Biogas comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

Plaster of Paris is calcium sulphate hemihydrate. The formula is given as, CaSO4.1/2 H2O or (2 CaSO4) . H2O. The powder is called plaster of Paris, because the gypsum which was used to get the powder was mainly found in Paris.

Polyvinyl chloride (PVC) is made from the monomer vinyl chloride (CH2 =CHCl). It is used for making rain coats, handbags, toys including dolls, electrical goods and as a covering of electrical wires.

Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 k) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.

 In the manufacture of tyre rubber, 5% of sulphur is used as a crosslinking agent

When iron or any other metal oxidizes, oxygen from the air combines with the iron to make iron oxide or rust. So, weight of the bar increases, due to the increased weight of oxygen which has combined with the iron. over time, the weight of the iron bar will tend to decrease, due to factors related more to erosion than to chemistry.

A cotton wick dipped in pure honey burns when ignited with a match stick. If adulterated presence of water will not allow the honey to burn, if it does will produce a cracking sound.

The speed of sound decreases when we go from solid to gaseous state.

Calamine- ZNCO3

Aspirin, also known as acetylsalicylic acid, is a salicylate drug, often used as an analgesic to relieve minor aches and pains as an antipyretic to reduce fever and an anti-inflammatory medication. Aspirin also has an anti-platelet, or anti-clotting, effect and is used in long-term , low does to prevent heart attacks, strokes and blood clot formation in people.

Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature.