The gas cylinder which we use in kitchen contain cooking gas in the liquid state. A change of state is brought about by changing the pressure. At high

• The gas cylinder which we use in kitchen contain cooking gas in the liquid state. A change of state is brought about by changing the pressure. At high pressure, the gas condenses to the liquid state and filled in gas cylinder. Opening the regulators releases the pressure and change it again it to gas for use in kitchen.
• The ancient Greeks were the first to identify three classes of matter based on their observations of water. But these same Greeks, in particular the philosopher Thales(624-545 bc), incorrectly suggested that since water could exist as a solid , liquid, or even a gas under natural conditions, it must be the single principal element in the universe from which all other substances are made. We now know that water is not the fundamental substance of the universe; in fact,it is not even an element.
• Carbon dioxide is a common example of a chemical compound that sublimates at atmospheric pressure-a block of solid CO₂ (dry ice) set on a table will turn into gas without melting
• Snow and ice also sublime, although more slowly, at below-freezing temperatures. This phenomenon, used in freeze drying, allows wet cloth to be hung outdoors in freezing weather and retrieved later in a dry state.
• Freezing is a common method of food preservation which slows both food decay and the growth of micro-organisms and, by turning water to ice, makes it unavailable for bacterial growth an d chemical reactions.