Charlene Sci 7.1 Practicals PDF

® Practical 7. 1 \ Tests for oxygen, carbon dioxide and nitrogen Aim To find out tests for identifying oxygen, carbon dioxide and nitrogen _— Apparatus and materials per group wooden spli...

® Practical 7. 1 \ Tests for oxygen, carbon dioxide and nitrogen Aim To find out tests for identifying oxygen, carbon dioxide and nitrogen _— Apparatus and materials per group wooden splint 6 test tube rack 1 | test tube filled with oxygen 5 gas lighter 1 test tube filled with carbon dioxide 5 hydrogencarbonate indicator™ test tube filled with nitrogen 5 lime water™ (~) Wear safety spectacles! Part | Oxygen 1 Your teacher will give you five test tubes filled with oxygen (A to E). 2 Observe the gas in tube A. Record the colour of the gas in the table on p. 7. 3 Remove the stopper of tube A. Fan the gas towards your nose and smell it. Record the smell of the gas. Caution Do not breathe in the gas directly. Pe LY LILA E TAN ALT INTIS AN INIT ALLL SA thts. OT TT Ll Ll Ld aa LTR RY LE PP I PPP a 4 EEE 1g/R%| hydrogencarbonate indicator #ixE lime water RIRIK  4 Light a wooden splint with a gas lighter to get a burning splint”. Remove the stopper of tube B and put the burning splint into the tube immediately. put into burning splint the tube immediately ; ETI Record your observations. £3} Skill tips When we test for gases, we must act quickly to minimize the escape of gases. 5 Light another wooden splint. Blow the flame out to get a glowing splint. Remove the stopper of tube C and put the glowing splint into the tube immediately. burning splint alowing splint en into the tube immediately burning splint fF EAE glowing splint A #2 ER) AE S 6 Remove the stopper of tube D. Add 10 drops of hydrogencarbonate indicator to the tube and stopper the tube immediately. Shake the tube gently. Record your observations. 7 Remove the stopper of tube E. Add 10 drops of lime water to the tube and stopper the tube immediately. Shake the tube gently. Record your observations. Part Il Carbon dioxide Your teacher will give you five test tubes filled with carbon dioxide (F to J). Repeat the steps in Part I with carbon dioxide. Part lll Nitrogen Your teacher will give you five test tubes filled with nitrogen (K to O). Repeat the steps in Part I with nitrogen.  Colour of the gas (Step 2) colourless colourless colonrless Smell of the gas What happens to the burning splint (Step 4) What happens to the glowing splint (Step 5) What happens to the hydrogencarbonate fwrns From red Ts remains indicator (Step 6) What happens to the : : colourless) (Ts To remains a its Romgins colourless Torn ke lime water (Step 7) Discussion Based on the results, suggest a test (if any) for identifying each of the gases below. 2 Oiygen of ovygen 1s present. ( ony S Jind b Nt ne the r.SSere 0) Burning spl? burns mere brphdh, # oxygen is present b Carbon dioxide Hydrogen carbonate dicafor fwrns from red 4 sella IE cunkon resent Lime wate Turns from colourless 1, Ie ctrdon Mogh”1s present. ¢ Nitrogen | Tlere iS no Simple Tes Tor hit  Pr actical 7.2 \ Test for water (water vapour) Aim To test for water with dry cobalt chloride paper Co ——— —— —— | Apparatus and materials per group | dropper 2 dry cobalt chloride paper” forceps 1 pair distilled water white tile 2 alcohol™ (100%) | beaker (glass or plastic) (250 cm?) 2 BR 1 Take out a piece of dry cobalt chloride paper from the desiccator” using a pair of forceps. Put it on a white tile. Record the colour of the paper. «4 Before the practical, the dry cobalt chloride dry cobalt a paper is kept in a chloride paper desiccator to prevent it from absorbing the ” moisture in the air. Do not touch the A ? —desiccator dry cobalt chloride paper with bare hands. Otherwise, | | the moisture on your By ————— drying agent hands will change the x 4 colour of the paper. 2 Use a dropper to add a drop of water to the dry cobalt chloride paper. Record the colour of the paper. 3 Use another dropper to add a dropof alcohol to a new piece of dry cobalt chloride paper. Record the colour of the paper. Caution * Wear disposable gloves. e Alcohol (100%) is flammable and harmful. Avoid contact with skin. «-«-s=s=e--+ Ensure the room is well-ventilated. Use it only in the absence of naked flame. EE LL LE EE. I LLL EL LE EE cobalt chloride paper &{c#tst4k alcohol jB¥ desiccator Figs  Results Colour of Colour of cobalt chloride paper after adding... dry cobalt chloride paper Discussion What do the results show? Dry cobalt chloride paper changes from blueto Pl in the presence of water. P nk to Blue Key point Test for oxygen: e [trelights a glowing splint. Tests for carbon dioxide: { e It turns hydrogencarbonate indicator from red to yellow. e It turns lime water from colourless to milky. ~ Test for water: eo It turns dry cobalt chloride paper from blue to pink. pm“ Did you know? (+ } | | & | Discovery of oxygen ‘Animation Before the 18th century, the existence of oxygen in SY air was not known. In 1775, Antoine Lavoisier® did an investigation on burning. During the investigation, he discovered oxygen. Watch the animation about this discovery and think about the questions below. 1 How did the understanding of burning change over time? 2 Was there any competition or collaboration™ between scientists in the discovery of oxygen? Fig 7.3 Antoine 3 How did the advancement in technology lead to the Lavoisier change in the understanding of burning? 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