British Sign Language Glossaries of Curriculum Terms

BSL Chemistry Glossary - balanced equation - Definition

I want to show you how to write a balanced equation.

For example, let's take methane burning with oxygen. What that results in is (writes 'carbon dioxide and water'). We want to change these into chemical symbols (writes 'CH4 + O2 ⇢CO2 + H2O') and make sure that we have the same numbers (of each element) on both sides of the equation.

So let's go ahead and check. On the left hand side we have one carbon here and one carbon on the right side of the equation, so that balances. If we look at the number of hydrogens; on the left hand side there are four, but on the right there are only two, so there is not enough. If we then count the number of oxygens; there are two on the left side but three on the right so they are not the same/balanced either.

What we need to do is work out whether we can add numbers to any of these chemical symbols so that the equation balances. Using a blue coloured pen for the carbon, we can see there is one dot on either side so they balance; with a green pen I can draw 4 dots to represent the hydrogen on the left side and draw two green dots for those on the left so there are not enough - we need double the number of green dots (hydrogen) on the right side to match the left to make four. We can do this by adding a 2 in front of the H2O to make it 2H2O.

If we then add in those extra hydrogen we now have the same number of green dots (hydrogen) on both sides. Next we need to work out how many oxygens there are so, using a black pen, we can put two black dots under the O2 (on the left hand side); two under the CO2 and one under the H2O but because it is now 2H2O, that is two oxygens/black dots.

Now what we have is two oxygens on the left and 4 on the right; we need to increase the number on the left by two by putting a 2 in front of the O2 and make it 2O2 and that means we can add two more black dots.

So, let's check - we've got one carbon on either side of the equation; 4 hydrogen on both sides and 4 oxygen on the left and two lots of two on the right (= four) and that means we now have a balanced equation.