Physical Changes:
1. Phase Change: LPG is a liquefied gas stored under pressure in a cylinder. When the valve of the cylinder is opened, the pressure inside the cylinder decreases, causing the LPG to undergo a phase change from liquid to gas. This is a physical change.
2. Expansion: As the LPG changes from liquid to gas, it rapidly expands in volume. This expansion is due to the increased molecular motion and spacing between the gas molecules compared to the liquid phase.
3. Cooling Effect: The expansion of LPG absorbs heat from the surroundings, resulting in a cooling effect. This is why you may feel a cold sensation when you release LPG from a cylinder.
Chemical Changes:
1. Combustion: When LPG comes in contact with an ignition source, such as a spark or flame, it undergoes a chemical change known as combustion. During combustion, the LPG reacts with oxygen (O2) from the air to produce carbon dioxide (CO2) and water vapor (H2O), along with heat and light energy.
2. Oxidation: The combustion process involves the oxidation of LPG's hydrocarbon molecules. The carbon (C) atoms in LPG combine with oxygen to form carbon dioxide, while the hydrogen (H) atoms combine with oxygen to form water vapor.
In summary, the physical changes that occur when LPG comes out of the cylinder include phase change (liquid to gas), expansion, and a cooling effect. The chemical change that takes place during combustion is oxidation, where LPG reacts with oxygen to produce carbon dioxide, water vapor, heat, and light energy.
