L9 Metals PDF - Principles of Chemistry

Metals PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 1 Official (Closed) - Non Sensitive Learning objectives  Describe the properties of metals  Explain why alloys have different physical properties to their constituent elements  Describe the metal reactivity series  Under...

Metals PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 1 Official (Closed) - Non Sensitive Learning objectives  Describe the properties of metals  Explain why alloys have different physical properties to their constituent elements  Describe the metal reactivity series  Understand the importance of iron metal and its application in daily life. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 2 Official (Closed) - Non Sensitive Metals Two thirds of all the elements in the Periodic Table are metals. Metals have the following properties:  They are good conductors of electricity  They are good conductors of heat  They usually have high densities, melting points and boiling points.  They are malleable and ductile*. *Malleable - able to be hammered or pressed into shape without breaking or cracking. *Ductile - able to be drawn out into a thin wire. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 3 Official (Closed) - Non Sensitive Weird Metals What is the most expensive metal in the world? Rhodium Gallium Coin Ruthenium fire (yanartas) Source: Hollywood pawn shop. Retrieved 1/6/2017 PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 4 Official (Closed) - Non Sensitive Source: Chemistryperiodictables.blogspot.sg. Retrieved 1/5/2017 PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 5  Why are pure metals Official (Closed) - Non Sensitive not widely used in industry? Although pure metals have many useful properties, they are not widely used because: 1. Pure metals are soft. In a pure metal, the atoms are packed regularly in layers. The layers can slide over one another easily when a force is applied. 2. Pure metals may react with air & water and corrode easily Structure, properties and uses. (n.d.). Retrieved October 10, 2015, from http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/bonding/ structure_propertiesrev5.shtml PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 6 Official (Closed) - Non Sensitive Alloys An alloy is a mixture of a metal with one or a few other elements. Metals are often used in the form of alloys: 1. To make metals harder & stronger – e.g. Brass (alloy of copper & zinc) is harder & stronger than pure copper or pure zinc 2. To improve the appearance of metals – e.g. Pewter (alloy of tin, antimony & copper) is used to make ornaments because it looks more beautiful than pure tin. 3. To lower the melting point of metals – e.g. Solder (alloy of tin & lead) has a lower melting point than most metals. 4. To make metals more resistant to corrosion – e.g. stainless steel (alloy of iron, chromium, nickel & carbon) is resistant to corrosion. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 7  Official (Closed) - Non Sensitive Why are alloys stronger & harder than their constituent metals? The atoms of different sizes break up the regular arrangement of atoms in the metal. The atoms in alloys cannot slide over each other easily. Metals & alloys. (n.d.). Retrieved January 8, 2016, from http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/rocks_metals/4_metals_alloys2.shtml PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 8 Official (Closed) - Non Sensitive Question 1. Why are metals often used in the form of alloys? 2. Why are alloys stronger and harder than their constituent metals? PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 9 Official (Closed) - Non Sensitive Chemical properties of metals Reaction of metals with water ◦ Potassium, sodium and calcium react with cold water to produce the hydroxides and hydrogen gas. 2Na (s) + 2H2O (l)  2NaOH (aq) + H2 (g) ◦ Magnesium, aluminium, zinc and iron react with steam to produce the oxides and hydrogen gas. Mg (s) + H2O (g)  MgO (s) + H2 (g) PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 10 Official (Closed) - Non Sensitive Chemical properties of metals Reaction of metals with acids ◦ Most metals react with dilute hydrochloric acid to form the chloride (salts) and hydrogen 2K (s) + 2HCl (aq)  2KCl (aq) + H2 (g) Zn (s) + H2SO4 (aq) → ZnSO4 (aq) + H2 (g) Most metals react with oxygen to give a metal oxide. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 11 Official (Closed) - Non Sensitive Chemical properties of metals Reaction of metals with oxygen Metals such as potassium, sodium and lithium react with oxygen very quickly. Calcium and magnesium are slightly less reactive and react with oxygen less quickly. Metals like copper and mercury react with oxygen very slowly and need to be heated continuously in order to see this happening. 2Mg (s) + O2 (g) → 2MgO (s) PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 12 Official (Closed) - Non Sensitive Potassium in water Official (Closed) - Non Sensitive The reactivity series How vigorously each metal reacts with water or hydrochloric acid depends on its chemical reactivity. The reactivity series is the order of reactivity of the metals ◦ Metals at the top of the series are most reactive ◦ Metals towards the bottom of the series are the least reactive. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 14 Official (Closed) - Non Sensitive The reactivity series PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 15  Official (Closed) - Non Sensitive The reactivity series Most Need help remembering? Potassium (K) reactive Sodium (Na) Please Send Camels, Monkeys & Calcium (Ca) Zebras In Large Heavy Crates Magnesium (Mg) Soon Zinc (Zn) Iron (Fe) Metals that are more reactive than hydrogen Lead (Pb) react with dilute HCl to produce hydrogen gas. Hydrogen (H) *Note: Lead should react with dilute HCl. Copper (Cu) However, the initial reaction between lead and Least HCl forms insoluble lead (II) chloride, which reactive Silver (Ag) prevents further reaction. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 16  Official (Closed) - Non Sensitive Displacement reactions of metals A more reactive metal can displace a less reactive metal from its salt solution. E.g. Magnesium displaces copper from copper (II) sulphate solution: Displacement reactions. (n.d.). Retrieved January 8, 2016, from http://www.bbc.co.uk/bitesize/intermediate2/chemistry/acids_bases_metals/metals/revision/2/ PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 17 Official (Closed) - Non Sensitive Displacement reactions of metals The atoms of the reactive magnesium give away electrons: Mg(s) → Mg2+(aq) + 2e- The ions of the less reactive copper are forced to accept these electrons: Cu2+(aq) + 2e- → Cu(s) The overall ionic equation for the displacement of copper by magnesium is: REDOX reaction Mg(s) + Cu (aq) → Mg (aq) + Cu(s) 2+ 2+ On the other hand, if copper metal was added to magnesium sulphate solution, no reaction would occur. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 18 Official (Closed) - Non Sensitive Question Write the ionic equation for the reaction (if any) between: a) Magnesium & iron (II) sulfate Mg (s) + Fe2+ (aq)  Mg2+ (aq) + Fe (s) b) Zinc & silver nitrate Zn (s) + 2Ag+ (aq)  Zn2+ (aq) + 2Ag (s) c) Copper & iron (II) sulphate No reaction. PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 19 Iron & Steel https://youtu.be/xAVCY0WE8uM PRINCIPLES OF CHEMISTRY, PFP, LSCT, NGEE ANN POLYTECHNIC 20