Answer:
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In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent.
4. A
because PbCl2 is an ionic compound and it's solid, so it's a substance.
It cannot be mixture, because it's a pure molecule.
5. D
despite that both substances are gases, colorless they are different molecules, so they should have different either chemical and physical properties
6. C
this substance made from W atoms and others are made from molecules
Chemistry is the study of the composition of matter and the ways in which matter interacts, combines, and changes under certain conditions. Although not as fundamental as physics, chemistry is a very basic and broad science. It helps us explain bodily interactions and natural process (biochemistry), it helps us to manufacture new medications, and true chemistry research will always follow the scientific method.
