Asap! 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 13 options: a pure substance is heterogeneous. mixtures cannot be separated by physical means. pure substances cannot be separated by physical means. a mixture is made of one substance. which of the following is true of pure substances and mixtures? (check all that apply.) question 10 options: a pure substance is heterogeneous. pure substances are separated by physical means. mixtures are made up of more than one component. mixtures can be separated by physical means. a mixture is made of one substance. pure substances are made up of mixtures.