Sec 2 Science Solutions and Suspensions

The leornlng Lab [ Chemistry Lower Secondary Intensive Practice Elements, Compounds and Mixtures Notes (ll) Solutions and Suspensions ‘ D as. ENC me |.D. Date Day LR___ Teacher s)ll"<l 5910'“)! /"l 31" Cloud 1e can dissolve In a variety of solvents to form solutions of carrying colours. olour me pretty No part of this publication may be reproduced without lhe prior permission of The Learning lab

Procedure (A) - m Notes (ll) 9 Learning Lob Lower Secondary Science lnlensrv'e Practice - Chemlslry — Elements. Compounds and Mixtures (1) Measu_re I New"; (2) Pour Ml j (3) Turn c {4) Colle ’rocer l) D i i L:[’ STUDENT OUTCOMES 1’ At the end of today’s lesson, students should be able to: Differentiate between solutes, solvents and solutions Recogm'sc that solutions and suspensions are mixtures define solutions and suspensions and describe their properties state the similarities and differences between solutions and suspensions define solubility Describe the factors affecting solubility of a solute DDDDDDD Describe the factors affecting the rate of dissolving of a solute Solutions A solution is a homogeneous mixture made up of two or more different substances physically combined together. A solution usually consists of a solvent, the substance used for dissolving, and one or more Usolute ) which are dissolved. For example, in an aqueous solution of sugar, the solvent is water anéthe solutes are the sugar molecules. X— solute (sugar molecules) 9‘ Mano, commemf m SolV‘WVl solvenllwuter) 5~ For a solvent to dissolve a solute, the particles of the solvent must be able to separate the particles of the solute and occupy the spaces in between. I The diagram below shows the arrangement of particles in a solution after the solute is completely dissolved and all the solute particles are evenly distributed throughout the entire solution. The“ can but]! Lg Ct change yam/£2“ Saute and Submit W‘U‘ WMWLII W 0” {ht 3a sr y. Shy ® solvent particle O solute particle When a solute is dissolved, the solute partirles are interspersed between the solvent partirles. No port of this publication may be reproduced without the pn'or permission of The Leornlng Lab

\-Hrr \ .Turn off the flame .ollect residue fo Notes (ll) ning Lab Lower Secondary Science Intensive Practice — Chemistry — Elements. Compounds and Mixtures .‘dure (B) _ Cry, me Lear AW“ Properties of solutions We .r r" Solutions have a homogeneous composition with uniform physical and chemical properties throughout. The colour, density, appearance and other physical and chemical properties are uniform throughout the solution. When a solution is filtered, no residue is left on the filter paper. When a solution is left to stand, the solute does not separate from the solvent. Examples of solutions Solutions can exist in any of the three physical states. Solid solutions "‘ Dental fillings (amalgam) are solutions consisting of mercury, silver, tin, copper and trace amounts of zinc. Sterling silver is a solution of silver and copper. 9‘"- Brass is a solution of copper and zinc. "5 Bronze is a solution of copper and tin. ioud U 3' Q 0 n: r V' 3 D E vs: < 'm a L7 m L" ‘ uos A-odsiafiuo/i alloys are better able to withstand the test of time. Statues made of bronz Brass is used in the making of musical instruments. No part of this publication may be reproduced without the prior permission of The Learning Lab

- Evaporation: ut approximate"T ‘ li'ride/ solution i _/15_;_r/Vn+ / Flame and ' reformer Notes (ll) he Learning Lob Lower Secondary Science lnlensive Practice - Chemistry — Elements, Compounds and Mixtures Liquid solutions Liquid solvents containing dissolved solutes, e.g. sugar solution rystall' Mixture of miscible liquids that can mix, e.g. ethanol and water Try it yourself! Identify the solvent and solute in each liquid solution below. a Sugar solution Solute Solvent b Seawater Solute Solvent c Vinegar Solute Ethanoic acid Solvent Gaseous solutions 9 u Air is a solution that consists mainly of elements such as nitrogen and oxygen. Noble gases are also present. It also consists of compounds such as carbon dioxide, water vapour. Natural gas is a solution of gases such as methane and ethane. No part of lhis publication may be reproduced without the prior permission of The Leoming Lab

\ 50’1' The Learning Lab Lower Secondary Science Intensive Practice — Chemistry — Elements, Compounds and Mixtures ’9‘. —~ F‘ Notes (ll) Solubility Solubility is a measure of the ability of a solute to dissolve in a given amount of solvent at a given temperature. It is usually measured in grams per 100 cm3 of solvent Concentration of solution The concentration of a solution is a measure of the amount of solute dissolved in a given amount of solvent. The more solute dissolved, the higher the concentration of the solution. A solution containing a small amount of dissolved solute particles per unit is known as a dilute solution. 0n the other hand, a solution containing a large amount of dissolved solute particles per unit is known as a concentrated solution. A solution is saturated if it contains the maximum amount of solute that can be dissolved at the given temperature. Any solute added would remain undissolved. For example, the solubility of table salt is 360 g per 1000 cm3, measured at 20 °C. This means that adding 360 g of table salt into 1000 cm3 of water at 20 °C will result in a saturated salt solution. Any additional table salt added to this solution would remain undissolved. Likewise, adding 36 g of table salt into 100 cm3 of water at 20 °C will result in a saturated salt solution. Factors affecting solubility Temperature As temperature increases, the solubility of most solid solutes in water increases. However, there are some exceptions. Type of solute Different (solid) solutes have different degrees of solubility in the same solvent. Type of solvent Based on the type and nature of the solvent used, a substance would show different solubilities. For instance. common salt is more soluble in water than in oil. This is because the particles in common salt can form more effective interactions with water molecules, than with oil molecules. No part of this publication may be reproduced without the prior permission oi lhn. learning lab

on: m’ately 25 into t +4 V11” How i" 1 thr if Notes (II) TheLearning Lob Lower Secondary Science Intensive Practice — Chemistry - Elements. Compounds and Mixtures . Rate of dissolving The rate of dissolving measures the amount of solute that dissolves in a given volume of solvent per unit time. Factors affecting the rate of dissolving Temperature As the temperature increases, the rate of dissolving for most solid solutes in water increases. Particle size of solute The particle size of a solute would affect the rate of dissolving. By breaking a solute into smaller pieces or using its powdered form, the total exposed surface area for interaction between the solute particles and solvent is increased. Thus, as the particle size of a solute decreases, the rate of dissolving increases. Stirring effect For solutions that contain liquid and/or solid solutes, stirring increases the rate of dissolving. No port of this publication may be reproduced without the prior permission of The Leoming Lab

ation: JXIm'ate / \ ‘ in e. '~ aI’ . ll Noles (Ill The Learning Lab Lower Secondary Science lnlensrv‘e Practice — Chemistry - Elements. Compounds and Mixtures Suspensions A suspension is a heterogeneous mixture made up of particles of an insoluble substance suspended In a liquid or gas. The liquid or gas is known as the medium. Properties of suspensions Suspensions have a heterogeneous composition with different physical and chemical properties throughout. ‘ Suspensions usually appear opaque. This is because some of the particles dispersed in the medium cause light to diffuse when light is passed through a suspension. The components of a suspension can be easily separated using