Chapter 10.2: Properties of Solutions
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Chapter 10.2: Properties of Solutions

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Grade 8 Integrated Science Chapter 10 Lesson 2 on properties of solutions, solubility, concentration, and understanding the "like dissolves like".

Grade 8 Integrated Science Chapter 10 Lesson 2 on properties of solutions, solubility, concentration, and understanding the "like dissolves like".

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  • 1. Chapter 10.2 – Properties of Solution – p 342-350 – page 1 Vocabulary • Solvent (343) – the substance that exists in the greatest quantity in a solution • Solute (343) – All other substances in a solution • Polar molecule (344) – a molecule with a slightly negative end and a slightly positive end • Concentration (346) – the amount of a particular solute in a given amount of solution • Solubility (348) – the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature and pressure • Saturated Solution (348) – a solution that contains the maximum amount of solute the solution can hold at a given temperature and pressure • Unsaturated Solution (348) - a solution that can still dissolve more solute at a given temperature and pressure Parts of Solution • _____________________ is the process of mixing one substance into another to form a solution. • There are two terms to refer to the substances that make up a solution • • _______________is the substance that exists in the greatest quantity in a solution All other substances in a solution are ________________ Air – What is the solvent? – What is the solute? Types of Solutions • Solutions can exist is all three states of_______________– solid, liquid, and gas • The state of the ____________________determines the state of the solution because it exists in the greatest quantity
  • 2. Chapter 10.2 – Properties of Solution – p 342-350 – page 2 Water as a Solvent • Water is one of the few substances on Earth that exists ______________in all three states – solid, liquid, gas • • • Much of the water found on Earth is not _______________________ Water almost always exists as a ___________________ Why is this? The Polarity of Water • A water molecule is a _______________________compound held together by the sharing a electrons between the atoms • However the electrons are not __________________ shared • Electrons in the hydrogen-oxygen bond are pulled more closely to the ________________________ • This unequal sharing gives the oxygen end of the water molecule a slight ________________________charge • It also gives the hydrogen end a slight ________________charge • Thus, the water molecule is ________________________ • A polar __________________________is a molecule with a slightly negative end and a slightly positive end Like Dissolves Like • Water is often called the ____________________________solvent because it dissolves many different substances • However, water cannot dissolve __________________________ • Polar solvents dissolve _________________________solutes easily • __________________________solvent dissolve nonpolar solutes easily – This is summarized by the phrase “_______________________________________________” • Because water is a polar solvent, it dissolves most polar and ____________________solutes Polar Solvents and Polar Molecules • Rubbing alcohol, or isopropyl alcohol, is a substance that is used as a disinfectant • Molecules of rubbing alcohol are also _____________________ • Therefore, when rubbing alcohol and water mix, the positive ends of the water molecules are attracted to the __________________ends of the alcohol molecules. • Similarly the negative ends of the water molecules are attracted to the _____________________________ends of the alcohol molecules • In this way, alcohol molecules dissolve in the solvent
  • 3. Chapter 10.2 – Properties of Solution – p 342-350 – page 3 Polar Solvents and Ionic Compounds • Many ionic compounds are also soluble in____________________________. • Recall that ionic compounds are composed of alternating positive and negative ions – Sodium Chloride (NaCl) is an ionic compound composed of sodium ions (Na+) and chloride ions (Cl-) • When sodium chloride dissolves these ions are pulled apart by the water molecules – The negative ends of the water molecules attract the positive _____________________ion – The positive ends of the water molecule attract the ______________________________chloride ions. Concentration – How much is dissolved • Have you ever tasted soup and wished it has more salt in it? – In a way your taste buds were measuring the amount, or________________________, of salt in the soup. • Concentration is the amount of a particular ________________in a given amount of solution – In soup, _____________________ is a solute – Soup with less salt has a lower concentration of salt Concentration and Dilute Solutions • One way to describe the saltier soup id to say that it is more __________________________ • The less saltier soup is more __________________________ • Concentrated and dilute are one way to describe how much solute is dissolved in a solution – However, these terms don’t tell us the exact ____________________of solute dissolved Describing Concentration Using Quantity • A more precise way to describe concentration is to state the quantity of solute in a given quantity of solution. • When a solution is made of a solid dissolved in a liquid, such as salt in water, concentration is the ____________________of solute in a given __________________________of solution. • Mass is usually stated in ________________and volume is usually stated in liters. – For example, concentration cam be stated as grams of solute per 1 L of solution – However, concentration can be stated using ________________unit of mass or volume
  • 4. Chapter 10.2 – Properties of Solution – p 342-350 – page 4 Calculating Concentration – Mass per Volume • One way that concentration can be calculated is by the following equation: – To calculate, you must know the mass of solute and the volume of solution that contains the mass. Concentration – Percent by Volume • Not all solutions are made of a ________________________dissolved in a liquid. • If a solution contains only liquids or gases, its concentration is stated as the ______________________of solute in a given volume of solution • In this case, the units of volume must be the_________________________– usually mL or L. • Because the units match, the concentration can be stated as a_____________________. • Percent by volume is calculated by _________________________the volume of the solute by the total volume of the solution and then multiplying the quotient by 100. What is the percent by volume? – If there are 1000mL of solution, how much isopropyl alcohol and water are in the solution? Solubility – How much can dissolve? • Have you ever put too much sugar into a glass of iced tea? – Not all the sugar _____________________________ – This is because these is a _________________________ to how much solute (sugar) can be dissolved in a solvent (water) • __________________________________is the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature and pressure – If a substance has a high solubility, __________________ of it can dissolve in a given solvent Saturated and Unsaturated Solutions • If you add water to a dry sponge, the sponge _______________________the water. – If you keep adding water, the sponge becomes__________________. It can’t hold anymore water • This is_______________________________, or similar, to what happens when you stir too much sugar into ice tea • Some sugar dissolves, but the excess sugar does not dissolve – The solution is saturated • A saturated solution is a solution that contains the _______________________amount of
  • 5. Chapter 10.2 – Properties of Solution – p 342-350 – page 5 solute the solution can hold at a given ____________________________and pressure • An ______________________________solution is a solution that can still dissolve more solute at a given temperature and pressure Factors that Affect How Much Can Dissolve • • Can you change the amount of a particular solute that can dissolve in a solvent? _________ • Changing either _____________________or _____________________, changes how much solute can dissolve in a solvent Recall the definition of solubility – – The maximum amount of solute that can dissolve in a given amount of solvent at a given temperature and pressure Effect of Temperature • The solubility of most solid substances _____________________________with temperature – However, some can become _______________soluble as temperatures increase • How does temperature affect the solubility of a gas in a liquid? – Recall soda, or soft drinks, contain carbon dioxide, a gas solute ___________________in liquid water – The warmer the soda the more ____________________ bubbles out than when it is cold – This is because the solubility of a gas in a liquid _______________________when the temperature of the solution increases Effect of Pressure • What keeps carbon dioxide in an unopened can of soda? • In a can, the carbon dioxide in the space above the liquid soda is under __________________ • This causes the gas to move to an area of lower__________________________– the solvent • The gas moves into the solvent, and a solution is formed – When the can is opened, this pressure is _________________________and the carbon dioxide gas leaves the solution. – *Pressure does not affect the solubility of a __________________________solute in a liquid
  • 6. Chapter 10.2 – Properties of Solution – p 342-350 – page 6 How Fast a Solute Dissolves • Temperature and pressure can affect how _______________________ solute dissolves • If solute and solvent particles come into contact more often, the solute dissolves _________________________ • There are three ways to increase how often solute particles contact solvent particles – ____________________ – Crushing • *Stirring and crushing will not make __________________solute dissolve; They will only increase how fast it dissolves – Increasing ___________________________________