Chapter 1: Matter, Measurement, and Problem Solving – General Chemistry Study Notes

Units of Measurement for Physical and Chemical Change

Introduction to Chemistry

Chemistry is the science that seeks to understand the properties and behavior of matter by studying the properties and behavior of atoms and molecules. It is foundational to many scientific disciplines and has applications in fields such as medicine, engineering, environmental science, and more.

• Atoms: Submicroscopic particles that are the fundamental building blocks of all matter.

• Molecules: Two or more atoms bonded together in a specific geometric arrangement.

• Matter: Any substance that has mass and takes up space.

Chemical Alphabet: Atoms and Elements

Atoms and the Periodic Table

Atoms are composed of protons, neutrons, and electrons. Each element is defined by the number of protons in its nucleus (atomic number). The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties together.

• Element: A substance that cannot be broken down into simpler substances by chemical means.

• Periodic Table: A chart that organizes all known elements according to their properties.

Molecules and Compounds

Structure and Properties of Molecules

Molecules are formed when two or more atoms are bonded together. The composition and structure of molecules determine their chemical and physical properties. For example, sodium chloride (NaCl) is a compound formed from sodium and chlorine atoms.

• Chemical Bond: The force that holds atoms together in a molecule.

• Compound: A substance composed of two or more different elements chemically bonded together.

• Example: NaCl (table salt) is made from sodium (Na) and chlorine (Cl).

Physical and Chemical Properties of Matter

Qualitative and Quantitative Observations

Observations in chemistry can be qualitative (descriptive, using senses) or quantitative (measurable, using instruments).

• Qualitative: Color, odor, texture, etc.

• Quantitative: Mass, volume, temperature, etc.

Physical vs. Chemical Properties

Physical properties can be observed without changing the substance's chemical identity, while chemical properties describe how a substance interacts with other substances.

• Physical Properties: State, color, melting point, boiling point, density, luster, etc.

• Chemical Properties: Reactivity with oxygen, acidity, flammability, toxicity, etc.

Physical and Chemical Changes

Types of Changes in Matter

Changes in matter are classified as physical or chemical. Physical changes alter the form or appearance but not the composition, while chemical changes result in the formation of new substances.

• Physical Change: Melting, freezing, condensation, vaporization, sublimation, deposition, dissolving.

• Chemical Change: Rusting, burning, reacting with acids or bases.

Signs of Chemical Change

• Bubbles of gas appear

• Precipitate (solid) forms

• Unexpected color change

• Energy change (heat or light)

• Change in electrical conductivity

• Change in melting/boiling point

• Change in odor or taste

Energy and Matter

Types of Energy

Physical and chemical changes are often accompanied by energy changes. Energy can be classified as kinetic (energy of motion) or potential (energy due to position or composition).

• Kinetic Energy (KE): $KE = \frac{1}{2}mv^2$

• Thermal Energy: Related to temperature and molecular motion.

• Potential Energy (PE): $PE = mgh$ (gravitational), $PE = \frac{1}{2}k x^2$ (spring)

• Chemical Energy: Associated with the arrangement of electrons and nuclei in atoms and molecules.

Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Measurement and Units

SI Units and Measurement Standards

Measurements in chemistry use the International System of Units (SI). Each measurement consists of a number and a unit.

Quantity	Unit	Symbol
Length	meter	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Amount of Substance	mole	mol

Mass vs. Weight

• Mass: Amount of matter in an object (measured in kg).

• Weight: Force of gravity on an object (measured in newtons, N).

• Weight depends on location (e.g., Earth vs. Moon), mass does not.

Temperature Scales

• Celsius (°C): Water freezes at 0°C, boils at 100°C.

• Kelvin (K): Absolute temperature scale. $T_K = T_C + 273.15$

• Fahrenheit (°F): $T_F = (9/5)T_C + 32$

Scientific Notation and Prefix Multipliers

Expressing Numbers

Scientific notation is used to express very large or very small numbers. Prefix multipliers are used in the metric system to indicate powers of ten.

• Scientific Notation: $N \times 10^n$ (N is a number between 1 and 10, n is an integer)

• Prefix Multipliers: kilo (k, $10^3$), centi (c, $10^{-2}$), milli (m, $10^{-3}$), micro (μ, $10^{-6}$), etc.

Prefix	Symbol	Multiplier
kilo	k	$10^3$
centi	c	$10^{-2}$
milli	m	$10^{-3}$
micro	μ	$10^{-6}$
nano	n	$10^{-9}$

Mathematical Operations with Scientific Notation

• Addition/Subtraction: Convert to same exponent before adding/subtracting.

• Multiplication: Multiply digit terms, add exponents.

• Division: Divide digit terms, subtract exponents.

Precision, Accuracy, and Significant Figures

Precision and Accuracy

• Accuracy: How close a measurement is to the true value.

• Precision: How close repeated measurements are to each other.

Significant Figures

• All nonzero digits are significant.

• Zeros between nonzero digits are significant.

• Leading zeros are not significant.

• Trailing zeros after a decimal point are significant.

When performing calculations, the result should reflect the precision of the measured quantities:

• Multiplication/Division: Result has same number of significant figures as the factor with the fewest significant figures.

• Addition/Subtraction: Result has same number of decimal places as the quantity with the fewest decimal places.

Dimensional Analysis and Unit Conversions

Dimensional Analysis

Dimensional analysis is a method of problem solving that uses the units to guide the calculation. Conversion factors are used to change from one unit to another.

• Conversion Factor: A ratio that expresses how many of one unit are equal to another unit.

• Example: To convert 15 miles to kilometers, use the conversion factor 1 mile = 1.609 km.

Derived Units: Volume and Density

Volume

• SI unit: cubic meter (m3), but liters (L) and milliliters (mL) are commonly used in chemistry.

• 1 L = 1 dm3 = 1000 mL = 1000 cm3

Density

• Density (d): $d = \frac{m}{V}$ (mass divided by volume)

• SI unit: kg/m3; commonly used: g/cm3 or g/mL for solids and liquids, g/L for gases.

• Density is an intensive property (independent of amount of substance).

Problem Solving in Chemistry

General Problem-Solving Strategy

1. Sort: Identify given information and what is to be found.

2. Strategize: Develop a conceptual plan (steps to follow).

3. Solve: Carry out the plan, paying attention to significant figures and units.

4. Check: Does the answer make sense?

Order of Operations in Calculations

• P – Parentheses

• E – Exponents

• M – Multiplication

• D – Division

• A – Addition

• S – Subtraction

Summary Table: Properties of Sodium, Chlorine, and Sodium Chloride

Property	Sodium	Chlorine	Sodium Chloride
Melting Point (°C)	97.8	-101	801
Boiling Point (°C)	881	-34	1413
Colour	Silver	Greenish-yellow	White
Density (g/cm3)	0.97	0.0032	2.16

Additional info: This study guide covers the foundational concepts of matter, measurement, and problem solving in general chemistry, including the structure of matter, types of properties and changes, measurement standards, significant figures, and basic problem-solving strategies.