The whole of EDEXCEL Chemistry Paper 2 or C2 in only 47 minutes. 9-1 GCSE Science Revision

00:47:47
https://www.youtube.com/watch?v=woYFftjEkeM

摘要

TLDRIn this video, comprehensive topics relevant to the second LXL chemistry exam are covered. It begins with an overview of the periodic table, detailing various groups such as alkali metals and noble gases. Key reactions, such as displacement reactions, are explained using examples and practical demonstrations. The video delves into the concepts of exothermic and endothermic reactions, factors affecting the rate of reaction, and the principles of hydrocarbons, including combustion processes. The significance of global warming and pollution, along with the effects of chemical reactions on the environment, are highlighted. Additionally, tests for identifying ions, different types of hydrocarbons, and the polymerization processes are discussed, along with the impact of nanotechnology. The video aims to aid students in their revision for their exams and offers encouragement for their upcoming tests.

心得

  • 🎓 Comprehensive exam guide for chemistry
  • 🧪 Overview of periodic table groups
  • ⚛️ Understanding of halogens' reactivity
  • 🔥 Explanation of combustion types
  • 🌍 Discussion on environmental impacts
  • 📊 Factors affecting the rate of reaction
  • 🌡️ Endothermic vs exothermic reactions
  • 🔬 Identifying ions through tests
  • 🔗 Importance of hydrocarbons and their combustion
  • 🧬 Insights into nanotechnology and its applications

时间轴

  • 00:00:00 - 00:05:00

    The video is a comprehensive guide for students preparing for their second LXL chemistry exam, covering essential topics including the periodic table, reactivity of metals, chemical reactions, and rates of reaction. A free guide is available on the host's website for additional support.

  • 00:05:00 - 00:10:00

    The periodic table is divided into groups with distinct properties. Group 1 contains alkaline metals, Group 2 contains alkaline earth metals, Group 7 has halogens, while Group 8 consists of noble gases. Noble gases are unreactive due to having a full outer electron shell, leading to various practical applications.

  • 00:10:00 - 00:15:00

    Halogens, which include chlorine and fluorine, are highly reactive nonmetals that often exist as diatomic molecules. They gain one electron during reactions and can displace less reactive elements. The reactions between halogens and metals produce salts, such as sodium chloride, and are important for sterilizing agents.

  • 00:15:00 - 00:20:00

    Alkaline metals are known for their violent reactions with water, often producing a lot of heat and hydrogen gas. These metals must be stored in oil to prevent reactions with water or oxygen in the air. When reacting with water, they form metal hydroxides, contributing to their classification as alkaline.

  • 00:20:00 - 00:25:00

    The rate of reaction can be influenced by the concentration of reactants, surface area, and temperature. Tracking changes in mass or volume during reactions can help quantify the rates. Measuring techniques such as using a measuring cylinder or tracking gas production are essential in experiments to understand reaction rates.

  • 00:25:00 - 00:30:00

    In chemical reactions, different factors such as temperature and concentration affect how quickly and efficiently particles collide. Higher temperatures increase energy and movement, leading to more frequent successful collisions, therefore increasing the rate of reaction.

  • 00:30:00 - 00:35:00

    Catalysts lower the activation energy required for reactions and can significantly increase reaction rates by providing a better pathway for the reacting particles. The difference between endothermic and exothermic reactions relates to energy change, with endothermic reactions absorbing energy and exothermic reactions releasing it.

  • 00:35:00 - 00:40:00

    The process of fractional distillation is vital for separating mixtures like crude oil into useful hydrocarbons. Both complete and incomplete combustion processes lead to different products, with incomplete combustion resulting in toxic substances like carbon monoxide.

  • 00:40:00 - 00:47:47

    Global warming and air pollution from greenhouse gases such as carbon dioxide and sulfur dioxide have significant environmental impacts. Understanding the composition changes in the atmosphere over time and the consequences of anthropogenic activities is critical for effective environmental management.

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思维导图

视频问答

  • What does the periodic table categorize?

    The periodic table categorizes elements into groups such as alkaline metals, alkaline earth metals, halogens, noble gases, and transition metals.

  • What do halogens want to do when they react?

    Halogens want to gain one electron when they react, resulting in the formation of minus one ions.

  • How does temperature affect the rate of reaction?

    Higher temperatures increase the rate of reaction by providing particles with more energy, leading to more frequent successful collisions.

  • What are hydrocarbons and how are they separated?

    Hydrocarbons are compounds made of only hydrogen and carbon. They are separated through fractional distillation.

  • What is the difference between complete and incomplete combustion?

    Complete combustion occurs with ample oxygen, producing water and carbon dioxide, while incomplete combustion occurs with limited oxygen, producing carbon monoxide and soot.

  • What causes global warming?

    Global warming is primarily caused by increased levels of carbon dioxide in the atmosphere due to human activities.

  • What is a catalyst?

    A catalyst is a substance that speeds up a chemical reaction by lowering the activation energy required for the reaction.

  • What happens during an endothermic reaction?

    An endothermic reaction absorbs energy, causing a decrease in temperature.

  • What do alcohols end with?

    Alcohols end with the suffix 'ol' and contain an -O-H functional group.

  • What is nanotechnology?

    Nanotechnology involves rearranging atoms at a small scale to create materials with different properties and potentially various applications.

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  • 00:00:00
    - Hello lovely kittens in this video I cover everything
  • 00:00:02
    you need for your second LXL chemistry exam,
  • 00:00:06
    I'm gonna go over a summary of everything,
  • 00:00:08
    But if you want to make sure you don't miss anything
  • 00:00:10
    you want loads and loads of quickfire questions,
  • 00:00:13
    all the bits you need to learn for chemistry,
  • 00:00:15
    all the irons, the activity series,
  • 00:00:17
    what goes with what,
  • 00:00:18
    you can get that in your free guide
  • 00:00:19
    which is over on my website,
  • 00:00:22
    there are loads of practicals
  • 00:00:23
    in this one guys so remember to pay attention to those,
  • 00:00:26
    loads and loads of videos if there's anything
  • 00:00:28
    you need just ask.
  • 00:00:29
    (cheerful music)
  • 00:00:35
    This beautifully colored periodic table
  • 00:00:36
    is because there are lots of different groups,
  • 00:00:38
    lots of different categories on the periodic table.
  • 00:00:42
    Number one also known as alkaline metals,
  • 00:00:46
    group number two other alkaline earth metals
  • 00:00:48
    or alkali metals,
  • 00:00:50
    group seven are the halogens,
  • 00:00:54
    and group eight are the noble gases,
  • 00:00:57
    the big chunk in the middle are the transition metals.
  • 00:01:01
    The group right on the far right-hand side
  • 00:01:03
    are group eight or group zero,
  • 00:01:04
    these are the noble gases,
  • 00:01:07
    they have a full outer shell,
  • 00:01:14
    and because they have a full outer shell they don't want
  • 00:01:17
    to gain or lose any electrons which means
  • 00:01:19
    they're really, really unreactive,
  • 00:01:23
    and because they're unreactive,
  • 00:01:24
    they actually have quite a lot of uses,
  • 00:01:27
    helium used in balloons,
  • 00:01:30
    and they are also used in neon lights,
  • 00:01:34
    as you can see here the amazing city of Osaka.
  • 00:01:38
    Moving over one group to group seven we have the halogens,
  • 00:01:42
    we are still in the nonmetals,
  • 00:01:46
    and these are gonna go around as diatonic molecules,
  • 00:01:50
    which means their formula is going
  • 00:01:53
    to be for a chlorine gas Cl2,
  • 00:01:55
    fluorine gas F2,
  • 00:01:56
    bromine gas Br2,
  • 00:01:58
    they're gonna go around together in pairs,
  • 00:02:01
    because they only want to gain one electron
  • 00:02:03
    a nice easy way for them to do that
  • 00:02:05
    is sharing an electron with something else that is the same,
  • 00:02:08
    so fluorine here can easily gain an extra electron
  • 00:02:11
    by sharing it with another florine.
  • 00:02:14
    They are highly reactive because they
  • 00:02:16
    only want to gain one electron.
  • 00:02:22
    And the most reactive ones are going to be at the top.
  • 00:02:36
    Boiling point is going to change as we move down the group,
  • 00:02:40
    so things that have low boiling point or a low melting
  • 00:02:43
    point are gonna be at the top,
  • 00:02:46
    High boiling point or high melting point
  • 00:02:48
    are going to be at the bottom.
  • 00:02:50
    When they react there gonna gain an electron.
  • 00:02:58
    Meaning they're going to form minus one ions.
  • 00:03:04
    And gaining an electron is reduction.
  • 00:03:12
    They're going to react violently and rapidly with group
  • 00:03:15
    one medals because group one metals want
  • 00:03:16
    to lose one electron,
  • 00:03:19
    for example sodium which is a soft gray metal,
  • 00:03:22
    while react very violently with chlorine
  • 00:03:25
    which is a yellow gas,
  • 00:03:26
    to form sodium cloride which is a white powder or salt.
  • 00:03:31
    A more reactive element will displace
  • 00:03:33
    a less reactive element,
  • 00:03:35
    so here we have sodium iodide reacting with bromine,
  • 00:03:39
    iodine is here below bromine on
  • 00:03:42
    the periodic table so bromine is more reactive,
  • 00:03:45
    so we will displace iodine in the compound
  • 00:03:49
    forming sodium bromide and iodine.
  • 00:03:52
    Whereas if you try and react bromine gas
  • 00:03:53
    with sodium chloride,
  • 00:03:55
    chlorine is higher than bromine on the periodic table,
  • 00:03:58
    so it's more reactive,
  • 00:03:59
    you are gonna get no reaction,
  • 00:04:01
    because bromine cannot displace chlorine out of this,
  • 00:04:04
    these are commonly known as displacement reactions.
  • 00:04:17
    The halogens are mostly used for sterilizing things,
  • 00:04:20
    for example chlorine,
  • 00:04:22
    you are commonly going to know that as from swimming pools.
  • 00:04:27
    Halogens want to gain one electron,
  • 00:04:29
    so the most reactive ones at the top,
  • 00:04:31
    that's where there's least shielding between
  • 00:04:34
    the electron they want to gain and the nucleus.
  • 00:04:38
    Alkaline metals react very violently with water,
  • 00:04:39
    and this is where your gonna see some flames coming from,
  • 00:04:42
    Some different colors coming from.
  • 00:04:45
    This is one of the things we use to make
  • 00:04:46
    the different colors in fireworks,
  • 00:04:48
    so the lovely lovely lilac flame of potassium
  • 00:04:51
    we can use in fireworks.
  • 00:04:54
    If you've seen these in schools these
  • 00:04:55
    are soft gray metals which are easily cutable,
  • 00:04:58
    they need to be kept in oil so it doesn't
  • 00:05:00
    react with oxygen or with water in the air,
  • 00:05:03
    because it's a very, very violent reaction.
  • 00:05:07
    When the metal reacts with oxygen
  • 00:05:08
    we're gonna get a metal oxide,
  • 00:05:09
    which if you've seen these in school when
  • 00:05:11
    it was cut it was shiny,
  • 00:05:13
    but it soon started to dull,
  • 00:05:15
    the dullness is the metal oxide,
  • 00:05:17
    the metal plus water is going to form a metal hydroxide,
  • 00:05:19
    this gives it its name,
  • 00:05:21
    it's alkaline metal because the metal hydroxide
  • 00:05:24
    is going to be alkaline,
  • 00:05:26
    you can see that by the change in indicator.
  • 00:05:29
    If that's what your teacher did.
  • 00:05:31
    And you will also notice this is a very exothermic reaction,
  • 00:05:34
    it releases a lot of heat,
  • 00:05:37
    it also releases hydrogen gas.
  • 00:05:41
    That's what the fizzing was.
  • 00:05:44
    The reactivity is most reactive at the bottom.
  • 00:05:52
    And least reactive at the top.
  • 00:06:00
    Things at the bottom are going to have
  • 00:06:02
    a low melting point or boiling point,
  • 00:06:05
    and a higher melting point or boiling point at the top.
  • 00:06:10
    Alkaline metals want to lose an electron,
  • 00:06:12
    and the ones at the bottom are the most reactive
  • 00:06:14
    because there's more shielding between the
  • 00:06:16
    the electrolyte they want to use and
  • 00:06:18
    the positive nucleus in the middle.
  • 00:06:22
    They are arranged in different ways,
  • 00:06:24
    you can follow a reaction,
  • 00:06:25
    for example you can look at the loss of mass,
  • 00:06:28
    this would be good if you are adding something solid,
  • 00:06:31
    like marble chips into a liquid,
  • 00:06:35
    and you knew that the gas was going to be produced,
  • 00:06:38
    the gas will just go up here through
  • 00:06:40
    the cotton wool and out,
  • 00:06:42
    and the mass will go down.
  • 00:06:45
    It will also for the same reaction if you have a solid,
  • 00:06:48
    and you're adding it into liquid,
  • 00:06:49
    and a gas was being produced,
  • 00:06:51
    you could collect the gas either in a measuring syringe,
  • 00:06:54
    or an inverted measuring cylinder.
  • 00:06:59
    When we are measuring the rate of a reaction
  • 00:07:00
    we need to look carefully at the units used.
  • 00:07:04
    For example here we have volume,
  • 00:07:07
    in centimeters cubed over time in minutes,
  • 00:07:10
    so here it would be centimeters cubed per minute,
  • 00:07:16
    and the second one we have time in seconds
  • 00:07:20
    and mass in grams.
  • 00:07:22
    So this would be grams per second.
  • 00:07:25
    In the first graph it is volume
  • 00:07:27
    of carbon dioxide being produced,
  • 00:07:29
    so you can see that is going up,
  • 00:07:32
    and in the second graph is mass being lost,
  • 00:07:35
    so you can see that is going down.
  • 00:07:38
    If you want to find the rate at a particular point,
  • 00:07:41
    say two minutes or five minutes,
  • 00:07:43
    you need to draw a tangent which is a straight line,
  • 00:07:47
    that touches the curve just at that point,
  • 00:07:50
    not at any other point,
  • 00:07:51
    just at the point you're interested in,
  • 00:07:53
    then you need to work out the gradient of that line,
  • 00:07:58
    to work out the gradient you need to draw a triangle,
  • 00:08:01
    the bigger triangle the better,
  • 00:08:03
    and we need to work out the change
  • 00:08:04
    up divided by the change in across,
  • 00:08:07
    and your units,
  • 00:08:08
    you need to take from the graph.
  • 00:08:12
    You can compare the rates of reaction
  • 00:08:13
    at different points in a reaction,
  • 00:08:16
    for example at the start of this reaction,
  • 00:08:19
    our line, our tangent is very, very steep,
  • 00:08:22
    whereas later on in the reaction at
  • 00:08:24
    a different point our tangent is very shallow,
  • 00:08:27
    different rates of reaction at different points.
  • 00:08:32
    We can follow the route of reaction by looking
  • 00:08:34
    at the color change taking place in the reaction,
  • 00:08:36
    or how it changes from clear colorless
  • 00:08:40
    to opaque where we can't see a cross underneath any more,
  • 00:08:44
    this reaction is between sodium iodosulfate
  • 00:08:46
    and hydrochloric acid,
  • 00:08:48
    and you need to be really, really careful with this one,
  • 00:08:50
    careful that when you're doing these you're
  • 00:08:51
    constantly washing things out
  • 00:08:53
    so you're not contaminating things,
  • 00:08:55
    careful you don't take it above 60 degrees,
  • 00:08:57
    because then nasty gases will start to come off at the end,
  • 00:09:01
    be careful that you don't get it on your hands,
  • 00:09:03
    because it's gonna start to irritate your hands,
  • 00:09:06
    so this is where health and safety is a really big concern.
  • 00:09:09
    You can see as the reaction is going on,
  • 00:09:12
    the cross which was visible at the beginning
  • 00:09:14
    is becoming less and less visible.
  • 00:09:17
    You need to make sure that the same person always measures
  • 00:09:20
    the rate of reaction here so differences
  • 00:09:23
    in people's eyes don't mean that the differences
  • 00:09:26
    in the time that the cross disappears
  • 00:09:29
    could affect the results.
  • 00:09:33
    One way that we can collect gas,
  • 00:09:35
    is by using an inverted measuring cylinder
  • 00:09:38
    and putting a delivery tube through there,
  • 00:09:41
    one of the things you need to be careful about,
  • 00:09:42
    is this gas in here that is already
  • 00:09:45
    in the measuring cylinder before you start the experiment,
  • 00:09:49
    that is one place that errors can be introduced.
  • 00:09:54
    The gas is going to move from the conical flask through
  • 00:09:56
    the delivery tube and into the measuring cylinder,
  • 00:10:00
    and it's gonna be collected and we can measure it.
  • 00:10:02
    Adding in large marble chips now you can
  • 00:10:06
    see that the bubbles are starting to collect,
  • 00:10:08
    in the measuring cylinder,
  • 00:10:11
    in this not only can you get errors,
  • 00:10:12
    because there's going to be gas in
  • 00:10:14
    the measuring cylinder before you start,
  • 00:10:16
    but there is also going to be some gas last
  • 00:10:19
    before you manage to get the bung on.
  • 00:10:25
    Adding in powdered calcium carbonate now,
  • 00:10:29
    you'll notice that the rate of reaction,
  • 00:10:30
    the bubbles are produced much, much faster,
  • 00:10:33
    the measuring cylinder fills up very quickly.
  • 00:10:39
    When we have particles moving around at
  • 00:10:40
    a low temperature they are moving
  • 00:10:42
    slowly with not much energy,
  • 00:10:45
    when two collide they hit each other and have a reaction,
  • 00:10:47
    but sometimes they are going to collide
  • 00:10:49
    and is not going to be a reaction.
  • 00:10:51
    When particles move around with high temperature
  • 00:10:54
    at high-speed with lots of energy,
  • 00:10:56
    when things collide you are going to get
  • 00:10:58
    a lot of reactions taking place,
  • 00:11:02
    rate of reaction is going to be affected by temperature,
  • 00:11:04
    here I've put sugar cubes into hot water and cold water,
  • 00:11:09
    and you can see the sugar cubes in hot water
  • 00:11:11
    dissolved much much faster than
  • 00:11:13
    the sugar cubes in cold water.
  • 00:11:20
    For the rate of reaction we can say that
  • 00:11:22
    the higher the temperature,
  • 00:11:32
    the faster the rate of reaction will be,
  • 00:11:49
    this is because the particles have more energy.
  • 00:12:05
    So they can move around faster.
  • 00:12:15
    And this will lead to more frequent successful collisions.
  • 00:12:34
    When we have a lump of something it has less surface
  • 00:12:37
    area so there's less space to react,
  • 00:12:39
    here the blue dots whatever that is can only
  • 00:12:41
    react with the pink dots on the outside,
  • 00:12:44
    the purple dots on the inside or exactly
  • 00:12:46
    the same thing they are just not available to react,
  • 00:12:48
    whereas here the pink dots are all spread out
  • 00:12:51
    in a powder format so they're all available to react.
  • 00:12:55
    This is really confusing because the lump
  • 00:12:57
    is larger than the powder,
  • 00:13:00
    but assuming we have exactly the same mass,
  • 00:13:02
    the powder has more surface area than the lump,
  • 00:13:06
    so more particles are available to react.
  • 00:13:09
    Here I have two identically sized blobs of glue,
  • 00:13:12
    and one spread out,
  • 00:13:15
    and one I haven't spread out,
  • 00:13:17
    I've just left it as a blob,
  • 00:13:18
    and you see the one that's spread out,
  • 00:13:19
    the one that has a large surface area has
  • 00:13:22
    dries much, much faster than the one
  • 00:13:24
    I've just left in a big blob.
  • 00:13:28
    I have a What's App group of all my YouTube friends
  • 00:13:31
    and they are super, super jealous when I told
  • 00:13:33
    I was making a video of glue drying.
  • 00:13:40
    We can say that the larger the surface area.
  • 00:13:54
    The faster the rate of reaction.
  • 00:14:07
    This is because.
  • 00:14:15
    There are more particles available to react.
  • 00:14:26
    Leading to,
  • 00:14:34
    more successful collisions.
  • 00:14:41
    If we have things at a high pressure or
  • 00:14:43
    a high concentration there are more of them,
  • 00:14:45
    which means they are much more likely
  • 00:14:47
    to bump into each other and react,
  • 00:14:48
    whereas at a low concentration they're not
  • 00:14:51
    very likely to bump into each other and react.
  • 00:14:54
    We can say that the higher the pressure or concentration.
  • 00:15:10
    The faster the rate of reaction will be.
  • 00:15:25
    This is because there are more particles.
  • 00:15:40
    In a fixed volume.
  • 00:15:50
    So there is a higher chance,
  • 00:15:59
    Of a successful collision.
  • 00:16:07
    When we have a catalyst it's something that makes
  • 00:16:10
    a reaction easier to happen,
  • 00:16:12
    it lowers the activation energy,
  • 00:16:13
    so for example this catalyst fixes
  • 00:16:15
    one of the reactants in place,
  • 00:16:17
    so it's easier for the other reactant to find it,
  • 00:16:20
    over this side they are both randomly
  • 00:16:22
    wandering around in the dark,
  • 00:16:23
    and it's quite hard to find people when
  • 00:16:24
    you're wandering around in the dark,
  • 00:16:28
    whenever we have a reaction there's an activation energy,
  • 00:16:32
    instead of just going straight from
  • 00:16:33
    the reaction to the product,
  • 00:16:34
    there's this hump it has to get over,
  • 00:16:37
    and this bit here,
  • 00:16:39
    this difference is the activation energy.
  • 00:16:47
    However what a catalyst does is it lowers
  • 00:16:49
    the activation energy,
  • 00:16:52
    so it's easier for the reaction to take place.
  • 00:17:01
    So the reaction is more likely to happen
  • 00:17:03
    because there's less of a hump for it to get over.
  • 00:17:07
    An endothermic reaction feels like it gets colder,
  • 00:17:12
    whereas an exothermic reaction feels like it get hotter.
  • 00:17:18
    Another way of saying gets colder is to take heat in,
  • 00:17:21
    another way to get hotter is to give out.
  • 00:17:25
    Now we can make this slightly more sophisticated
  • 00:17:26
    by replacing the word heat with the word energy.
  • 00:17:35
    So now a sophisticated answer is that
  • 00:17:36
    an endothermic reaction takes energy in
  • 00:17:39
    and an exothermic reaction gives energy out.
  • 00:17:43
    During an endothermic reaction energy is going
  • 00:17:46
    to get taken in so we have our reactants down here.
  • 00:17:51
    Energy gets taken in so our products up here.
  • 00:18:00
    So we can say that the energy of the products,
  • 00:18:11
    is higher,
  • 00:18:16
    than the energy,
  • 00:18:23
    reactants.
  • 00:18:26
    During an exothermic reaction energy reaction
  • 00:18:28
    is given out, so reactants.
  • 00:18:34
    Energy is given out,
  • 00:18:36
    so our products are going to be down here,
  • 00:18:40
    which means our products,
  • 00:19:00
    have lower energy than the reactants.
  • 00:19:03
    For example an endothermic reaction would be electrolysis.
  • 00:19:11
    An exothermic reaction would be burning.
  • 00:19:15
    Or neutralization.
  • 00:19:22
    You need to be able to calculate the energy
  • 00:19:24
    change when a reaction takes place,
  • 00:19:26
    remembering a bonds energy breaking takes energy in,
  • 00:19:28
    and bond making gives energy out.
  • 00:19:31
    So burning hydrogen in oxygen will give out water,
  • 00:19:34
    calculate the energy change for this reaction.
  • 00:19:36
    The first thing we need to do is write a balanced equation.
  • 00:19:39
    Hydrogen plus oxygen
  • 00:19:45
    gives water,
  • 00:19:47
    we need to put the two there to balance out the oxygens,
  • 00:19:50
    and two there to balance out the hydrogens,
  • 00:19:53
    draw everything we have,
  • 00:19:56
    so we have hydrogen and we have two of them,
  • 00:20:00
    so I'm gonna draw that twice,
  • 00:20:02
    plus oxygen turns into
  • 00:20:09
    water.
  • 00:20:14
    And while the examiner will probably expect
  • 00:20:16
    you to be able to work out the formula,
  • 00:20:18
    balance the equation and draw them by yourself,
  • 00:20:19
    they would not expect you to write all the bonds in,
  • 00:20:22
    the bond energies will be given to you in the exam,
  • 00:20:26
    next we're going to list the type of bonds
  • 00:20:27
    that we have and the number,
  • 00:20:28
    so we have hydrogen hydrogen bonds,
  • 00:20:31
    and we have one, two of those,
  • 00:20:36
    we have an oxygen oxygen double bond,
  • 00:20:38
    and we have just one double bond in there,
  • 00:20:43
    we have oxygen hydrogen bond,
  • 00:20:46
    and we have one, two, three, four of those,
  • 00:20:53
    now we need to take that and multiply
  • 00:20:55
    it by our bond energies,
  • 00:20:56
    so two bonds for hydrogen,
  • 00:20:58
    that's two times 436,
  • 00:21:01
    one times 498,
  • 00:21:05
    four time 464,
  • 00:21:09
    we can do the maths and work out how much is on each side,
  • 00:21:12
    adding those up,
  • 00:21:13
    872 plus 498 gives us 1370,
  • 00:21:19
    it's just 1856 on that side,
  • 00:21:25
    now we need to do the energy of the reactants,
  • 00:21:26
    minus the energy of the products,
  • 00:21:27
    so 1370 minus 1856,
  • 00:21:31
    giving us minus 486 kilojoules per mole.
  • 00:21:40
    In this type of equation if you got the symbol wrong
  • 00:21:42
    you'd probably only lose one mark,
  • 00:21:45
    it having a negative sign in front of
  • 00:21:47
    the tells us it is exothermic.
  • 00:21:52
    So any reaction that is burning you can
  • 00:21:54
    check yourself because it should always be exothermic.
  • 00:21:58
    We can pretty much guarantee that a big calculation
  • 00:21:59
    is going to come up on this paper,
  • 00:22:01
    so it's worth practicing these really well,
  • 00:22:04
    to help you I've written a book.
  • 00:22:08
    A couple of key definitions you need to know,
  • 00:22:10
    A hydrocarbon is a compound
  • 00:22:17
    that is made up of hydrogen
  • 00:22:25
    and carbon only and nothing else.
  • 00:22:31
    Crude oil,
  • 00:22:37
    is a mixture of different length
  • 00:22:47
    hydrocarbons.
  • 00:22:53
    To separate out the mixture of crude oil,
  • 00:22:56
    we need to use fractional distillation.
  • 00:22:59
    Crude oil goes in gets heated up until it is a gas,
  • 00:23:04
    then it goes into a condensing column,
  • 00:23:07
    all of the really, really long chain hydrocarbons
  • 00:23:11
    which don't evaporate come off here as a residue,
  • 00:23:14
    and we can use that,
  • 00:23:15
    the bitumen,
  • 00:23:16
    we can use that for making roads.
  • 00:23:19
    It is very, very hot at the bottom,
  • 00:23:21
    and as we move up the condensing tower
  • 00:23:24
    the temperature goes down,
  • 00:23:26
    at each different point,
  • 00:23:29
    different length hydrocarbons are going to come off,
  • 00:23:32
    so we have gases at the top,
  • 00:23:34
    petrol, naphtha and kerosene which is fuel for planes,
  • 00:23:39
    diesel and then fuel for boats.
  • 00:23:43
    Short hydrocarbons are going to come off at the top,
  • 00:23:45
    and long hydrocarbons are gonna come off at the bottom.
  • 00:23:49
    Things at the top are gonna be really, really flammable,
  • 00:23:52
    things at the bottom aren't going
  • 00:23:53
    to be really, really flammable,
  • 00:23:55
    things at the bottom are going to be really viscous,
  • 00:23:57
    whereas things at the top aren't going to be viscous.
  • 00:24:02
    The long hydrocarbons that come out
  • 00:24:05
    of fractional distillation,
  • 00:24:05
    aren't always the most useful ones,
  • 00:24:08
    we get large amounts of long ones which aren't very useful,
  • 00:24:11
    but we don't get very many short ones which
  • 00:24:12
    we need because they are useful,
  • 00:24:15
    so we can crack the long ones using heat and a catalyst,
  • 00:24:20
    and this is going to give us short alkanes
  • 00:24:22
    which we want and alkenes.
  • 00:24:27
    The complete combustion of hydrocarbon involves
  • 00:24:30
    lots of oxygen,
  • 00:24:32
    that is your roaring blue flame on a Bunsen burner,
  • 00:24:36
    this is gonna be hydrocarbon plus oxygen,
  • 00:24:39
    turning into water and carbon dioxide.
  • 00:24:43
    Incomplete combustion as well as not enough oxygen,
  • 00:24:46
    this is going to be your orange flame in the Bunsen burner,
  • 00:24:49
    this is much more problematic,
  • 00:24:50
    because as well as the water and carbon dioxide,
  • 00:24:52
    we're gonna get carbon monoxide,
  • 00:24:53
    which is highly toxic,
  • 00:24:54
    your white blood cells prefer it to oxygen,
  • 00:24:59
    so you will actually suffocate to death
  • 00:25:02
    generally in your sleep,
  • 00:25:03
    and carbon which is black suit,
  • 00:25:06
    which gets everywhere.
  • 00:25:10
    There are three main greenhouse gases
  • 00:25:12
    with the biggest culprit being carbon dioxide,
  • 00:25:14
    and to a much smaller extent water vapor and methane.
  • 00:25:19
    The bonds in carbon dioxide are really,
  • 00:25:21
    really good at absorbing infrared or heat radiation,
  • 00:25:25
    which traps it inside our atmosphere and warms the planet.
  • 00:25:30
    Which means that when heat light energy
  • 00:25:34
    from the sun comes to us,
  • 00:25:36
    it will be reflected back by the earth,
  • 00:25:39
    and normally this would go straight back out into space,
  • 00:25:45
    but it's not,
  • 00:25:46
    it's being trapped by the greenhouse gases,
  • 00:25:50
    by the carbon dioxide,
  • 00:25:51
    by the methane,
  • 00:25:53
    which means it stays in our atmosphere heating it up.
  • 00:25:59
    We can see a gradual increase in the levels
  • 00:26:01
    of carbon dioxide which has taken up speed in recent years,
  • 00:26:06
    and there are lots of things that humans do
  • 00:26:08
    that have a massive amount to do with the levels
  • 00:26:10
    of carbon dioxide in the atmosphere,
  • 00:26:13
    global warming is a slightly confusing term,
  • 00:26:15
    because not everywhere is getting hotter,
  • 00:26:17
    where we do have places getting hotter,
  • 00:26:19
    where deserts, countries, farmland is drying out completely,
  • 00:26:25
    and the ice poles are getting hotter as well,
  • 00:26:27
    which is really, really bad for the polar bears.
  • 00:26:30
    Because they live on these blocks of ice,
  • 00:26:33
    they hunt in the water,
  • 00:26:35
    and when they need a break from swimming and hunting,
  • 00:26:37
    they jump onto the blocks of ice and have a rest,
  • 00:26:40
    the bottom of these blocks of ice are melting,
  • 00:26:42
    there is nowhere for the polar bears to have a rest,
  • 00:26:44
    so loads and loads of polar bears are drowning,
  • 00:26:47
    and while the ice caps are melting,
  • 00:26:49
    it means we are seeing increased levels
  • 00:26:49
    of flooding in other places.
  • 00:26:53
    As the sea levels go up certain places on
  • 00:26:56
    the coast are going to start to end up underwater,
  • 00:27:00
    while Australia is having it's hottest Christmases ever,
  • 00:27:04
    us here in the UK are having our coldest Christmases ever,
  • 00:27:06
    with unprecedented levels of snow.
  • 00:27:09
    And the climate change doesn't just fit people,
  • 00:27:11
    it affects animals and plants as well,
  • 00:27:14
    as the temperature changes the top of
  • 00:27:16
    the mountain which perhaps used to be under snow,
  • 00:27:18
    is now available for habitation by new animals and plants,
  • 00:27:23
    now say you have a little house here,
  • 00:27:25
    and you knew it was protected from certain types of animals,
  • 00:27:28
    because it was too cold or too warm for them there,
  • 00:27:31
    with the changing climate,
  • 00:27:33
    animals are moving up and down slopes,
  • 00:27:35
    their habitats are changing as the temperature changes
  • 00:27:37
    and as the location of their food source changes.
  • 00:27:41
    Your carbon footprint is how much carbon
  • 00:27:44
    your daily activities contribute to the atmosphere,
  • 00:27:48
    this can be impacted by things such as
  • 00:27:50
    whether you decide to drive or whether
  • 00:27:52
    you walk to your location,
  • 00:27:54
    and whether you decide to eat food that is grown locally
  • 00:27:56
    or food that has had to travel a long distance.
  • 00:28:00
    Lots of human activities contribute to
  • 00:28:02
    the production of carbon dioxide.
  • 00:28:05
    Burning fossil fuels for use as electricity,
  • 00:28:08
    deforestation cutting down trees,
  • 00:28:10
    so that the trees can't take up carbon dioxide
  • 00:28:12
    from the atmosphere any more,
  • 00:28:14
    and our reliance on petrol cars.
  • 00:28:18
    The predictions for the levels of carbon dioxide
  • 00:28:20
    in our atmosphere is that they are just going to increase,
  • 00:28:23
    and global warming is going to increase as well,
  • 00:28:26
    unless we as a population decide to do something about it.
  • 00:28:32
    One of the major pollutants is sulfur dioxide,
  • 00:28:34
    when this goes up into the atmosphere
  • 00:28:35
    it dissolves in the clouds,
  • 00:28:37
    it is gonna come back down as acid rain.
  • 00:28:40
    This is going to have an effect on a wide range of things,
  • 00:28:42
    it is gonna have,
  • 00:28:43
    animals that come into contact with it,
  • 00:28:45
    if a lake or ocean or pond becomes too acidic,
  • 00:28:49
    that's gonna start to kill the fish and the plants in there,
  • 00:28:52
    plants are not going to appreciate having
  • 00:28:53
    acid rained on them,
  • 00:28:55
    so they are going to die,
  • 00:28:55
    and it's also going to destroy limestone statues,
  • 00:28:58
    which are going to dissolve in acid rain.
  • 00:29:02
    Too much carbon in the air is gonna lead
  • 00:29:04
    to larger levels of smog and global dimming,
  • 00:29:08
    this is particularly prevalent in developing countries,
  • 00:29:10
    when I was in Beijing it was really hard
  • 00:29:12
    to see out the window because it was so smoggy.
  • 00:29:17
    Water vapor is going to contribute To
  • 00:29:18
    the warming of the planet,
  • 00:29:20
    carbon monoxide is a toxic gas,
  • 00:29:22
    and nitrogen oxides are going to contribute
  • 00:29:24
    to both smog and acid rain.
  • 00:29:28
    The air we breathe is made up of lots of different gases,
  • 00:29:31
    predominantly nitrogen gas with about 20, 21 percent oxygen
  • 00:29:35
    and then lots of other gases including
  • 00:29:37
    a small amount of carbon dioxide.
  • 00:29:41
    This is very different to the early atmosphere
  • 00:29:43
    which was mainly formed by things coming out of volcanoes.
  • 00:29:48
    So we have a large amount of ammonia,
  • 00:29:53
    methane,
  • 00:29:57
    water vapor in the air,
  • 00:30:00
    carbon dioxide,
  • 00:30:06
    this would have been a pretty unpleasant place to be,
  • 00:30:09
    ammonia smells like hair dye
  • 00:30:12
    or like really, really old baby nappies,
  • 00:30:15
    and methane smells like farts,
  • 00:30:17
    so the early atmosphere the early Earth would
  • 00:30:19
    have smelled like farts and week-old baby nappies.
  • 00:30:23
    The level of water vapor in the atmosphere
  • 00:30:25
    decreased as it rained,
  • 00:30:27
    which made the oceans,
  • 00:30:29
    the levels of carbon dioxide decreased as
  • 00:30:32
    the carbon dioxide dissolved in the newly formed oceans,
  • 00:30:36
    it turned into fossils became locked up in rocks,
  • 00:30:38
    and photosynthesis started to take place.
  • 00:30:42
    The evolution of green plants,
  • 00:30:44
    oxygen started to increase as photosynthesis
  • 00:30:47
    was taking place.
  • 00:30:50
    Well done you little superstars fantastic work,
  • 00:30:52
    the rest of this video is for chemistry,
  • 00:30:54
    so some of you can go and have a rest now,
  • 00:30:56
    some of you still have a bit more work to do.
  • 00:31:00
    I love flame tests,
  • 00:31:01
    they are so, so pretty,
  • 00:31:03
    you need to know that lithium will burn with
  • 00:31:05
    a crimson flame,
  • 00:31:06
    sodium will burn with a yellow flame,
  • 00:31:08
    potassium will burn a lilac flame,
  • 00:31:09
    calcium a red flame,
  • 00:31:10
    barium with a green flame,
  • 00:31:12
    even though it doesn't look green,
  • 00:31:13
    and copper is going to burn with the blue green flame.
  • 00:31:20
    If you're going to use sodium hydroxide
  • 00:31:21
    to test for your positive ions,
  • 00:31:23
    we need to look at the ionic equations,
  • 00:31:25
    and we need to look at the precipitates.
  • 00:31:28
    Testing for aluminum in sodium hydroxide is going
  • 00:31:30
    to give you a white precipitate which
  • 00:31:32
    is then going to dissolve,
  • 00:31:34
    testing for calcium with sodium hydroxide,
  • 00:31:36
    is just going to give you a white precipitate
  • 00:31:37
    which will not dissolve,
  • 00:31:39
    testing for magnesium with sodium hydroxide
  • 00:31:41
    will give you a white precipitate,
  • 00:31:43
    so in this circumstance you would need another
  • 00:31:45
    test to differentiate between calcium and magnesium.
  • 00:31:49
    Copper ions will give you a light blue precipitate,
  • 00:31:52
    iron two ions will give you a gray green precipitate,
  • 00:31:55
    and iron three ions will give you an orange precipitate.
  • 00:31:59
    For the ionic equations,
  • 00:32:00
    we have our hydroxide ion and then our metal ions,
  • 00:32:03
    and you are expected to know all of these,
  • 00:32:05
    then you just need to make sure your number
  • 00:32:07
    of negative hydroxide ions is equal
  • 00:32:09
    to the number of positive ions.
  • 00:32:12
    So aluminum is three positives,
  • 00:32:14
    so it needs three negative ions to become neutral overall.
  • 00:32:18
    Calcium is two positive so it needs
  • 00:32:21
    two negative ions to become neutral overall.
  • 00:32:22
    Magnesium OH2,
  • 00:32:26
    calcium OH2,
  • 00:32:28
    iron OH2,
  • 00:32:30
    iron three OH3.
  • 00:32:35
    If you want to test something for Carbonate ion,
  • 00:32:38
    you need to add hydrochloric acid,
  • 00:32:40
    set up a delivery tube so any gas evolved
  • 00:32:43
    will be collected down into limewater,
  • 00:32:45
    and if it's carbon dioxide the limewater will go cloudy.
  • 00:32:50
    If you want to test a sample to see if
  • 00:32:51
    it contains sulfate ions,
  • 00:32:52
    you need to add hydrochloric acid you
  • 00:32:54
    need to add barium chloride,
  • 00:32:56
    and if it contains sulfate irons you will
  • 00:32:58
    get a white precipitate formed.
  • 00:33:02
    If you want to test for hyalite ions
  • 00:33:04
    you can add silver nitrate,
  • 00:33:05
    and chloride ions will give a white precipitate.
  • 00:33:09
    Bromide ions will give a cream precipitate,
  • 00:33:11
    and iodide irons will give a yellow precipitate,
  • 00:33:13
    yellow but not as yellow as the walls of my lab used to be.
  • 00:33:16
    Now this can sometimes be a very, very subtle difference,
  • 00:33:18
    and the best way to do it is by comparing
  • 00:33:20
    it with the other things.
  • 00:33:23
    In some cases doing tests in class might
  • 00:33:25
    not be as good as using an instrumental method.
  • 00:33:29
    Instrumental methods can be faster,
  • 00:33:30
    they can be more accurate and they are unbiased.
  • 00:33:35
    Alkanes are hydrocarbons with single bonds only,
  • 00:33:39
    and the general formula for them is Cn H2n+2,
  • 00:33:47
    the first one with one carbon is methane,
  • 00:33:51
    two carbons is ethane,
  • 00:33:55
    three carbons is propane,
  • 00:33:59
    and four carbons is butane.
  • 00:34:03
    When we're drawing organic compounds,
  • 00:34:04
    the important thing to remember is
  • 00:34:06
    that hydrogen always makes one bond,
  • 00:34:08
    and one bond only,
  • 00:34:09
    and carbon always makes four bonds and four bonds only.
  • 00:34:14
    So you can see when I've drawn them,
  • 00:34:15
    eight of the hydrogens here,
  • 00:34:18
    only ever makes one bond,
  • 00:34:21
    whereas the carbons each make
  • 00:34:23
    one, two, three, four bonds,
  • 00:34:25
    one, two, three, four bonds,
  • 00:34:27
    one, two, three, four bonds,
  • 00:34:30
    and because these are alkanes they
  • 00:34:32
    are only ever going to have single bonds,
  • 00:34:35
    this line here represents a bond,
  • 00:34:37
    and that is a pair of electrons,
  • 00:34:39
    this is a covalent bond between these.
  • 00:34:42
    You need to know the names and be able
  • 00:34:44
    to recognize the pictures of these.
  • 00:34:49
    And we can see the formula for these follows
  • 00:34:51
    our general formula of Cn H2n+2.
  • 00:34:56
    So methane has one carbon and four hydrogens,
  • 00:35:00
    Ethane two carbons six hydrogens,
  • 00:35:03
    propane three carbons eight hydrogens,
  • 00:35:05
    and butane four carbons and 10 hydrogens.
  • 00:35:10
    Alkanes have a double bond and are unsaturated,
  • 00:35:12
    the general formula for them is Cn H2n,
  • 00:35:18
    all of these are going to end in ene,
  • 00:35:21
    so there is with two carbons ethene
  • 00:35:25
    with three carbons,
  • 00:35:28
    propene, with four carbons,
  • 00:35:32
    butene, with five carbons,
  • 00:35:37
    pentene.
  • 00:35:38
    When we are drawing things in organic chemistry
  • 00:35:40
    we need to remember that hydrogen always makes
  • 00:35:42
    one bond and carbon always makes four bonds.
  • 00:35:46
    So ethene down here,
  • 00:35:47
    hydrogen is making one bond,
  • 00:35:49
    and carbon is making one, two, three, four bonds.
  • 00:35:53
    This second carbon is making one, two, three, four bonds.
  • 00:35:57
    A bond is a pair of electrons that are covalently shared.
  • 00:36:01
    So a bond can be used by more than one carbon or hydrogen
  • 00:36:05
    when we're counting things.
  • 00:36:07
    You need to be careful looking at these ones,
  • 00:36:09
    one, two, three, four,
  • 00:36:10
    it would be very easy to make a mistake,
  • 00:36:12
    drawing some of the carbons in the middle here
  • 00:36:16
    you need to know how to name,
  • 00:36:17
    recognize and draw the first four alkenes.
  • 00:36:22
    The formulas for these,
  • 00:36:23
    ethene, C2H4,
  • 00:36:25
    propene C3H6,
  • 00:36:26
    butene C4H8,
  • 00:36:28
    pentene C5H10.
  • 00:36:32
    To make this slightly harder the examiners
  • 00:36:34
    might throw in some isomers.
  • 00:36:36
    So this double bond for butane doesn't need to be here,
  • 00:36:39
    it could be here,
  • 00:36:40
    and these are named differently.
  • 00:36:44
    Here the double one is in carbon number one,
  • 00:36:46
    so that is but-1-ene,
  • 00:36:48
    here the double bond is an carbon number one too,
  • 00:36:50
    so this is but-2-ene
  • 00:36:52
    here the double bond is an carbon number one,
  • 00:36:54
    so this is pen-1-ene,
  • 00:36:56
    whereas here the double bond is an carbon number two,
  • 00:36:59
    so this is pen-2-ene.
  • 00:37:02
    You need to know how to test for alkenes,
  • 00:37:04
    this also tests for double bonds on saturation.
  • 00:37:07
    You can see alkenes have two Es in there ,
  • 00:37:11
    it means they have double bonds.
  • 00:37:14
    For this test we use Bromine water
  • 00:37:16
    and it goes from orange to colorless,
  • 00:37:18
    colorless is really important here,
  • 00:37:20
    clear is not going to be enough to get you the marks,
  • 00:37:23
    it has to be colorless.
  • 00:37:27
    The complete combustion of a hydrocarbon
  • 00:37:30
    involves lots of oxygen,
  • 00:37:32
    that is your roaring blue flame on a Bunsen burner.
  • 00:37:36
    This is gonna be hydrocarbon plus oxygen turns
  • 00:37:38
    into water and carbon dioxide.
  • 00:37:42
    Incomplete combustion is where there's not enough oxygen,
  • 00:37:45
    this is going to be an orange flame in a Bunsen burner,
  • 00:37:48
    this is much more problematic,
  • 00:37:50
    because as well as the water and carbon dioxide,
  • 00:37:52
    we're gonna get carbon monoxide,
  • 00:37:53
    which is highly toxic,
  • 00:37:56
    your white blood cells prefer it to oxygen,
  • 00:37:58
    so you'll actually suffocate to death generally
  • 00:38:01
    in your sleep,
  • 00:38:03
    and carbon which is black suit,
  • 00:38:05
    which gets everywhere.
  • 00:38:09
    The word mono means one,
  • 00:38:12
    and mer means bit,
  • 00:38:16
    Poly means lots and mer mean bits.
  • 00:38:23
    So we can say a monomer is one bit and
  • 00:38:25
    a polymer is lots of bits that have all been put together.
  • 00:38:30
    If you're going to have our monomer of the ethene,
  • 00:38:32
    that will just become Polyethene.
  • 00:38:37
    So you just put Poly in front of the name there,
  • 00:38:40
    and if we want to take the drawing
  • 00:38:41
    and turn it into a polymer,
  • 00:38:43
    we need to take this double bond and break it,
  • 00:38:47
    so that bond goes outside,
  • 00:38:48
    we have a single one between our two carbons,
  • 00:38:50
    that's the other half of the bond,
  • 00:38:53
    drawing in our hydrogens,
  • 00:38:57
    square brackets,
  • 00:38:59
    you need to make sure your bond extends
  • 00:39:00
    outside the square brackets,
  • 00:39:03
    and a little n after it,
  • 00:39:05
    and you need to have a big N in front of your monomer.
  • 00:39:10
    If we want to have a polymer of propene,
  • 00:39:12
    we're gonna turn that into polypropene,
  • 00:39:14
    we need to draw it in a slightly different way
  • 00:39:16
    to the way you may be used to drawing it,
  • 00:39:18
    with our double bond here,
  • 00:39:19
    and third carbon up here going round a corner.
  • 00:39:23
    Exactly the same way,
  • 00:39:25
    break one of the bonds,
  • 00:39:26
    one left in the middle,
  • 00:39:27
    the other bond goes outside,
  • 00:39:29
    and then all of the other groups around hydrogen
  • 00:39:31
    stay the same.
  • 00:39:37
    Little n after it,
  • 00:39:39
    big N in front of it.
  • 00:39:42
    If they want to try to make this more complicated,
  • 00:39:43
    make a change this CH3 group for
  • 00:39:45
    a fluorine group or a bromine group,
  • 00:39:48
    all you do there is exactly the same,
  • 00:39:50
    just replace the fluorine group in the same place.
  • 00:39:56
    When we polymerized something,
  • 00:39:57
    and I'm gonna show you condensation polymerization,
  • 00:40:00
    we add monomers together,
  • 00:40:03
    in condensation polymerization,
  • 00:40:04
    we're going to add these bits together here,
  • 00:40:07
    and we are gonna lose a water molecule,
  • 00:40:11
    for condensation polymerization,
  • 00:40:11
    you can see we have two different functional groups here,
  • 00:40:16
    the opposite ends of amino acids,
  • 00:40:18
    which I have drawn here,
  • 00:40:20
    and we have lost water as a small molecule.
  • 00:40:24
    Condensation polymerization is where
  • 00:40:25
    we lose a small molecule from the reaction,
  • 00:40:27
    and it is usually water but not always.
  • 00:40:32
    Thermosetting and and thermosoftening polymers
  • 00:40:34
    have very, very different properties,
  • 00:40:36
    and this is based on their structures.
  • 00:40:39
    Both have long polymer chains in,
  • 00:40:41
    the thermosetting have cross links,
  • 00:40:44
    whereas thermosoftening don't have cross links.
  • 00:40:47
    This means upon heating the thermosetting
  • 00:40:50
    polymers can just slide past each other,
  • 00:40:52
    whereas thermosetting polymers cannot
  • 00:40:53
    slide past each other.
  • 00:40:56
    Which means thermosetting polymers are going to burn,
  • 00:41:00
    and thermosoftening polymers are going to melt.
  • 00:41:06
    Here is the structure of DNA that I have sitting on my desk,
  • 00:41:09
    and you can see there are two lines going through it,
  • 00:41:13
    because DNA is double helix structure.
  • 00:41:17
    You can see each of the bases in here,
  • 00:41:21
    all with different colors,
  • 00:41:23
    the bases are A T C and G,
  • 00:41:26
    and they go together in that format,
  • 00:41:28
    A always bonds with T, C always bonds with G.
  • 00:41:32
    This is to do with the number of connections they can make,
  • 00:41:36
    so you're always going to get A bonding with T,
  • 00:41:39
    and C bonding with G,
  • 00:41:41
    it has a sugar phosphate backbone.
  • 00:41:48
    And there are two of those,
  • 00:41:49
    these that go up the side,
  • 00:41:51
    around the DNA.
  • 00:41:56
    Two strands that can break apart down
  • 00:41:58
    the middle when the DNA wants to replicate.
  • 00:42:03
    A section of DNA such as this can be called a gene,
  • 00:42:07
    and then genes with the information
  • 00:42:09
    for making amino acids and proteins which
  • 00:42:11
    are the building blocks of you and me.
  • 00:42:18
    Sections of DNA can be red,
  • 00:42:21
    so three bases of DNA can be read,
  • 00:42:25
    and turned into an amino acid.
  • 00:42:28
    These amino acids can then build altogether
  • 00:42:31
    to make the gene.
  • 00:42:39
    Alcohols have an -O-H functional group,
  • 00:42:43
    and they end in ol.
  • 00:42:45
    So one with the one carbon is going to be methanol,
  • 00:42:50
    with two carbons,
  • 00:42:51
    ethanol,
  • 00:42:53
    with three carbons,
  • 00:42:57
    propanol,
  • 00:42:58
    with four carbons,
  • 00:43:01
    butanol,
  • 00:43:03
    when we draw our alcohols,
  • 00:43:05
    we need to put -O-H groups on here,
  • 00:43:08
    and we need to remember make sure everything
  • 00:43:10
    has the right number of bonds,
  • 00:43:11
    hydrogen is only ever going to make one bond,
  • 00:43:13
    carbon makes four bonds,
  • 00:43:15
    oxygen makes two bonds.
  • 00:43:20
    Organic chemistry is a very natural place
  • 00:43:21
    for them to stick nasty questions in,
  • 00:43:23
    and this is one of the nasty questions they could sneak in.
  • 00:43:27
    Propan-1-ol has our alcohol group right on the end,
  • 00:43:32
    butan-1-ol has a alcohol group right on the end,
  • 00:43:37
    propan-2-ol has it in the middle,
  • 00:43:39
    here is our alcohol group up here,
  • 00:43:41
    and Butan-2-ol has it in the middle here,
  • 00:43:45
    learn these and recognize them.
  • 00:43:49
    Alcohol can be used for drinking,
  • 00:43:50
    or as a solvent,
  • 00:43:52
    when you react it with sodium it's going to fizz,
  • 00:43:54
    when you react with oxygen it's going to burn,
  • 00:43:55
    it's just a combustion reaction,
  • 00:43:57
    when you reacted with water it's going to dissolve.
  • 00:44:01
    Another way of producing alcohol is fermentation,
  • 00:44:04
    this is where we take sugar and mix it with yeast,
  • 00:44:06
    keep it nice and warm and we're going to get ethanol
  • 00:44:09
    which you can use for alcohol,
  • 00:44:10
    or carbon dioxide which makes the bubbles in bread.
  • 00:44:14
    Exactly the same process beer making and breadmaking.
  • 00:44:19
    If you want to measure the energy released
  • 00:44:21
    by burning alcohols,
  • 00:44:22
    and you can always compare different types
  • 00:44:24
    of alcohol with this,
  • 00:44:25
    you need unknown volume of alcohol,
  • 00:44:27
    you can weigh this on the scales,
  • 00:44:29
    burn it use it to heat a known volume of water,
  • 00:44:32
    and measure the temperature change.
  • 00:44:34
    We can then work out the energy by using
  • 00:44:36
    the mass times temperature change times
  • 00:44:38
    specific heat capacity of water.
  • 00:44:43
    Carboxylic acids have this as a function group.
  • 00:44:48
    Something with one carbon is methanoic acid,
  • 00:44:54
    two carbons is ethanoic acid.
  • 00:45:00
    Three carbons propanoic acid.
  • 00:45:07
    Four carbons butanoic acid.
  • 00:45:14
    Methanoic acid one carbon making four bonds,
  • 00:45:17
    double bonded to oxygen and an alcohol group,
  • 00:45:20
    ethanoic acid propanoic acid and butanoic acid
  • 00:45:24
    you need to be able to recognize and draw these.
  • 00:45:29
    You use carbocyclic acid,
  • 00:45:30
    much more than you recognize,
  • 00:45:32
    because ethanoic acid is vinegar,
  • 00:45:34
    it is an acid,
  • 00:45:35
    so if you react it with any carbonate,
  • 00:45:37
    You're going to get your standard acid carbonate
  • 00:45:39
    reaction and it's going to fizz,
  • 00:45:40
    and if you react it with alcohol you
  • 00:45:41
    are going to make Esther.
  • 00:45:45
    If you react an alcohol with a carboxylic acid
  • 00:45:47
    you're going to get an Esther,
  • 00:45:49
    for example if you react ethanol with ethanoic
  • 00:45:50
    acid you're going to get ethyl ethanoale and water.
  • 00:45:56
    Nanotechnology is absolutely fascinating,
  • 00:45:59
    it is taking atoms and rearranging them
  • 00:46:01
    into specific locations and specific sizes
  • 00:46:06
    so that we can use it,
  • 00:46:08
    it is much much smaller than technology,
  • 00:46:10
    it is very small.
  • 00:46:15
    But it is made up of lots of different atoms,
  • 00:46:19
    now the potentials for this are massive,
  • 00:46:21
    because as we get smaller we are increasing
  • 00:46:24
    the surface area.
  • 00:46:30
    And when we get the small things have very
  • 00:46:31
    very different properties,
  • 00:46:33
    things look see-through,
  • 00:46:34
    things are flexible,
  • 00:46:35
    things start to behave very differently than
  • 00:46:37
    they would if they were much, much larger.
  • 00:46:42
    The potential for this is massive,
  • 00:46:44
    communication and drug delivery,
  • 00:46:45
    personalized medicine,
  • 00:46:47
    but people are wary about this because
  • 00:46:48
    it is a new technology.
  • 00:46:52
    The majority of glass we use is made up of
  • 00:46:53
    a silicon dioxide.
  • 00:47:01
    Ceramics such as clay ceramics are a mixture
  • 00:47:03
    of silicon dioxide and aluminum oxide.
  • 00:47:17
    Well done for making it to the end of this video,
  • 00:47:18
    you are all absolute superstars,
  • 00:47:22
    all the best in your exams I am keeping all
  • 00:47:24
    of my fingers crossed for you.
  • 00:47:36
    (upbeat music)
标签
  • LXL chemistry
  • periodic table
  • reactivity series
  • displacement reactions
  • rates of reaction
  • exothermic
  • endothermic
  • hydrocarbons
  • global warming
  • nanotechnology