Chapter 1: Chemistry and Measurement – Foundational Concepts and Methods

Chemistry and Measurement

What Is Chemistry?

Chemistry is the scientific study of the composition, structure, and properties of matter and energy, as well as the changes that matter undergoes. It is a central science that connects physical sciences with life sciences and applied sciences.

• Matter: Anything that has mass and occupies space.

• Energy: The capacity to do work or produce heat; involved in all changes of matter.

Major Areas of Chemistry

Chemistry is divided into several specialized fields, each focusing on different aspects of matter and its transformations.

• Biochemistry: The study of chemical processes within and related to living organisms at the molecular level.

• Organic Chemistry: The study of compounds containing carbon and hydrogen.

• Inorganic Chemistry: The study of compounds not covered by organic chemistry, typically those without carbon-hydrogen bonds.

• Analytic Chemistry: The analysis of matter to determine its identity and composition.

• Physical Chemistry: The study of the physical properties and behavior of matter, often using principles of physics.

Characteristics of the Scientific Process

The scientific method is a systematic approach to investigation and discovery in chemistry and other sciences.

• Observation: Gathering information about phenomena.

• Formulation of a Question: Identifying what is to be explained.

• Pattern Recognition: Looking for cause-and-effect relationships.

• Developing Theories (Hypothesis): Proposing explanations for observations.

• Experimentation: Testing hypotheses through controlled experiments.

• Summarizing Information: Formulating scientific laws or theories based on repeated experimental support.

Example: The discovery of cisplatin as an anticancer agent followed the scientific method, starting from observation, hypothesis, experimentation, and theory development.

Matter: Physical State and Chemical Constitution

Classification of Matter

Matter can be classified by its physical state or by its chemical constitution.

• Physical State: Solid, liquid, or gas.

• Chemical Constitution: Element, compound, or mixture.

Solids, Liquids, and Gases

The three states of matter differ in their physical properties:

• Solid: Rigid, incompressible, fixed shape and volume.

• Liquid: Relatively incompressible, fixed volume, no fixed shape (takes shape of container).

• Gas: Easily compressible, no fixed shape or volume (fills any container).

Example: Water exists as ice (solid), liquid water, and steam (gas) under different conditions.

Physical vs Chemical Change

Changes in matter can be classified as physical or chemical.

• Physical Change: Alters the form of matter but not its chemical identity (e.g., melting, boiling).

• Chemical Change (Chemical Reaction): Transforms matter into new substances with different chemical identities (e.g., rusting of iron).

Physical vs Chemical Property

Properties of matter are either physical or chemical.

• Physical Property: Can be observed without changing the substance's chemical identity (e.g., color, melting point).

• Chemical Property: Describes the substance's ability to undergo chemical changes (e.g., iron's ability to react with oxygen).

Elements, Compounds, and Mixtures

Matter can be further classified based on its chemical constitution.

• Element: A substance that cannot be decomposed into simpler substances by chemical means. The smallest unit is the atom.

• Compound: A substance composed of two or more elements chemically combined. The smallest unit is the molecule.

• Mixture: A material that can be separated by physical means into two or more substances. Mixtures have variable composition.

Law of Definite Proportions: A pure compound always contains the same elements in the same proportion by mass.

Types of Mixtures

• Heterogeneous Mixture: Consists of physically distinct parts; properties are not uniform throughout.

• Homogeneous Mixture (Solution): Properties are uniform throughout.

Example: Salt water is a homogeneous mixture; sand and iron filings is a heterogeneous mixture.

Distinguishing Between Elements, Compounds, and Mixtures

Type	Can be separated by physical methods?	Can be separated by chemical methods?
Element	No	No
Compound	No	Yes
Mixture	Yes	May contain compounds/elements

Measurement and Significant Figures

Measurement

Measurement is the process of comparing a physical quantity to a standard unit. Precision and accuracy are important aspects of measurement.

Significant Figures

Significant figures indicate the precision of a measured or calculated quantity.

• All nonzero digits are significant.

• Zeros between significant figures are significant.

• Zeros preceding the first nonzero digit are not significant.

• Zeros to the right of the decimal after a nonzero digit are significant.

• Zeros at the end of a nondecimal number may or may not be significant (use scientific notation).

Rules for Calculations

• Multiplication/Division: The result should have as many significant figures as the measurement with the least number of significant figures.

• Addition/Subtraction: The result should have the same number of decimal places as the measurement with the least number of decimal places.

Example:

• $14.0\,\text{g} / 102.4\,\text{mL} = 0.137\,\text{g/mL}$ (three significant figures)

Exact Numbers

Exact numbers arise from counting or definitions and have an infinite number of significant figures. They do not affect the number of significant figures in calculations.

• Example: 12 inches in a foot (exact by definition)

Accuracy vs Precision

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

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

Example: A set of measurements can be precise but not accurate if they are close to each other but far from the true value.

SI Units and SI Prefixes

SI Base Units

The International System of Units (SI) is the standard system of measurement in science. There are seven SI base units.

Quantity	Unit	Symbol
Length	Meter	m
Mass	Kilogram	kg
Time	Second	s
Temperature	Kelvin	K
Amount of substance	Mole	mol
Electric current	Ampere	A
Luminous intensity	Candela	cd

SI Prefixes

SI prefixes indicate powers of ten and are used to express larger or smaller units.

Multiple	Prefix	Symbol
$10^6$	mega	M
$10^3$	kilo	k
$10^{-1}$	deci	d
$10^{-2}$	centi	c
$10^{-3}$	milli	m
$10^{-6}$	micro	μ
$10^{-9}$	nano	n
$10^{-12}$	pico	p

Temperature Scales

Temperature can be measured in Celsius, Kelvin, or Fahrenheit. The SI base unit is the kelvin (K).

• Celsius to Kelvin: $K = ^\circ C + 273.15$

• Fahrenheit to Celsius: $^\circ C = \frac{(^\circ F - 32)}{1.8}$

• Celsius to Fahrenheit: $^\circ F = 1.8(^\circ C) + 32$

Example: Water freezes at 0°C (273.15 K, 32°F) and boils at 100°C (373.15 K, 212°F).

Derived Units

Volume and Density

Derived units are formed by combining SI base units. Volume and density are common derived units in chemistry.

• Volume: $1\,\text{L} = 1\,\text{dm}^3$; $1\,\text{mL} = 1\,\text{cm}^3$

• Density: $d = \frac{m}{V}$, where $d$ is density, $m$ is mass, and $V$ is volume.

Example: A sample of galena (lead sulfide) weighing 12.4 g and having a volume of 1.64 cm³ has a density:

• $d = \frac{12.4\,\text{g}}{1.64\,\text{cm}^3} = 7.56\,\text{g/cm}^3$

Extensive and Intensive Properties

Properties of matter can be classified as extensive or intensive.

• Extensive Property: Depends on the amount of substance present (e.g., mass, volume).

• Intensive Property: Independent of the amount of substance (e.g., density, temperature, color).

Units: Dimensional Analysis

Dimensional Analysis (Factor-Label Method)

Dimensional analysis is a method of calculation in which units are carried through all steps to ensure correct results. 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 (e.g., $1\,\text{yard} = 3\,\text{feet}$, so $\frac{3\,\text{ft}}{1\,\text{yd}}$).

Example: To convert 20 yards to feet:

• $20\,\text{yd} \times \frac{3\,\text{ft}}{1\,\text{yd}} = 60\,\text{ft}$

Common Conversion Relationships

Length	Mass	Volume
2.54 cm = 1 in	1 lb = 0.4536 kg	1 qt = 0.9464 L
1 yd = 0.9144 m	1 lb = 16 oz	4 qt = 1 gal
1 mi = 1.609 km	1 oz = 28.35 g
1 mi = 5280 ft

Additional info: Some context and examples have been expanded for clarity and completeness.