There are some things that are never covered in the text books and you are just supposed to ‘know’ at A level 😬.
You should have come across Avogadro’s number and atom economy at GSCE, but I suspect you couldn’t confidently convert parts per million into grams or nanometres into centimetres if I were to put you on the spot. These posts are short and sweet, with explainer videos and practice questions 🙂.
And then there are logarithms, natural logarithms and using them to simplify equations so that we can elicit the exact nature of the relationship between an observed and a control variable. This material is firmly in the realm of A level Maths but not everyone does A level Maths. These posts are to bring you up to speed and to be used as a reference or crib sheet when needed!
Understanding indices and powers
Numbers expressed as an index or power of a base number are common in chemistry and you need to be confident in manipulating them, both in terms of completing calculations and in being able to simplify equations written in this format.
Understanding logarithms and natural logarithms in chemistry
A logarithm is simply the number of times we need to multiply one number together to make another number i.e. it is the power to which a number must be raised to get another number.
Logarithms allow us to deal with extremely large or extremely small numbers without getting our heads in a spin.
Rearranging equations to give straight line graphs in Chemistry
Graphs are one of the best ways we have to determine the quantitative relationship between an observed (plotted on the y-axis) and a controlled variable (plotted on the 𝑥-axis).
Avogadro’s number and the mole
Atoms are really, really small. Too small to count.
But we still need to know the actual numbers of particles (atoms, molecules or ions) taking part in a reaction, rather than just the mass or volume of the substances.
A mole is an amount of substance.
Significant figures in chemistry
What is an ‘appropriate number’ of significant figures for a calculation answer?
Essentially the only rule you need to remember is that your answer cannot be more precise than the least precise piece of information you put into the calculation.
Working with different units in chemistry
We can convert between the units by multiplying by the appropriate factor – to convert from 10a to a factor of 10b, simply multiply by factor 10a-b.
Atom economy
Atom economy or percentage atom economy is simply a measure of how ‘green’ a chemical process is – it essentially calculates the amount of atoms ‘wasted’ in a reaction because these atoms don’t end up in the desired product.
Empirical vs. molecular formulae
Empirical formula: simplest ratio of the atoms of different elements in a compound.
Molecular formula: the actual number of each kind of atom in a molecule of a substance.