Wetness and why materials change shape

In summary, certain materials such as plastic and metal, which lack a strong attraction to water molecules, retain their shape when wet. On the other hand, materials like paper, which contain hydroxyl groups, form hydrogen bonds with water molecules and swell, causing them to not return to their original shape when dry. This is likely due to differences in polarity and bond formations.
  • #1
kosovo dave
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Why is is that certain materials -- like plastic, metal (assuming it doesn't rust), glass -- retain their shape when they get wet, and some materials -- like paper -- don't return to their original shape even after they become dry again?

My knowledge of chemistry is pretty limited, but my initial guess would be that it has something to do with polarity or new bonds forming/old bonds breaking.
 
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  • #2
Hi...

For metals and some kinds of plastic does not have a strong attraction with water molecules,
so it is not affected when they become wet.
While materials containing hydroxyl groups like paper attached to water molecules by hydrogen bonding and swell .
 

FAQ: Wetness and why materials change shape

1. What makes a material wet?

When a material comes in contact with a liquid, the liquid molecules adhere to the surface of the material. This causes the material to become wet.

2. Why do some materials absorb water while others repel it?

The ability of a material to absorb or repel water is determined by its surface tension and chemical composition. Materials with low surface tension and hydrophilic (water-loving) properties tend to absorb water, while those with high surface tension and hydrophobic (water-repelling) properties will repel water.

3. How does wetness affect the shape of a material?

When a material becomes wet, the liquid molecules fill in the spaces between the material's particles, causing it to expand and change shape. This can be seen in materials such as paper, which becomes wrinkled when wet.

4. Can a material change shape without becoming wet?

Yes, materials can change shape without becoming wet through processes such as heating, cooling, and mechanical stress. These changes are typically due to the rearrangement of molecules within the material.

5. How does wetness impact the strength and durability of a material?

Wetness can weaken some materials by breaking down their molecular bonds, causing them to become more pliable and prone to tearing or breaking. However, for some materials such as plants and certain fabrics, wetness can actually increase their strength and durability due to the structure and composition of their molecules.

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