Why might a scientist repeat an experiment if he/she did not make a mistake in the first one? an experiment should be repeated

In which situation can a mixture always be called a solution

Which property of a rock remains unchanged by mechanical weathering? a. total surface area b. size and shape c. mineral composition d. sharpness

Asample of tin (ii) chloride has a mass of 0.49 g. after heating, it has a mass of 0.41 g.  what is the percent by mass of water in the hydrate?   %