CHEM 1110 Exam 2 Study Guide: Matter, Energy, Atoms, and Elements

General Exam Preparation

This study guide outlines the key topics and concepts to review for CHEM 1110 Exam 2, focusing on matter and energy, as well as atoms and elements. Students should be familiar with definitions, calculations, and applications of these concepts.

• Definitions: Know the vocabulary introduced in each chapter.

• Calculations: Practice problems from chapters 3 & 4, including unit conversions and application of formulas.

• General/Metric Units: Understand what each unit measures and how to convert between them.

• Memorization: Memorize important information and equations as indicated in each section.

• Homework & Practice: Review homework questions and Mastering Chemistry assignments.

• Class Discussions: Revisit class discussions and practice problems for additional context.

Chapter 3: Matter and Energy

Key Concepts and Definitions

• Energy: The capacity to do work or produce heat. Includes kinetic energy (energy of motion), potential energy (stored energy), heat, and thermal energy.

• Calorie: A unit of energy; 1 calorie (cal) is the amount of energy needed to raise the temperature of 1 gram of water by 1°C. The nutritional Calorie (Cal) is equal to 1 kilocalorie (kcal).

• Mixtures: Understand the difference between homogeneous (uniform composition) and heterogeneous (non-uniform composition) mixtures.

• Compounds: Substances composed of two or more elements chemically combined in fixed proportions.

Physical and Chemical Properties/Changes

• Physical Properties: Characteristics that can be observed without changing the substance's identity (e.g., melting point, boiling point, density).

• Chemical Properties: Characteristics that describe a substance's ability to change into a different substance (e.g., flammability, reactivity).

• Physical Changes: Changes that do not alter the chemical composition (e.g., melting, freezing).

• Chemical Changes: Changes that result in the formation of new substances (e.g., burning, rusting).

Temperature Scales

• Fahrenheit (°F), Celsius (°C), Kelvin (K): Know how to convert between these temperature scales.

Formulas:

• Fahrenheit to Celsius: $C = \frac{5}{9}(F - 32)$

• Celsius to Kelvin: $K = C + 273.15$

Calorimetry and Nutrition

• Calorimetry: The measurement of heat flow in chemical reactions or physical changes.

• Calculating Nutritional Calories: Use caloric values for fats, proteins, and carbohydrates to determine total energy content.

• Caloric Values:

  • Fat: 9 kcal/g

  • Protein: 4 kcal/g

  • Carbohydrate: 4 kcal/g

• Heat Calculations: Use the formula $q = m \times c \times \Delta T$ where $q$ is heat, $m$ is mass, $c$ is specific heat, and $\Delta T$ is the temperature change.

Chapter 4: Atoms and Elements

Atomic Structure and Isotopes

• Atoms: The smallest unit of an element that retains its chemical properties.

• Atomic Number (Z): The number of protons in the nucleus of an atom.

• Mass Number (A): The sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Isotope Notation: $^{A}_{Z}\text{X}$, where X is the element symbol, A is the mass number, and Z is the atomic number.

Periodic Table and Element Symbols

• Element Symbols: One- or two-letter abbreviations for elements (e.g., H for hydrogen, He for helium).

• Groups and Periods: Columns are groups (families) and rows are periods. Elements in the same group have similar chemical properties.

• Special Groups: Alkali metals (Group 1), alkaline earth metals (Group 2), halogens (Group 17), noble gases (Group 18).

Distribution of Subatomic Particles

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles in orbitals around the nucleus.

• Calculating Subatomic Particles:

  • Number of protons = atomic number (Z)

  • Number of neutrons = mass number (A) - atomic number (Z)

  • Number of electrons = number of protons (for neutral atoms)

Electron Configuration and Orbitals

• Electron Configuration: The arrangement of electrons in an atom's energy levels and sublevels (s, p, d, f).

• Energy Levels: Principal quantum numbers (n = 1, 2, 3, ...).

• Sublevels: s, p, d, f (each with a specific number of orbitals and electrons).

• Blocks: s-block, p-block, d-block, f-block on the periodic table.

Valence Electrons and Lewis Structures

• Valence Electrons: Electrons in the outermost energy level, important for chemical bonding.

• Lewis Dot Structures: Diagrams showing valence electrons as dots around the element symbol.

Periodic Trends

• Atomic Size: Increases down a group, decreases across a period.

• Ionization Energy: Energy required to remove an electron; increases across a period, decreases down a group.

• Metallic Character: Increases down a group, decreases across a period.

Sample Table: Subatomic Particles in Selected Isotopes

Isotope	Protons	Neutrons	Electrons
$^{12}_{6}\text{C}$	6	6	6
$^{14}_{6}\text{C}$	6	8	6
$^{23}_{11}\text{Na}$	11	12	11

Example: Drawing Lewis Structures

• For oxygen (O): 6 valence electrons, so the Lewis structure is O with 6 dots around it.

• For carbon dioxide (CO2): Draw the central carbon atom with double bonds to each oxygen, and lone pairs on the oxygens.

Additional info: Students should also be able to explain how periodic trends affect chemical reactivity and bonding, and apply these concepts to predict properties of elements and compounds.