The typical disposable hand warmer contains iron, salt, activated carbon, water and an absorbent material. Opening the outer packet allows oxygen to contact the iron, forming iron oxide, commonly known as rust, through an exothermic reaction that produces heat. Choices for the absorbent material are polymers, sawdust or vermiculite.Know More
The rusting reaction creates temperatures up to 135 degrees Fahrenheit. The manufacturer includes activated carbon to improve the distribution of heat from the warmer.
Producing the hand warmer requires engineering. The product should provide sufficient heat quickly, but should also continue producing heat for several hours. To meet these goals, the manufacturer sometimes increases the amount of iron in the packet. However, a second option is to vary the texture of the iron powder. Increasing the surface area of the iron, by using finer powder, increases the amount of heat the warmer produces, but increases the speed at which it rusts, reducing the time the warmer produces heat. The material the manufacturer chooses for the inner pouch affects the rate at which oxygen enters the pouch.
The manufacturer must also consider shelf life of the product. Hand warmers sometimes spend several months in the warehouse or on the store shelf. Consumers purchase hand warmers and store them before use. The outer pouch is made of polyethylene sheeting that does not allow oxygen to enter the warmer until the purchaser opens it.Learn more about Chemistry
Methane is utilized as fuel and in chemical reactions to produce commercially used chemicals such as carbon tetrachloride, carbon black and as a source of hydrogen. Methane reacts at high temperatures with steam to yield the hydrogen used in the manufacturing of explosives and ammonia-based fertilizers.Full Answer >
Six methods of separating chemicals are filtration, chromatography, distillation, evaporation, centrifugation and using a separating funnel. Chromatography, distillation and evaporation are used to separate solutions, in which one or more chemicals are dissolved in a solvent. Filtration, centrifugation and separating funnels are used to separate mixtures of insoluble chemicals.Full Answer >
The primary function of a stirring rod is to stir solutions by hand. Stirring rods have other uses in the laboratory, however, including helping to decant liquid from containers, breaking up emulsions and inducing crystallization.Full Answer >
Robots are used for a variety of purposes, including welding, handling chemicals, marine exploration and space missions. Advanced robots are designed to serve and assist people. There are other robots that mow lawns and vacuum floors.Full Answer >