This is a good explanation of relationships that are NOT proportional and why. The candle problem is a good one--ask students, "How could you turn this into a proportion?" They would want to say that the statement should change to something like "How much candle is burned each hour?"
Need a great activity to get your students working on problems while moving about the room? This middle school math activity is explained in a short video, but while the topic is math, you can adapt the exercise to other topics too!