[Music] welcome to my channel on chemistry lessons please make sure you like and subscribe to make sure you don't miss out on future content so this is a btec applied science lesson it's unit 5 chemistry and it looks at the amphoteric behavior of alumina so there are two learning aims for chemistry in this unit a1 and a2 and this is an a1 lesson and it's going to look at the amphoteric behavior of alumina which is the very first point here next video we'll be looking at metal oxides and metal hydroxides so first thing then is for us to look at some definitions definition of acid is a substance that dissociates in water to form h plus ions most common examples would be something like hcl which will dissociate in solution to form h plus ions and cl minus ions you may also be familiar with h2so4 which is sulfuric acid this will release two h plus ions and a sulfate ion so we'd actually call h2so4 a diprotic acid because it's releasing two h plus hcl would class as monoprotic because it's releasing one h plus definition for base a base is a substance that will react with acids to form salt and water more on that next lesson when we look at hydroxides and oxides or metal often confuses people students will often use the terms alkaline base as if they're the same thing they are not an alkali is a base that will dissolve in water to form oh minus or hydroxide ions so metal hydroxides tend to be alkalized because they will dissolve in water to release oh minus ions so just to be clear all alkalis are bases but not all bases are alkalized you can only classify it as an alkali if it will dissolve to release hydroxide ions and finally amphoteric which is quite an unusual property it's when a substance can act as both an acid and the base usually it would be classified as either an acid or a base however something that's amphoteric such as alumina can act as both an acid and a base so the main aim of this video then is to look at lumina which is aluminium oxide aluminium is in group three so it's three plus oxygen or oxide is in group six it will form two minus ions so the formula the chemical formula for alumina or aluminium oxide is al2 or three so alumina is actually chemically inert which means it's very unreactive except only in certain conditions so it will react with hot acid or base so since it reacts with acids and bases we say it's amphetaric and here we look at an equation of aluminum reacting with hcl so that would be hot hydrochloric acid we can simplify that and have h plus so it doesn't have to be hot hydrochloric acid that's how it would react with acid remember an acid is h plus so we can look at either of those two equations i suggest you remember one of those two to show how alumina reacts with acid and because it's amphoteric it will also react with bases in this case we are looking at hydroxide now you may see in different textbooks and revision guides you may have different equations for how it reacts with the base don't worry just know one of them it just depends on conditions for example if it's hot hydroxide we have the second reaction and if it's not we have the top reaction but again don't learn both of them just be aware of one of those two finally we will look at some uses of alumina now it's chemically inert which means unreactive and therefore that makes it very useful it's used a lot in fillers paints sunscreens and glass it's also used in chromatography you may recall from unit 2 learning amc when you did your tlc your thin layer chromatography it was in fact a thin layer of alumina it's also an effective desiccant now a desiccant is a drying agent it removes water you actually have little packets of desiccants in um when you buy new products you know that kind of little thing that says do not eat quite often inside a new pair of trainers that's a desiccant although that desiccant isn't alumina but it does the same thing it removes moisture which is to protect the product and prolong its life this video was useful then if it was please make sure you subscribe and like so you don't miss out on the future videos