Which example best demonstrates the benefit of understanding physical properties? engineers can design safer structures because they understand flammability of building materials engineers can design better bridges because they know how metal changes shape scientists can easily classify mixtures of unknown substances scientists can predict how well two substances will react

 Engineers can design better bridges because they know how metal changes shape.

Explanation:  Physical Properties are those properties which are also regarded as observable because they can be easily seen or observe through naked eyes like melting point etc.

These are those properties which do not change chemical identity of the species.

Thus out of the given options, only physical property is the change of shape of metal.

And the rest one represents the chemical property as chemical property are the one which changes the chemical identity of the substance.

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explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.