Think of a substance that does not dissolve in water. Explain what happens when this substance is added to water.

An example would be oil. Oil is considered to be hydrophobic (which translates to "fear of water" so it is repelled by water). It floats on the top of water, which is why oil spills result in black blobs that float on the surface of the ocean rather than mix underneath the surface.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.

a