Intro to Chemistry: Matter and Measurement

Introduction to Chemistry, Matter, and Measurement

• Chemistry seeks to understand matter's properties and behavior by studying atoms and molecules.
• Chemistry enhances one's understanding of matter and provides insights into modern science and technology.

Uncertainty in Measurement

• Uncertainty is inherent in all measured quantities and indicated by significant figures.
• Significant figures express uncertainty in calculations using measured quantities.

Dimensional Analysis

• Units, along with numbers, are carried through calculations for verification.
• Obtaining correct units confirms the accuracy of a calculation.

Why Study Chemistry?

• Chemistry explains why stars shine, leaves change color, and batteries generate electricity.
• It lies at the heart of matters related to health, resources, environment, and basic needs.
• Chemical principles apply to both everyday activities and complex processes.
• Chemistry is central to other sciences, aiding comprehension of interactions within the material world.

The Study of Chemistry

• Chemistry studies matter's properties and behavior; matter has mass and occupies space.
• A property is a characteristic that distinguishes one type of matter from another.
• Elements combine to form matter, and each element consists of unique atoms.
• Molecules are two or more atoms joined in specific shapes.
• Altering molecular composition/structure creates new substances with different properties.
• Every change has a basis in atoms and molecules.
• Chemistry studies properties/behavior of atoms and molecules to understand matter.

Classifications of Matter

• Matter is classified by physical state (gas, liquid, solid) and composition (element, compound, mixture).

States of Matter

• Gas lacks fixed volume/shape, conforming to its container; easily compressed.
• Liquid has distinct volume, assumes container's shape; not easily compressed.
• Solid has fixed shape/volume, essentially incompressible.
• Temperature/pressure changes cause matter to transition between states.

Pure Substances

• Pure substances have distinct properties, with consistent composition; examples are water and sodium chloride.
• Substances are categorized as elements or compounds; elements cannot be broken down into simpler substances.
• Compounds consists of two/more elements, mixtures contain two/more substances that retain their chemical identities.

Elements

• 118 known elements vary in abundance.
• Oxygen, silicon, aluminum, iron, and calcium make up over 90% of Earth's crust.
• Oxygen, carbon, and hydrogen account for over 90% of human body mass.
• Each element is denoted by a one- or two-letter symbol, with capital letters capitalized.

Compounds

• Elements interact to form compounds like water from hydrogen and oxygen.
• Water consists of 11% hydrogen and 89% oxygen by mass, regardless of source.
• Table 1.3 shows that water's properties differ from those of its elements.

Law of constant composition

• Elemental composition in a compound remains constant.
• Pure compounds possess uniform composition/properties, source-independent.

Mixtures

• Mixtures consist of combined substances that retain chemical identities/properties.
• Unlike pure substances with fixed compositions, mixture compositions vary.
• Components make up mixtures.
• Heterogeneous mixtures have inconsistent composition/appearance.
• Homogeneous mixtures exhibit uniformity, also called solutions; states include solids, liquids, and gases.

Measuring Uncertainty

• Exact numbers values are known exactly, while those of inexact have some uncertainty, such as measurement.
• Precision indicates measurement agreement and accuracy measures closeness to true value.

Significant Figures

• Report known plus one estimated digit
• More digits = less uncertainty
• Two rules are listed for significant figures in calculations, for both addition/subtraction and multiplication/division

Physical and Chemical Changes

• Substances undergo physical (appearance change, composition unchanged) or chemical changes (new substance formed).
• Physical changes include changes of state