The gray form has a specific gravity of 6.6. It burns in an atmosphere of chlorine. It has been proposed that we apply the SI system to our daily measurement of time. In such a system, instead of hours, minutes and seconds, we would have decidays, centidays and millidays. Only pure substances have a homogenous composition.
Compounds consist of two or more elements in fixed proportions.
The composition of a heterogenous mixture varies throughout. Elements cannot be broken down into simpler substances by chemical means. A sample of matter contains three different elements. Which response lists all the substances below that are mixtures and not pure substances.