Conservation of mass: The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
Percentage by mass: A value representing the concentration of an element in a compound or a component in a mixture. It is calculated by the mass of a component divided by the total mass of the mixture, multiplied by 100
Relative formula mass: The sum of the relative atomic masses of the atoms in the numbers shown in the formula. It is numerically equal to the mass of one mole of a substance in grams
Uncertainty: All measurements have a degree of uncertainty regardless of precision and accuracy. Uncertainty can be due to the limitations of the measuring equipment or due to the skill of the experimenter carrying out the measurements