The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG) etc.

Physical Properties of Metals

• Shiny (lustrous) in nature.
• Metal is a good conductor of electricity and heat.
• Density and melting point is high.
• Mouldable (Malleable)
• Ductile.
• At room temperature, it is in solid form except for mercury.
• Opaque.

The lowest temperature at which a substance catches fire and undergoes combustion liberating heat and light is called ignition temperature. In other words it is the minimum temperature at which a combustible substance such as air or gas, must be heated up prior to burning in the absence of any source of the heat.

Oxygen

Heated molecules are loosened, moving apart to form a gas. The gas molecules combine with oxygen in the air resulting in burning. The heat generated by the reaction is what sustains the fire. The heat of the flame will keep remaining fuel at ignition temperature.

Flames consist primarily of carbon dioxide, water vapor, oxygen and nitrogen. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the fire’s intensity will be different.

Fire is the result of applying enough heat to a fuel source, when you’ve got a whole lot of oxygen around. As the atoms in the fuel heat up, they begin to vibrate until they break free of the bonds holding them together and are released as volatile gases. These gases react with oxygen in the surrounding atmosphere.

Oxygen. Air contains about 21 percent oxygen, and most fires require at least 16 percent oxygen content to burn. Oxygen supports the chemical processes that occur during fire. When fuel burns, it reacts with oxygen from the surrounding air, releasing heat and generating combustion products (gases, smoke, embers, etc.).