People are at varying stages of the work at present, so I have included some work from last week for those that haven’t completed it.

To do:

·         Finish doing the NCEA questions we were looking at in the VC

·         Do Act 4F in the learning workbook

·         Read p135-138 in the study guide. In your notes

1.       write a definition for an exothermic reaction and draw an energy level diagram

2.       write a definition for an endothermic reaction and draw an energy level diagram.

3.       Write a definition for enthalpy and write the equation for enthalpy change (DH).

4.       Note: bond making is an exothermic process and bond breaking is exothermic.

The section on “determining enthalpy changes”, DH, is the change in enthalpy. Different quantities of reactants will release/absorb different amounts of energy.  You have to look at the stoichiometry of the balanced equation  and multiply the value of the DH given by the number of moles reacting.

·         Do Act 11B

·         Do Act 4G in the learning workbook

·         Read p144-146 in the study guide on bond energies. When doing these problems I find it easiest to draw a structural formal of the reactants and the products.  Then calculate the energy to break all the bonds on the left hand side and calculate the energy released when the bonds are formed on the right hand side.

DH   =   bond breaking minus bond forming.

I have put a worked example in the attachments.

·         Do Act 11C in the study guide.

·         Do Act 4I in the learning workbook

·         Do worksheet 6 in the attachments.

This week­­­­­­ you need to make sure you have a clear idea of the 4 different types of solids: metallic, ionic, covalent networks and molecular. The properties of each and be able to explain the properties using your knowledge of the particular structure.

In the attachments there are some NCEA questions on the topic. I will post the answers later in the week and we can discuss in the VC session.

The 2^nd part of the week, you will start the 3^rd component of this standard, “Energy changes”.

To do:

·         Worksheets 3, 4 and 5 in the attachments.

·         NCEA questions in attachments

·         Read p135-138 in the study guide. In your notes

1.       write a definition for an exothermic reaction and draw an energy level diagram

2.       write a definition for an endothermic reaction and draw an energy level diagram.

3.       Write a definition for enthalpy and write the equation for enthalpy change (DH).

4.       Do Act 11B

Bring your study guide, a calculator and your completed NCEA questions to the VC please.

Things to do:

·         Read p117/118 in study guide.

·         Write a definition of physical change and a chemical change

·         Do Act 10A

·         Read p119-130

·         Look at the powerpoint “BONDING IN SOLIDS”

·         Complete the attachment “classification of substances”. This will form the basis of your notes, also there is a good summary in the attachments “characteristics of crystalline solids”.

·         Youtube  https://www.youtube.com/watch?v=Rw_pDVbnfQk

·         Ionic solids https://www.youtube.com/watch?v=yrswsrW7OwMds

                                  https://www.youtube.com/watch?v=Lf_kRPVK8ZQ

·         Metallic bonding https://www.youtube.com/watch?v=EXeppL4UXXw

·         Network solids https://www.youtube.com/watch?v=b_SXwfHQ774

·         Molecular and network solids https://www.youtube.com/watch?v=POpGcnwnKP0

·         Molecular solids https://www.youtube.com/watch?v=S8WzTAXlTTM

·         Comparison of solids https://www.youtube.com/watch?v=clnGFNmEDdo

·         ABA worksheets in attachments

·         We will look at Act 10B in the study guide in the VC session. If you have nothing to do you can start it!!!!

Hopefully people have worked out the skill of drawing Lewis structures. Eventually it will become intuitive. Practice makes perfect!

It is important to be able to draw the Lewis structures because a L

A Lewis structure is required for you to be able to determine the shape of a molecule. That is the topic for this week.

The  links below were in last weeks’ work but just in-case you haven’t watched them or you want to refresh yourself, I have included them again (the 2^nd one is better than the 1^st)

·         https://www.youtube.com/watch?v=-pq2wum1uDc

·         https://www.youtube.com/watch?v=nxebQZUVvTg

To determine the shape of a molecule follow the following steps:

1.       Draw a Lewis diagram.

2.       Find the total number of regions of negative charge (note: a double or a triple bond counts as only one region).

3.       Determine how many of the regions are bonding and how many are non- bonding (lone pairs).

4.       Use the table below to determine the shape.

VSEPR  ( valence shell electron pair repulsion) theory: Each region of electron density around a central atom repels other regions of electron density.

Molecules are most stable when the repulsive forces are at a minimum. This occurs when the electron regions are as far apart as possible.

See page 106 black for the symbols of how each bond is drawn to make your molecule look 3 dimensional.

·         Do Act 9C black

·         Complete p48-50 in ABA manual

·         Do Act 4D in learning workbook.

Determining the polarity of a molecule:

https://www.youtube.com/watch?v=uYtwU0uRK7o

To determine the polarity of a molecule follow these steps:

1.       Draw the Lewis structure

2.       Determine the shape of the molecule

3.       Does the molecule contain polar bonds? (do the atoms in a bond have a difference in electronegativity of greater than 0.4).If the answer is ‘no’ the molecule is non-polar. If the answer is ‘yes’ go to step 6.

4.       Are the polar bonds arranged symmetrically around the central atom?

If ‘yes’ the molecule is non-polar.

If ‘no’, the bonds are asymmetrically arranged the molecule is polar.

Things to do :

·         Act 9D study guide

·         Act 4E learning workbook

·         p51-53 in ABA manual.

This week you will be learning about:

·         Covalent bonding

·         Lewis diagrams

·         Polar and non-polar bonds

·         Shapes of molecules (will be discussing this at Friday’s VC)

Covalent bonding-

·         Valence electrons are shared

·         Form between atoms of the non-metals

Electronegativity-

·         Is the measure of how strongly bonding electrons are attracted to the nucleus of an atom in a bond.

·         Electronegativities increase across a period

·         Electronegativities decrease down a group

Lewis structures-

·         Only use the valence electrons of the atoms

·         A pair of electrons can be shown  as 2 dots or a single line

·         All atoms try to get an octet ( 8 electrons in their outer shell). The exception is hydrogen which must get 2 electrons in its outer shell.

·         Watch this video clip: https://www.youtube.com/watch?v=1ZlnzyHahvo

The 5 rules for drawing Lewis structures are:

1.       Find the total number of valence electrons

2.       Put the least electronegative atom at the centre of the molecule

3.       Put 2 electrons between the atoms to form a chemical bond

4.       Complete octets on the outside atoms

5.       If the central atom doesn’t have an octet, move electrons from outer atoms to form double or triple bonds.

Things to do:

·         Read p99-102 in the study guide

·         Do Act 9A in study guide

·         Do Act 4B in the learning workbook

·         Do p44/45 in the attachments (there will be an overlap of some of the molecules but lots of practise will make you an expert at drawing Lewis structures).

·         Read p103-105 in the study guide

·         Make notes on:

1.       Definition of electronegativity

2.       If 2 atoms have the same electronegativity, the bond is non-polar.

3.       If the electronegativity difference is between 0.4 and 1.6, the bond is polar covalent

4.       If the electronegativity difference is greater than 1.6, ionic bonding occurs. (see the table at the bottom of p105.

·         Do Act 9B in study guide

·         Do Act 4C in the learning workbook

·         Do p46/47 in the attachments

·         Read about shapes of molecules p106-110 before the VC and watch the video clips below.

·         https://www.youtube.com/watch?v=-pq2wum1uDc

·         https://www.youtube.com/watch?v=nxebQZUVvTg

This week you need to do the formal assessment for the calculations. This will probably only take 30 minutes.

The 2^nd part of the assessment is a practical but there are calculations involved with it!

You will be working with 2 formulas:

and                                                                             

c= concentration (mol L^-1) ,   n= number of moles (mol)    and  V= volume (L)

It is very important that volume is always in litres.

Usually concentration is written in moles per litre (molL^-1) but sometimes it can be given in grams per litre (gL^-1).   The calculation for this is just divide the mass ( in grams ) by the number of litres of water it is dissolved in.

What to do:

·         Read p31-34 in the study guide

·         Write a definition for solute, solvent and aqueous.

·         Draw the triangle for the equation c=n/Vc=n/V  and make a special note that the volume must be in litres.

·         To convert mL to L simply divide the number of mL by 1000 or alternatively push the EXE button on your calculator followed by (-) then 3 (it will be displayed as 30E-3).

·         Attempt Act 3A, although this is not essential, you really just need to be able to work with the equation c=n/V and rearranged to get n=cXV

·         We will talk about the technique of titrations in the VC session. It would be beneficial if you have read p43-47 of the study guide beforehand.

Things to do this week:

·         P18-26 in the ABA lab (see attachments)

·         Each day practice writing the formula of the 6 complex ions (you should have your green cue cards early next week).

·         Act 6A in the learning workbook.

·         Act 2E and F in the learning workbook.

All going well we will aim to do the assessment in week 10 (2^nd last week of the term).