11. QA1 Effect of heat on substances 4E1template

PC_Prac_QA1_Effect_of_heat_on_substances 41 NAME: ___________________________ ( ) DATE: _______ CLASS: ________ QA1 – Thermal Decomposition of Solids & Flame Tests PART 1: Thermal Decomposition of solids Aim: To record the colour changes of the solid observed during the thermal decomposition of the solid and identify the gases given off during heating. Apparatus and chemicals: test tubes safety goggles ammonium chloride test tube holder wooden splints copper(II) carbonate test tube rack limewater lead(II) nitrate spatula red and blue litmus papers zinc carbonate dropper distilled water Bunsen burner Procedure: Conduct the tests on pages 2 & 3 on the thermal decomposition of solids labelled P, Q, R and S. 1. Place 3 spatula of the solid into a clean and dry hard glass test tube. 2. Light the Bunsen burner with the air hole fully closed. Upon lighting the Bunsen burner, adjust the air hole until it is fully opened to obtain a non-luminous flame for heating. 3. Adjust the gas tap to control the size of the flame. 4. Hold the test tube just below its mouth using a test tube holder. 5. Heat the sample in the test tube gently first for about 30 seconds before heating very strongly using a non-luminous flame until there is no further change. 6. Test for any gas formed. [using litmus papers / limewater / glowing splint] 7. Observe and record the colour changes of the solid on heating and on cooling. 8. During the course of heating, observe and record any coloured gases / fumes as well as condensation of any liquid at the mouth of the test tube. For gentle heating: move the test tube in and out of the flame. For strong heating: position the test tube at the hottest part of the flame and heat. On heating, ___________ (to fill in colour) solid turns / melts into a ___________ (to fill in colour) solid / liquid. On cooling, ___________ (to fill in colour) solid remains / turns into a ___________ (to fill in colour) solid. On heating, ___________ (to fill in colour) gas / fumes are observed. On heating, droplets of ______________ (to fill in colour) liquid are formed at the mouth of the test tube. 25

PC_Prac_QA1_Effect_of_heat_on_substances 42 Observations Solid Test Observation(s) Identity of gas evolved (if any) P a) Heat the sample in the test tube gently first for about 30 seconds before heating very strongly flame until no further change is seen. b) While heating the sample strongly, test any gas evolved using moist red and blue litmus papers. c) Allow the heated sample to cool. On heating, __________ fumes are observed. ______ solid sublimes. Gas produced turn ____________ ____________________________. On further heating, gas produced turn _________________________ ____________________________. On cooling, ___________________ _______________ near the mouth of the test tube. Ammonia gas is produced. An acidic gas is produced. Q a) Heat the sample in the test tube gently first for about 30 seconds before heating very strongly flame until no further change is seen. b) During the heating process, withdraw several samples of gas from inside the test tube using a teat pipette. Each time bubble the gas from the teat pipette through the limewater. c) Allow the heated sample to cool. On heating, _________ solid turns ___________. Gas produced ________________ _____________________________ ____________________________. On cooling, _________ solid turns __________. Carbon dioxide gas is produced. R a) Heat the sample in the test tube gently first for about 30 seconds before heating very strongly flame until no further change is seen. b) While heating the sample strongly, test any gas evolved using moist red and blue litmus papers, as well as using a glowing splint. c) Allow the heated sample to cool. On heating, __________ solid turns ___________. _________________ are observed. Gas produced turn ____________ ____________________________. Damp/moist red litmus paper ____________________________. Gas produced ________________ ____________________________. On cooling, ___________ solid turns ____________. Nitrogen dioxide gas is produced. (students need not identify) An acidic gas is produced. Oxygen gas is produced.

PC_Prac_QA1_Effect_of_heat_on_substances 43 Solid Test Observation(s) Identity of gas evolved (if any) S a) Heat the sample in the test tube gently first for about 30 seconds before heating very strongly flame until no further change is seen. b) During the heating process, withdraw several samples of gas from inside the test tube using a teat pipette. Each time bubble the gas from the teat pipette through the limewater. c) Allow the heated sample to cool. On heating, __________ solid turns ___________. Gas produced ____________ ________________________. On cooling, ______________ ________________________. Carbon dioxide gas is produced. PART 2: Flame Tests Flame tests can be used to identify a relatively small number of metal ions in a compound. In your syllabus, you are n ot required to know which metal ion gives what colour. However, you must know how to make observations when performing a flame test. Aim: To perform flame tests on solids A, B, C and D. Procedure: 1. Adjust the Bunsen burner to give a blue flame. 2. Moisten the end of a wooden splint with water and dip the moist end of the splint into solid A. 3. Place this end of the splint in the Bunsen burner flame. 4. Record your observations. 5. With a clean splint, repeat steps 1 – 4 with solids B, C and D. Salt Observation A The splint burns with a ____________________ flame. B C D What to observe − The colour of the flame obtained. For example: A pink flame was seen / The splint burns with a pink flame.