Reactions of Group 1 metals


Method:


We tested three metals in group 1 to see which was the most reactive. First a piece of lithium (Li) was placed in a trough of water. After that had finished reacting a piece of sodium (Na) was placed in a trough of water. And finally a piece of potassium (K) was placed in a trough of water.


Observations:


Lithium


The lithium was stored in oil to prevent it from reacting with the oxygen in the air. The lithium was floating in the oil which meant it was less dense than the oil. It was a dull silver grey colour. When it was cut it was shinny inside because the inside had not come into contact with oxygen, which prevented it from forming lithium oxide. It was quite easily cut. After a few minutes the inside had tarnished as it had reacted with oxygen and formed lithium oxide.


lithium + oxygen lithium oxide


4Li(s) + (g)O2 2Li2O(s)


When the piece of lithium was added to the trough of water it fizzed and moved on the surface of the water (floating) Hydrogen gas was given off. It then got smaller and smaller until it disappeared.


Lithium +Water Lithium Hydroxide + Hydrogen


2Li(s) + 2H2O(l) H2(g) + 2LiOH(aq)





Sodium


The sodium was stored in oil, again to prevent it from reacting with the oxygen in the air. The sodium was not floating in the oil which meant it was denser than the oil. It was a silvery white colour, and this was also dull. When it was cut it was shinny inside because the inside had not come into contact with oxygen, which prevented it from forming sodium oxide, as with the lithium. It was quite easier than the lithium to cut. It tarnished quicker than the lithium as it is more reactive.


sodium + oxygen sodium oxide


4Na(s) + (g)O2 2Na2O(s)





The sodium turned into a molten ball as soon as it touched the water. It moved on top of the water, but did not fizz like the lithium. Like the lithium a hydrogen gas was released. The reaction was exothermic, which meant the reaction gave off heat. The ball got smaller and smaller until it disappeared.


Sodium + Water Sodium Hydroxide + Hydrogen


2Na(s) + 2H2O(l) H2(g) + 2NaOH(aq)





Potassium


The potassium was stored in oil, like the lithium and the sodium; preventing it from reacting with the oxygen in the air. The potassium was not floating in the oil which meant it was denser than the oil, like the sodium. It was a silvery grey colour, with a purple tinge. When it was cut it was shinier on the inside than the outside, because the inside had not come into contact with oxygen. It was easier than the lithium and the sodium to cut. It tarnished a lot quicker than the lithium and sodium. Showing it was the most reactive with oxygen of the three metals.


potassium + oxygen potassium oxide


4K(s) + (g)O2 2K2O(s)





Like the sodium the potassium turned into a molten ball, but the potassium caught fire and produced orange sparks. Hydrogen gas was produced again. It also moved around a lot quicker than the lithium or the sodium. Potassium was the most reactive.


potassium + water potassium hydroxide + hydrogen


2K(s) + 2H2O(l) H2(g) + 2KOH(aq)


Similarities and Differences between the metals:



o All three of the metals were dull in appearance, but shiney when cut.
o All three of the elements were relatively easy to cut.
o All three of the metals reacted with water.
o All three metals produced Hydrogen(g)
o Sodium and potassium both turned into a molten ball.
o Only lithium fizzed when added to water.
o Sodium and potassium were denser than oil, but lithium was not.
Where did the hydroxides go?


After the reactions had finished the sodium hydroxide was aqueous in the water (present). To test this we added universal indicator to both plain water and the water in the trough. The plain water went green which meant it was neutral, but the water in the trough went blue which meant it was alkali; therefore there was hydroxide present in the water.


Safety:


For safety we wore goggles and there was a safety screen surrounding the experiment. The pieces of metal were only handled with tweezers, in case of moisture on the hands which would cause the metal