2Handling Chemicals 1. Solids From reagent bottle Use a clean and dry spatula or spoonNever return unused chemicals to the reagent bottle
3Transfer a liquid(a) Pouring a liquid from a reagent bottle to a test tubePlace the stopper upside down on the bench.Mouths of test-tube and reagent bottle are at the eye level.Never return unused chemicals to the reagent bottle
4Pouring a liquid from a beaker Pour the liquid along the spout of the beaker.spout of the beakerMouths of test-tube and beaker are at the eye level
5Produce and collect a gas Use gas generatorProduce and collect a gasIt can produce a large amount of gaseasily control the flow of the product gas
6Use of gas generator What are the advantages of using tap funnel? Rate of addition of liquid can be controlledPrevent the gas escaping from the funnel
7Collection of Gases 1. Displacement of water For gases that do not dissolve in water
8Precaution: Sucking back It a gas is produced from a hot vessel and heating is stopped, water may be sucked back to the hot vessel is
9Precaution: Sucking back How to prevent sucking back?The delivery tube must be removed from water before heating is stopped.
10Collection of gas: Displacement of air (i) upward delivery (downward displacement)(ii) downward delivery (upward displacement)
11Collection of gas - Upward delivery For gases having densities much smaller than air.Examples:hydrogen, ammonia
12Collection of gas - Downward delivery For gases having densities much larger than air.Examples:carbon dioxide, chlorine
13Gas syringe Two uses: For collecting all kinds of gases Can be used to measure volume of the gasHorizontal positionPrevent the plunger from falling outKeep the syringe clean, dry and free from grease.Precaution
14ExerciseDraw a labelled diagram for preparation of gas
15Heating TechniqueUse of Bunsen BurnerBunsen flameHeating liquids
16Use of Bunsen burnerConstruction of a Bunsen burner
17The use of a Bunsen burner How to light a Bunsen burner?air holetowngasbasejetcollarbarrelClose the air hole.Put a lighted match near the top of barrel.Turn on the gas supply
18The use of a Bunsen burner How to control the size of a Bunsen flame?by using the gas tapWhen there is no immediate use of a burner, what should you do?Turn it off; orleave it with a small luminous flame.
19Bunsen Flame Non-luminous flame Luminous flame Large air-hole Turn the collar to adjust the size of the air-holeSmall air-holeLuminous flameor air hole is closed
20Luminous Flame The air hole is closed completely There are 3 zones. Non-luminous zoneLuminous zoneDark zoneThere are 3 zones.Non-luminous zoneLuminous zoneDark zoneThis flame is not very hot.
21Non-luminous Flame The air hole is open. There are 3 zones. Non-luminous zoneGreen-blue zoneDark zoneThere are 3 zones.Non-luminous zoneGreen-blue zoneDark zoneThis flame is hotter than luminous flame.
22Precaution: Striking back What is ‘striking back’?Gas burns at the jet instead of the mouth of the barrel.How do you know that there is ‘striking back’?A high pitched sound will usually be heard.Why does striking back occur?The amount of air getting into the barrel is too much.The gas supply is too low.
23Precaution: Striking back What should you do?Turn off the gas supply immediately.Caution!The collar is very hot.
25Heating non-inflammable liquids in a test tubeUse test-tube holderUse a small non-luminous flameHeat the upper part of the liquid firstHow to get uniform heating?shake the tubemove the tube around the flame
26Heating non-inflammable liquids Safety precautionThe tube should not be more than 1/3 full.The tube should be pointed to open area, never to anybody
27Heating non-inflammable liquids in a beakerFor larger amount of liquidA wire gauze is placed between the beaker and the flameThe beaker should not be filled more than 1/2 full.
28Heating inflammable liquids The liquid is heated indirectlyOil bath may be used to achieve a higher temperature.Why are inflammable liquids heated indirectly?Inflammable liquids may easily catch fire.