Up Learn – A Level Chemistry (aqa) – Thermodynamics
Entropy: Order and Disorder
Theoretical lattice enthalpy calculations are based on the perfect ionic model, which assumes that the bonding in salts is 100% ionic.
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Last time, we said it’s not just enthalpy that determines whether reactions can happen…
That something called entropy plays a role too.
Unfortunately, defining entropy is a little tricky.
And so, rather than talking about entropy straight away, we’re first going to talk about disorder…
For example, we’d say these bricks are more disordered than these bricks.
We’d say that these trees are more disordered than these trees.
And we’d say this kitchen cupboard is more disordered than this kitchen .
Really, disorder is just the opposite of order. If things are ordered, they might be neatly arranged, put into groups and so on. If they’re disordered, not so much.
So now, for each of these pairs, decide which is the more disordered.
These are all more disordered than their counterparts.
Now, having a sense of what disorder means is going to help us get a very rough sense of what entropy is…and so we’ll look at entropy, next…
But to sum up for now, disorder is just the opposite of order.