An element is a substance that cannot be broken down into simpler substances by chemical means. It is made up of atoms that all have the same number of protons in their nucleus.
A compound is a substance made up of two or more elements that are chemically bonded together. Unlike elements, compounds have different physical and chemical properties than the elements that make them up.
A chemical formula is a shorthand way of representing the elements and their proportions in a compound. A chemical equation is a representation of a chemical reaction, showing the reactants on the left side and the products on the right side.
A physical change is a change in the physical properties of a substance, such as its shape or state, without altering its chemical composition. A chemical change, on the other hand, results in the formation of new substances with different chemical properties.
An acid is a substance that donates hydrogen ions (H+) in a chemical reaction, while a base is a substance that accepts hydrogen ions. Acids have a pH less than 7 and bases have a pH greater than 7 on the pH scale.