Chapter 2 Summary
Key Takeaways
- Basic Composition of Matter: All living things are made of matter, which consists of elements that cannot be broken down chemically. Atoms, the smallest unit of an element, contain protons, neutrons, and electrons, with each element having a unique number of protons defining its atomic number.
- Chemical Bonds and Stability: Atoms form molecules through chemical bonds—ionic, covalent (polar and nonpolar), and hydrogen bonds—to achieve stability, often following the octet rule, where atoms aim for eight electrons in their outer shell.
- Properties of Water: Water’s unique properties, such as cohesion, high heat capacity, ice expanding, and its role as a universal solvent, are due to hydrogen bonding. These properties are essential for sustaining life on Earth.
- Isotopes and Ions: Isotopes are variants of elements with the same number of protons but different numbers of neutrons, while ions are atoms with unequal numbers of protons and electrons, resulting in a net charge. Ions form through electron transfer, creating ionic bonds.
- The Periodic Table’s Role: The periodic table organizes elements based on their atomic structure, revealing patterns in electron configuration, reactivity, and bonding tendencies. It helps predict how elements interact chemically.
- pH, Acids, Bases, and Buffers: The pH scale measures a solution’s acidity or alkalinity, influenced by hydrogen ion concentration. Buffers maintain pH balance in biological systems, which is crucial for proper cellular function, by neutralizing excess acids or bases.
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into six key takeaways.
Flashcards
Text Description
- Matter: Anything that occupies space and has mass, composed of atoms
- Elements: Pure substances are composed of one type of atom; they cannot be broken down into simpler substances by chemical reactions
- Compound: Molecules that contain more than one element in a fixed ratio
- Atom: The smallest unit of matter that retains all of the chemical properties of an element
- Protons: Positively charged particles found in an atom’s nucleus; determine an element’s identity
- Electrons: Negatively charged particles orbiting around an atom’s nucleus; involved in chemical bonding and reactions
- Neutrons: Particles with no charge found in the atom’s nucleus; contribute to the atom’s mass
- Nucleus: Central region of an atom containing protons and neutrons; contains almost all of an atom’s mass
- Atomic Number: The number of protons in the nucleus of an atom, unique for each element
- Mass Number: The total number of protons and neutrons in an atom’s nucleus
- Periodic Table of Elements: An organized chart listing all known elements, arranged by atomic number and chemical properties
- Isotopes: Atoms of the same element with the same atomic number but different numbers of neutrons, resulting in different mass numbers
- Radioactive Isotopes: Unstable isotopes that spontaneously emit radiation (particles and energy) to become more stable
- Valence electrons: The electrons in an atom’s outermost energy shell; determines chemical reactivity and bonding
- Valence number: The number of electrons required to fill the valence shell
- Chemical Bonds: Forces holding atoms together through interactions involving electrons (ionic, covalent, and hydrogen bonds)
- Octet Rule: Atoms tend to gain, lose, or share electrons to obtain eight electrons in their outermost energy level (stable configuration)
- Ion: An atom or molecule with a positive or negative charge due to the gain or loss of electrons
- Cations: Positively charged ions formed by the loss of electrons
- Anions: Negatively charged ions formed by the gain of electrons
- Electron Transfer: The movement of electrons from one atom to another, forming ions
- Ionic Bond: Attraction formed when electrons are transferred from one atom to another, creating oppositely charged ions that attract each other
- Covalent Bond: Chemical bond formed when atoms share pairs of electrons
- Molecule: A group of two or more atoms held together by covalent bonds
- Nonpolar Covalent Bonds: Covalent bonds where electrons are shared equally between atoms, creating no charge difference
- Polar Covalent Bond: Covalent bond where electrons are shared unequally, creating slightly charged poles in the molecule
- Hydrogen Bonds: Weak attractions between partially positive hydrogen atoms and partially negative atoms (e.g., oxygen or nitrogen)
- Hydrophilic: Substances that easily interact or dissolve in water (“water-loving”)
- Hydrophobic: Substances that repel or do not dissolve in water (“water-fearing”)
- Temperature: A measure of the average kinetic energy (motion) of molecules in a substance
- Evaporation: The transformation of liquid into vapour, usually involving energy absorption and cooling effects
- Cohesion: Attraction between molecules of the same substance (e.g., water molecules sticking together)
- Surface Tension: Cohesion at a liquid’s surface creating a “film” or resistance to external force
- Adhesion: Attraction between different substances or molecules (e.g., water clinging to glass)
- Solution: uniform mixture of liquid and substances dissolved in that liquid
- Solvent: substance capable of dissolving another substance
- Solute: substance dissolved in the solvent
- Litmus Paper: Paper strips treated with dye that change colour in response to acidity or alkalinity
- pH Scale: Numeric scale (0–14) measuring the acidity or alkalinity of a solution, where 7 is neutral, below 7 acidic, and above 7 basic
- Acids: Substances releasing hydrogen ions (H⁺) in water, lowering pH (below 7)
- Bases: Substances releasing hydroxide ions (OH⁻) or reducing hydrogen ions (H⁺), raising pH (above 7)
- Buffers: Substances or systems that resist changes in pH by accepting or releasing hydrogen ions, maintaining a stable pH
- 4 elements common to all living organisms: Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N)
- 3 subatomic particles: protons (+), electrons (-), neutrons (o)
- Structure of water: 2 hydrogen atoms and 1 oxygen atom, bonded via polar covalent bonds, resulting slight positive charge (δ+) on each hydrogen atom and a slight negative charge (δ-) on the oxygen atom
- Properties of water: Water expands upon freezing, Water stabilizes temperature, Water is a versatile solvent, Water is cohesive
- Polar Molecule: A molecule with a partial positive charge on one end and a partial negative charge on the other
- Why is water cohesive? Hydrogen bonds between water molecules allow them to “stick” together
- What is the biological significance of water being cohesive? It ensures bulk movement of water through living organisms (e.g. up a tree)
- How does water stabilize temperature? To heat up, energy must be invested to break the hydrogen bonds that hold water molecules together before those water molecules can move freely. As water cools, the molecules slow their movement and energy is released as the hydrogen bonds between water molecules re-form.
- What is the biological significance of water stabilizing temperatures? Water can absorb and release heat to ensure the temperature on Earth’s surface does not exceed a livable temperature.
- Why does water expand upon freezing? Hydrogen bonds form between water molecules as it freezes, which creates a rigid, lattice-like structure that prevents water molecules from packing close.
- What is the biological significance of ice being less dense than water? Ice will float on the water’s surface in lakes, ponds, and oceans, creating an insulating barrier to protect the animal and plant life beneath from freezing in the water.
- Why is water a versatile solvent? Because water is polar, with slightly positive and negative charges, ionic compounds (such as salt) and polar molecules (such as sugar) can readily dissolve. The charged particles will form hydrogen bonds with a surrounding layer of water molecules.
- What is the biological significance of water as a solvent? Water can dissolve substances to facilitate chemical reactions and transport of nutrients and waste within organisms (e.g. blood is mostly water)
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Can you give me brief summaries of these key terms.