Balancing Equations

This sometimes seems hard, but it isn’t really.

Reactants go on the left, products on the right. The number of reactant and product particles has to be the same on both sides, which means that we can’t actually lose anything. The see-saw balances, or mass is conserved in other words – the particles are  like money and we have to account for every single atom. Here’s an example.

When heated, aluminium reacts with solid  black copper oxide to produce copper metal and aluminium oxide:

Writing the reaction down in symbols, making sure you KNOW them:

Al + CuO Al2O3 + Cu

The equation doesn’t balance, until we do this:

2Al + 3CuO Al2O3 + 3Cu

To solve this, I started by saying ‘I need 2 Al’s on the left and 3 more oxygens, so 3CuO’s’

A few tricks:

You can only put numbers in front of molecules, never change  the formula of the compound itself.

H4O5 No! No! This isn’t water!

Don’t worry if  when you start adding up, the numbers turn out to be fractions – you can always double or treble all the numbers at a later stage.


Balance complicated molecules with lots of different atoms first. Putting numbers in front of these may mess up other molecules, so use the simpler molecules to adjust these major changes.

If you recognise the atoms making up a standard group such as sulphate, nitrate, phosphate, ammonium etc.that survive unscathed throughout the chemical reaction, treat them as an indivisible item to be balanced as a whole. This makes life easier and helps understanding of the chemistry.

Leave molecules representing elements until last. This means that any numbers you put in front of those molecules won’t unbalance any other molecule.

Click here for all the details. Work through all of  this, there’s an exercise at the end.

The End of Physics?

The universe is full of magical things patiently waiting for our wits to grow sharper.  ~Eden Phillpotts, A Shadow Passes

Just when you thought you knew everything there is to know, remember the misguided professor, who told one of his students  ‘I shouldn’t pursue physics if I were you. Most of the important stuff has already been discovered’.

Oh yeah?

Look here for timeline…THIS IS IT. Or, is it…? Most of the names are just for the record, but a few of them are worth pursuing…

When the really big stuff like the supernova above and the really small stuff finally hold hands and make friends, the title of this post will become reality, perhaps.