Pure Substances and Mixtures

Pure Substances and Mixtures – Chapter 2 Review 1. Use each of the following terms appropriately in a sentence. (Write one sentence for each term.) (a) dissolve - When the particles of a solute dissolve, the solute cannot be seen anymore. (b) Solute - A solute dissolves in a solvent to form a solution. (c) solvent - Water is the solvent in ocean water. (d) Concentrated - Concentrated solutions contain a lot of solute particles in a given volume. (e) Dilute - Dilute solutions have relatively few solute particles in a given volume. (f) Solubility - The solubility of sugar in water is higher than the solubility of salt in water. 2. (a) List three examples of common solvents. Water, ethanol, and oil (b) List three examples of common solutes. Sugar, salt, and juice powder 3. Which of the solutions in Figure 1 is concentrated? Which solution is dilute? Explain. (a) (b) Figure 1 (a) is dilute, and solution (b) is concentrated. The solute particles give the solutions their colour. Therefore, the darker the colour of the solution, the more solute particles there are in it. Since solution (b) is darker, it must be more concentrated. Pure Substances and Mixtures – Chapter 2 Review 4. Hassan dissolved a spoonful of salt in a glass of water. (a) Draw a labelled diagram showing the particles in Hassan’s solution. Explain your picture. When the salt dissolved in the water, the salt particles in the solid split apart and mixed evenly with the water particles. My drawing shows the salt particles evenly mixed with the water particles. (a) What is in the space between the particles? The spaces between the particles are empty. 5. Figure 2 shows a green solid in a glass of water. After a while, the green solute dissolves in the water. (a) Draw a picture of the final solution. (b) Explain your drawing. Figure 2 After the solute dissolves, its particles are evenly mixed with the water particles. My drawing shows that the solute particles are evenly mixed with the water particles. 6. Ling is dissolving some sugar cubes in water. List three things Ling can do to dissolve the sugar cubes faster. To get the sugar cubes to dissolve faster, Ling should break them into pieces, mix them with hot water, and stir the mixture. What Do You Understand? 7. Look back at the information about maple syrup in the chapter opening. (a) Why is maple syrup an example of a solution? Maple syrup looks like a pure substance, but it is made up of many pure substances mixed together. (b) What is the solvent in maple syrup? Water is the solvent in maple syrup. Pure Substances and Mixtures – Chapter 2 Review (c) What are some of the solutes in maple syrup? Sugar and flavour particles are some of the solutes in maple syrup. (d) Is maple syrup more or less concentrated than maple sap? Explain why. T/I A Maple syrup is more concentrated than maple sap. Maple sap tastes just a bit sweet, but maple syrup tastes very sweet. Maple syrup has less water (solvent) than maple sap, but the same amount of solute, so it is more concentrated. 8. Jordan’s iced tea contains 96 % water, 3 % sugar, and 1 % caffeine and other tea flavours. T/I (a) What is the solvent of this solution? Water is the solvent in iced tea. (b) What are the solutes in this solution? Sugar, caffeine, and tea flavours are the solutes in the iced tea. 9. Why is water called “the universal solvent”? Water is called the universal solvent because many different solutes can dissolve in water. T/I 10. Malcolm dissolves 50 mL of drink powder in 150 mL of water. He is surprised that the final volume is only 170 mL. A (a) Why do you think Malcolm is surprised at the final volume? Malcolm is surprised because 50 mL + 150 mL = 200 mL. He probably expected the final volume to be the sum of the volume of drink powder and water. (b) Use the particle theory to explain Malcolm’s observation. When the powder dissolved in the water, the different kinds of particles were attracted to each other. The attractions caused the particles to move closer together, reducing the volume of the solution. 11. Your teacher gives you a solution of salt in water. How can you find out if it is a saturated solution? /I A I could try to dissolve more salt in the water. If no more salt will dissolve in the water, the solution is saturated. T Pure Substances and Mixtures – Chapter 2 Review T/I A 12. Mohan dissolved a lot of sugar in a glass of water until no more sugar would dissolve. Mohan says, “This is a saturated solution.” Raven says, “It is a concentrated solution.” Are both correct? Explain your answer. T/I A Both girls are correct. The solution is saturated because no more sugar will dissolve in it. The solution is also concentrated because Mohan dissolved a lot of sugar in the glass of water, which means that there are a large number of solute particles in the water. T/I 13. The solubility of sugar in water at room temperature is 204 g/100 mL. (a) How much sugar will dissolve in 100 mL of water at room temperature? 204 g of sugar will dissolve in 100 mL of water at room temperature. (b) How much sugar will dissolve in 2000 mL of water at room temperature? 14. A coffee shop attendant added instant coffee powder to hot water until no more would dissolve. He added 30 g of powder to 100 mL of water. What is the solubility of the instant coffee powder in hot water? T/I A The solubility of the coffee powder is 30 g/100 mL in hot water. 15. Malcolm added table salt to water until no more would dissolve. He added 108 g of salt to 300 mL of water. What is the solubility of the table salt in water at that temperature? T/I A 16. Calculate the concentration (in g/100 mL) of each of the following solutions: (a) 3 g of sugar in 100 mL of solution 3 g/100 mL (b) 10 g of sugar in 50 mL of solution (c) 54 g of sugar in 200 mL of solution T/I A