Recall: Describe what happened in your activity? What was the mixture that you evaporated? What substance could you collect after the distillation process? What about after evaporation? Differentiate mixtures from substances.
Characteristics of Mixturesmay be solid, liquid or gasmay be homogeneous or heterogeneousmade up of two or more componentscomponents may be separated/recovered by physical means such as filtration, evaporation and distillation
Looks can be deceiving! For the unknown solid, determine its melting point to identify whether it is a substance or a mixture. A substance melts sharply, while a mixture takes longer time to completely melt. For the unknown liquid, determine its boiling point to identify whether it is a substance or a mixture. A substance has a constant boiling point, while a mixture boils at a temperature range. Note that the method has to be repeated at least three times before the student can conclude if their unknown sample is a substance or a mixture.
There are mixtures that are homogeneous which may be mistaken as substances. Being so, appearance may not be the best basis to differentiate substances from mixtures. However, there are ways to tell by noting how a sample behaves during boiling and melting.
During boiling, the temperature of a substance changes at the start then it does not change anymore after; while, the temperature of a mixture changes.During melting, the substance melts completely almost at the same time while mixtures have portions that do not melt.
All substances are homogeneous. Some mixtures are also homogeneous. Being so, it is difficult to distinguish mixtures and substances based on appearance. You will find out that substances may further be classified into two: compound and element. How are elements different from compounds? How are they similar?
Activity: Water, “Wat-er”you made of? Follow the procedures.