If you can’t understand the heat, get into the kitchen!

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If you can’t understand the heat, get into the kitchen!

By Linda | February 13, 2008

Your kitchen is an excellent place to demonstrate many scientific principles including the properties of heat energy and the effects that heat energy has on various substances. Invite your kids into the kitchen while you cook a meal and your prep time doubles as a science class! Here are just a few of the useful lessons they can learn while you whip up dinner.

Heat Transfer Heat is a type of energy. As a substance heats up, the molecules in it absorb this energy which causes them to vibrate rapidly. The more heat energy is transferred to them, the more the molecules bounce off one another. As the molecules move, they collide with nearby molecules, causing a transfer of heat energy. All this bouncing around also causes the molecules to take up more room. This is why most things expand when they are heated and contract when they are cooled.Heat energy can be transferred to foods through conduction, convection, or radiation. Heat travels through foods by conduction. Conduction Conduction, one of the most basic principles of cooking, is the movement of heat from one item to another through direct contact. For example, when a flame touches the bottom of a pan, heat is conducted to the pan. Generally, metals are good conductors. Copper and aluminum are the best conductors, while liquids and gases are poor conductors. Conduction is a slow method of heat transfer because there must be physical contact from one molecule to another. Convection Convection is the transfer of heat through a fluid. The fluid may be in a liquid or gas state. According to the principles of cooking, there are 2 types of convection: natural and mechanical. Natural convection causes a natural circulation of heat because warm liquids and gases have a tendency to rise while cooler ones fall. Mechanical convection causes heat to circulate more evenly and quickly through fans or stirring. Radiation Radiation is energy transferred by waves of heat or light striking the food. Two types of radiant heat are infrared and microwave. Infrared cooking is commonly used with toasters and broilers. These devices use an electric or ceramic element heated to such a high temperature that it gives off waves of radiant heat. Microwave cooking relies on radiation generated by an oven to heat the food. The Effects Of Heat Proteins Coagulate Coagulation is when proteins transform from a liquid state to a solid state. Examples: the firming of meat fibers and egg whites changing from a clear liquid to a white solid when heated. Starches Gelatinize When a mixture of starch and liquid is heated, starch granules swell. The liquid thickens because the starch granules swell to occupy more space. Examples: The thickening of sauces when starch is added. Sugars Caramelize As sugars cook, they turn brown and change flavor. Caramelized sugar is used in many sugars, candies, and desserts. In fact, caramelization is used in most flavors we associate with cooking. Water Evaporates All foods contain some water. The evaporation of water drys foods during cooking. Fats Melt Fats are a greasy, smooth substance that do not dissolve in water. Oils are fats that remain liquid at room temperature. Fats melt when heated and then gradually liquefy. Fats will not evaporate.