c2 1st half

Página 1

isotopes , atomic structure,compound

keywords:

mass number= no.of proton and neutron

atomic number= no. of proton

isotope: an atom of an element that has the same number of proton but different number of neutron. they have different mass number.

compound: when two different element are chemically bonded from a chemical reaction together.they cant be separated easily.

the mass of and electron is very small

A neutron has 0 charge because no. of proton = to no. of electron

https://www.youtube.com/watch?v=hhbqIJZ8wCM (Incorporar)

c2 isotope, atomic structure and compund

ionic bonding

https://www.youtube.com/watch?v=DEdRcfyYnSQ (Incorporar)

keywords:

ionic bond- is when an atom loses or gains electrons to form charged particles . they are formed by strong electrostatic attraction between the opposite charges. they occur in metals and non-metals.

they are formed because their outer shell in incomplete therefore they are unstable,

an ionic (metal+nonmetal) compound form a giant ionic lattice

the ions are formed in a closely packed regular lattice arrangement. they are held together by a strong electrostatic attraction between opposite charges in all direction.salt crystals are in a shape of a cube because it has on giant ionic lattice. na+ and cl- are held in a regular lattice.

how the ionic compounds could be separated?

1. by dissolving it in water - the electron is free to move in solution carrying out electric current.

2. heating it at high temperature( because they have strong force of attraction)- the electrons are free to move carrying out an electric current.

noble gas in group 0 are unreactive gas because they have stable arrangements of electrons in their outer shell. they have the highest energy level in their outer shell.

look in your science book to look at for some examples

ionic bonding

covalent bonding

keywords:

covalent bonding- sharing electrons. they only occur in non-metals only. the new particles formed are neutral molecules

allotrope: different form of the same element - there are three: diamond,graphite and silicon dioxide

. a covalent bond could be simple molecules or giant structures. they have a week intermolecular force therefore they have a low melting point. they don't conduct electricity- since they have no ions(no charge) therefore there's no electrical current.

giant covalent are macromolecules:

. they are bonded by strong covalent bond. they are heated at high temperature. examples are:

diamond- each carbon atom form 4 covalent bond. they have a high melting point since they have a strong covalent bond. they are hard since they have a rigid network. they don't conduct electricity because the electrons are not free to move.

graphite- each carbon atom form 3 covalent bond. they are soft and slippery since the layers of an atom can slide over each other. they are good conductor of electricity because they have one free electron. (delocalised electron)

silicon dioxide- (sand) one giant structure of silicon and oxygen

https://www.youtube.com/watch?v=v9XDHKzsRF0 (Incorporar)

covalent bond

metallic bond

metallic bond: it the electrostatic attraction between a lattice of positive ions surrounded in a mobile sea of electrons(delocalised electrons)

. they need higher energy level to overcome this reaction.

. they can be malleable( hammered into shape) and ductile

. they are good conductors of electricity

alloys: is mixture of metals in different sized atom are mixed with pure metal. this maakes it harder then pure metal since they distort the layers making it difficult to slide over each other

https://www.youtube.com/watch?v=S08qdOTd0w0 (Incorporar)

metallic bond

relative atomic mass

Ar is the relative atomic mass and Mr is the molecular mass

eg1: find the relative atomic mass of co2

mr of c= 12(mass no.)

mr of o= 16x2-32

ar(relative mass) 32+16 =48

eg 2 :H2SO4 = 1x2 + 32 + 16x4 = 98

percentage calculation: you need to find the percentage of an element in a compound

Percentage = Ar (element mass) /Mr (compound mass) x100

eg:1 find the percentage of hydrogen in water.

ar-h-1x2=2

ar-o-16x1=16

mr-16 +2=18

perccentage of hydrogen- 2 divided by 18=0.111

0.111x100=11.1%

finding a mole in a substance(mass moles and mr) its on the website

finding out the emperical formula is on the website

calculating mass in reactions: the important steps are

. write down the balanced equation.

. write down the mr( relative molecular mass)

. divide one and multiply to get all.

percentage yield: actual yield/predicted yield x100

the product doesn't come out 100% accurate because:

. it could be reversible( when the product react themselves together to produce the original reactant)meaning lower yield.

.sometimes there could be unexpected reactions which could use up the reactant

. the reaction may have not been completely finished.

. it could have been lost when it's separated from the reaction mixture

https://www.youtube.com/watch?v=JN_qmij-pkQ (Incorporar)

https://www.youtube.com/watch?v=R-DgsodSxf0 (Incorporar)

https://www.youtube.com/watch?v=6KRcO3e36ZU (Incorporar)

https://www.youtube.com/watch?v=qxjr1wES8V4 (Incorporar)

https://www.youtube.com/watch?v=-HlNgQxHGvo (Incorporar)

C2 CALCULATION

polymers keywords:

polymers: they are long chain made up of small molecules called monomers which is linked together

weak forces: an individual tangled chaain have a weak intermolecular force therefore there is no cross-linking between the polymer chain so they can slide

them softening: they have no cross-linking. because they can slide they can be remolded and shaped once cooled down( after being heated.

strong force: they have a strong intermolecular force between the polymer chain called crosslinks

thermosetting: it has a cross linking. they have a rigid, hard and strong solid structure. they cant be remolded and they can be shaaped when its heated.

what will affect the property of a polymer? the staarting material and the reaction condition

the two types of polythene made in different condition-

low density-(LD) when it's heated at a high temperature (200) with out a catalyst under high-pressure EG:bag and bottle

high density -(HD) when its heated at low temperature using a catalyst. EG: water tank and drain pipe

polymers

collision theory

the rate of reaction is explained by the collision theory. the rate of rate of reaction depends on how fast or how hard the particles collide. more collisions increases the rate of reaction.

temperature

. increase of temperature means faster collision. when the particles get heated they move faster and collide often. the reaction only occurs if there's energy. minimum amount of energy is needed to start the reaction and this is called activation energy.

concentration: