Glossary
Chemical Changes
Transformations that result in the formation of new chemical substances with different molecular structures, involving the breaking and/or forming of intramolecular bonds.
Example:
The browning of an apple after being cut is a chemical change due to oxidation.
Chemical Equations
A symbolic representation of a chemical reaction that shows the reactants on the left and the products on the right, indicating the substances involved and their stoichiometric ratios.
Example:
The equation 2H₂ + O₂ → 2H₂O is a chemical equation showing hydrogen and oxygen reacting to form water.
Combustion
A rapid chemical reaction, typically involving a fuel and an oxidant (usually oxygen), that produces heat and light.
Example:
The burning of propane in a grill is a combustion reaction.
Covalent Bonds
Chemical bonds formed by the sharing of electron pairs between atoms, typically between two nonmetal atoms.
Example:
The bond between two oxygen atoms in an O₂ molecule is a covalent bond.
Digestion
The process by which food is broken down into smaller, absorbable molecules through a series of chemical reactions catalyzed by enzymes in the body.
Example:
The breakdown of starches into sugars in your mouth is part of the digestion process.
Dissolving
The process by which a solute disperses uniformly into a solvent to form a solution, often involving the breaking of intermolecular forces in both substances and the formation of new solute-solvent interactions.
Example:
When you add sugar to hot tea, the dissolving process occurs as sugar molecules spread throughout the water.
Intermolecular
Refers to forces or interactions that occur *between* molecules, affecting their arrangement or state but not their internal chemical structure.
Example:
When water boils, the intermolecular hydrogen bonds between water molecules are overcome, allowing them to escape as gas.
Intramolecular
Refers to forces or bonds that exist *within* a molecule, such as ionic or covalent bonds, which are broken or formed during chemical changes.
Example:
The strong intramolecular covalent bonds hold the hydrogen and oxygen atoms together within a single water molecule.
Ionic Bonds
Chemical bonds formed by the electrostatic attraction between oppositely charged ions, typically resulting from the transfer of electrons between a metal and a nonmetal.
Example:
Sodium chloride (NaCl) forms through an ionic bond where sodium donates an electron to chlorine.
Phase Changes
Physical transformations of matter from one state (solid, liquid, gas) to another, involving changes in intermolecular forces but not chemical bonds.
Example:
The melting of ice into liquid water is a common phase change.
Physical Changes
Transformations that alter the form or appearance of a substance but do not change its chemical composition or molecular structure, primarily involving intermolecular forces.
Example:
Crushing a can is a physical change because the aluminum atoms themselves remain unchanged.
Products
The new substances formed as a result of a chemical reaction, appearing on the right side of a chemical equation.
Example:
When wood burns, ash and carbon dioxide are the products of the combustion reaction.
Reactants
The starting substances in a chemical reaction that undergo a transformation to form new substances.
Example:
In the reaction where baking soda and vinegar produce carbon dioxide, baking soda and vinegar are the reactants.
Rusting
The common term for the corrosion of iron and its alloys, typically involving the reaction of iron with oxygen and water to form iron oxides.
Example:
Leaving a bicycle out in the rain can cause its iron parts to undergo rusting.