Class notes Science

Combustion & Flame

⭕ Combustion:


Combustion is a chemical reaction in which a substance combines with
oxygen and releases energy in the form of heat and light.

Substance + O2 Light + Heat
Example:

Combustion of Wood: When wood undergoes combustion, it produces
carbon dioxide, water vapour, light, and heat.

Wood + O2 CO2 + H2O + Light + Heat

→ Conditions of Combustion:

1. Presence of a Combustible Substance
2. Supply of Oxygen (or Air)
3. Ignition Temperature (Minimum Temperature to Start Burning)

o Ignition Temperature:
Ignition temperature is the lowest temperature at which a
combustible substance starts burning.


→ Types of Substances:

1. Combustible Substance:

These substances burn in air and produce heat and light.

Examples: Wood, paper, petrol, LPG, kerosene, coal.

2. Non-combustible Substances:

These substances do not burn in air.

Examples: Glass, metals (like iron), sand, stone, water.

3. Inflammable (Highly Combustible) Substances:

These substances catch fire very easily and have low ignition
temperature.

Examples: Petrol, alcohol, LPG, acetone.




SANKALP CLASSES ‖ ASHWANI KUMAR 1

, 🔬 Experiment
→ To Show Oxygen is Needed for Combustion:

Material Requires:

o A small candle
o A glass jar or transparent jar
o A matchbox or lighter
o A plate

Steps:

1. Place the candle upright on a plate.
2. Light the candle with a matchstick.
3. Now cover the burning candle with the glass jar carefully.
4. Watch what happens.

Observation:

The flame foes out after a few second.

Conclusion:

(i) The candle stops burning because the oxygen inside the glass gets
used up.
(ii) This proves that oxygen is essential for combustion.




SANKALP CLASSES ‖ ASHWANI KUMAR 2