We can use an instrument called a calorimeter to determine how much potential energy is stored in molecules.
Strain is a super general word. So now let’s go more into specifics of the types of strain you need to recognize.
The ideal bond angle for sp3 hybirdized carbon is 109.5°, so the more we deviate from that number, the more unstable the angle will be! (Aka cyclopropane sucks).
Torsional strain increases with the number of eclipsing hydrogens in a molecule. Some of these rings are so small they can’t twist to prevent these interactions, which makes them unstable.
Example: Which of the following conformations of cyclohexane would have the lowest heat of combustion?3m