Introduction to Chemistry

Introduction to Chemistry

• Chemistry is the study of the composition, structure, and changes of matter.

Branches of Chemistry

• Health & Medicine
  • Sanitation systems
  • Surgery with anesthesia
  • Vaccines and antibiotics
  • Gene therapy
• Energy & Environment
  • Fossil fuels
  • Solar energy
  • Nuclear energy
• Materials & Technology
  • Polymers, ceramics, liquid crystals
  • Room-temperature superconductors
  • Molecular computing
• Food & Agriculture
  • Genetically modified crops
  • "Natural" pesticides
  • Specialized fertilizers

The Study of Chemistry

• Macroscopic: Visible, large-scale properties of matter
• Microscopic: Atomic and molecular level properties of matter
• Examples of macroscopic and microscopic views of a chemical process are shown, with rusting iron as a key example

The Scientific Method

• A systematic approach to research
• Includes observation, representation, and interpretation
• A hypothesis is a tentative explanation
• Hypotheses need to be tested and potentially modified

Laws and Theories

• A law is a concise statement of a relationship between phenomena
• Example: Force = mass x acceleration
• A theory is a unifying principle that explains a body of facts and/or laws
• Example: Atomic Theory

Scientific Method Cycle

• Experiments lead to results
• Results lead to a modified or new hypothesis

Definitions of Scientific Terms

• Hypothesis: A tentative explanation of a phenomenon
• Theory: A tested explanation of a natural phenomenon
• Law: A concise statement or mathematical equation about a fundamental relationship
• Observation: A description of what is happening
• Interpretation: An explanation or understanding of the observation

Experiment

• A controlled observation of natural phenomena to allow for replication of results and reasonable conclusions

Matter and Substances

• Matter is anything that occupies space and has mass
• A substance is a form of matter with definite composition and distinct properties

States of Matter

• Solid: rigid, fixed volume and shape
• Liquid: relatively incompressible, fixed volume, no fixed shape
• Gas: compressible, no fixed volume or shape

Physical and Chemical Changes

• Physical change: change in form but not chemical identity
  • Examples: melting, dissolving
• Chemical change (or chemical reaction): one or more kinds of matter transform into a new kind or kinds of matter
  • Examples: rusting, burning

Physical and Chemical Properties

• Physical property: can be observed without changing chemical identity
  • Examples: state, boiling point, color
• Chemical property: involves a chemical change
  • Examples: ability to react with oxygen, with fluorine

Classification of Matter

• Mixture: combination of two or more substances where each retains its own identity
  • Heterogeneous: physically distinct parts, different properties
    • Examples: salt/iron filings, oil/vinegar
  • Homogeneous: uniform properties, often called a solution
    • Examples: saltwater, air
• Pure substance: cannot be separated into other substances by physical means
  • Element: cannot be decomposed into simpler substances by chemical reaction
    • Examples: hydrogen, carbon, oxygen
  • Compound: composed of two or more elements chemically combined
    • Examples: water (H₂O), carbon dioxide (CO₂)

Measurement

• Comparison of a physical quantity with a fixed standard (a unit).
  • Examples: centimeter, kilogram

Precision and Accuracy

• Precision: closeness of repeated measurements of the same quantity
• Accuracy: closeness of a single measurement to its true value

Significant Figures

• Digits in a measurement that include all certain digits plus a final digit with some uncertainty

Significant Figures-Rules

1. All nonzero digits are significant.
2. Zeros between nonzero digits are significant.
3. Leading zeros are not significant.
4. Terminal zeros are significant if they are to the right of the decimal point.
5. Terminal zeros in a number without a specified decimal point may or may not be significant.

Calculations and Significant Figures

• Multiplication and division: answer has the same number of significant figures as the measurement with the least number of significant figures
• Addition and subtraction: answer has the same number of decimal places as the measurement with the fewest decimal places

Exact Numbers

• Counted or defined numbers, have unlimited significant figures

SI Units (International System of Units)

• International system of units made up of a particular choice of metric units
• Base units: seven metric units from which all other units are derived
  • 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)

Scientific Notation

• Representation of a number in the form A x 10ⁿ where 1 ≤ A < 10 and n is an integer.

Converting Units (Dimensional Analysis)

• Using conversion factors to express quantities in different units.

Temperature

• Measure of "hotness"
• Heat flows from higher to lower temperature

Temperature Scales

• Celsius (°C), Fahrenheit (°F), and Kelvin (K)

Converting Between Temperature Scales

• Formulas for converting between Celsius, Fahrenheit, and Kelvin scales are provided.

Derived Units

• Combinations of fundamental units
• Examples: speed, volume, density

Density

• Mass per unit volume
• Common units: g/cm³ for solids, g/mL for liquids, g/L for gases

Explore the foundational concepts of chemistry, including its branches and the scientific method. Understand the macroscopic and microscopic properties of matter and the relevance of chemistry in daily life, from health to energy. This quiz will test your knowledge on various chemistry topics.