Key Difference: Steam forms when water is boiled to the point where it transitions from the liquid phase to the gaseous phase. Steam is basically heated water vapor that is the gaseous phase of water. Smoke is simply a collection of airborne solid, liquid and gasses emitted when a substance undergoes combustion. Smoke is a by-product of combustion.

The terms ‘steam’ and ‘smoke’ are often confusing for many people because of the similarity in their appearance. At first glance, it can be difficult to tell them apart. However, they have different properties that make it easier to tell these two from each other.

Steam is basically heated water vapor that is the gaseous phase of water. Steam forms when water is boiled to the point where it transitions from the liquid phase to the gaseous phase. Although, steam is considered to be invisible, it can be seen as a white mist escaping a boiling pot or kettle. Steam is required to be hot and can transform back to water droplets when it cools down. Steam is believed to be generated when water is boiled at boiling point, which is at 100 ˚C. At high temperatures steam is invisible, but it becomes visible as the temperature drops. This can be seen when water is boiling, as the steam rises above the pot it gets cooler and the steam can be seen as mist.

Smoke is produced by burning matter such as wood, petrol, oil, rubber, etc. Burning is a process that converts oxygen into carbon dioxide. When burning an object, it takes the surrounding oxygen and converts it into carbon dioxide, along with the carbon produced from the substance which is being burned to produce smoke. Smoke is simply a collection of airborne solid, liquid and gases emitted when a substance undergoes combustion.

Smoke combines the soot and other gases along with the carbon dioxide emitted to create a brownish/greyish gas-like byproduct. Smoke is full of harmful green house gases that can contribute to global warming. In addition to being just a by-product of combustion, it can also be used for various purposes such as pest control, defensive and offensive capabilities in the military, cooking, or rituals (for purification). The composition of the smoke depends on the substance that is being burned.

Steam and smoke seem similar because at first glance they seem the same. However, steam is always produced from water being heated, while smoke is by product of combustion. Steam will automatically condense if the temperature were to drop, while smoke will not condense but rather dissipate into the air. Steam is not dangerous to inhale, while smoke dangerous to inhale and can cause damage to lungs. The massive damage to smoker’s lungs is caused by the smoke rather than the tobacco. The easiest way to tell these two apart to see how it is being produced. Also, the color steam would be more white and misty color, while smoke would be darker in color.

Image Courtesy: home.howstuffworks.com, rmrblog.com