Fluids. and Solutions

Transcription

1 relate the properties of mixtures and solutions to the particle model of matter investigate and identify factors that affect solubility and the rate of dissolving a solute in a solvent investigate the solubility of different materials, and describe their concentration distinguish among pure substances, mixtures and solutions, using common examples 2. Investigate and describe the composition of fluids, and interpret the behaviour of materials in solution SLE 2 - Fluids and Solutions

2 Liquids - have no definite but they do have a has the type of particle. another. The strength of the attractive force depends on 5. The particles in a substance are attracted to one 4. The particles are always in motion. 3. The particles have spaces between them. particles. bifferent pure substances are made of different 2. All particles in a pure substance are the same. 1. All substances are made of tiny particles. The Particle Model of Matter \ QEO Gases - have no definite and no definite definite Solids - a definite and a definite Properties arid the Particle Model

3 move around freely but only vibrate. Solids can be poured particles have enough room between them to move around. Only liquids and gases are considered true fluids because their against one another because they are tightly packed together. molecules. Particles in solids do not move, they only vibrate The particles in substances which can flow are able to move around one another. This can occur only in liquid and gas Flowing Fluids down or sideways. particles. Gases appear to be invisible because there is so much gases do not flow to the lowest level possible. Gases fill up, brief time they fill up the shape and space they are in. Most empty space. Gas particles can spread out so much that in a Gas particles have a lot of empty space between neighbouring Particles in Gases level surface. cannot hold their shape. The particles in liquids are tightly packed together and will flow to the lowest level, forming a vibrating close together in small clusters. These particles each other. They can slide around each other while they are Particles in liquids have enough energy to pull away from Particles in Liquids (stop flowing). Solids are not true fluids. when ground into small pieces, e.g. sugar and will form piles The particles in solids are tightly packed together and cannot Particles in Solids

4 Student Exploration: Temperature and Particle Motion Name: Date: Ex1earning 4 I zmos 2. Are all of the molecules moving at the same speed? 1. Describe the motion of the hydrogen molecules: Temperature is 300 K. The Temperature and Particle Motion GizmoTM illustrates Check that the selected gas is Hydrogen and the H K= 100 C. Kelvin scale is equivalent to I C: K = 0 C, and which measures temperature from absolute zer, the this Gizmo, temperature is measured on the Kelvin scald, how the molecules of gas move at different temperatures. In Gizmo Warm-up coldest possible temperature ( C). Each unit on the c19 and in cold air? 3. Air consists of tiny particles called rnolecj. How do you think the molecules move in hot 2. Why is cold air cold? 1. Why is hot air hot? Prior Knowledge Questions (Do these BEFORE using the Gizmo.) mass, molecule, temperature, universal gas constant Voàabjjijd: absolute zero, Kelvin scale, kinetic energy, Maxwell-Boltzmann distribution, molar

5 Temperature is set to 300 K Question: How is the temperature of a gas related to the motion of gas molecules? - Molecular motions,jiiflo% move more slowly than hydrogen molecules at the same temperature. 5. Exrlain: Based on the definition of temperature given above, explain why oxygen molecules What do you see? 4. Check: Test your prediction by choosing Oxygen from the Select a gas menu. same temperature, which type of molecule would you expect to move faster? Explain. 3. Predict: Oxygen molecules are sixteen times as massive as hydrogen molecules. At the B. How will the temperature change if you increase the mass of the gas molecules? increase the average velocity of the molecules in a gas? A. Based on the formula for kinetic energy, how will the temperature change if you 2/2 KE=mv equal to its mass times the square of its velocity, divided by two: particles (kinetic energy is the energy of motion). The kinetic energy (KE) of a particle is 2 Analyze The ternperatuid of a substance is a measure of the average kinetic enerqj of its you notice? What do 1. Observe: Move the Temperature slider back and forth. Focus on the particle motion at left.. Check that the selected gas is Hydrogen and the. Activity A: Get the Gizmo ready:

6 velocity Set the Temperature to 300 K..izmos (Activity B continued on next page) or slower than the most probable velocity? C. Base on the shape of the curve, do you think most of the particles are moving faster B. Turn on Show most probable velocity. What is the actual value? estimate? A. Estimate the most probable velocity by looking at the peak of the curve. What is your Set the temperature to 200 K (the selected gas should still be Hydrogen). most probable velocity (va), mean velocity (v), and root mean square velocity (V,ms). - to calculate the average velocity. Physicists express the average velocity in three ways: 3. Estimate: Because particles have a range of velocities at any given temperature, it is useful C. In general, is the Maxwell-Boltzmann curve a symmetrical or an asymmetrical curve? B. At what temperature do you see the widest variety of particle velocities? A. Even at the highest temperatures, are there still a few slow particles? 2. Analyze: Look at the left side of the graph as you raise the temperature from 50 to K. What do you notice about the shape of the graph? 1. Observe: Move the Temperature slider back and forth. This time focus on the graph at right. Question: How are particle velocities distributed? finding a particle moving at that velocity will be. the velocity shown on the x-axis of the graph. The higher the curve, the greater the probability of distnbutjój of particle velocities The curve represents the probability of a particle moving at Introduction: The graph on the right side of the Gizmo represents the MiUB1ian Average particle Select Hydrogen gas. / Activity B: Get the Gizmo ready:

7 be greater than or less than the most probable velocity? Explain your reasoning. of the curve and your answer to the previous question, do you expect the mean velocity to 4. Predict: The mean velocity is the average velocity of all of the particles. Based on the shape izmos F. Check by turning on Show root mean square velocity. Were you correct? E. Calculate the root mean squared velocity (v,): D. Check by turning on Show mean velocity. Were you correct? C. Calculate the mean velocity (): B. Check by turning on Show most probable velocity. Were you correct? A. Calculate the most probable velocity (va): molar mass of kg I mol. Kelvin temperature, and M stands for the molar rnas, in kg I mol. Hydrogen gas (H2) has a In each formula, R stands for the universal gsconstan, or J / K mol, Tstands for vr=j v ys 2rM 2RT - 8RT 3RT (va), mean velocity (p), and root mean square velocity (V,ms) using the following formulas: Hydrogen and set the Temperature to 100 K. You can calculate the most probable velocity 7. Calculate: Turn off Show most probable velocity and Show mean velocity. Select Explain why this is so: greater than the most probable velocity? 6. Experiment: Try a variety of other gases and temperatures. Is the mean velocity always Was your prediction correct? 5. Check: Turn on Show mean velocity. What is the mean velocity? Activity B (continued from previous page)

8 shape. Lemonade and water are called liquids because they as rocks and wood, are called solids. They don t change their bathe in, even though there is snow insidethe earth. Th the surface of the earth from deep on the ground. The water bubbles to have found a hot, steamy poolto These Japanese macaque monkeys 26 Solid,Iiquid,orgas heat water until it boils, the liquid water becomes a gas. a refrigerator, the liquid water changes into a solid, ice. If you If you pour water into a container and leave it in the freezer of Substances remain as solids, liquids, or gases at certain any space. up the shape of the container. The surface of the liquid is temperatures. If they are heated or cooled, they change. flow easily. If you pour a liquid into a container, it flows to fill always level. Gases, like the air we breathe, spread to fill is liquid, and the air is a mixture of gases. Some matter, such Our world is made of matter. The earth s crust is solid, the sea

9 Z) - I, 1,---- I 2 form a solid. I V spread out. molecules move quickly and When water becomes a gas, the The molecules in ice do not move around much. They cling together to 4 I H (. :- The molecules in liquid water move around freely. (

10 solid to gas freezing gas to solid melting solid to liquid evaporation liquid to solid sublimation liquid to gas condensation gas to liquid sublimation 6 changes of state of state. will gain energy and the particles will speed up causing a change of the substance changes. The substances as they are heated another state. Changes of state occur when the temperature when the physical state of a substance is transformed into All solids can become liquids through melting. Melting occurs Changes of State

11 Student Exploration: Phase Changes 4. In which phase(s) do the molecules take the shape of their container? 3. In which phase(s) are the molecules held in a defined shape? 2. In which phase(s) do the molecules move freely? 1. In which phase(s) are the molecules held rigidly together? phased. molecules in the so!14 (ice), liquid (water), and ga (air) set the Ice volume to 50 cc. Click Play() and observe In the Phase Changes GizmoTM, select the Micro view and Gizmo Warm-up mountains. Why do you think this is so? 2. Spaghetti takes about 9 minutes to cook at sea level, but about 14 minutes in the they come home, all of their water pipes have burst. What do you think happened? 1. A family from Minnesota turns off the heat and flies to Florida for a winter holiday. When Prior Knowledge Questions (Do these BEFORE using the Gizmo.) phase, solid VdcabuIai: altitude, boil, boiling point, freeze, freezing point, gas, liquid, melt, melting point, Name: Date:

12 Question: How is temperature related to phase changes? Set Ice volume to 0 cc. Phase changes Iirnos phase change? If possible, discuss your answer with your classmates and teacher. 6. Extend your thinking: Why do you think the temperature does not change much during a 5. Interpret: Select the GRAPH tab to see a graph of temperature vs. time. Click the button until the whole graph is visible. What does the graph look like during a phase change? either of these phase changes is occurring? 4. Explore: Use the Gizmo to investigate melting and boiling. Does the temperature change as while the water is in the process of freezing? 3. Observe: Set up the Gizmo to observe freezing. What do you notice about the temperature B. At what temperature does ice melt? A At what temperature does water freeze? C. At what temperature does water boil? This is the boillngpohi. This is the freezlngpoin This is the meit1ngpojj. observations in your notes, then answer the questions below: Addlremove heat energy sliders to control the water temperature. Record your 2. Investigate: Use the Gizmo to explore phase changes. Use the Water temperature and C. At what temperature will water change from a liquid to a gas (b1)? B. At what temperature will water change from a solid to a liquid (mel])? A. At what temperature will water change from a liquid to a solid (freei)? 1. Predict: Based on your prior knowledge, predict the following: Click Reset (ED) and select Macro view. Activity A: Get the Gizmo ready:

13 Question: Why do phase changes occur?. Set Addlremove heat energy to 0 J15 Temperature and molecular motion Set Ice volume to 0 cc. I!fllOS (Activity B continued on next page) interact with the molecules in the solid? Set Add/remove heat energy to 0 JIs. Click Play. How do the molecules in the liquid 4. Observe: Click Reset. Set the Water temperature to 20 C and the Ice volume to 50 cc. 3. Explain: How is temperature related to the motions of molecules? water heats up? Explain. B. Does the mean molecular speed change as much as the temperature as the A. How does the average speed of the water molecules change as they are heated? 400 J/s. Click Play. below the container. Set the Water temperature to 0 C and Addlremove heat energy to 2. Observe: Click Reset. The mean molecular speed of the water molecules is displayed What do you notice? Click Reset, set the Water temperature to 100 DC, and click Play again. 1. Compare: Set the Water temperature to 0 C and click Play. Observe the water molecules. Click Reset, and select the Micro view. Activity B: Get the Gizmo ready: I

14 Click Play. How does this situation compare to the previous one? 5. Observe: Click Reset. Set the Water temperature to 100 C and the Ice volume to 50 cc. umos B. Why do water pipes sometimes burst in the winter? A. What volume of ice is created from 200 cc of water? cc, and Add/remove heat energy to -400 JIs. Click Play and wait until all the water freezes. 7. Extend your thinking: Click Reset. Set the Water temperature to 0 DC, the Ice volume to 0 occur. If possible, discuss your theory with your classmates and teacher. 6. ProDose a theory: Based on what you have observed, explain why you think phase changes Activity B (continued from previous page)

15 Set the Altitude to 5,000 meters (16,404 feet). phase changes Set Ice volume to 0 cc. Altitude and. Click Reset. 6. Apply: A pressure cooker allows food to be cooked under high pressure. Why is this useful? 5. Apply: Why does pasta take longer to cook in the mountains? altitude, If possible, discuss your ideas with your classmates and teacher. 4. Challenge: Try to explain these results based on the fact that air pressure decreases with 3. Analyze: How did altitude affect the freezing, melting, and boiling points of water? Freezing point: Melting point: Boiling point: meters (16,404 feet). Write these values below. 2. ExDeriment: Use the Gizmo to find the freezing, melting, and boiling points of water at 5,000 C. Boiling point: Increase Stay the same Decrease B. Melting point: Increase Stay the same Decrease A. Freezing point: Increase Stay the same Decrease lower pressure will affect the following? (Circle your answers.) 1. Form a hypothesis: As altitude increases, the air pressure decreases. How do you think the Question: The aititiid of a location is its vertical distance above sea level. How does altitude affect phase changes? Extension: Get the Gizmo ready:

16 0 of atom contains only one type - a substance which one type of atom substance contains more than bee seen -appear to be one -a substance which -two or more parts can (solid, liquid, and gas) -can exist in all 3 states of matter substances -contains two or more pure 4 -contain only one type of particle Classification of Matter

17 Goal Practise classifying materials as pure substances and mixtures. and Mixtures I SKILL BUILDER i Classifying Pure Substances GLM This page may be reproduced for classroom use by the purchaser of this book without the written permission of the publisher. Copyright 2001, McGraw-Hill Rycrson limited, a Subsidiary of the McGraw-Hill Companies. All rights reserved. Element or Mixture or Pure substances compound Mixtures Solution aluminum baking soda silicon rubbing alcohol mouthwash helium black coffee cement quartz scrambled eggs sugar food colouring cooking oil sulfur salt sand sulfuric acid toothpaste ginger ale raisin bread gold glucose carbon dioxide crude oil liquid oxgen fresh-squeezed orange juice iron mechanical mixture or a solution. substance identify it as an element or a compound. Beside each mixture identify it as a Classify each substance below as a pure substance or a mixture. Then beside each pure What to Do TOPIC I DAFE: NAME: CLASS:

18 of. Fluids usually fit into three categories, depending on what they are made Copyright Resource Development Serviret, Ia1nIt1r itt I1hlk Si I ink..jiii,i t$ \ iii.i I I. latter and crystals in it. ingredients. When you pinch ketchup you can feel the Hny lumps 7. Ketchup is made with vinegar, tomato paste, salt, sugar and other left to stand for a while to be shaken before it is used because it separates into layers when 6. Salad dressing made by mixing oil, vinegar and other substances has 5. Olive oil is the natural juice of the fruit of an olive tree 4. Mouthwash contains a mixture of alcohol and flavouring water 3. Iced tea made by mixing crystals of tea flavouring and sugar into other substances in it 2. Distilled water created by treating water to make sure there are no 1. Orange juice made by mixing frozen coricentrate with water examples is pure, solution or mechanical mixture. Mark each example as A, B or C. Use the information above to help you identify whether each of the following may not be able to see the different particles In the mixture. can easily be separated. Depending on the size of the particles, you may or C A mechanical mixture is made up of two or more different materials that Mechanical Mixture evaporation. the different particles, but they could be separated through heatln9 or are so small and they are mixed together so well that it is impossible to see A solution Is made up of two or more different materials but the particles Solution different substances. unique way (nothing else Is exactly the same) and can t be separated into A A pure substance is made up of one type of matter (material), behaves in a Pure Substance Part D: What is a substance?.

19 substances in the right category. Hint: Try the following tests to help you put adult supervision. j your home or school. should be completed with 5 Copyright Resource Development Services, Edmonton Public SchooI Grade 8 Mix and Flow of Matter into a fluid to make a solution (mixed) into to make a solution The substance that is dissolved (mixed) The fluid that a solute is dissolved Solute Solvent Before you continue, read and learn the following definitions: Pure Substances Solution Mixture Let it stand overnight. Do the different ingredients separate? Check the list of ingredients. Is there more than one? Let a sample dry overnight. Do parts of the fluid stay and others disappear? Hold it up to the light. Can you see different particles? pure substances; mixtures and solutions you can find in WARNING: This activity Complete the following chart by listing examples of

20 stronger attraction to the particles of the same substances). bissolving occurs because of the attraction between particles (there may be a dissolving. Forming a solution by mixing two or more materials together is called What makes Materials bissolve?

21 solution. The solvent is the substance that dissolves the solute to form a The solute is the substance thqt dissolves in a solvent. that can be harmful). about 0.5% is usable (and even this has materials already dissolved in 2% is frozen 97% of water on Earth is Ocean Water (salt water) so many materials. Water is called the universal solvent because it can dissolve Water- The Universal Solvent Solute Solvent Examples Solutes and solvents can be gases or liquids. Solutes and Solvents

22 U [ solvent solute a., different solids into a glass of water. You will soon find out The substance that dissolves is called the solute, and the the crystals seem slowly to disappear. The salt has dissolved in the water. When something is dissolved in a liquid, the water is a very good solvent. Try stirring half a teaspoonful of result is called a solution. liquid that does the dissolving is called the solvent. Liquid which substances are soluble, and will dissolve, and which If you stir a spoonfui of ordinary salt crystals into some water, Salty water are insoluble, or cannot dissolve.

23 The particles in a solid are fixed firmly together but the What happens to solids like salt crystals when they dissolve? Why does salt dissolve? 19 I I I I surrounded by molecules of water. and chlorine are separated and In a salt solution, the ions ofsodium solution more water to dissolve the salt completely. Some solid If you put a lot of salt into a little water, there will not be with water, the ions of sodium and chloride attract the water particles in a liquid are free to move around. When salt mixes them from each other. As more and more ions break free from molecules. The molecules surround the ions and separate the solid salt, it gradually seems to disappear. enough water molecules to dissolve the salt ions. You need substances will not dissolve. The water molecules can t separate the solid s atoms or ions from each other.

24 V I D all white powders will dissolve in water Hypothesis: (check the one you agree with) 0 1 Consider: Will all white powders dissolve in water? What will dissolve? -. V ( - 6 Copyright Resource 1)eveloprnent Services, Edmonton Public Schools, Grade 8 Mix and Flow of Matter your hypothesis was correct. 2. Now, answer the original question using evidence from your investigation OR prove why 1. What seemed to have an effect on whether or not the powder would dissolve? Explain. Analysis/Conclusion: ipowder: Powder. Powder Powder - yes/no yes/no yes/no yes/no yes/no Prediction: Prediction: Prediction: Prediction: Prediction: Powder 1. Begin by predicting which powders you think will dissolve in water. 4 clear containers and spoons (or other utensils) and a supply of water 2. Stir each powder (in turn) into a clean sample of water (at least icup). 3. Stir until the powder dissolves (if it will) and then watch for 1 minute. powder) Procedure: (record information in the chart below) 1/2 cup (each) of baking soda, flour, sugar, salt and talc (baby Materials: D only certain white powders will dissolve in water i V V.4 -

25 dissolving simulator Agitation (stirring or shaking), Temperature pressure. the rate of dissolving and can be affected by: The speed at which the solute dissolves in a solvent is called The Rate of bissolving

26 Hypothesis: (check the one you agree with) Consider: Does solvent temperature affect the rate (speed) of dissolving? 7 Copyright Resource Development Services, Edmonton Public Schools, Grade 8 Mix and [low of Matter experiment and find out for sure. solute is in a solution. If you were to continue stirring salt dissolved)? Make a prediction OR continue with your I predict/have proven that: Concentration is a word used to describe how much of a be able to get a higher concentration (more salt into each of your solutions, which ones do you think would Challengel Answer the original question using evidence from your investigation OR prove why your hypothesis was correct. Analysis/Conclusion:. j hot/warm/cold hot/warm/cold hot/warm/cold Solvent temperature: Solvent temperature: Solvent temperature: takes for the crystals to dissolve (disappear) 3. Stir 4 spoonfuls of salt into a beaker of boiling water (2 cups) while timing how long it while timing how long it takes for the crystals to dissolve (disappear). 2. Stir 4 spoonfuls of salt into a clear sample of warm (halfway to boiling) water (2 cups) 1. Stir 4 spoonfuls of salt into a clear sample of room temperature water (2 cups) while stopwatch (or clock with a seconds hand) clear container and spoon (or other utensil) and a supply of water kettle Materials: Procedure: (record information in the chart below) 0 increasing solvent temperature will decrease the rate at which solute dissolves 0 increasing solvent temperature will not affect the rate at which solute dissolves D increasing solvent temperature will increase the rate at which solute dissolves timing how long it takes for the crystals to dissolve (disappear). How fast will it dissolve? i

27 the particles of the solvent. particles become balanced and no more particles can be attracted by Using the particle model of matter, the attractive forces between the chart p. 20). in a specific solution at the same specific temperature. (see solubility An solution is one in which more solute can be dissolved will be dissolved in a specific amount of solvent at a A solution is one in which no more solute specific temperature. The limit to concentration is called solubility. How much can be dissolved?

28 , that it will not dissolve with a particular solvent. If a substance is considered to be it means dissolve in the solution. the solvent is key to make more would at a certain temperature is a A solution that contains more solute than it normally solutions. it is possible to pass the saturation limit in some Beyond the Limit: Supersaturated solutions

29 Goal Practise your graphing skills, and demonstrate your understanding of solubility. d SKILL BIJILOER i Solubility and Concentration BLM This page may be reproduced for classroom use by the purchaser of this hook without the written permission of the publisher. Copyright 2001, McGraw-Hill Ryerson Limited, a Subsidiary of the McGraw-Hill Companies. All rights reserved. (e) Which solution is the least saturated at 0 C, with only 2 g dissolved? (b) Which substance has the greatest solubility at 100 C? (d) Which solutions are saturated at 60 C, with 40 g dissolved in 100 g of water? 2. Answer the following questions using the data in the graph and the table. (a) Which substance has the greatest solubility at 0 C? (c) Which substance decreases in solubility as its temperature increases? ammonium chloride lithium sulfate copper sulfate C 20 C 40 C 60 C 80 C 100 C Substance Solubility (giloo g water) at Temperature ( C) Cl) 20 4o 0) LJ Ca 80 a) Legend 100 legend to identify the three substances represented by the three lines. 1. Make a line graph using the data in the table below. Give your graph a title. Provide a Answer the following questions in the space provided. What to Do [ToPic 2 DATE: \AME: (ThiSS: D