Rust of iron is a physical change or a chemical change

Rust of iron is a physical change or a chemical change?

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Iron rusting chemical or physical change?

Rusting of iron is a chemical change

›  Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. Some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. Understanding chemical changes is a major part of the science of chemistry.

›  For example, if a wood is burned in a fireplace, there is not wood anymore but ash. Other examples include burning of a candle, rusting of iron, baking a cake, etc. Special details that describe how a chemical change takes place are called chemical properties.

Why is rusting of iron a chemical change?

›  Rusting is very simple chemical process involves in decaying of Iron ore and its alloy metals including steel. In chemistry rusting is called as oxidation. Oxidation is a chemical process where metal gains oxygen and become oxide.

›  When iron rusts, iron molecules react with oxygen molecules to make a compound called iron oxide. Rusting would only be a physical change if iron molecules remained pure iron throughout the process.

›  Hence Rusting is a chemical change.

›  Chemical reaction taking place during rusting is shown below.

The rusting of iron is a chemical change because it is two substances reacting together to make a new substance.

Physical Change

Properties such as shape, size, state of the substance and its color are known as physical properties. Physical properties are affected by the physical change.

Evidence of a chemical change

The following can indicate that a chemical change has taken place, although this evidence is not conclusive:

·   Change of odor.

·   Change of color (for example, silver to reddish-brown when iron rusts).

·   Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat

·   Change of composition - paper turning to ash when burned.

·   Light and/or heat is given off.

·   Formation of gases, often appearing as bubbles in liquids.

·   Formation of a precipitate (insoluble particles).

·   The decomposition of organic matter (for example, rotting food).

·   The change is difficult or impossible to reverse.