The best sentence that describe an independent variable would be : The factor in an experiment that could be deliberately changed.
The scientist use deliberately change this factor to find out which factor actually caused the occurrence in the experiment.
Hope this helps
The answer is; hydrophilic heads; hydrophobic tails
The hydrophilic heads of a phospholipid are composed of a phosphate and glycerol molecule. Since the phosphate has a charge, the head are able to interact with water molecules through hydrogen bonds (Remember water is a polar molecule). The hydrophobic tails are composed of hydrocarbon chains that are uncharged hence do not interact with water. When phospholipids are immersed in water, they form a bilipid layer - with the hydrophobic tails clumped up together in the center and the hydrophilic heads on the outside.
Its less energy and longer wavelengths