Question

give one example. (a) change substance's colour during a chemical reaction.

Answer 1

A chemical change may not always be visible to human eye but at times, it so happens that the colour of chemicals changes after undergoing a chemical change. When two or more substances combine to react, they produce a different structure, which has a total different composition and color.

 Example:

 Reaction of iron and copper sulphate

  CuSO4+Fe=FeSO4+Cu

 Color changes from blue to light green.

OR

Copper reacts with oxygen, H2O and CO2 to give copper carbonate, which changes color from brown to blue or blue green.

Rusting, blackening of surfaces of cut vegetables and fruits are other examples of change of color in a chemical reaction.

Answer 2

Answer:

Copper reacts with oxygen, H2O and CO2 to give copper carbonate, which changes color from brown to blue or blue green.

Explanation:

A chemical reaction isn't always visible to the human eye, but sometimes it results in an impressive color change and makes science experiments more fun to witness. When two or more substances combine, they create one or more new substances, which sometimes have different molecular structures from the original substances, meaning they absorb and radiate light in different ways, leading to a color change.

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