Metals, non-metals and corrosion in daily life

Metals, non-metals and corrosion in daily life

1. Metals, non-metals and corrosion

2. Positions of metals, non-metals and metalloids in the periodic table

3. Alkali metals Properties Soft (Can be cut into smaller pieces with a knife) Low density (The density of Li, Na and K are less than that of water and hence they will float in it). Low melting point. React very vigorously with water, unlike most metal.

4. Metal in liquid state at room temperature Properties- Mercury is a silvery white metal The melting point is -38.842*C The boiling point is 356.58*C Mercury is used to make thermometers and barometers In some cases it is used to make batteries Symbol - Hg

5. Forms of Carbon Have high melting point (35500C). Hardest substance Diamond is a good conductor of heat but a bad conductor of electricity Have high melting point (37200C). It sublimes ( turn directly from solid to a gas without melting). Good thermal and electrical conductors.

6. Tests to identify gases Test for chorine gas Hydrogen - lighted splint goes out with a squeaky pop When hydrogen reacts with oxygen – water is the product made which won’t see because it is present as steam due to the heat of the reaction . O xygen - a glowing splint relights Chlorine - damp blue litmus paper turns red and is then bleached white

7. Decomposition reaction The chemical reaction in which one reactant breaks down into two or more products.

8. Electrolysis of water Observations In positive platinum electrode: Oxygen gas liberates . In negative platinum electrode: Hydrogen gas liberates Word equation : Water (l) electricity ⟶ Hydrogen (g) + Oxygen ( g) V H = 2 V O

9. Electrolysis of Copper sulfate solution Observations In positive carbon electrode: Oxygen gas liberates . In negative carbon electrode: Copper metal deposit on the surface of electrode The blue colour of copper sulfate fades due to the transfer of copper from the solution to the negative electrode .

10. Electrolysis of Sodium chloride solution Observations In positive carbon electrode: Chlorine gas liberates . In negative carbon electrode: Hydrogen gas liberates. Word equation : Sodium chloride (s) electricity ⟶ Sodium (s) + Chlorine (g)

11. Reaction of metal with dilute acid E.g. Copper, Silver and Gold. Because these metals are not reasonably reactive for the reaction with hydrogen.

12. Corrosion Iron + oxygen + water ⟶ hydrated iron oxide (rust) Rusting is a form of corrosion . This is an oxidation reaction, since oxygen is a reactant and an oxide is the product Bad effect : It spoils the appearance of objects and can weaken their structures. Factors that affect the rate of rusting of iron object Humidity (water vapour content in air) Salinity (salt content in air) Temperature

13. Different ways which help to protect iron from rusting . Covering with oil or grease Painting Coating in plastic Coating in tin (Method: Electroplating) Coating in zinc or magnesium (Galvanising) Corrosion

14. or Mg (in extreme condition)

15. Electroplating is the protection of the surface of one metal (Iron) by coating it with a thin layer of another metal (tin) applied by electrolysis.

16. Stainless steel Stainless steel is a rust proof alloy made by adding nickel and chromium to molten steel . Steel is usually over 95% iron with carbon present in varying amount. The amount of carbon determines the strength and hardness of steel.

17. Tarnished metal Surface loses their shiny appearance due to reaction with substances included water vapour, carbon dioxide, sulfur dioxide etc. in the air.