40 Vocabulary for Chemistry Terms You Should Know

This is a list of important chemistry vocabulary terms and their definitions.
 

1. accuracy - Accuracy is a measure of how close a measured value is to its true value. For example, if an object is exactly a meter long and you measure it as 1.1 meters long, that is more accurate than if you measured it at 1.5 meters long.

2. acid - There are several ways to define an acid, but they include any chemical that gives off protons or H⁺ in water. Acids have a pH less than 7. They turn the pH indicator phenolphthalein colorless and turn litmus paper red.

3. addition reaction - An addition reaction is a chemical reaction in which atoms add to a carbon-carbon multiple bond.

4. alcohol - An alcohol is any organic molecule that has an -OH group.

5. aldehyde - An aldehyde is any organic molecule that has a -COH group.

6. alkali metal - An alkali metal is a metal in Group I of the periodic table. Examples of alkali metals include lithium, sodium, and potassium.

7. alkaline earth metal - An alkaline earth metal is an element belonging to Group II of the periodic table. Examples of alkaline earth metals are magnesium and calcium.

8. alkane - An alkane is an organic molecule that only contains single carbon-carbon bonds.

9. alkene - An alkene is an organic molecule that contains at least one C=C or carbon-carbon double bond.

10. alkyne - An alkyne is an organic molecule that contains at least one carbon-carbon triple bond.

11. allotrope - Allotropes are different forms of a phase of an element. For example, diamond and graphite are allotropes of carbon.

12. alpha particle - An alpha particle is another name for a heliumnucleus, which contains two protons and two neutrons. It's called an alpha particle in reference to radioactive (alpha) decay.

13. amine - An amine is an organic molecule in which one or more of the hydrogen atoms in ammonia have been replaced by an organic group. An example of an amine is methylamine.

14. amine - An amine is an organic molecule in which one or more of the hydrogen atoms in ammonia have been replaced by an organic group. An example of an amine is methylamine.

15. base - A base is a compound that produces OH^- ions or electrons in water or that accepts protons. An example of a common base is sodium hydroxide, NaOH.

16. beta particle - A beta particle is an electron, although the term is used when the electron is emitted in radioactive decay.

17. buffer - A liquid that resists change in pH when an acid or base is added. A buffer consists of a weak acid and its conjugate base. An example of a buffer is acetic acid and sodium acetate.

18. calorimetry - Calorimetry is the study of heat flow. Calorimetry may be used to find the heat of reaction of two compounds or the heat of combustion of a compound, for example.

19. catalyst - A catalyst is a substance that lowers the activation energy of a reaction or speeds it up without being consumed by the reaction. Enzymes are proteins that act as catalysts for biochemical reactions.

20. cathode - A cathode is the electrode which gains electrons or is reduced. In other words, it is where reduction occurs in an electrochemical cell.

21. chemical equation - A chemical equation is a description of a chemical reaction, including what reacts, what is produced, and which direction(s) the reaction proceeds.

22. chemical property - A chemical property is a property that can only be observed when a chemical change occurs. Flammability is an example of a chemical property, since you can't measure how flammable a substance is without igniting it (making/breaking chemical bonds).

23. crystal - A crystal is an ordered, repeating three-dimensional pattern of ions, atoms, or molecules. Most crystals are ionic solids, although other forms of crystals exist.

24. diffusion - Diffusion is the movement of particles from an area of higher concentration to one of lower concentration.

25. dissociation - Dissociation is when a chemical reaction breaks a compound into two or more parts. For example, NaCl dissociates into Na⁺ and Cl^- in water.

26. electrolysis - Electrolysis is using electricity to break the bonds in a compound to break it apart.

27. endothermic - Endothermic describes a process that absorbs heat. Endothermic reactions feel cold.

28. ester - An ester is an organic molecule with a R-CO-OR' function group.

29. excess reagent - Excess reagent is what you get when there is leftover reagent in a chemical reaction.

30. excited state - An excited state is a higher energy state for an electron of an atom, ion, or molecule, compared with the energy of its ground state.

31. exothermic - Exothermic describes a process that gives off heat.

32. kinetic energy - Kinetic energy is energy of motion. The more an object moves, the more kinetic energy it has.

33. ketone - A ketone is a molecule that contains a R-CO-R' functional group. An example of a common ketone is acetone (dimethyl ketone).

34. ligand - A ligand is a molecule or ion stuck to the central atom in a complex. Examples of common ligands include water, carbon monoxide, and ammonia.

35. redox reaction - A redox reaction is a chemical reaction that involves oxidation and reduction.

36. resonance structure - Resonance structures are the set of Lewis structures that can be drawn for a molecule when it has delocalized electrons.

37. reversible reaction - A reversible reaction is a chemical reactionwhich can go both ways: reactants make products and products make reactants.

38. sublimation - Sublimation is when a solid changes directly into a gas. At atmospheric pressure, dry ice or solid carbon dioxide goes directly into carbon dioxide vapor, never becoming liquid carbon dioxide.

39. synthesis - Synthesis is making a larger molecule from two or more atoms or smaller molecules.

40. titration - Titration is a procedure in which the concentration of an acid or base is determined by measuring how much base or acid is required to neutralize it.