Chemistry Unit 1. Chapter 1 Chemical Overview

Transcription

1 Chemistry Unit 1 Chapter 1 Chemical Overview

2 Chemistry Unit 1 Section 1 Overview Scientific Method Measurement Significant Figures Dimensional Analysis

3 A main challenge of chemistry is to understand the connection between the macroscopic world that we experience and the microscopic world of atoms and molecules. You must learn to think on the atomic level. Chemistry: study of the composition, structure, and properties of matter and the changes it undergoes

4 Chemical Elements Handout

5 Branches of Chemistry Organic Chemistry Inorganic Chemistry Physical Chemistry Analytical Chemistry Biochemistry Theoretical Chemistry

6 Atoms vs. Molecules Matter is composed of tiny particles called atoms. Atom: smallest part of an element that is still that element. Molecule: Two or more atoms joined and acting as a unit.

7 This should be review from all previous science courses you have ever taken. Read and know Section 1.2 from the book.

8 Measurement - Quantitative observation consisting of two parts number scale (unit) The Fundamental SI Units Physical Quantity Name of Unit Abbreviation Mass kilogram kg Length meter m Time second s Temperature kelvin K Electric current ampere A Amount of substance mole mol

9 Prefixes Used in the SI System Prefixes are used to change the size of the unit.

10 Prefixes Used in the SI System You are expected to be able to convert measurements from kilo- to milli- You will be given the conversion for prefixes that are larger or smaller

11 Derived Unit combinations of other SI base units Area - Length x Width (unit: length 2 ) Volume - Length x Width x Height 1 dm 3 = 1 cm 3 = 1 L 1 ml = 1cc (unit: length 3 )

12 A measurement always has some degree of uncertainty. A digit that must be estimated is called uncertain. The last number of a measurement is called the Number of Uncertainty

13 Measurement of Volume Using a Buret The volume is read at the bottom of the liquid curve (meniscus). The Meniscus of this liquid occurs at about ml Certain digits: Uncertain digit: 20.15

14 Precision and Accuracy Accuracy Agreement of a particular value with the true value. Precision Degree of agreement among several measurements of the same quantity.

15 Precision and Accuracy

16 Exponential Notation (Scientific Notation) M x 10 n where 1 M<10 Two Advantages Number of significant figures can be easily indicated. Fewer zeros are needed to write a very large or very small number.

17 Rules for Determining Significant Figures 1. Nonzero digits are always significant. 2. All final zeros after the decimal point are significant. 3. Zeros between two other significant digits are significant. 4. Zeros used only as placeholders are NOT significant. 5. Exact numbers have an infinite number of significant figures.

18 Significant Figures in Mathematical Operations 1. For multiplication or division, the number of significant figures in the result is the same as the number in the least precise measurement used in the calculation. (always round to the amount) 2. For addition or subtraction, the result has the same number of decimal places as the least precise measurement used in the calculation. (always round to the amount) Note: follow order of operation when solving problems.

19 Example #1 How many seconds are there in 1 month? Assume there are 31 days in a month Show your work

20 Use when converting a given result from one system of units to another. (Start with what you are given) To convert from one unit to another, use the equivalence statement that relates the two units. (Use true statements that you know) Derive the appropriate unit factor by looking at the direction of the required change. (Let the units guide you) Multiply the quantity to be converted by the unit factor to give the quantity with the desired units. (Multiply the top; multiply the bottom; top divided by the bottom)

21 Example #2 An iron sample has a mass of 4.50 lb. What is the mass of this sample in grams? (1 kg = lbs) 4.50 lbs 1 kg lbs 1000 g 1 kg 3 = g

22 Chemistry Unit 1 Section 1 Homework Set pg 32: #22, 24, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 47, 83, 85, 87, 93 (20)