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chemical change

Primary Information
Secondary Information

Definition

A chemical change is a change in matter that occurs when the atoms or molecules of a substance are rearranged to form new substances.

Chemical changes are often irreversible, meaning that the original substance cannot be recovered.

Chemical changes are also accompanied by the release or absorption of energy.

Some examples of chemical changes include:

  • Combustion: This is the process of burning a substance, such as wood or gasoline.
  • Oxidation: This is the process of a substance combining with oxygen, such as when iron rusts.
  • Hydrolysis: This is the process of a substance combining with water, such as when sugar dissolves in water.

How can the word be used?

The scientist chemically changed the compound to create a new substance with different properties.

chemical change

Different forms of the word

Noun:

Singular: chemical change.

Plural: chemical changes.

Adjective:

Chemical: relating to chemistry.

Chemical change: a change in the composition of a substance.

Verb:

Change: to make or become different.

Chemically change: to change the composition of a substance through a chemical reaction.

Etymology

The word "chemical change" comes from the words "chemical" and "change". The word "chemical" comes from the Greek word "khēmikós", which means "of or relating to alchemy". Alchemy was a medieval practice that attempted to transform base metals into gold. The word "change" comes from the Old English word "ceap", which means "to barter".

Question

Provide three examples of objects going through a chemical chance.

AQA Science Exam Question and Answer

Question:

Define "chemical change" and provide an example of a chemical reaction.

Answer:

A "chemical change" is a process in which one or more substances undergo a transformation to form new substances with different chemical properties.

Example of a Chemical Reaction:

An example of a chemical reaction is the combustion of methane (CH4) in the presence of oxygen (O2) to produce carbon dioxide (CO2) and water (H2O):

CH4 (methane) + 2O2 (oxygen) → CO2 (carbon dioxide) + 2H2O (water).

In this chemical change, the methane and oxygen molecules react to form new substances, carbon dioxide, and water, with different chemical properties from the original reactants.