Final answer:
In chemistry, the term 'inflammable' refers to substances that ignite easily, such as napalm or acetylene. These substances either spontaneously catch fire or require minimal activation energy to start burning.
Step-by-step explanation:
The substance that catches fire easily is inflammable. This term is used to describe materials that ignite quickly and sustain burning easily. An example is napalm, an incredibly flammable substance made by converting gasoline into a gel and mixing it with incendiary agents. Materials such as wood, which is used in campfires for heat and light, release energy through combustion. Similarly, living cells obtain energy by 'burning' glucose in a process known as cellular respiration.
Certain chemical properties affect how easily substances burn. For instance, many covalent compounds, particularly those involving carbon and hydrogen, are prone to burning, while most ionic compounds do not. Furthermore, the concept of activation energy is fundamental to understanding when a substance will ignite. Fireworks, for example, require heat from a lit fuse to supply this activation energy and initiate the reaction that results in a beautiful display.
In more practical applications, acetylene and other alkynes are known for burning rapidly, which is why an acetylene torch takes advantage of the high heat of combustion for these substances. It's worth noting also that the reaction rate of a substance increases with greater surface area, as evidenced in the use of kindling to start a wood fire.