Chapter: 08. Some Properties Of Water
Chapter Objectives
in the bucket that you use for bathing? over a pan in which water is boiling? ACTION TIME - Soluble or Insoluble!SubstanceDo you think it will dissolve in water?Did it dissolve?
Do you think it will dissolve in water?
ACTION TIME - Float or Sink!
Quick Check
Feather : Float :: Coin : Sink Oil in water : Insoluble :: Sugar in water : Soluble Water Vapour : Gas :: Water : Liquid Solid to liquid : Melting :: Gas to liquid : Condensation Sugar : Solute :: Water : Solvent Run-Through
I. Very Short Answer Questions
A. Give one word for the following.
The most familiar form of water: The process in which ice melts into water: Freezing / Solidification Substances that do not form a solution when mixed in water: B. Fill in the blanks.
Steam (Steam/Ice) does not have a fixed shape or size. The process in which a liquid changes into a solid is called solidification (condensation/solidification). A solute and a solvent together form a solution (solution/steam). An object that weighs more than the water displaced by it sinks (sinks/floats) in water. Oil (Oil/Sugar) is insoluble in water. C. State True or False.
Bigger things float in water. The substance that dissolves in water is called the solvent. Water exists in three different forms. Evaporation is the process in which a liquid changes into a solid. A solution can be formed in less time if the solvent is cooled. D. Unjumble the given letters and define the terms.
MELTING: The process in which a solid changes into a liquid on heating. SOLUTION: A mixture in which a solute dissolves in a solvent. FORM: One of the three states in which water can exist (solid, liquid, gas). SOLUBLE: Substances that dissolve in a solvent to form a solution. E. Complete the concept map.
Top left box: Solid (Ice) Middle question mark box: Gas (Water Vapour) Right-side question mark box (top right): Condensation Right-side empty box below evaporation: Liquid (Water) Right-side empty box below middle question mark: Freezing / Solidification II. Short Answer Questions
Name the three forms of water. The three forms of water are solid (ice), liquid (water), and gas (water vapour). Condensation is the process in which a gas changes into a liquid on cooling. Define ‘solution’. Give examples. A solution is a mixture in which a solute dissolves in a solvent at a particular temperature. Examples include sugar dissolved in water (lemonade) or salt dissolved in water (salty water). a. a tray with water is kept in the freezer? When a tray with water is kept in the freezer, the water (liquid) changes into ice (solid) through the process of solidification or freezing. b. a cold plate is kept over a pan of very hot water? When a cold plate is kept over a pan of very hot water, the hot water produces water vapour (gas). This water vapour comes in contact with the cool surface of the plate, condenses, and changes back into liquid water droplets. III. Long Answer Questions
Can water change its form? Explain. Yes, water can change its form. Water commonly exists in three states: solid (ice), liquid (water), and gas (water vapour). These forms can change into one another depending on whether heat is added or removed. Melting: Solid ice changes to liquid water when heated. Evaporation: Liquid water changes to gaseous water vapour when heated. Condensation: Gaseous water vapour changes back to liquid water when cooled. Solidification/Freezing: Liquid water changes to solid ice when cooled to freezing temperatures. Some objects float while some objects sink in water. Explain. Whether an object floats or sinks in water depends on its density compared to water, or more precisely, according to Archimedes’ principle, on the amount of water it displaces relative to its own weight. Sinking: An object sinks if it displaces less water than its own weight. This means the object is denser than the water it displaces, and it will go to the bottom. Floating: An object floats if it displaces more water than its own weight. This means the object is less dense than the water it displaces, and it will stay on the surface. Solute: The substance that dissolves in a solvent (e.g., sugar in water). Solvent: The substance in which the solute dissolves (e.g., water when dissolving sugar). b. Freezing and evaporation Freezing: The process where a liquid changes into a solid due to cooling. Evaporation: The process where a liquid changes into a gas (vapour) due to heating. c. Soluble and insoluble substances Soluble substances: Substances that can dissolve in a solvent to form a solution (e.g., salt in water). Insoluble substances: Substances that cannot dissolve in a solvent (e.g., oil in water). d. Melting and condensation Melting: The process where a solid changes into a liquid due to heating. Condensation: The process where a gas changes into a liquid due to cooling. List any three conditions that affect the making of a solution. Three conditions that affect the making of a solution are: Heating the solvent: The solution forms faster when the solvent is heated. Stirring the solute: The solution forms faster when the solute is stirred in the solvent. Form of the solute: If the solute is in powdered form or broken into smaller pieces, it dissolves faster. Quantity of solvent: Increasing the quantity of the solvent can make the solution faster. (Any three from these four) IV. Challenge
A bottle of chilled lemonade is kept on a table. Water droplets are formed on the bottle and some water collects on the table too. Why and how does this happen? This happens due to condensation. The air around the bottle contains water vapour (water in gaseous form). When this warm, moist air comes into contact with the cold surface of the chilled lemonade bottle, the water vapour loses heat, cools down, and changes back into tiny liquid water droplets. These droplets then collect on the bottle’s surface and eventually some may fall onto the table. Two glasses, Glasses A and B, were filled with water and one tablespoon of sugar was added to both. Glass A was kept undisturbed. Glass B was stirred continuously. In which glass will the sugar dissolve faster? The sugar will dissolve faster in Glass B. Stirring the solute in the solvent helps the particles of the solute to spread out and interact with the solvent more quickly, leading to faster dissolution. V. Enrichment
A. Case Study
What solvent would have been used in the above solution? Water would have been used as the solvent. What was the solute in the above solution? The tablet (medication) was the solute. Why are children usually given solutions of tablets instead of whole tablets? Discuss. Children are usually given solutions of tablets because: Easier to swallow: Solutions are liquid and much easier for children to swallow than a solid, often bitter, whole tablet. Faster absorption: The medication is already dissolved, so it can be absorbed into the child’s body more quickly. Accurate dosage: It can be easier to measure and administer a precise small dose of medication in liquid form. B. Project 7E Explore
Naphthalene balls are substances that undergo sublimation. Find out three more substances that sublime. Paste their pictures in a scrapbook. Three more substances that sublime are: Dry ice (solid carbon dioxide) Science Quest
Take a few fruits and vegetables. Predict and test if they float or sink in water. After you are done with the test, draw the picture showing fruits and vegetables floating or sinking. Common predictions and observations: Oranges (unpeeled): Float Funway learning
Riddle Time!
Unjumble the following letters. Make a crossword using them. Also write the clues. Clue: Frozen water, solid form. Clue: Form of water that fills all available space. Clue: The substance in which something dissolves. Clue: Process of water turning into ice. OSLDIIIFACTONI: SOLIDIFICATION Clue: The general process of a liquid turning into a solid. Clue: What an object does if it displaces more water than its weight. Picture Survey
Name the process shown in this picture. The process shown is evaporation (or boiling, which leads to evaporation). What happens in this process? In this process, liquid water is heated and changes into water vapour (gaseous state), which can be seen as steam rising from the pot. 
Answers to textbook exercises
