<P> Crystals in metals have a major effect of the physical properties of the metal including strength and ductility . Crystal type, shape and size can be altered by physical hammering, rolling and by heat </P> <P> Mixtures of substances that are not soluble are usually readily separated by physical sieving or settlement . However mixtures can have different properties from the individual components . One familiar example is the mixture of fine sand with water used to make sandcastles . Neither the sand on its own nor the water on its own will make a sand - castle but by using physical properties of surface tension, the mixture behaves in a different way . </P> <P> Most solutions of salts and some compounds such as sugars can be separated by evaporation . Others such as mixtures or volatile liquids such as low molecular weight alcohols, can be separated by fractional distillation . </P> <P> The mixing of different metal elements is known as alloying . Brass is an alloy of copper and zinc . Separating individual metals from an alloy can be difficult and may require chemical processing--making an alloy is an example of a physical change that cannot readily be undone by physical means . Alloys where mercury is one of the metals can be separated physically by melting the alloy and boiling the mercury off as a vapour . </P>

What are some different ways that you can make a physical change to a piece of string