Verify the water generated by chemical reactions. Anhydrous copper sulfate has extremely strong water absorption. When anhydrous copper sulfate solid meets water, it changes from white to blue, generating copper sulfate pentahydrate (CuSO4·5H2O). It can verify the existence or generation of water in chemical reactions and absorb water vapor. Note: CuSO4 and CuSO4·5H2O are both pure substances. Chemical equation: CuSO4+5H2O==CuSO4·5H2O (reaction conditions: heating)

The phenomenon that anhydrous copper sulfate solid changes from white to blue when it meets water is a typical chemical reaction process. The following is a detailed explanation of this phenomenon:

1. Reaction principle

Anhydrous copper sulfate (CuSO₄) is a white or light blue powdery substance. When it meets water, it quickly absorbs water and dissolves to form a blue copper sulfate pentahydrate (CuSO₄·5H₂O) solution. This change not only changes the color of copper sulfate, but also changes its physical form and chemical composition.

Specifically, the copper ions (Cu²⁺) in anhydrous copper sulfate form hydrated copper ions when they combine with water molecules. These hydrated copper ions have specific coordination numbers and ligands, usually appearing as tetrahydrated copper ions ([Cu(H₂O)₄]²⁺) or pentahydrated copper ions (when forming copper sulfate pentahydrate). These hydrated copper ions appear blue in water, so the entire solution also appears blue.

2. Reaction process

Dissolution: When anhydrous copper sulfate solid meets water, it will first dissolve in water to form a copper sulfate solution.

Hydration: The dissolved copper ions will combine with water molecules to form hydrated copper ions.

Crystallization: As hydrated copper ions are formed, water molecules in the solution are gradually "captured" and form crystals, namely copper sulfate pentahydrate crystals. These crystals are suspended in the solution, making the solution appear blue.

3. Chemical equation

This reaction process can be expressed by the following chemical equation:

CuSO₄ (anhydrous) + 5H₂O → CuSO₄·5H₂O (copper sulfate pentahydrate)

4. Application and significance

Detecting moisture: The characteristic of anhydrous copper sulfate changing color when it comes into contact with water is often used to detect the presence of moisture. For example, in sailing or survival in the wild, you can determine whether the sample contains moisture by observing whether the anhydrous copper sulfate changes color.

Desiccant: Since anhydrous copper sulfate is very easy to absorb water and change color, it can also be used as an effective desiccant. However, it should be noted that anhydrous copper sulfate needs to be properly handled after use to avoid pollution to the environment.

Teaching demonstration: The experiment of anhydrous copper sulfate changing color when it comes into contact with water is also often used as a simple demonstration experiment in chemical education and laboratory work to illustrate the basic principles of chemical reactions and the differences in the properties of substances in different states.

In summary, the phenomenon of anhydrous copper sulfate solid changing from white to blue when it comes into contact with water is a typical chemical reaction process involving multiple steps such as dissolution, hydration and crystallization. This phenomenon not only has theoretical significance, but also plays an important role in practical applications.