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Year 9 Science Chemical Reactions — Transcript

by Robin Williams · 4,300 words · 596 segments · language en · Watch on YouTube

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0:00some things I want to go through with
0:01you today generally today's lesson is
0:03going to be teaching you guys some
0:05general formulas that we use in
0:07chemistry these are formulas that will
0:10help us predict what will happen in a
0:12chemical reaction between two chemicals
0:14but the real focus today is going to be
0:17looking at some metals okay because this
0:19chapter is all about metals and then how
0:22they affect chemical reactions okay so
0:27far in Year seven and eight you guys
0:29will have spent most of your time doing
0:31what are called word equations and while
0:34word equations are okay they actually
0:36have limitations and so now we're in
0:39your nine we're gonna start moving that
0:41on to what are called symbol equations
0:43okay and so symbol equations just when
0:46we use the element symbols to basically
0:48help explain what's going on a bit
0:49better so in this example you can see
0:51here this sodium plus chlorine goes to
0:54sodium chloride these are the symbols
0:56that we get from the periodic table okay
1:00so some things that you need to know
1:01basically now you're in your nine there
1:04are three common chemicals that we use a
1:06lot in the lab and you guys need to know
1:08the name the formula and then what
1:11happens with them when we react them
1:13with another chemical
1:14so this chemical here which is called
1:16hydrochloric acid and you'll have to
1:19bear with my terrible handwriting so
1:22hydrochloric acid and you guys can fill
1:25this in as we go along does anyone know
1:27what the formula for hydrochloric acid
1:29is
1:35thank you yes it is HCl embrose so HCl
1:40so what does this formula tell me what
1:42elements are in hydrochloric acid I
1:51whatever
1:52yeah so there's some hydrogen certainly
1:55which is the symbol H yeah and the CL
1:59what's the CL stand for is it one or two
2:01elements one how can I tell but if the
2:06letter of behind the main letter is in
2:10lowercase then it's yes okay so one of
2:13the ways you can tell is if we have an
2:16uppercase letter and a lowercase letter
2:21no that just is lower lowercase letter
2:24then basically what this tells me is it
2:26must be one element so C L stands for
2:34Orion thank you yes it's chlorine okay
2:38which if you are defined on the periodic
2:40table it would be CL capital C lowercase
2:43L so this is all one element so this is
2:46one of the ways that we can build a
2:49formula for a chemical hydrochloric acid
2:53its name comes from the fact that it
2:55only contains hydrogen and chlorine
2:58hydro for hydrogen chloric for chlorine
3:03the thing is though hydrochloric acid is
3:05actually kind of a common name a
3:07household name if it was to be given a
3:10proper scientific name does anyone know
3:13what we would call it
3:19I'll take that silences are no really
3:22what we should do is we should use
3:24hydrogen because that's the first part
3:27and instead of saying claw is not called
3:30hydrogen chlorine what we do is we
3:33change chlorine to chloride and in this
3:38case I'd basically means reacted with so
3:43if we were to draw this molecule if I
3:44was actually draw it in 3d or s or in 2d
3:47it would be one hydrogen attached to one
3:50chlorine and so if we were to name it it
3:52should be called hydrogen from the first
3:54part and then chloro from chlorine and
3:58then we change it to ID which means
4:00bonded with so this is quite an
4:08interesting thing because this chloride
4:10is going to be the same no matter what
4:13chlorine is bonded to so when we use
4:17hydrochloric acid in a chemical reaction
4:19it will always make a product which
4:23means the thing at the end like this
4:25which is named chloride so that might
4:32sound a bit confusing but let's take
4:33this example above sodium plus chlorine
4:35makes sodium chloride or if I took
4:41hydrochloric acid
4:46and I reacted it with some sort of metal
4:50like magnesium it would make two things
4:56does anyone know what those two things
4:58are yes thank you Derrick it would make
5:03something called
5:04magnesium but the chlorine from the
5:07hydrochloric acid would form this
5:09chemical code chloride and so what's
5:12left over
5:15hey yeah exactly
5:20hydrogen and so very simply we can start
5:24to put together word equations purely
5:28because we know what elements are found
5:31in the acids so let's do another example
5:35here is the next most common acid that
5:38you'll find in a science lab which is
5:39cool sulfuric acid sulfuric acid does
5:48anyone know what the formula for
5:50sulfuric acid is it's getting more
5:55difficult now
6:00if you're not sure the formula and you
6:02guys need to learn this is h2so4 so just
6:12like before can anyone tell me how many
6:14elements are there in sulfuric acid or
6:20which elements I should say once once
6:25there's a sulfur yeah okay what's this
6:28one that we did before so we have just
6:33like before we have hydrogen we also
6:38have two other elements which are sulfur
6:47and we have some oxygen
6:55symbol for sofa is s okay so these are
7:00the three elements that make up sulfuric
7:01acid to make things easier for you guys
7:05though is instead of treating sulfur and
7:08oxygen as separate elements what we've
7:12done in chemistry is we've actually
7:14combined them to make what's called
7:18sulfate so so4 is called sulfate so
7:28anyone know what the proper chemical
7:30name for sulfuric acid is like
7:32hydrochloric acid is hydrogen chloride
7:34what word sulfuric acid be called it's
7:46not we take the name guys from this
7:49sulfate ion here so it actually becomes
7:52technically called hydrogen because
7:57that's the first part and then the
7:59second part we combine this whole name
8:03so we should really call it hydrogen
8:06sulfate we don't because it's much nicer
8:09to say sulfuric acid but the technical
8:11name for it of the elements is called
8:13hydrogen sulfate now just like with our
8:18hydrogen chloride when we react hydrogen
8:22chloride with something it makes
8:25chlorides at the end so whatever we
8:28react it with will be something chloride
8:30and with hydrogen sulfate you can do
8:33exactly the same thing when you react
8:37hydrogen sulfate or sulfuric acid with
8:39us something else it will make a sulfate
8:45takes its name from it exactly like
8:47before so let's take our earlier example
8:51where we took sulfuric acid
8:58and reacted it with some magnesium can
9:04anyone figure out what we're gonna make
9:12no it's gone quiet today it's very quiet
9:15so I'm doing a terrible job being a
9:17teacher thank you we're gonna make
9:22magnesium sulfate excellent plus what
9:26what's left what haven't we used yes
9:30some hydrogen nice so what that's closed
9:37one night let's go back what I would
9:38like you guys to do is see if you can do
9:40the same thing for nitric acid all of
9:44the steps I've just done above so
9:45sulfuric acid the proper name for it and
9:48then what it's formula is now to help
9:50you I will give you the formula so the
9:53formula for nitric acid is hno3 and just
10:01like before we don't have a separate
10:05part here we combined it does anyone
10:09know what we call this combined thing
10:10here this box I can't do anything crazy
10:13yeah here's you Scott um sound in the
10:16background can they mute peaceful nice
10:22if you if you want to talk just unmute
10:23talk and then mute again it's easier do
10:26you guys know what we call this no.3
10:27anyone know begins with an N it's called
10:37a nitrate just like this is called a
10:42sulfate this is called a nitrate so the
10:45proper name for this chemical guys is
10:47going to be nitric acid that's the
10:51common name oh that's the wrong color
10:55I'm doing everything wrong at the moment
10:57let's go back use the right colors to
11:01make it so the same so this is called
11:06nitric acid its chemical name is
11:15hydrogen nitrate that's what it should
11:21be called and it's ending of the word
11:25which we get from its chemical name is
11:27going to be nitrate so just like before
11:34if we were to take nitric acid and add
11:41some magnesium to it what would we make
11:49in this case we take our magnesium
11:56but we use the end of the word so it
11:58makes magnesium nitrate plus just like
12:02before you would make hydrogen the one
12:08thing that I didn't do is I didn't label
12:09these and let me just do that for you
12:11quickly
12:14hydrogen if you don't know what these
12:18are called
12:18the middle one here is nitrogen and
12:23finally we have
12:27oxygen in there as well anyone tell me
12:31what the three acids I've mentioned have
12:32in common
12:40they're all the city they are all acidic
12:42that's true but looking at their
12:44chemical formulas guys HDL h2so4 and
12:48hno3 what are they all yes thank you
12:52Ambrose so something that we learn when
12:54we start to get to GCSE is that
12:56something that makes something can acid
12:59in the first place is all acids must
13:02contain hydrogen
13:09must
13:16and the other thing we learn is you know
13:19we measure acids using something called
13:21a pH scale don't we she learned in year
13:27seven and eight the pH what do you think
13:30it stands for why do you think we write
13:36the H as a capital H it stands for
13:44hydrogen yes okay in fact pH stands for
13:48potential hydrogen basically so strong
13:53strong acids have more hydrogen in them
13:55than weak acids deep that's where the pH
13:59scale gets his name from we don't teach
14:01you that in year seven and eight but
14:03it's actually that's a GCSE fact okay so
14:06you're probably thinking well that's
14:08great mr. Williams you've made a very
14:09nice colorful page there but we need to
14:11know why so why is this quite important
14:14well these word equations that we're
14:16writing at the end this section over
14:18here this is important because what it's
14:21showing me is that we have patterns it
14:24doesn't really matter which acid I use
14:27as long as I know the ending I can work
14:29out that we're gonna make the same
14:31things look acid plus metal magnesium
14:34gives me a chemical plus hydrogen acid
14:37plus metal gives me a chemical plus
14:40hydrogen acid plus metal gives me a
14:42chemical plus hydrogen so I'm starting
14:45to see some patterns and anytime we have
14:48patterns in science it allows us to
14:50write what's called a general formula so
14:54what I want to do is go through some
14:56general formula with you guys today once
14:59that you will need to learn and if you
15:01can just learn them off by heart so that
15:03you can just say metal plus oxygen gives
15:06me this it's gonna make your life a lot
15:08easier when you come to your exam so
15:12there are only four general formula that
15:15you need to know and then there's a
15:17bonus one that you might need to know
15:18okay when we talk about chemicals and
15:21especially metals the most basic one is
15:25going to be if we take a metal and we
15:28add oxygen
15:29and you guys looked at this for me two
15:32lessons ago do you remember I asked you
15:34to find five pictures of metals and
15:41oxygen that was the first task so here's
15:45the first picture and what we need to do
15:47is we need to start looking at a general
15:49formula so here it is your first formula
15:51you need to know is metal plus oxygen
15:57can anyone tell me what would happen if
16:00I reacted a metal with an oxygen
16:03molecule it was it would rust yes deric
16:06but what would the product B this is the
16:08reactants the things that are being
16:12mixed together and the products are what
16:17is made so what would the products be of
16:19metal plus oxygen close and you're very
16:28close so yeah yeah the first word is
16:31metal just not oxygen eat oxide oxide
16:36Thank You max yes okay so this would be
16:38called a metal oxide notice this IDE
16:42which means bonded with or reacted
16:46together basically so we take the word
16:48oxygen we get rid of again and we add
16:51IDE IDE which means bonded together so
16:55let me give you an example let's take an
16:58example color so example name a metal
17:03sodium sodium plus oxygen will give me
17:11what I need to find a name yes the name
17:17of the metal which is sodium and then I
17:20add oxide because that's the suffix that
17:23you get from oxygen or let's do another
17:27one
17:27someone Derek give me a name of a metal
17:32aluminium aluminium nice okay
17:36so aluminium plus oxygen goes to
17:44aluminium oxide so do you see guys how
17:50just by knowing metal plus oxygen gives
17:53me metal oxide I can use it for any
17:56metal out there I could say silver plus
17:58oxygen gives me silver oxide or
18:01strontium plus oxygen gives me strontium
18:04oxide I can pick anything I could say
18:06plutonium plus oxygen gives me plutonium
18:09oxide all of these chemicals will give
18:12me exactly the same thing as long as I
18:14know my general formula so here is the
18:18general formula for metal plus oxygen
18:22and you guys should know this off by
18:24heart okay the next one that you need to
18:27know is going to be sorry I should ask
18:30does anyone have any questions about
18:31this no I'll take that as a no it's
18:37pretty simple isn't it's not too
18:39complicated okay so the next one you
18:43need to know is going to be metals plus
18:45water and hopefully those people who
18:48were here for last lesson you looked at
18:50this I showed you a Brainiac video which
18:54had I have no idea how super brainiacs
18:58like that which was sodium plus water
19:03wasn't it
19:04and what happened
19:08it exploded bang so let's have a look at
19:13our general formula for the metal what's
19:16water now it really depends this expect
19:21this equation the general formula should
19:24be metal plus water goes to now this
19:32one's a bit trickier we have a new type
19:34of chemical that you maybe haven't seen
19:36before which is called a hydroxide let
19:42me redo that ëcoz that's terrible a
19:45hydroxide now for those of you who don't
19:48know a hydroxide is simply an OHA an
19:53oxygen bonded to a hydrogen basically
19:56and we make one other thing which is
20:00going to be hydrogen and I'll explain
20:05why this is in a second
20:07so for most of you you should by now
20:10know that water is made of two
20:14hydrogen's and one oxygen we write the
20:17formula h2o which means that if you were
20:20to Jory what it would look like would be
20:22one oxygen attached to one hydrogen
20:25attached to another hydrogen when we mix
20:31this with water sorry when we mix this
20:34with a metal the metal is able to come
20:37in and basically break apart part of
20:42this water molecule it can actually
20:44break a piece of it away and so what it
20:47does let's use sodium as an example
20:50sodium comes along and it goes I want
20:52this but I don't really want this bit
20:54this fits boring so it breaks this piece
20:57off and it throws it away
20:58and it takes the O H molecule for itself
21:01and it makes this new type of chemical
21:03which is called a hydroxide so let's
21:07take an example
21:10so do excuse me that's not one trying to
21:14D sodium doesn't begin with an L sodium
21:20plus water will make sodium hydroxide
21:30plus this little piece that nobody
21:33wanted which is a hydrogen so it makes
21:36some hydrogen over here and that's
21:41basically our simple chemical reaction
21:44for metal plus water we can take any
21:49metal and we should make the same things
21:52so in this example if I took some
21:55calcium and I added water what do you
22:03guys think I would make
22:10what would be the products
22:17in this case you just take the name of
22:19the metal which is calcium and you take
22:23the hydroxide which is always made now
22:31what's left we have some hydrogen left
22:34okay are you guys okay with this
22:38metals plus water yes thank you
22:43this is called our general formula here
22:46metal plus water is going to give you a
22:49metal hydroxide plus hydrogen and like I
22:52said again you just really have to learn
22:54these names if you don't know what this
22:56is this hydroxide just learn that metal
22:59plus water gives you metal hydroxide
23:00plus hydrogen okay the most interesting
23:05one acid and I'm gonna need more space
23:08let's move this down so metals plus acid
23:14I sort of explained to you guys at the
23:15very top so I've worked been too long
23:17going through what we did up here all of
23:19this stuff this is basically the
23:21explanation for why metals plus acids
23:23give us what they do it really depends
23:26on the acid that you use so if you
23:29choose to use hydrochloric acid or HCl
23:38this will give us the outcome so what we
23:43could say is metal no sorry let me use
23:46blue so it's the same color as above I'm
23:48gonna get rid of that let's try that
23:50again if I say metal plus acid gives us
24:00the ending of the acid so it will give
24:05us a metal with the ending of the acid
24:14plus hydrogen so like before let me just
24:20break that down so HCl plus no I want
24:24mister Williams you're not doing very
24:25well today
24:26let's take any metal let's say magnesium
24:31plus HCl will give me magnesium plus the
24:36ending which is chloride CL plus
24:40hydrogen or we can do that in your word
24:44equation so magnesium except I can't
24:49write the word magnesium apparently plus
24:53hydrochloric acid well go to you
25:01magnesium chloride plus
25:08hydrogen this is if we use hydrochloric
25:14acid
25:15just like before though I could use
25:16another metal I can use any metal so
25:18let's take sodium for example let's use
25:22sodium plus let's use nitric acid will
25:32give me
25:35sodium and I need to use the end of this
25:37type of acid which is nitrate we learned
25:40that earlier plus hydrogen well here's
25:46the tricky part does anyone know what we
25:48call these these are a group of
25:50chemicals these this this here and this
25:53does anyone know what we call these in
25:56chemistry normally it's a metal and
26:01nonmetal combined together anyone know
26:06what the name of this is take that as a
26:15no these are often called assault
26:21assault I'm an assault although you guys
26:25are probably familiar with table salt
26:27which is a common salt actually salts
26:31are a group
26:32Yesi so right does anyone know what the
26:34formula of C so is anyone know what's in
26:42it C HCl it's not HCl but there is CL in
26:49it
26:52technically guys this is called sodium
26:56chloride so sea salt the salt be put on
27:02your food and we eat is called sodium
27:04chloride but this is just one of
27:05thousands of different salts so sodium
27:08nitrate is a salt and magnesium chloride
27:11is also a type of salt you don't want to
27:14eat these ones because they would poison
27:15you sodium chloride is actually really
27:17important for us to stay alive but the
27:19other ones could be really dangerous to
27:20us how could I make some sodium chloride
27:24I wanted to make them at home without
27:26buying it in their supermarket
27:36for those people who are wondering what
27:38I could do is I could take some sodium
27:41and I could add some hydrochloric acid
27:49what I would make would be sodium
27:54chloride delicious
27:56plus some hydrogen gas and then if I was
28:01to take this and put it on my food it
28:02would make it taste delicious that would
28:06be one of the ways that we could use
28:07this general formula so the reason I
28:10mentioned these are called salts is
28:11because this actually helps us to write
28:13our general formula our real general
28:16formula should be metal plus acid goes
28:22to a new type of chemical which is
28:25called salt plus hydrogen
28:39yeah this is our general formula for
28:42metal plus acid guys if you're thinking
28:48that oh my god mr. Williams is going
28:49really fast I don't understand that's
28:51fine there are some questions I have got
28:53you guys to have a go at the bottom
28:55which will help you kind of practice and
28:56really the only way to get this is to
28:59practice okay so that's our last general
29:06formula for metal plus acid there is one
29:08last one too low general formula the
29:15very last one is if we take an acid and
29:18we add it to what's called an alkali
29:21now you guys hopefully should remember
29:23that acids and alkalis are like
29:25opposites acids are pH 1 to 6 and
29:29alkalis are pH 8 to 14 and they are kind
29:33of opposites each other on the pH scale
29:36these ones have hydrogen because we
29:41learnt this today and these ones have Oh
29:44H or hydroxide this is what makes
29:50something an alkaline so let's take a
29:54very common alkali that we find in our
29:57science lab which is called sodium
29:59hydroxide sodium hydroxide if you're not
30:02sure is na o H this is what makes it a
30:08hydroxide an alkaline because it has a H
30:12now we need a general formula for this
30:15so let's take some examples and this is
30:17the one that's going to be the most
30:18complicated let's take an acid a common
30:23acid as we've named before is
30:26hydrochloric acid just to help you I'm
30:31gonna write the symbol for it underneath
30:33and to that I'm gonna add my new
30:37chemical this alkaline that I've seen
30:39before which is called sodium
30:45hydroxide the symbol for it as I wrote
30:48is na o H and we have to work out
30:53exactly what's going to be made now the
30:58easiest way to do this guys is to
31:00realize that when an acid reacts with an
31:05alkaline the metal whatever the metal
31:09element in the alkaline is is going to
31:11be basically the main product that is
31:14formed so sodium in this example is the
31:18important metal that we need to keep an
31:20eye on sodium will actually react with
31:24the nonmetal that's in the acid so in
31:29this case in our acid the chlorine the
31:32CL is the nonmetal and in this example
31:36the sodium which is a metal will react
31:38together and we will make it chemical
31:42which is called sodium chloride or table
31:47salt as we mentioned earlier
31:55thing is though I haven't used up
31:57everything that's left in this one I've
32:00got a little bit of hydrogen and in this
32:04one I've got
32:05well basically not this part I've got
32:08this left
32:08I've got o and H so if I take the H from
32:14here and the O H from over here and I
32:17mix them together what I will make is
32:20two hydrogen's and one oxygen or also
32:23known as water now this is one example
32:29of an acid plus an alkali and I can see
32:31by far that is the most complicated
32:33thing that you have to work in let me
32:36show you a couple more examples and then
32:37I'll write your general formula because
32:39if you learn your general formula it's
32:41really simple let's do one more let's
32:46pick a different acid as you know I'm
32:50gonna write a general formula first so
32:52the general formula is going to be acid
32:59plus alkali
33:03goes to you sodium fluoride which is a
33:06salt plus water this is going to be your
33:15general formula for the acid plus alkali
33:17and you just need to learn this this is
33:20the important part let me show you a
33:24couple more examples and then you guys
33:25can have a go yourself and if you don't
33:27understand it's your opportunity to ask
33:28me questions so let's pick another one
33:33let's pick sulfuric acid sulfuric acid
33:38plus let's use let's use to use sodium
33:43hydroxide again
33:49so just like before I take the beginning
33:54part of my alkali this is the important
33:56part the metal which is this so I take
33:59sodium and I write it over here I then
34:02can go back and look right at the very
34:05beginning if I just zoom out when I
34:06showed you what the ending part of the
34:09word for sulfuric acid was which was all
34:11the way up here here if I've used
34:16sulfuric acid the word that will be
34:20ending with will be sulfate yeah this is
34:22the part that we use so if I go down
34:25here I can just write sulfate comes from
34:33the sulfuric acid now looking at my
34:37general formula I've now worked out what
34:39my salt is all I need to do is add
34:41what's left which in this case is always
34:43going to make water yeah so this is my
34:49far the most complicated one guys and
34:51we'll do some more practice on acids
34:53plus alkalis what I want you guys to do
34:55today because it's a bit simpler is to
34:57practice your metals plus acids so what
34:59I'd like you to do is have a go at this
35:01bit down here chemical reactions of
35:03acids plus metals ok have a go see if
35:06you can work out the answers and if you
35:08don't understand I'll be here you can
35:10ask me questions ok

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