11. Which of the following is a physical appearance of a substance? B. Heterogeneous A. Complicated C. Homogeneous D. Non-uniform 12. What does it indicate when a sugar is heated in a test tube until it is completely changed into a black mass and droplets of water? The sugar is - a/an B. Mixture A. Compound D. Solution C. Element 13. What is the difference between a substance and a mixture? A. Substance can be separated while mixture cannot be separated. B. Substance has many components while mixture has one only. C. Substance is heterogeneous while mixture is homogeneous. D. Substance is pure while mixture is impure. 14. Which of the following statements distinguishes pure substances from mixtures? A. Can be separated by physical means. B. Consists of two or more kinds of matter. C. Have no specific solubility and densities. D. Have constant boiling temperature and melting temperature. 15. All are techniques which help to separate components of mixtures EXCEPT ONE. A. Condensation B. Evaporation C. Distillation D. Filtration 16. What is/are true for substance and mixture? I. Pure substance melts completely. II. Pure substance has a varying boiling point. III. Mixture does not melt completely. IV. Mixture has a fixed boiling point. A. I and II only B..ll and IV only C. I and Ill only D. I and IV only​