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### Chapter 1

The Study of Chemistry

Topics

- Introduction
- Scientific Method
- Classifications of Matter
- Properties of Matter
- Units of Measurement – Metric system
- Temperature Conversion
- Metric Conversion (Prefixes)
- Accuracy vs. Precision
- Significant Figures
- Density

States of Matter

- Solid
- Liquid
- Gas
- Plasma

ATOM

- Is the simplest unit of matter.

Definitions

- Elements – can’t be decomposed further into simpler substances
- - 111 elements presently
- - Ds (element 110)
- - Rg (element 111)
- Compound – combination of 2 or more elements

Definitions

- Mixtures – combinations of 2 or more substances (ex. sugar in water)
- 2 Types of Mixtures
- 1. Homogenous Mixtures (solutions) = 1 phase
- 2. Heterogeneous Mixtures = > 2 phases

SOLUTIONS

- Homogeneous mixtures are called SOLUTIONS.

Solution

- Solution – homogenous mixture
- A solution is not necessarily a liquid. Can be gas or solid.

Physical vs. Chemical Properties

- Physical properties – can be measured w/o changing identity and composition of substance (ex. Boiling pt.,freezing pt., color, odor, density, hardness)
- Chemical properties – describe how substance reacts or changes to form other compounds (ex. Flammability, toxicity)

Changes of State and Properties

- Physical changes – does not change composition of compound
- Chemical changes – converts to a different chemical substance
- Intensive Properties – independent of amt. (ex. Density, Temperature, Melting Pt)
- Extensive Properties – dependent on amt. (ex. Mass, Volume)

Units of Measurement

- Mass – grams; kilogram
- Length – centimeter; meter
- Volume – milliliter or cubic centimeter (cm3)
- Temperature – Celcius; Kelvin

Prefixes in Metric System

- Mega - million
- Kilo - 1,000
- Hecto - 100
- Deka - 10
- ----- - 1 (liter, gram, meter)
- Deci - 1/10 or 0.1
- Centi - 1/100 or 0.01
- Milli - 1/1000 or 0.001

Temperature Conversions

- 0 oC = 273.15 K
- oF = 1.8 oC + 32

Things to Remember!

- 1 milliliter = 1 cc
- 1000 milliliter = 1 liter
- 0 oC = 32 oF = 273.15 K

Precision vs Accuracy

- Accuracy – when acquired value agrees with true value
- Precision – when acquired values exhibit reproducibility

Significant Figures

- More significant figures = more certainty
- Helps in determining how to round measured values and still precise

SIGNIFICANT FIGURES

- In counting and definitions, there are an infinite number of sig figs
- In measurements, the number of sig figs consists of all certain and the first uncertain digits
- Unit conversions do not determine # of sig. figs.

Rules of Significant Figures 2. Captive zeros are always significant.

- 1. Non-zero integers always count.
- Ex. 1234.5 grams = 5 Sig. Figs.

- Ex. 100.3 grams = 4 Sig. Figs.

Rules of Significant Figures 4. Trailing zeroes are significant ONLY if there is a decimal point

- 3. Leading zeros are NEVER significant.
- Ex. 0.6780 grams = 4 Sig. Figs.

- Ex. 12.0 grams = 3 Sig. Figs
- 120 grams = 2 Sig. Figs

Rules of Significant Figures

- 5. Exact numbers (obtained by counting) are infinite and do not determine the number of significant figures.
- Example: 4 cows = ?

Determine the # of Sig. Fig.

- 200.0
- 1050
- 3003
- 0.0006
- 10,000
- 0.5

Rules of Significant Figures

- Multiplication/Division
- Answer will have the same # of sig figs as the value with the least # of sig figs
- Ex: 3.8 x 200.0 = 2 Sig. Figs.

- Answer will have the same # of sig figs as the value with the least # of sig figs

Rules of Significant Figures

- Addition/Subtraction
- Answer has the same # of decimal places as the number with the least # of decimal places
- Ex. 3.1 + 2.500 + 5.76 = 11.4

Order of Operations

- Parenthesis
- Multiplication/division
- Addition/subtraction

Rounding

- Look only to the right of the number you are rounding to:
- - If 5 or more, round up
- - If less than 5, round down

General Rule

- Carry ALL figures through to the end of a problem. Round the final answer to the correct number of significant figures

Problem

- Indicate the number of sig. figs. in each of the following measured quantities:
- A. 358 kg
- B. 0.054 s
- C. 6.3050 cm
- D. 0.0105 L
- E. 7.0500 x 10-3 m3

Problem

- Round each of the following numbers to 4 sig. figs. And express the result in standard exponential notation.
- A. 102. 53070
- B. 656, 980
- C. 0.008543210
- D. 0.000257870
- E. - 0. 0357202

Problem

- Carry out the following operations and express the answer with the appropriate number of sig. figs.
- A. 12.0550 + 9.05
- B. 257.2 – 19.789
- C. (6.21 x 103)(1.1050)
- D. 0.0577 / 0.753

Density

- Is the amount of mass in a unit volume of the substance
- Is affected by Temperature.
- The higher the temp., the lower the density.
D = mass of substance = grams volume of substance mL or cm3

- The higher the temp., the lower the density.

Density

- Density = mass volume = gram mL

Different ways of calculating volume

- I. For solids with regular shapes:
- A. For a cube: Vcube = s3
- B. For a rectangular solid, V = L x W x H
- C. For a cylinder: V= pr2h
- D. For a sphere: V = 4/3 pr3

Different ways of calculating volume

- II. For an Irregular Solid
- Water displacement

Different ways of calculating volume

- III. For a liquid
- Use of graduated cylinder, beaker, pipet or buret.

Problem

- A cube of osmium metal 1.500 cm on a side has a mass of 76.31 grams at 25 oC. What is its density in g/cm3 at this temperature?

Problem

- The density of titanium metal is 4.51 g/cm3 at 25 oC. What mass of titanium displaces 65.8 mL of water at 25 oC?

Problem

- The density of benzene at 15 oC is 0.8787 g/mL. Calculate the mass of 0.1500 L of benzene at this temperature.

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