Water is the most abundant substance onearth.Like any other substances, water has its ownunique characteristics.
5.1 Physical Characteristics of Water A. Physical Characteristics of Water 1. Water can exist in three states:a. Solid b. Liquid c. Gas
5.1 Physical Characteristics of Water2. At room temperature, pure water is a a. colourless, b. odourless and c. tasteless.
5.1 Physical Characteristics of Water Freezing Point of Water1.Water changes from liquid to solid at its freezingpoint. liquid solid Freezing point of water is the temperature at which water freezes into ice.
5.1 Physical Characteristics of Water2. The freezing point of pure water is 0 oC.3. The temperature remains constant at 0 oC until waterfreezes completely.
5.1 Physical Characteristics of Water When the temperature drops, the water particles move slower.Therefore, the forces of attraction among the particles grow stronger.At 0 oC, the forces of attraction are so great that the water particles are held in fixed positions. Waterfreezes into ice!
5.1 Physical Characteristics of Water Boiling Point of Water1. Water boils at its boiling point. liquid gasesBoiling point of water is the temperature atwhich water boils and becomes steam.
5.1 Physical Characteristics of Water2. The boiling point of pure water is 100 oC.3. The temperature remains constant at 100 oC untilwater boils completely.
5.1 Physical Characteristics of WaterWhen the temperature rises, the water particles move faster and further apart. Therefore, the forces of attraction among the particles grow weaker. At 100 oC, water particles move so fast thatthey overcome the forces of attraction and leave the liquid’s surface. Waterbecomessteam!
5.1 Physical Characteristics of Water5. Water conducts heat slowly. Water is a poor thermal conductor.6. Water is also a poor electrical conductor.7. The density of water varies with temperature. Pure water has the maximum density of 1 g per cm3 at 4 oC.
5.1 Physical Characteristics of Water B. Effects of Impurities on the Physical Characteristics of Water1. Impurities in water can change thephysical characteristics of water. Sometimesthe change is noticeable and sometimes it is not.
5.1 Physical Characteristics of Water 2. Here are some examples: Physical Example characteristic Taste Purewateristastelessbutseawaterissalty. Odour Purewaterisodourless.Waterwithdecayedmatterhasanunpleasant smell. Colour Purewateriscolourlessbutmuddywaterisbrownishincolour. Density Purewaterislessdensethanseawater.Electricalconductivity Purewaterwithafewdropsofsulphuricacidcanconductelectricity.Freezingpoint o Purewaterfreezesat0Cbutseawaterfreezesatalower temperature.Boilingpoint o Purewaterboilsat100Cbutseawaterboilsatahighertemperature.
5.2 Composition of Water Composition of Water1. Water is a compound. It is made of two different elements. Water Hydrogen Oxygen
5.2 Composition of Water2. Water can be broken down to its elementsthrough electrolysis. A method to break down a compound by passing an electric current through its liquid or solution
5.2 Composition of Water 3. The volume of hydrogen released is always twice the volume of oxygen released. Oxygen is Hydrogen isreleased at the released at the anode cathode
5.2 Composition of Water4. Water is made up of one part of oxygen and two parts of hydrogen. Oxygen atom Hydrogen atoms Each water molecule consists of one atom of oxygen and two atoms of hydrogen.
5.2 Composition of Water5. Therefore, scientists represent water with the following formula: H2O H – Represents the hydrogen atom 2 – Shows that there are two atoms of hydrogen O – Represents the oxygen atom
Applying the principle of water evaporation In our daily life.1. To drying clothes2. To drying hair3. To drying agricultural produce4. To drying fish and prawn5. To cooling the body6. To producing the common salt
5.4 Solution and SolubilitySolution and Solubility
5.4 Solution and Solubility1. What is a solution? • A solute is the substance that dissolves. • A solvent is the substance that the solute dissolves in.
5.4 Solution and Solubility 2. Depending on the amount of solutes in solutions, there are three types of solutions. Solution Dilute solution Concentrated solution Saturated solutionContains a little Contains a lot of Contains the maximumdissolved solute dissolved solute amount of dissolved soluteCan dissolve a lot Can dissolve a little bit Cannot dissolve any more more solute more solute solute All these solutions have a clear appearance
5.4 Solution and Solubility1. What is a suspension? A suspension is a mixture containing insoluble substances.2. There are many suspensions around us. Muddy water, fruit juices, chocolate drink, blood
5.4 Solution and Solubility1. What is ‘solubility’?The solubility of a solute is the maximum amount of solute in grams that will dissolve in 100 g of solvent at a given temperature.For example, the solubility of sodium chloride is 38 g per 100g of water at 20 oC.This means that you can dissolve not more than 38 g of sodiumchloride in 100 g of water at 20 oC.
5.4 Solution and Solubility2. Factors Affecting the Solubility of a Solute a. The nature of the solvent b. The nature of the solute c. The temperature of the solvent
5.4 Solution and Solubilityi. The nature of the solvent- The solubility of a solute differs indifferent solvents. Example:Only a little iodine can dissolve in water. Iodine can dissolve very well in alcohol.
5.4 Solution and Solubilityii. The nature of the soluteDifferent solutes have different solubilityin the same solvent. Example: At the same temperature, sodium chloride has alower solubility in water compared to copper chloride.
5.4 Solution and Solubility1. What are the factors affecting the rateof dissolving a solute? a. Temperature b. Rate of stirring c. Size of solute particles
5.4 Solution and Solubility i. Temperature The higher the temperature of the solvent, the higher the rate of dissolving.:We use hot water to maketea. One reason for this isthat hot water increasesthe rate of dissolving ofcertain substances in thetea leaves.
5.4 Solution and Solubilityii. Rate of stirringThe higher the rate of stirring, the higher the rate ofdissolving.:The faster you stir thesoup, the faster the saltdissolves in it.
5.4 Solution and Solubilityiii. Size of solute particlesThe smaller the size of the solute particles, the higher therate of dissolving.Smaller pieces of palmsugar can dissolve in waterfaster than a big piece ofit.
5.4 Solution and SolubilityWater is a good solvent. Almost everything can dissolve in it to produce solutions. Therefore, water is also known as the universal solvent. Water acts as a medium in many chemical reactions in our body. Water dissolves and transports many substances in our body such as digested food and waste products. Water dissolves cleaning agents such as soap powder, dishwasher liquid and toilet cleaner.
5.4 Solution and SolubilityWater dissolves various substances. This enables us touse water in cooking and making drinks.Water is used extensively in food industry as a solvent.Water is used to prepare traditional and modern liquidmedicines.Farmers use water to dissolve pesticides.Water is needed in plants to transport food anddissolved minerals.
5.4 Solution and SolubilitySome substances cannot dissolve in water but they can dissolve in organic solvents. What are organic solvents?Organic solvents are carbon compounds that are used as solvents. Examples: • Alcohol • Turpentine • Acetone
5.4 Solution and Solubility1. We use many organic solvents in various products. To produce lacquers and varnishes To produce various types of ink Alcohol To prepare iodine solution (as an antiseptic) To produce perfume To produce paintsTurpentine To remove paint stains To produce nail polish Acetone To remove nail polish
5.4 Solution and Solubility 2. Organic solvents are very useful to us.a. They are volatile. Therefore, products such aspaints, lacquers, varnishes and inks become dry in ashort period of time.b. They can dissolve many solutes that do not dissolvein water.3. However, products containing organic solventsshould be handled carefully. a. They are flammable and should be stored away from heat. b. They are toxic and carcinogenic (likely to cause cancer).
1. An acid is a substance that has a hydrogen atom, which can be replaced by a metal or ammonium.2. Acid can be divided into two groups and differences are shown below
3.An acid exist in three state which are a. solid – tartaric acid b. liquid – ethanoic acid c. gas – hydrogen chloric4. The properties of acids a. Taste sour b. Are corrosive c. Change blue litmus paper to red d. Have pH values of less than 7 e. React with carbonates to release carbon dioxide and form salt and wateracid + cabonates salt + water + carbon dioxide
f. React with active metals to release hydrogen and form salt. acid + metal salt + hydrogeng. React with alkalis to form salt and water acid + alkali salt + water
1. An alkalis is hydroxide or metal oxide that dissolves in water.2. Example: potassium hydroxide, sodium hydroxide, calcium hydroxide, ammonium hydroxide solutions.
5.5 Acid and Alkali Neutralisation Neutralization is a process where acid + alkali salt + waterNote: Where acid reacts with alkali, salt and water are formed. Different kinds of acids and alkalis will form different types of salt.
5.6 Water Purification Natural Sources of Water Natural Sources of Water From Ocean From lakes, streams, rivers, ground water•Salty (well) and rain• Not suitable forhuman consumption • Fresh Water • But not pure, need to be purified
a. Most pureb. Has very little dissolved substances and a little dust
a. Not cleanb. Has a lot of dissolved substances and dirt such as microorganisms and silt
a. Has microorganisms and dissolved substancesb. Cleaner than river
a. Has the most substances of saltb. Has the most of dirt.
5.7 Water Supply System Usage of Water Usage of WaterDomestic Use Agricultural Use Direct Use of Industrial Use of Water of Water Rivers and of Water Streams• Drinking • Irrigation • Cooling• Washing • Generate • Aquaculture • Washing• Watering Hydroelectric Plants • Disposal Power of Waste • Recreation • Transportation
METHOD OF PURIFICATIONChlorination Chlorine solution
Filtration Muddy water Fine sand Coarse sand Pebbles Gravel filtrate
Distillation Water out Liebig condenserMuddyWater Water in Distilled water
1. Water from natural sources have various impurities such as microorganisms, dissolved gases, mineral salts and silt.2. Water from natural sources must be purified so that it save to drink and use.3. Table shows the advantage and disadvantage of water purification.
b. Distillation Water is free Water does Prepares pure or from all not make distilled water suspended good substances, drinking microorganisms because it and dissolved does not substances. contain dissolved mineral with our body need.
c. Boiling and chlorination Water is free from Water still has Only kills dangerous dissolved microorganisms in microorganisms substances and water suspended substances.
WATER TREATMENT PLANT1. Refer to your text book pg. 36 and draw figure 5.34PRESERVATION OF WATER QUALITY1. Find out the ways to control water pollution on page 41.