You are about to take a short trip. However, you will not be traveling by car or bus; instead you will be traveling up in a hot air balloon. You know that hot air balloons, like the ones pictured, are able to rise when the air contained in them is heated. Why does the balloon rise? What is happening at the molecular level to make the balloon rise?

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.