Chemistry of Life - Chapter 2 Flashcards

Flashcards covering key vocabulary from Chapter 2: Chemistry of Life, including elements, molecules, compounds, atomic structure, chemical bonds, properties of water, and pH.

Elements

Basic form of all matter that cannot be broken down into different components. There are 92 naturally occurring elements listed on the periodic table.

Essential Elements (96% of living things)

Carbon (C), Oxygen (O), Nitrogen (N), Hydrogen (H).

Essential Elements (4% of humans)

Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg).

Trace Elements (0.01% of humans)

Iron (Fe), Iodine (I), Fluorine (F).

Element (definition)

Consists of only one type of atom.

Molecule

Two or more atoms joined together chemically. Elements can be the same or different. All compounds are molecules, but not all molecules are compounds.

Compound

Two or more different elements chemically bonded in a fixed proportion. The compound takes on different physical and/or chemical properties than the individual elements and is difficult to separate.

Mixture

A combination of two or more substances (molecules) that are not chemically bonded. Can be separated using physical means like filtration, density, or evaporation.

Atom

The smallest unit of an element. Elements differ in the number of protons.

Atomic Number

Equal to the number of protons, defines the element.

Atomic Mass

The average mass of an element's naturally occurring isotopes.

Protons

Positively charged subatomic particles located in the nucleus. Their number defines the element and equals the atomic number. They hold negatively charged electrons close to the nucleus.

Neutrons

Neutral subatomic particles located in the nucleus. Their number equals the atomic mass minus the number of protons, and they stabilize the nucleus.

Electrons

Negatively charged subatomic particles located in orbitals around the nucleus. In the natural state, their number equals the number of protons and they are the basis of chemical reactions.

Isotopes

Varying forms of an element that differ in the number of neutrons. They behave similarly in chemical reactions but could lead to instability of the element.

Radioisotope

An isotope where a change in the number of neutrons causes the nucleus to become unstable, leading atoms to release energy waves and particles (radiation).

Dangers of Radiation

Uncontrolled exposure can damage molecules, especially DNA, leading to increased incidences of cancers and birth defects.

Free Radicals

Molecules that have lost electrons and steal replacement electrons from essential molecules in the body (like DNA), causing damage.

Antioxidants

Molecules that easily give up their electrons to free radicals, protecting essential molecules from damage.

Electron Shells

Different energy levels where electrons exist in an atom. Electrons farther from the nucleus possess more energy. The innermost shell holds 2 electrons, and the outermost shell typically holds 8 electrons.

Inert Atoms

Atoms with a full outer electron shell that do not tend to react with other atoms.

Ionic Bond

A chemical bond formed when one atom donates an electron to another, creating a positive ion (cation) and a negative ion (anion). The charge difference creates an attraction that holds the atoms together. They are weak and easily dissolve in water.

Covalent Bond

A strong chemical bond formed by the sharing of electrons between atoms. Atoms can share more than one pair of electrons to form double or triple bonds.

Non-polar Covalent Bond

A type of covalent bond where electrons are shared equally between atoms.

Polar Covalent Bond

A type of covalent bond where electrons are pulled toward the more electronegative atom, resulting in a molecule with a slight charge at each pole.

Hydrogen Bond

A weak bond formed by the interaction of a positively charged hydrogen atom with the negative charge of polar covalent molecules. Easily disrupted and reformed, important for chemical reactions, signaling, 3D shapes, and water properties.

Chemical Reaction

The making or breaking of chemical bonds, leading to the composition of a different form of matter. Matter is not created or destroyed, only rearranged.

Reactants

The starting materials in a chemical reaction.

Products

The resulting materials in a chemical reaction.

Water (H2O)

Essential for life, making up 67-70% of the human body. It is involved in metabolic processes, moderates temperature, acts as a solvent, and exists naturally in three states.

Cohesion

The tendency of individual water molecules to stick together, held by hydrogen bonds.

Adhesion

The clinging of one substance to another, characteristic of water molecules.

Surface Tension

A property of water that allows its surface to resist external force, due to cohesion.

Water's Role in Temperature Stabilization

Hydrogen bonds absorb and store large amounts of heat energy before breaking (evaporation) and release heat when they reform. Ice is less dense than liquid water, forming an insulating layer. Water also moderates global temperatures and dissipates cellular heat.

Solute

The substance(s) to be dissolved in a solution.

Solvent

The dissolving agent in a solution, typically water due to its universal solvent capabilities.

Solution

A liquid containing two or more substances homogeneously mixed.

Hydrophilic

Refers to a 'water-loving' substance that dissolves easily in water.

Hydrophobic

Refers to a 'water-hating' substance that does not dissolve easily in water.

Hydrogen Ions (H+)

Ions formed when water dissociates (H2O → H+ + OH-). A higher concentration indicates acidity.

Hydroxyl Ions (OH-)

Ions formed when water dissociates (H2O → H+ + OH-). A lower concentration of H+ (and thus higher relative OH-) indicates basicity.

pH Scale

A logarithmic scale based on the concentration of H+ ions, ranging from 0 (most acidic) to 14 (most basic), with 7 being neutral. Each unit represents a 10x increase in H+ ions.

Neutral pH

A pH of 7, where the concentration of H+ and OH- ions are equal.

Acidic

A substance with a pH less than 7, indicating a higher concentration of H+ ions.

Basic (Alkaline)

A substance with a pH greater than 7, indicating a lower concentration of H+ ions.

Buffers

Substances that minimize changes in pH by accepting H+ if the solution is too acidic or donating H+ if it is too basic. Essential for maintaining the pH of cells (e.g., pH 7.4).