Pure Substances and Mixtures – Unit Review

Pure Substances and Mixtures – Unit Review 1. Write a definition of matter. Matter is anything that takes up space and has mass. 2. What is matter made of? Matter is made of tiny particles. 3. Write, in your own words, the five main ideas of the particle theory. The five main ideas of the particle theory are the following. All matter is made of particles too small for the unaided eye to see. The particles have empty space between them. The particles are in constant motion. When the particles are heated, they move faster and farther apart. There is an attraction between particles that holds them together. 4. What is the difference between the particles of a solid and the particles of a liquid? The particles in a solid are packed closer together than those in a liquid. The particles in a solid do not move about freely, as particles in a liquid do. Particles in a solid vibrate in place. 5. (a) What are the three states of matter? The three states of matter are solid, liquid, and gas. (b) Use the particle theory to describe each of the three states of matter The particles of a solid are packed so closely together that they cannot move about freely, only vibrate in place. The particles of a liquid are still close together, but there is enough space between them to allow the particles to move about freely and bump into each other. Gas particles are the farthest apart. They have more energy than particles in solids and liquids, so they move the fastest and collide with each other with the most force. 6. (a) What is the difference between a pure substance and a mixture? A pure substance is made up of only one kind of particle. A mixture contains more than one type of particle. (b) Give one example of each. Sample answer: Oxygen is an example of a pure substance. The air we breathe is an example of a mixture. 7. (a) Name the two types of mixtures and explain how they are different. The two kinds of mixtures are mechanical mixtures and solutions. You can see the different kinds of matter that make up a mechanical mixture, but you cannot see the different kinds of matter that make up a solution. A solution looks like it contains only one kind of matter. (b) Give one example of each. Milk and cereal is an example of a mechanical mixture. Salt water is an example of a solution. 8. Can you tell if a sample of matter is a pure substance or a solution by looking at it? Explain why or why not. No, you cannot tell by looking at it if something is a pure substance or a solution. In a solution, the different particles combine so thoroughly that it appears to contain only one kind of particle throughout, just like a pure substance. 9. Name two industries that separate mixtures. Two industries that separate mixtures are the recycling industry and the petroleum industry 10. Can you tell if a mixture is a mechanical mixture by looking at it? Explain. You can usually tell if a mixture is a mechanical mixture by looking at it because you can see the different kinds of matter that make up the mixture. 11. Identify each of the following kinds of matter as a pure substance, a mechanical mixture, or a solution: (a) salt – pure substance (b) clear shampoo - solution (c) table sugar – pure substance (d) a salad – mechanical mixture (e) 14-karat gold - solution (f) soil – mechanical mixture 12. Distinguish between a homogeneous mixture and a heterogeneous mixture. A homogeneous mixture is uniform, but a heterogeneous mixture is not. 13. Is air a solution or a pure substance? Explain your answer. Air is a solution. It is made up of a mixture of different kinds of gases. 14. (a) What is the difference between a solute and a solvent? A solute is the substance that dissolves and a solvent is the substance that does the dissolving. (b) Give one example of each. Sample answer: Salt is an example of a solute. Water is an example of a solvent. 15. Draw a model that shows the particles of a gas. Explain your model. 16. Is a piece of paper a solid, a liquid, or a gas? Explain your answer. A piece of paper is a solid because it has a definite shape and a definite volume. 17. List three different ways pollutants get into the water system. Pollutants get into the water system from fertilizers and pesticides used on farms and lawns, from sewage and household products put down a drain, and from industrial waste emptied out into lakes and rivers. 18. (a) List three solutions in your home. Sample answer: Three solutions in my home are iced tea, vinegar, and ammonia. (b) What is the solvent of each solution? The solvent in each solution is water. 19. Devawn says, “Solutions can be solids, liquids, or gases.” Do you agree? Explain. Sample answer: Yes, I agree. A solution is a mixture where one substance dissolves in another. The substances can be solids, liquids, or gases. 20. Describe what happens to the sewage that goes down your drain and toilet before it is released into the environment. Before it reaches the environment, the sewage that goes down the drain and toilet is first passed through a metal grid that removes objects that will not decompose, such as plastic. Next, the sewage is poured into a large pool and allowed to settle for several hours, allowing the solids to settle to the bottom and the components that float to rise to the top. The remaining water is passed through tanks containing bacteria that will break down any remaining human waste and plant material. The water is then allowed to settle, and the bacteria settle to the bottom and are removed. Next, other kinds of bacteria are added to the water that will remove other pollutants. In this stage, the water can be filtered again, treated with ozone, or treated with ultraviolet radiation to kill some of the harmful organisms. Finally, chlorine is added to the water to kill any remaining organisms. 21. (a) Aluminum foil is a solid pure substance. Draw a model of the particles of a piece of aluminum. (b) Brass is a solid solution. Draw a model of the particles of a piece of brass. 22. You dissolve 10 mL of sugar in 30 mL of water. The total volume is less than 40 mL. Use the particle theory to explain this observation. Particles of matter have empty space between them. When sugar dissolves in water, the smaller water particles move into the empty spaces between the larger sugar particles. This makes the volume of the solution less than the volume of the two substances before they combine. 23. Give one way to separate each of the following mixtures into its components. Describe the characteristics that make each separation possible. (a) iron filings and sand - You can use a magnet to separate the iron filings from the sand because the iron fillings will be attracted to the magnet but the sand will not. (b) sugar and water – You could boil the mixture and evaporate all the water, leaving behind the sugar crystals. Water will evaporate when boiled and the solids will not. (c) tea leaves and water – You can use a filter to separate the water from the tea leaves. The water can move through the tiny holes in the filter but the tea leaves cannot. 24. (a) What methods does a flour mill use to separate wheat grains from other kinds of matter? A flour mill uses screens or sieves to separate wheat grains from larger particles such as sticks and stones. The mill also uses magnets to pick out any iron or steel particles mixed in with the grain. (b) What method does a flour mill use to separate the different parts of the wheat grains after they are ground up? A flour mill uses a series of sieves to separate the different parts of the wheat grains after they are ground up. 25. Use the particle theory to explain each of the following observations: (a) Sugar dissolves in water even if you do not stir or heat the mixture. The attraction between the water particles and the sugar is strong enough to separate the sugar crystals into particles. The smaller water particles surround each sugar particle moving into the empty spaces between the sugar particles. By stirring the mixture, you add energy to the particles, making the sugar dissolve faster in the water. (b) Stirring or heating makes sugar dissolve in water faster. Stirring or heating water gives the water particles more energy. The energized water particles move faster and bump into the sugar particles with more force, making the sugar dissolve faster. (c) You add a drop of red food colouring to a glass of water. You do not stir the mixture, but the food colouring spreads throughout the water. Particles in a liquid have enough energy to be in constant motion. When food colouring is added to water, the colouring particles and the water particles move around and bump into each other, which spreads the colouring throughout the water. 26. Give one reason why someone might want to separate a mechanical mixture. Someone might want to separate a mechanical mixture because there may be a part of the mixture that they want to save, such as gold ore mixed with soil and stones. 27. “Pure orange juice” may contain water, pieces of orange pulp, sugar, Vitamin C, potassium, protein, and flavour particles. (a) Is pure orange juice a pure substance, a mechanical mixture, or a solution? Pure orange juice is a mechanical mixture. (b) Suggest two methods that could be used to separate out some of the components of orange juice. The pieces of pulp in orange juice can be separated out by filtration. The sugar can be filtered out by evaporation. 28. Explain why water is an important solvent in (a) your body Water is used in the body to dissolve substances that the body needs, such as salts, oxygen, and sugars. Once in a liquid solution, these solutes can be easily transported throughout the body. (b) the environment As it moves on Earth, water dissolves minerals and other solutes. These solutes are then transported to almost every part of the world by rivers, lakes, and other forms of ground water. The solutions also fall to Earth in the form of rain and snow. Plants and animals absorb the solutes carried by water. 29. (a) When you boil a mixture of sugar maple sap to make maple syrup, what part of the mixture are you removing? You are removing the solvent when you boil a mixture of sugar maple sap to make maple syrup. (b) Is the process of making maple syrup likely to harm the environment? Explain why or why not. The process of making maple syrup can harm the environment because fuel must be used to heat the syrup to boil it. That fuel may come from trees that are cut down. Burning the wood from the trees will add pollution to the air 30. Ali dissolves 3 g of sugar in water to make 10 mL of solution. What is the concentration of Ali’s solution in grams per 100 mL? The concentration is 30 g/100 mL. 31. At 20 °C, you can dissolve no more than 36 g of salt in 100 mL of water. (a) How many grams of salt can you dissolve in 50 mL of water? You can dissolve 18 g of salt in 50 mL of water. (b) If you dissolve 20 g of salt in 100 mL of water, is the solution saturated or unsaturated? Explain. The solution is unsaturated because 100 mL of water will dissolve 36 g of salt. You have only dissolved 20 g of salt. That means the solution still has room for more solute to dissolve. (c) If you dissolve 1 g of salt in 100 mL of water at 20 °C, is the solution concentrated or dilute? Explain why. The solution is dilute because it contains only 1 g of salt, which makes a small number of solute particles in 100 mL of water.