introduction: matter and measurement sc 131 chem 1 chemistry: the central science cm lamberty

Introduction: Matter and

Measurement

SC 131 CHEM 1 Chemistry: The Central Science

CM Lamberty

Homework Chapter 1 Exercises (p 31-35)

12, 14, 18, 20, 22, 24, 26, 28, 30, 32 36, 40 42, 46, 48a, 50, 52 56, 58, 60, 62, 65, 68, 71, 72, 78

Chemistry The study of materials and the changes

that materials undergoes Where is chemistry present in your life?

The Study of Chemistry The Atomic and Molecular Perspective Matter

Anything with mass and occupies space Property

Characteristic that helps recognize a type of matter and distinguish from other types

Elements 100+ basic substances that make up matter

either alone or in various combinations

The Study of Chemistry Atom:

submicroscopic particles Fundamental building blocks

Molecules Two or more atoms joined in specific geometric

arrangement Bonds

Electronic force that holds atoms together in molecule

The Study of Chemistry Why Study Chemistry?

Impacts daily lives Informs citizens Fulfills curriculum requirements

Classification of Matter Substance: specific instance of matter Solid: mq close and little movement

Fixed volume, rigid shape Crystalline or amorphous

Liquid: mq close but free to move Fixed volume, no fixed shape

Gas: mq far apart, compressible No fixed volume, no fixed shape

Classification of Matter

Classification according to Composition Kinds and amt of substances that make up

matter Pure substance: single type of atom/mq

Element—cannot be broken down further Compound—can be broken down into elements

Fixed definite composition

Mixture Heterogeneous Homogeneous

Physical & Chemical Properties Physical Property—displays w/o changing

appearance Examples

Chemical Property—only displayed by changing composition Examples

Physical & Chemical Changes Physical Change

Alter only appearance not composition

Ex

Chemical Change Composition changes Ex

Separation of Mixtures Individual sorting by color or shape Use of physical properties

Magnetic Filtration Distillation Chromatography

Chemical reactivity One substance reacts while the other does not.

Need to be able to get back original substance.

The Scientific Approach to Knowledge Empirical

Observation and experimentation Hypothesis

Tentative explanation of observations Experiments

Highly controlled experiments reproducible

Theory Well-established hypotheses

Scientific Law Summarize past observations and predicts future ones

Units of Measurements International System of Units (SI)

Length m m

Mass Kilogram kg

Time Second s

Temperature Kelvin K

Amt of Subst Mole mol

Electric current Ampere A

Luminous intensity Candela cd

Length and Mass Length

Meter Distance light (598 nm) travels in 1 second Just a bit more than a yard

Mass Amount of material in an object Not weight (which is a force) 1 kg ~ 2.2 pounds Cube of Platinum in Sorbonne????

Temperature Hotness or coldness of an object Direction of heat flow Heat flows from higher T to lower T

spontaneously Celsius and Kelvin

Kelvin is absolute scale and does not have negative values

Conversion Factor °F = 1.8(°C) + 32 K = °C + 273.15

Derived Units Combination of other units Volume—amount of space matter occupies

Vol of cube = (edge length)3

Liter or milliliter (L or mL) for liquids

Density—mass per unit volume Density = mass/volume = m/V

Intensive vs. Extensive Properties Intensive—independent of the amount of

substance

Extensive—dependent upon the amount of substance

Uncertainty in Measurement Precision vs. Accuracy

Precision is measure of how closely individual measurements agree with one another

Accuracy is how closely measurement agrees with the correct or “true” value

Perform several trials and average the results Standard deviation reflects how much results

differ from average Significant Figures

Uncertainty in Measurement Scientific measurements are

reported so that every digit is certain except the last, which is estimated.

Uncertainty in Measurement Significant Figures—only for measured

values The greater the number of significant figures,

the greater the certainty fo the measurement Exact Numbers—actual counts

No uncertainty, unlimited sig fig

Significant Figure Rules All nonzero digits are significant Interior zeros are significant Leading zeros are not significant Trailing zeros

After decimal point always significant 3.9000

Before decimal point are significant 40.00

Before implied decimal point are ambiguous 1200 use sci notation 1.200 x 103 or 1.20 x 103

Significant Figures in Calculations Multiplication/division—result uses fewest

number of sig fig Addition/subtraction—fewest number of

decimal places Rounding—4 or less round down, 5 or

greater round up Round at the end of all calculations not

individual steps Calculators are stupid & do not know rules

Solving Chemical Problems Generally 2 types:

Unit conversion (dimensional Analysis) or specific equation

Dimensional Analysis

Calculate the displacement of a 5.70 L automobile engine in cubic inches

Watch units raised to a power and account for that mathematically

General Problems Solving Strategy Identify starting point (given info) Identify the end point (what you want) Devise a way to get from start to end—

conceptual plan

Sort Strategize Solve Check