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 produc