Bio150 Final

Properties of Matter

Physical properties are characteristics of a substance that are measurable without changing the basic identity of the substance. Example: color, density, and state of matter.

Chemical Properties

The way a substance reacts to form other substances. Example: flammability and pH (acidity).

Matter

Anything that has mass and occupies space.

Physical Change

Changes the physical appearance of a substance but does not change its basic identity.

Chemical Change

A change in physical appearance and chemical properties.

Mass

The amount of matter in an object, measured in grams.

Atoms

The fundamental unit of matter.

Element

A substance made from one type of atom.

Compound

A substance consisting of two or more elements chemically combined.

Mixtures

Substances composed of two or more elements or compounds that are present in variable amounts and can be separated by physical changes.

Pure Substance

Has a fixed composition and distinct properties.

Homogeneous Mixture

Components cannot be distinguished. Example: solution (salt and water).

Heterogeneous Mixture

Components remain separate and distinct. Example: suspension (dirt and water).

Solution

A homogeneous mixture in which the components are evenly distributed.

Suspension

A heterogeneous mixture in which particles are visible and may settle or be filtered out.

Elements

The building blocks of all matter.

Atoms

The fundamental units of elements and all matter.

Nucleus

The center of an atom containing protons and neutrons.

Protons

Positively charged particles found in the nucleus. Relative charge: +1. Relative mass: 1.

Neutrons

Neutral particles found in the nucleus. Relative charge: 0. Relative mass: 1.

Electrons

Negatively charged particles found outside the nucleus in electron shells. Relative charge: -1. Relative mass: approximately 1/1836 (often treated as 0).

Electron Shells

Energy levels surrounding the nucleus where electrons are found.

Atomic Number

The number of protons in the nucleus of an atom.

Mass Number

The total number of protons and neutrons in the nucleus.

Identity of an Element

Determined by the total number of protons in the nucleus.

Energy

The capacity to do work.

Electron Energy Levels

States of potential energy associated with the location of electrons in an atom.

Electron Shell

The energy level or distance of electrons from the nucleus of an atom.

Valence Shell

The outermost energy shell of an atom.

Valence Electrons

Electrons in the valence shell that participate in chemical bonding.

Chemical Bonding

Occurs when atoms share, gain, or lose valence electrons to form stable compounds.

Unpaired Electrons

Valence electrons that are not paired with another electron and are available for chemical bonding.

Orbital

A region within an energy level where electrons are likely to be found.

Ground State

The lowest energy state of an atom.

Excited State

A higher energy state reached when electrons absorb energy.

Photon

A packet of light energy absorbed or released when electrons move between energy levels.

Emission of Light

Occurs when an electron falls back to a lower energy level and releases energy as a photon.

Isotopes

Different forms of the same element that differ in the number of neutrons.

Chemical Bonding

Occurs when atoms share, gain, or lose valence electrons to form stable compounds.

Ionic Bonds

Electrostatic force of attraction between oppositely charged ions.

Ionic Compounds

Compounds formed by ionic bonds, usually between metals and nonmetals. Also called salts.

Ion

An atom that has lost or gained electrons.

Anion

A negatively charged ion.

Cation

A positively charged ion.

Covalent Bonds

Bonds formed by sharing electrons between two atoms.

Molecules

Groups of two or more atoms chemically bonded together.

Molecular Compounds

Compounds made of molecules, usually containing common elements such as hydrogen, oxygen, carbon, and chlorine.

Polar Covalent Bonds

Covalent bonds in which electrons are shared unequally, creating partial charges.

Nonpolar Covalent Bonds

Covalent bonds in which electrons are shared equally.

Electronegativity

The ability of atoms or molecules to attract electrons.

Hydrogen Bonds

Weak, temporary attractions between a slightly positive hydrogen atom in one molecule and a slightly negative atom, such as oxygen, nitrogen, or fluorine, in another molecule.

Proteins

Organic compounds made of amino acids.

Amino Acids

The building blocks of proteins.

Glucose

The primary source of energy for many living organisms. Chemical formula: C6H12O6.

Water

A polar molecule and a vital property of matter for life.

Observation

The collection of information using your senses.

Temperature

A measure of the average kinetic energy of particles.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

REDOX Reaction

A chemical reaction involving the transfer of electrons.

Cohesion

Attraction between water molecules due to hydrogen bonding.

Adhesion

Attraction between water molecules and other substances.

Hydrophilic

Water-loving; substances that interact well with water.

Hydrophobic

Water-fearing; substances that do not mix well with water.

Emulsions

Mixtures of two or more liquids that normally do not mix.

Emulsifying Agent

A substance with hydrophilic and hydrophobic regions that helps keep mixtures from separating.

Amphipathic Molecules

Molecules with both polar and nonpolar regions.

Molecular Weight

The sum of the weights of all atoms in a molecule.

Mole

A unit used to measure the amount of a substance.

Molarity

A measure of concentration defined as moles of solute per liter of solution.

Acid

A substance that donates hydrogen ions (H+) when dissolved in water.

Base

A substance that produces hydroxide ions (OH−) or accepts hydrogen ions (H+) when dissolved in water.

Buffer

A solution that resists changes in pH.

pH

A logarithmic scale from 0 to 14 that measures acidity based on the concentration of hydrogen ions.

Macromolecules

Large molecules composed of thousands of covalently connected atoms.

Polymer

A large molecule made of many similar building blocks called monomers.

Monomer

A small repeating unit that builds polymers.

Redox Reaction

A chemical reaction involving the transfer of electrons.

pH = Potential of Hydrogen

A measure of hydrogen ion concentration in a solution.

Water Molecule (H₂O)

Water contains two polar covalent O-H bonds. Oxygen is more electronegative than hydrogen, so oxygen carries a partial negative charge and hydrogen carries partial positive charges.

Covalent Bond

A strong bond formed by sharing electrons.

Hydrogen Bond

A weak attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen of another water molecule.

Surface Tension

The tendency of water molecules to resist separation because of hydrogen bonding.

Evaporation

The process by which water molecules transition from liquid to gas.

Heat of Vaporization

The energy required to convert liquid water to gas by breaking hydrogen bonds.

Hydration Shell

A layer of water molecules surrounding ions or polar molecules.

Solvent

A substance, such as water, that dissolves other substances.

Solute

A substance dissolved in a solvent.

Aqueous Solution

A solution in which water is the solvent.

Hydrophilic Molecules

Polar or charged molecules that interact well with water.

Nonpolar Molecules

Molecules with little or no charge and poor interaction with water.

pH Formula

pH = -log[H⁺]

Carbon

An element that forms the backbone of organic molecules.

Organic Molecules

Molecules containing carbon atoms.

Isomers

Molecules with the same molecular formula but different structures and properties.

Hydrocarbon

An organic compound composed only of carbon and hydrogen.

Structural Formula

A representation that shows how atoms are connected in a molecule.

Carbonyl Group

A functional group containing a carbon double-bonded to oxygen (C=O).

Hydroxyl Group

A functional group consisting of an oxygen bonded to hydrogen (-OH).

Ketone

A carbonyl group located within the carbon skeleton.