4.7 is the answer!
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Solid is the answer.
When matter is in its solid state, its molecules are more rigid and move less. they are also more resistant to changes in shape. Think of water in its solid form, ice. Ice is much harder to change the shape of than liquid water, and is much more rigid in its structure.
Answer:
Cleaning up oil spills and metal contaminates in a low-impact, sustainable and inexpensive manner remains a challenge for companies and governments globally.
But a group of researchers at UW–Madison is examining alternative materials that can be modified to absorb oil and chemicals. If further developed, the technology may offer a cheaper and “greener” method to absorb oil and heavy metals from water and other surfaces.
Aerogels, which are highly porous materials and the lightest solids in existence, are already used in a variety of applications, ranging from insulation and aerospace materials to thickening agents in paints. The aerogel prepared in Gong’s lab is made of cellulose nanofibrils (sustainable wood-based materials) and an environmentally friendly polymer. Furthermore, these cellulose-based aerogels are made using an environmentally friendly freeze-drying process without the use of organic solvents.
It’s the combination of this “greener"material and its high performance that got Gong’s attention.
“For this material, one unique property is that it has superior absorbing ability for organic solvents — up to nearly 100 times its own weight,” she says. “It also has strong absorbing ability for metal ions.”
Treating the cellulose-based aerogel with specific types of silane after it is made through the freeze-drying process is a key step that gives the aerogel its water-repelling and oil-absorbing properties.
