Chemistry Basics Quiz

CHEM 101 - Book Information

• Textbook title: Principles of Chemistry: A Molecular Approach
• Author: Nivaldo J. Tro
• Publisher: Pearson

CHEM 101 - Syllabus Information

• Chapter 1: Matter, Measurement, and Problem Solving
• Chapter 2: Atoms and Elements
• Chapter 3: Molecules, Compounds & Chemical Equation

Chapter 1 Details

• 1.1 Atoms and Molecules
• 1.2 The Scientific Approach to Knowledge
• 1.3 The Classification of Matter
• 1.4 Physical and Chemical Changes and Physical and Chemical properties
• 1.5 Energy: A Fundamental Part of Physical and Chemical Change
• 1.6 The Unit of Measurement
• 1.7 The Reliability of a Measurement
• 1.8 Solving Chemical Problems

Matter and Chemistry

• Matter: Anything that has mass and occupies space.
• Chemistry: The science that helps to understand the behavior of matter by studying the behavior of atoms and molecules.

Atoms and Molecules

• Atoms: Tiny particles that compose matter.
• Molecules: Two or more atoms joined together by chemical bonds.

Scientific Method

• Systematic approach to research.
• Observation
• Representation
• Interpretation
• Hypothesis: A tentative explanation for a set of observations.
• Theory (model): A set of tested hypotheses that provides an overall explanation of a natural phenomenon.

Observations

• Qualitative observations: Describing how a process happens.
• Quantitative observations: Measuring something about a process.
• Scientific models:
  • Law: Summarizes what happens.
  • Hypothesis: A possible explanation for an observation.
  • Theory (model): An attempt to explain why something happens and a set of tested hypotheses.

Classification of Matter

• 3 states of matter:
  • Solid: Particles are packed closely together and fixed in position (fixed volume & shape).
  • Liquid: Particles are closely packed but have some ability to move around (fixed volume & indefinite shape).
  • Gas: Particles have complete freedom from each other (no fixed volume or shape) and are compressible.
• Classification of solids:
  • Crystalline solids: Particles arranged in an orderly geometric pattern (salt, sugar, diamond).
  • Amorphous solids: Particles randomly distributed (plastic, glass, charcoal).
• Classify matter by composition:
  • Pure substances:
    • Element: Cannot be separated into simpler substances (helium).
    • Compound: Composed of two or more elements chemically combined (pure water).
  • Mixtures:
    • Heterogeneous: Composition is not uniform throughout (wet sand).
    • Homogeneous: Composition is uniform throughout (tea with sugar).

Changes in Matter

• Physical Change: Alters the state or appearance of matter without altering its composition (boiling water).
• Chemical Change: Alters the composition of matter, rearranging atoms into new molecules (burning natural gas).
• Common Physical Changes: Evaporating/condensing, melting/freezing, subliming, dissolving.
• Common Chemical Changes: Rusting of metal, burning.

Properties of Matter

• Physical Properties: Characteristics of matter that can be changed without changing its composition (color, smell, attraction to magnets, density).
• Chemical Properties: Characteristics that determine how the composition of matter changes (flammability, acidity, toxicity, reactivity with chemicals).

Energy

• Capacity to do work (action of a force through a distance).
• All matter possesses energy.
• Physical and chemical changes usually come with energy changes.
• Example:
  • Water evaporation (physical change): Absorbs energy.
  • Burning natural gas (chemical change): Releases energy.

Conversion of Energy

• Energy can be converted from one form to another.
• Energy is neither created nor destroyed. (Conservation of Energy)

Units of Measurement

• Measurement is a quantitative observation.
• Measurements have a number and a unit (standard quantities).
• Most common unit systems:
  • English system (USA)
  • Metric system (rest of the world)
• SI units: - Standard units used by scientists - Includes: Meter (m), Kilogram (kg), Second (s), Kelvin (K), Mole (mol), Ampere (A)

Measure of Temperature

• Common temperature scales: Fahrenheit (°F), Celsius (°C), Kelvin (K)
• 0 K = Absolute zero

Converting between Temperature Scales

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

Prefix Multipliers in SI Units

• Used for expressing very large or very small quantities in a compact manner
• Includes: tera-, giga-, mega-, kilo-, deci-, centi-, milli-, micro-, nano-, pico-

Derived Units

• Derived units are combinations of other units.
• Speed (distance/time), volume (length × width × height), density (mass/volume).

Density

• Density of a substance is the ratio of its mass to its volume (mass/volume)
• Density is affected by temperature

Reliability of a Measurement

• Last digit of a measurement is estimated (uncertain).
• All other digits are certain.
• Uncertainty is assumed to be ±1

Measurement & Significant Figures

• For instruments with a scale, the last digit is determined by estimating between the marks.
• Number of digits reported in a measurement depends on the measuring device.
• Scientific notation is used to express very large or very small quantities.

Scientific Notation

• Positive exponents mean multiplying by 10 n times.
• Negative exponents mean dividing by 10 n times.

Significant Figures in Calculation

• Multiplication or division: Result has the same number of significant figures as the number with the fewest number of significant figures.
• Addition or subtraction: Result has the same number of decimal places as the number with the fewest number of decimal places.
• Combined calculations (x or + with + or -): Parentheses and intermediate answer must be calculated first to avoid rounding errors and the final answer should be written to correct number of significant figures

Solving Chemical Problems

• Always write every number with its associated unit.
• Include units in calculations.
• Type of chemical problems:
  • Unit conversions
  • Dimensional analysis
  • Conversion factor (converting_from) / (given_unit) = (find_unit) / (converting_to)

Converting from One Unit to Another

• Using units as a guide to problem solving, called dimensional analysis.
• Conversion factor: A fractional quantity with the unit to be converted to from the bottom.

Calculating Moles

• Moles are a measure of the amount of substance, containing 6.022 x 10²³ particles (atoms or compounds).
• Molar Conversions: (Mass) × (1 mol/molar mass)= (moles).
• Avogadro's number = 6.022 × 1023

Mass and Amount (moles)

• Molar mass is the mass in grams of 1 mole of atoms.
• Mole relationships between and numbers of atoms.

Empirical Formula

• Simplest, whole-number ratio of the atoms (of elements) in a substance.
• Determination from experimental data using percentages or masses of elements.
• Calculate moles of each element and divide by the smallest number of moles.
• Multiply all to give integer subscripts.

Molecular Formulas

• Molecular formulas are multiples of the empirical formula
• Calculation using the molar mass of the compound and the empirical formula .

Writing and Balancing Chemical Equations

• Reactions involve chemical changes in matter resulting in new substances involving rearrangement and exchange of atoms resulting in new molecules.
• Elements are not changed during a reaction.

Symbols Used in Equations

• (g)= Gas;(l)= Liquid;(s)= Solid; (aq)= Aqueous - dissolved in water.
• Energy is indicated above the arrow in a reaction equation
  • ∆= heat; hv = light; shock = mechanical; elec= electrical

Combustion of Methane

• Methane burns with oxygen to produce carbon dioxide and water.

Homework

• Exercises are given for each chapter. Corresponding page numbers are provided.