Answer:
When substances do not mix thoroughly and evenly (like sand and gravel), the mixture is said to be heterogeneous. A heterogeneous mixture consists of visibly different substances. Another example of a mixture is salt dissolved in water.
Hope it helps!
Since protons are postive and neutrons are neutral. Then it is postive.
in order for a scientific theory to become a scientific law it needs to be tested with generations of data to confirm that it is really true.