Why can coffee that is hot enough to burn someone be drank (perhaps sipped) with out harm? Why is eating hot pizza more likely to burn the mouth than eating hot soup at the same temperature?
Some factors of this are what the temperature of the item is, the amount of item, the time of contact with the mouth, and the amount of contact area.
The first factor that matters is what the actual temperature is. This is, it may feel really hot but the temperature is not actually as high as it feels. Vaporization comes into play here, which is where a liquid changes state to a vapor or more commonly a gas; this happens at 100°C at sea level, and according to HyperPhysics.edu the process of heating 1 gram of water from 0 to 100 °C takes 100 calories or 1 calorie equals heat to raise 1 gram of liquid water 1°C. An additional way to think about this is the total energy transfer increases the temperature of your mouth. So this amount of energy is created just to cool off your coffee when you sip it. Therefore it transfers air into the liquid you place into your mouth causing it to cool faster and so it does not transfer that heat to your mouth. No vaporization no cooling down of temperature.
This becomes an issue more so with the pizza than with the hot coffee. This is because the pizza has little water in the cheese so it will hold more heat. With the hot pizza this is a different story. Any food that has hot cheese that was heated per microwave oven or even in conventional oven can be harmful because it may not look hot but in reality is, and the cheese has a greater possibility of having contact area of your mouth. This means, it may seem that the pizza is not as hot because a phase change has happened from solid to liquid. A phase change is a change from one state (solid or liquid or gas) to another without a change in chemical composition. Cheese holds its heat for a long time because it does not have much water to lose in the evaporation process. Also the thermal energy that is in the cheese tends to transfer more so because of the amount of surface area that the cheese has, which has a greater chance of burning your mouth.
Next the amount of the food or drink you put into your mouth. The more food or drink the higher the temperature in your mouth. More than likely you would take a larger bite of pizza than you would a large drink of hot coffee. The coffee seems to be hotter more often so we tend to take more caution with the coffee than we would with the pizza.
Another thing is how long the food makes contact with your mouth. So if coffee is sipped you allow the hot water to evaporate, which uses lots of energy, creating less contact area. However, if you were to take a bit of pizza the cheese tends to stick to your mouth unlike the hot coffee. Making more contact area with your mouth. Sipping may subsequently create less contact area than if you were to take a full drink.
Overall the reason your mouth burns more when you take a bit of pizza is because there is more surface area, the cheese is primarily made of fats so water is not vaporized and the thermal energy makes your mouth burn more than a cup of coffee.
Bolanowski, S., Gescheider, G., Fontana, A., Niemiec, J., & Tromblay, J. (2001). The effects of heat-induced pain on the detectability, discriminability, and sensation magnitude of vibrotactile stimuli. Somatosensory & Motor Research, 18(1), 5-9.
This website was used very minimal. I did use it for looking at how temperature effects burning your mouth and the stimuli that make you feel it. I used it in looking at the temperature of actually burning your mouth.
Phase changes. (2005). Retrieved from Hyperphysics
This site if very useful for finding how phase changes actually happen, I used this site to help me grasp the concepts of what an actual phase change was and how to describe one. This site also gave me the ratio of raising temperature of grams of water and how many calories it took.
Phase change. (2009). In Encyclopedia Britannica. Retrieved October 19, 2009, from Encyclopedia Britannica Online:Britannica.com
This website was also used to define phase changes. I used this one also because I wanted a different opinion on what a phase change was. I believe that this gave me a wider range of this topic.
Walker, J (1977). The Flying Circus of Physics. Wiley.
This of course is where I got the question and the outline of my answer. This I believe was the resource that I used the most. It helped me base all of my research for this whole project.
