Chapter 5 Test: Mixtures...And How To Separate Them

Volume cannot be used to separate mixtures because it is a measure of the amount of space occupied by a substance, not a property that can be used to differentiate or isolate different components of a mixture. Separation of mixtures is typically achieved using properties such as solubility, melting point, boiling point, and density, which can be used to selectively separate the components based on their different physical or chemical characteristics.

The boiling point is the characteristic property that allows us to separate a mixture of isopropanol and water. Isopropanol and water have different boiling points, with isopropanol having a lower boiling point than water. By heating the mixture, the isopropanol will evaporate first, leaving behind the water. This process is known as distillation and is commonly used to separate mixtures of liquids with different boiling points.

Characteristic properties of substances, such as boiling point, density, and solubility, are useful for separating mixtures and identifying pure substances. These properties can be used to determine the composition of a mixture and distinguish between different substances. However, they do not provide information about the quantity or amount of the substance present. To determine the amount of a substance, other techniques such as measuring mass or volume are required. Therefore, the statement that characteristic properties can tell you how much of the substance you have is incorrect.

To separate potassium nitrate and sodium chloride, both substances can be dissolved in hot water. Since they have similar solubilities, they will dissolve to some extent. However, upon cooling, the solubility of potassium nitrate decreases more than that of sodium chloride. This allows for the separation of the two substances by filtration. By repeating this process, the substances can be separated more purely.

The substance with the highest melting point would turn into a solid first when the mixture is frozen. In this case, Decane has the highest melting point of -30°C compared to the other substances. Ethane has a melting point of -183°C, Pentane has a melting point of -129°C, and Hexane has a melting point of -94°C. Therefore, Decane would solidify first when the mixture is frozen.

Density is the characteristic property that could be taken advantage of to separate the metal from the sawdust in this mixture. Density is the measure of how much mass is contained in a given volume. Since metal is denser than sawdust, it will sink to the bottom when the mixture is placed in water. Sawdust, being less dense, will float on top. This allows for the separation of the metal bits from the sawdust by simply skimming off the floating sawdust or collecting the sinking metal bits.

Solubility is the characteristic property that allowed us to separate the pigments found in ink. This is because solubility refers to the ability of a substance to dissolve in a solvent. By using different solvents with varying solubilities, we can effectively separate the pigments based on their solubility properties.

The isopropanol in rubbing alcohol is a pure substance and not a mixture because it consists of only one type of molecule. It is a homogeneous substance with uniform properties throughout. In contrast, the dirt under your feet, the blood in your veins, and the seawater in the Atlantic Ocean are all mixtures that contain multiple types of substances.

If given time, the isopropanol would float to the top of the mixture because isopropanol has a lower density than water.