Most cold packs utilize water and ammonium chloride or ammonium nitrate to create endothermic reactions. Endothermic reactions require energy and obtain it by absorbing heat from the environment.Know More
While the majority of commercial cold packs use ammonium nitrate or ammonium chloride, many types of salts create endothermic reactions. Instant cold packs maintain water and ammonium salt in separate sections, with a thin barrier in-between. Breaking the barrier allows the salt and water to mix, dissolving the salt. As the ammonium salt dissolves, it absorbs heat from the air around it, lowering the temperature of the water to its freezing point. Once the water reaches its freezing point, it becomes less effective at dissolving the salt, meaning that some salt remains. Eventually the water begins to warm, allowing more salt to dissolve and then cooling the water again. In this way, cold packs retain their cool temperature for an extended period of time.
Endothermic reactions do not just occur in cold packs. Mixing an acid, such as vinegar or citric acid, with baking soda, a base, absorbs heat and cools its container for a short amount of time. Because endothermic reactions are those that absorb energy rather than releasing it, photosynthesis is also an endothermic reaction as it requires the absorption of energy in the form of sunlight.Learn more about Chemistry
The molecules of one reactant are combined with those of another reactant to form a new substance during a chemical reaction. As the chemical bonds are broken, the positions of electrons change, resulting in a product with properties that are different from the properties of the reactants. Various temperatures and catalysts are needed for different chemical reactions to occur.Full Answer >
Burning a match is a chemical reaction because the reactant, primarily wood, is chemically altered into a different substance, ash. A chemical reaction or change involves one or more reactants having bonds broken or altered to form new substances. In the case of burning a match, wood and oxygen are transformed into ash and smoke, two distinctly new products.Full Answer >
The chemical reaction between aluminum and bromine is an exothermic one that produces aluminum bromide. The equation of the chemical reaction is 2 Al + 3 Br2 ? 2 AlBr3. It indicates that two molecules of aluminum combine with three molecules of bromine to produce two molecules of aluminum bromide.Full Answer >
The term "chemical reaction" refers to any process that changes a set of chemical substances to another. That is, the substances that are put into a chemical reaction are different, on a molecular level, from those that result.Full Answer >