more science questions. please please please please help!?

4: Mixtures are generally separated by what methods?
Chemical
Physical
Mechanical
Optical


5: All solutions are mixtures, but not all mixtures are solutions.
Always true
Always false
True, with the exception of water
False, with the exception of water


6: As the temperature of a mixture increases, one part of the mixture may melt while the other parts remain solid.
Always true
Always false
True for all liquid mixtures
False for all liquid mixtures


7: Which of these is not a mixture?
Oil and water
Sand and water
Diet Soda
All are mixtures