Specific heat for common products and materials can be found in the Material Properties section. The enthalpy - or internal energy - of a substance is a function of its temperature and pressure. The change in internal energy with respect to change in temperature at fixed pressure is the Specific Heat at constant pressure - c p.
The change in internal energy with respect to change in temperature at fixed volume is the Specific Heat at constant volume - c v. Unless the pressure is extremely high the work done by applied pressure on solids and liquids can be neglected, and enthalpy can be represented by the internal energy component alone.
Constant-volume and constant-pressure heats can be said to be equal. For solids and liquids. The specific heat represents the amount of energy required to raise 1 kg of substance by 1 o C or 1 K , and can be thought of as the ability to absorb heat. Water has a large specific heat of 4. The amount of heat needed to heat a subject from one temperature level to an other can be expressed as:. Consider the energy required to heat 1. Work and energy are from a technical viewpoint the same entity - but work is the result when a directional force vector moves an object in the same direction.
The amount of mechanical work done can be determined by an equation derived from Newtonian mechanics. The unit of work is joule, J, which is defined as the amount of work done when a force of 1 newton acts for a distance of 1 m in the direction of the force. Some examples include ceramics and styrofoam. Foods also have a different specific heat capacity and heat capacity. This often depends on the amount of water that makes up that food, but other factors are also at play. It is helpful to know the heat capacity of foods both when cooking and when eating them.
Some foods act as insulators and, when placed on top of other foods, trap the heat underneath. They also do not lose water, because there is no place for it to evaporate.
Cheese is a good example of insulator food. When it is placed on top of another food, such as pizza, it melts and insulates the ingredients under it. There are usually ingredients under the cheese that have high water content, such as vegetables and sauce. Because of this, they have high heat capacity, so after they become hot, they do not lose this heat easily, and this property is further enhanced by the cheese insulator.
This is why pizza straight out of the oven is very hot, and it does not cool down quickly. Sauces are sometimes used in a similar manner as cheese. They are especially good insulators if they have a high-fat content, for example, cream sauces. Inedible insulators are also sometimes used in cooking. For example, chefs in Central America, the Philippines, India, Thailand, Vietnam, and many other countries use banana leaves in place of edible insulators.
Aluminum foil is often used in the same way as well. Not only does it prevent the water from evaporating and keeping the heat inside, but it also stops the protruding parts like chicken or turkey wings from overheating and burning as a result.
Foods high in fat or oil, such as cheese, have low heat capacity. They become hot with less heat than high heat capacity foods, and this often allows them to reach temperatures high enough for a browning reaction, known as the Maillard reaction. It is a chemical reaction between certain sugars and amino acids that changes the look and the flavor of food and is essential in many cooking methods such as baking and frying.
We use oils for frying and deep-frying to increase the temperatures on the surface of different foods, to create conditions necessary for the Maillard reaction. Sugar has an even lower heat capacity than oil. It becomes hot very quickly and can be a hazard during cooking, especially when making candy or caramel. When melting sugar, the chef must take necessary precautions to make sure that melted sugar is not spilled accidentally on the skin. In some cases, the chef may need to check the temperature and consistency of the sugar, but it must be done with a thermometer, to avoid touching it with bare skin.
When sugar or sugar syrups are cooked at different temperatures they have different properties. Heated sugar syrup could be liquid like the most liquid honey, solid, or anything in between. Recipes usually specify what temperature the sugar needs to reach to be ready to use, but they also often specify the name of the stage that it reaches, such as the soft-ball stage or the hard-ball stage. The stage name corresponds to the consistency of the sugar. To determine this consistency the chef places several drops of the melted sugar in icy water to cool it down instantly, and then examines these drops with bare hands for consistency.
For example, if the sugar is not liquid but pliable enough to make a ball, it is in a soft-ball stage. If it is solid once cool and it is difficult but possible to change its shape with fingers, then it is in a hard-ball stage.
This is the cold water drop method. Often chefs use both the thermometer readings and the cold water drop method to check if the sugar is cooked to the right consistency.
It is useful to know the heat capacity of foods to ensure that they are heated or chilled to the right temperature, to prevent spoilage or growth of parasites. For example, to reach a given temperature, foods that have higher heat capacity need to be cooked or chilled longer or with more intensity, compared to foods with low heat capacity.
Cooking times are, therefore, determined based on the heat capacity of the ingredients, which, in turn, is dependent on the water content and on the amount of the water that is evaporating. The latter is because water evaporation requires a large amount of energy. We wish to determine the value of Q — the quantity of heat. A high specific heat of a substance means that a large amount of heat is required to raise the temperature of the substance.
The high specific heat of water helps to 1 moderate temperature in coastal areas, 2 stabilize ocean temperatures, creating a favorable environment for marine life, 3 because it covers most of the earth it keeps temperature fluctuations within the limits for life, 4 helps organisms that are made primarily out of ….
Begin typing your search term above and press enter to search. Press ESC to cancel. Be it buying grocery or cooking, units play a vital role in our daily life; and hence their conversions. When you are converting specific heat capacity, you need a Joule per Kilogram per K to Kilojoule per Kilogram per K converter that is elaborate and still easy to use. Units Converters.
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