Hot and Cold

When teaching any concept, you will have faster acquisition and greater retention if the learner is motivated, and the target is presented in terms of a relevant choice. For instance, if the hot or cold thing is something he REALLY WANTS, and would have a strong preference to have it hot or cold, then that is your key.

So, the point is, who cares whether an ice pack is warm or cold? Unless you create a motivating game around an ice pack, your learner's not going to care. So I suggest using his food. Does he have a food that he really enjoys warm that would taste AWFUL cold? Maybe eggs? Or even foods that could be enjoyed both cold and hot, and his choice is more subjective. Maybe you could make two batches of cook on the stove pudding. Have one already chilled in the fridge. Make up some fresh on the stove. Put them in identical bowls. Ask him if he wants it hot or cold. (Don't do it ten times and count the data) Just make sure he gets his finger stuck in both a few times while you repeat Hot/ cold. Do one example like this every day. It won't take long. Make hot eggs/hot pancakes/hot syrup, whatever. But have a cold backup in the fridge, ready to go so that he is offered a choice between hot and cold consistently. Good luck!