An example of how a change in color indicates a chemical change is copper, which turns from a bronze color to a greenish color when it oxidizes. Color changes are particularly noticeable in transition metals. Change Of Color вЂ“ A substance changing in color is an excellent indication that some form of chemical change has happened.Bubbles вЂ“ When a chemical change occurs in a liquid solution, it very often produces gas bubbles, which can be seen in the liquid.Light Emission вЂ“ Certain chemical reactions produce light as a result of the reaction.Indications of a chemical change include:

There are various physical phenomena that can indicate an occurrence of a chemical change. The light and heat produced are the results of chemical reactions that produce new compounds. The snow deposited over there absorb heat from the atmosphere and melts down and makes it cool.Fireworks are examples of chemical changes. This is the reason why hill stations are cool during summer. The ice absorb heat energy from the surroundings and changes into liquid. Heat energy is needed for the melting of ice, ice cream, etc. Some changes in which heat energy is generated and liberated are, igniting a match stick, burning of wood, LPG, coal, etc. Heat transformation during action and reactionsДuring the course of a change either heat energy is released or absorbed. Once we cook the raw material the appearance and taste of food changes. We can not get back the milk from curd by any means.Д¬ooking of food is an irreversible chemical change. The bacteria Lactobacillus present in the milk convert milk into curd.

Alloy formation - Stainless steel is an alloy.

Galvanisation - It is the process of depositing a layer of zinc on iron.

Rusting can be prevented by adopting any of these methods. The process of rusting can be represented as:ДЇe + O 2 (from air) +H 2 O (water) в†’ Fe 2 O 3 (rust) Rusting of iron occurs only if iron comes in contact with moist air. This process of iron changing into rust is called rusting. If articles made of iron are left in open air for some time, they get coated with a brown powdery substance, called rust. Rusting of iron is an irreversible chemical change. The original form of substance can be obtained, thus these changes are physical changes. Only change in the state of the substances takes place. In all the above phenomena there is no new substance is formed. The sublimation of Naphthalene and camphor can takeВ place without heating them. These vapors get condensed to the solid state by condensation process. The process, where aВ solid,В on heating,В directly changes into gasВ withoutВ changing into liquid, andВ a gas, on cooling, directly changes toВ solid without changing into liquidВ is calledВ sublimation.Д®xample: Solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state.

When ice, ghee, wax are heated they melt and form liquid. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point. MeltingВ is the process whereВ solid changes into a liquid at a particular temperature.

Ice creams and kulfis are formed due to freezing. The process, where aВ liquid converts into a solid, is calledВ freezing or solidification. The process whereВ vapor changes to a liquidВ is calledВ condensation.Д®xample: The water vapour condenses and we receive the same water in the form of rain.Д®vaporation and condensations are observed in nature in the form of water cycle. The process where aВ liquid changes into vaporВ at anyВ temperature below its boiling point isВ evaporation.Дrying of wet cloths in sunlightВ and drying of wet floor when wiped with a wiper are the examples of evaporation that are observed in our daily life. Some physical and chemical changes in nature and daily life When a change occurs in the composition of matter and a new substance is formed, it is called a chemical change.Д®xamples:Rusting of Iron, Burning Magnesium ribbon. When a change occurs in the physical properties of matter like shape, size, colour and state of matter, and no new substance is formed, it is called a physical change.Д®xamples: Melting of ice, Boiling of water, Freezing of water, Condensation, etc.

Examples of chemical changes