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Hydroxides & Oxides

D. Crowley, 2007. Hydroxides & Oxides. Hydroxides & Oxides. To be able to describe the reaction between metals + water and metals + oxygen. Metal or Non-metal?. Using the sheet, cut out the summary for metals & non-metals Stick these into your books. Metals & Non-metals.

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Hydroxides & Oxides

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  1. D. Crowley, 2007 Hydroxides & Oxides

  2. Hydroxides & Oxides • To be able to describe the reaction between metals + water and metals + oxygen

  3. Metal or Non-metal? • Using the sheet, cut out the summary for metals & non-metals • Stick these into your books

  4. Metals & Non-metals • Metals: conduct electricity; conducts heat well; is malleable, I.e. can bend without breaking; is usually a hard material; has strong forces between atoms which are very close together • Non-metals: does not usually conduct electricity; does not conduct heat well; is brittle and not strong; usually has a low melting point; has weak forces as the atoms are not very close together

  5. Reaction • Today you are doing an experiment • You are going to see what happens when you react some metals with warm water • You’ll be testing for hydrogen, and identifying the pH

  6. Experiment • You will need a Bunsen burner (on the safety flame) • A heat-proof mat • Some splints • A boiling tube (half filled with water) • 1 piece of magnesium, calcium & copper

  7. Procedure • Place one of the metals in the boiling tube and half fill this with water • After a short while light a splint, and place this in the end of the boiling tube - has hydrogen been produced - how will you know? • Finally, add a few drops of UI in, and record the pH

  8. Findings • Hopefully you found that when some metals were placed in water they reacted • Hydrogen was produced (squeaky pop) • The pH also changed - it went from neutral to alkaline (purple) • However not all the metals react - so some are reactive, others are not • Watch the demo of some very reactive metals…

  9. Key Point • When a metal reacts with water, it produces a metal hydroxide + hydrogen metal + water metal hydroxide + hydrogen

  10. Equations • Some metals react with water, forming a hydroxide and releasing hydrogen… • The copper did not do anything in the water (no reaction) • The magnesium did not do much in the water - you may have got a slight pop (slight reaction) • The calcium was more reactive in the water - it produced a squeaky pop (stronger reaction)

  11. Equations Remember: metal + water metal hydroxide +hydrogen Calcium + WaterCalcium hydroxide + Hydrogen Ca (g) + 2H2O (l)  Ca(OH)2(aq) + H2(g) Magnesium + WaterMagnesium hydroxide + Hydrogen Mg (g) + 2H2O (l)  Mg(OH)2(aq) + H2(g)

  12. Reactivity • So, some metals are un-reactive in water - such as copper and gold • This is why copper pipes at great at carrying water, and you can wear gold safely • However others are more reactive, such as calcium and magnesium…

  13. Oxygen • We’ve seen some metals react with water to form a metal hydroxide + hydrogen • Other metals react with oxygen, forming a metal oxide • Watch the demo of magnesium & copper in oxygen…

  14. Key Point • When a metal reacts with oxygen, it produces a metal oxide metal + oxygen metal oxide

  15. Equations • Some metals react with oxygen, forming an oxide • The copper and the magnesium both produced metal oxides - which one was more reactive?! • The magnesium was extremely reactive in the oxygen - producing a very bright white light Copper oxide – made by copper atoms and oxygen atoms joining

  16. Equations Remember: metal + oxygen metal oxide Copper + OxygenCopper oxide 2Cu (s) + O2 (g)  2CuO(s) Magnesium + OxygenMagnesium oxide 2Mg (s) + O2 (l)  2MgO(s)

  17. Summary • Metals differ in how reactive they are - some are very reactive, others are less so • Some metals react with water, producing a metal hydroxide + hydrogen (e.g. caclium) Metal + water metal hydroxide + hydrogen • Some metals react with oxygen, producing a metal oxide (e.g. magnesium) Metal + oxygenmetal oxide

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