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studying for chem half yearly in need of HELP!!! (1 Viewer)
- Thread starter inoan2
- Start date
mitochondria
*Rawr*!
*starts yelling* (about how people are lazy and there are all sorts of wonderful resources which are bloody simple to use)
*finshes yelling*
Polymers are molecules that consists of units of smaller identical molecules called monomers. (i.e. You make polymers by joining monomers together) To help you visualising it, let's think about the metal chains people use to secure their bicycles. Such chains are made of up individual metal rings - and they are your monomers. When you join these monomers together you will get a chain and there you have your polymer. It is very much the same in the chemical sense, an example of a monomer would be chloroethene (vinyl chloride), ClHC=CH2. We can polymerise such molecule by putting more than one of them together, and under suitable conditions the C=C double bond will break and join with neighbouring molecules (provided that they collide at the right angle, location and their sp3 orbitals have the same spin blah blah blah..) and you will have a polymer called poly(chloroethene) or poly(vinyl chloride):
- (CClHCH2)n -
where n is the number of monomers in your chain.
I should probably note that this type of polymer is called additional polymer, where molecules are added together. Another type of polymerisation in the syllabus is called condensation polymerisation. A small molecule such as water is eliminated during condensation polymerisation, an example would be the formation of cellulose from glucose. In this case glucose is your monomer and cellulose the polymer. Since the joining site two glucose molecules are both C-O-H bonds, one of them will lose an O-H and the other an H to gives you H2O.
As for enthalpy, it is formally given by the equation H = U + PV where H is the enthalpy, U is the internal energy, P the pressure and V the volume. We cannot directly measure the enthalpy of a system, so what we do is we measure the change of enthalpy, ∆H, instead. Obviously ∆H = ∆U + ∆(PV). Anyways, enthalpy is measured in Joules. An exothermic reaction, one that gives off heat, will have a negative enthalpy value whereas an endothermic reaction will have a positive enthalpy. You may also want to know that we talk about the enthalpy of formation, enthalpy of ionisation, enthalpy of of atomisation... etc. And these all have the same idea behind: how much energy is realeased or absorbed during a reaction (please be reminded that you can't judge whether a reaction is spontaneous by looking at the change in enthalpy).
Finally.. dissociation.. for this one you need an english lesson. Dis- is a Latin prefix which suggests separation and the suffix which I think also comes from the Latin verb socio meaning share, come together, associate.
So, dissociate would mean separating into smaller components
and this is exactly what dissociation means in chemistry. When you dissolve something in water, very often it dissociates into ions, e.g.
NaCl(s) --------> Na+(aq) + Cl-(aq)
Another example of dissociation would be heating Calcium Carbonate:
CaCO3(s) --------> CaO(s) + CO2(s)
Another thing which would be nice to learn is learn to read a book.. good luck
*finshes yelling*
Polymers are molecules that consists of units of smaller identical molecules called monomers. (i.e. You make polymers by joining monomers together) To help you visualising it, let's think about the metal chains people use to secure their bicycles. Such chains are made of up individual metal rings - and they are your monomers. When you join these monomers together you will get a chain and there you have your polymer. It is very much the same in the chemical sense, an example of a monomer would be chloroethene (vinyl chloride), ClHC=CH2. We can polymerise such molecule by putting more than one of them together, and under suitable conditions the C=C double bond will break and join with neighbouring molecules (provided that they collide at the right angle, location and their sp3 orbitals have the same spin blah blah blah..) and you will have a polymer called poly(chloroethene) or poly(vinyl chloride):
- (CClHCH2)n -
where n is the number of monomers in your chain.
I should probably note that this type of polymer is called additional polymer, where molecules are added together. Another type of polymerisation in the syllabus is called condensation polymerisation. A small molecule such as water is eliminated during condensation polymerisation, an example would be the formation of cellulose from glucose. In this case glucose is your monomer and cellulose the polymer. Since the joining site two glucose molecules are both C-O-H bonds, one of them will lose an O-H and the other an H to gives you H2O.
As for enthalpy, it is formally given by the equation H = U + PV where H is the enthalpy, U is the internal energy, P the pressure and V the volume. We cannot directly measure the enthalpy of a system, so what we do is we measure the change of enthalpy, ∆H, instead. Obviously ∆H = ∆U + ∆(PV). Anyways, enthalpy is measured in Joules. An exothermic reaction, one that gives off heat, will have a negative enthalpy value whereas an endothermic reaction will have a positive enthalpy. You may also want to know that we talk about the enthalpy of formation, enthalpy of ionisation, enthalpy of of atomisation... etc. And these all have the same idea behind: how much energy is realeased or absorbed during a reaction (please be reminded that you can't judge whether a reaction is spontaneous by looking at the change in enthalpy).
Finally.. dissociation.. for this one you need an english lesson. Dis- is a Latin prefix which suggests separation and the suffix which I think also comes from the Latin verb socio meaning share, come together, associate.
So, dissociate would mean separating into smaller components
and this is exactly what dissociation means in chemistry. When you dissolve something in water, very often it dissociates into ions, e.g.NaCl(s) --------> Na+(aq) + Cl-(aq)
Another example of dissociation would be heating Calcium Carbonate:
CaCO3(s) --------> CaO(s) + CO2(s)
Another thing which would be nice to learn is learn to read a book.. good luck