Scientists pam and alejandro were discussing a liquid found in the science lab that was missing it's label. in classifying the unknown liquid, they first needed to determine if the liquid is a mixture or pure substance. how is a pure substance different from a mixture? question 11 options: a. mixtures cannot be separated by physical meansa pure substance is heterogeneous. b. pure substances cannot be separated by physical means. c. mixture is made of one substance. d. a pure substance is heterogeneous.

Answer is: B. Pure substances cannot be separated by physical means.

Pure substance is made of only one type of atom (element) or only one type of molecule (compound), mixtures and solutions are made from two or more types of pure substances.

Elements (for example copper, iron, sulfur) and compounds (water, sodium chloride) have definite and constant composition with distinct chemical properties.  

Pure substances can be separated chemically, not physically, that is difference between pure substances and mixtures.

if you mean hydrogen and oxygen then water is the product