examples: 100, 100.01, .800, .00180, 1002

Practice Problems: 3.0 ____ .10004 ____ .0020 ____ 3000 ____ 2.4421 ____

Determining Significant Figures

Refer to Lab 1: Thickness of a Zinc Coating for further details on this topic!!

Dimensional Analysis is a problem solving technique that uses conversion factors to change one unit to another.

*Key Steps: Analyze (identify known and unknown) Plan Compute Evaluate (units, reasonable, sig. figs.)

What is a conversion factor?• An equivalent relationship that is expressed as a fraction. Ex: 1 kg = 1000 g 1 kg or 1000 g 1000 g 1 kg• Conversion factors are used to switch units within • comparable measurements.

Problem Solving in Chemistry—Dimensional Analysis

1. Convert 14 cm to meters.

2. Convert 1.47 X 10 5 mm to kilometers.

Dimensional Analysis Examples:

km. meter

km

mm

meter

meter

mm147

1000

1

1000

1

1

10 x 1.47 5

meter.cm

meter cm 14

100

1 14

3. A buret delivers .15 cm3 of water per second. How much time is required to transfer 18 grams of water? Assume 1 cm3 = 1 gram for water.

4.The density of an object is 7.5 g/ml. Calculate the mass in grams of a 1.2 L sample.

sec 120 15.

sec1

1 g 18

3

3

cmg

1 cm

g109.0 g 9000ml 1

7.5g

L 1

ml 1000 L 2.1 3