Adrian from Romania & Wales asked:
What happens when you get burned at the molecular level when you touch something hot?
We put this to Peter Djiewulski, Plastic and Reconstructive Surgeon, Director of Burns Centre at St Andrew's Centre for Burns.
What happens when somebody gets burned and their tissue is burned is that heat causes direct damage to cells. It denatures proteins within and without cells. It's that injury and the breakup of cells and the contents with in the cells, particularly some of the enzymes within the cells that will initially cause pain but secondarily bits of cells that break down cause local irritation. The cell wall breaks down and that leads to a number of breakdown products which are involved in inflammation and the inflammatory response. Most people have burnt themselves and therefore would be well-aware of the local effects that the burn and the body's reaction to the burn will cause. That is usually swelling, redness and tenderness. At a molecular level these events are mediated by the inflammatory mediators which have effects on, particularly, the tiny ittle blood vessels that go up to and into the skin to make them leaky. This allows fluid which is usually in the blood vessels to leak out and this gives rise to swelling.
It's a matter of energy transfer. Temperature can be thought of as a measure of the average kinetic energy of the molecules in a substance. When a hot object (like a stove eye) comes into contact with a cooler object (like a human hand), the faster moving molecules in the stove eye bump into (and tranfer some of their kinetic energy into) the molecules in your hand. This causes the molecules in your hand to move faster, creating a rise in the temperature of your hand. This is called thermal conduction.