Metals and Non-metals PDF - Activity 3.9
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This document describes an activity about the burning of metals in air, examining how different metals react with oxygen. It details the formation of metal oxides and the properties of these oxides, such as their reaction with acids, alkalis, and water.
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3.2.1 What happens when Metals are burnt in Air? You have seen in Activity 3.8 that magnesium burns in air with a dazzling white flame. Do all metals react in the same manner? Let us check by performing the following Activity. Activity 3.9 CAUTION: The following activity needs the tea...
3.2.1 What happens when Metals are burnt in Air? You have seen in Activity 3.8 that magnesium burns in air with a dazzling white flame. Do all metals react in the same manner? Let us check by performing the following Activity. Activity 3.9 CAUTION: The following activity needs the teacher’s assistance. It would be better if students wear eye protection. n Hold any of the samples taken above with a pair of tongs and try burning over a flame. Repeat with the other metal samples. n Collect the product if formed. n Let the products and the metal surface cool down. n Which metals burn easily? n What flame colour did you observe when the metal burnt? n How does the metal surface appear after burning? n Arrange the metals in the decreasing order of their reactivity towards oxygen. n Are the products soluble in water? Almost all metals combine with oxygen to form metal oxides. Metal + Oxygen → Metal oxide For example, when copper is heated in air, it combines with oxygen to form copper(II) oxide, a black oxide. 2Cu + O2 → 2CuO (Copper) (Copper(II) oxide) Similarly, aluminium forms aluminium oxide. 4Al + 3O2 → 2Al2O3 (Aluminium) (Aluminium oxide) Recall from Chapter 2, how copper oxide reacts with hydrochloric acid. We have learnt that metal oxides are basic in nature. But some metal oxides, such as aluminium oxide, zinc oxide show both acidic as well as basic behaviour. Such metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. Aluminium oxide reacts in the following manner with acids and bases – Al2O3 + 6HCl → 2AlCl3 + 3H2O Al2O3 + 2NaOH → 2NaAlO2 + H2O (Sodium aluminate) Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows – Na2O(s) + H2O(l) → 2NaOH(aq) K2O(s) + H2O(l) → 2KOH(aq) Metals and Non-metals 41 2024-25
