Flammable substances are materials that can easily ignite and catch fire when exposed to a heat source, spark, or flame. These substances can be in various forms, including liquids, solids, and gases. Common examples include gasoline, alcohol, and paper. Proper storage and handling are essential to prevent accidental fires. The flammability of a substance is often determined by its flash point, which is the lowest temperature at which it can produce enough vapor to ignite. Understanding the properties of flammable substances is crucial for safety in environments like laboratories, factories, and homes to minimize fire hazards.