The phenomenon you're experiencing when you open the oven door and feel a blast of hot air is due to convection. Most modern ovens are designed with a convection feature, which circulates hot air inside the oven to ensure even cooking and baking.
Here's the scientific explanation behind the hot air blast:
Convection Currents: Inside the oven, there is a heating element (usually located at the bottom) that heats the air around it. Hot air rises because it is less dense than cold air. As the air near the heating element gets warm, it becomes lighter and starts to rise towards the top of the oven.
Cool Air Inflow: As the hot air rises, it creates a region of lower pressure near the heating element. Nature always seeks to balance pressure, so cooler air from the surrounding environment is drawn in through any openings or gaps in the oven's structure. The oven door, especially when it is slightly ajar, provides an easy path for this cooler air to enter.
Air Blast Effect: When you open the oven door, you create a larger opening for the cool air to rush into the oven. Simultaneously, the hot air inside, being less dense, tries to escape. This creates a convection current, where the hot air moves upward and out of the oven, while the cooler air moves in, producing the sensation of a hot air blast on your face.
Convection Cooking: The circulation of hot air within the oven is also the basis for convection cooking. By moving the hot air around, the oven ensures that the heat is distributed evenly throughout, resulting in more consistent and faster cooking or baking.
It's essential to be cautious when opening the oven door to avoid getting burned by the hot air or steam that may be released. Some ovens have safety features that limit the flow of hot air when the door is opened, but it's always a good idea to open the door carefully and use oven mitts or pot holders to protect your hands and face.