Year: 2019

1. how the teacher introduces scientific terminology
2. hwo the teacher uses scientific terms that students should already know
3. which language and how langugage is sued by the teacher
4. which language is sue by students and how it is used
5. any foreign students present and how these are addressed/integrated
6. any language difficultors observed, any specific anecdotes

Task 1: Use of language in the classroom

There are 8 students in the class, with all the students being Maltese, though it must be noted that whilst all the students can understand Maltese, not all of them feel comfortable speaking in Maltese. One of the students has shown some signs of struggle when the lesson was explained in Maltese as he comes from an English speaking family.

During the observed lessons, the teacher introduced a number of different concepts, including the introduction of the chapter of separating mixtures, how to write a practical and revising the chapter of solids, liquids, and gases by correcting the homework.

On introducing the chapter of separating mixtures it was immediately noted that the teacher was switching between Maltese and English, mainly to make sure that all of the students could understand the new concept and some of the new definitions. This enabled all of the students to be able to understand the concept of the new chapter, giving them a good base to understand future lessons. On explaining the concept of dissolution the teacher made a reference to the Maltese version of ‘tinhall’, which is the translation of melting. Mr Cassar explained that whilst in the Maltese language students might be using this term at home, this is not the correct terminology when it comes to chemistry.

When talking about the dissolution of gases some students could not understand how gases can dissolve in water. After trying to re-explain this concept in Maltese, as this student was more fluent in Maltese, the teacher used two short real-life examples. The first was reaffirming the simple fact that fish can breathe underwater and that therefore oxygen must have been dissolved in water. The second example was an actual story that happened to the teacher a few years prior. Whilst he was swimming he saw this metal rod underwater. Since he loved fishing he decided to dive and get the rod to the surface, expressing his relief that the rod had not rusted. The following morning this rod had rusted, showing that whilst oxygen can dissolve in water, this is not done in large amounts.

When analysing the most common mistakes found in the homework the teacher spoke only in Maltese, as this was the language that both him and most of his students feel most comfortable with. This allowed the teacher to help students understand what they did wrong and what could have been done better in a way they could understand. In fact, it was easily noticeable that all students, irrespective of their mark in the homework, felt that they were satisfied with the explanation, and left the classroom knowing that next time, they could do better.

After the lesson, I had a meeting with my mentor and we had a small discussion about the language used in classroom. This allowed me to be able to discern on the language used in my classroom, especially in the areas where I differ from the teacher that I was observing. During the conversation, I questioned the use of the Maltese language during the lesson, especially when considering that the exam will be in English. My mentor pointed out that whilst the exam is in English it is important that the students first understand the concepts prior to being able to answer questions in an exam. In fact, after this conversation I realised hat code-switching from Maltese to English and vice versa should not be frowned upon during a lesson, but rather be used as a tool to ensure that all students are given the same opportunities to understand all the concepts that I am putting forward during the lesson.

1) Dr Spiteri discusses nine dimensions that influence school climate. What are they, and how do these relate to the KIPP schools he mentions earlier?

The school climate is the quality and character of school life. As seen in the Maltese environment there seems to be a correlation between the school climate and the performance of students, with better environment resulting in higher grades. The removal of the junior lyceum exams seems to be motivated to try and establish all governmental schools to try and have a similar school climate.

The 9 dimensions as discussed in the video are:

• Clarity: The students should know what is being expected of them
• Fairness: Every student expects to be treated equally
• Environment: This is the place where students will spend most of their times, therefore this will need to be clean and comfortable.
• Interest: A student should be motivated when they go to school.
• Order: A nurturing environment for students to grow.
• Participation: students should be encouraged to participate in class.
• Standards: There should be a high expectation for all students.
• Safety: When at school, students have the right to feel safe.
• Support: A student should know that at school there is a support system in place for whatever is necessary, especially with regards to encouragement and guidance.

These 9 dimensions are crucial in KIPP schools, which are a set of American schools that offer free education to students who come from poorer backgrounds. In fact, 95% of students come from Afro-American or Hispanic families. These schools provide a climate for students to be able to get the grades to go to college, with the whole system being set up to provide the perfect environment for these students to succeed.

2) Prof. Darmanin discusses five key factors that contribute to a positive learning environment and allow secondary school students to learn, and learn well. What are these, and how are they related to the dimensions of school climate discussed earlier by Dr. Spiteri?

Professor Darmanin starts her vidcast emphasising that students want to learn. This is very important, cos when the students are willing then it will be the students themselves who demand that they are thought in a positive manner.

The five key factors mentioned by Prof Darmanin are:

• Teacher order and discipline: Students want to be in an environment where they are allowed to learn.
• Work should be demanding and salient: The work done should be challenging and should make students think about what they are doing.
• Lessons should have a good pace: Students want to learn something new all the time, and it is important not to spend too much time saying the same thing.
• Students do not want to be bored: A bored student is a student who is not loving the lesson and therefore a student who is not learning.
• Subjects should be horizontally connected: whatever a student is learning should be seen and understood in a wider context and not just for that one particular subject.

In fact, in other terms, it could be said that students want to have a classroom climate where they can learn. These seem to be extensions of what Dr Spiteri said in his vidcast where he mentioned a number of different dimensions that affect the school climate. If the school climate is not good and does not nurture learning than it would be very difficult to have a positive learning outcome, even if all the factors mentioned by Prof Darmanin are in place.

The Ionisation Energy is the energy require to remove an electron from a gaseous atom or ion at stp.

There can be multiple ionisation energies, such as:

First Ionisation Energy: Energy required to remove an electron from a gaseuos atom to form a uni-positive ion.

 

 

The periodic table contains a lot of information. The numbers of the neutrons, electrons and protons can all be found using such information.

Proton Number = Atomic number

Neutron Number = Mass number – Atomic Number

Electron Number =  Atomic Number – Charge

Once the number of electrons has been established these should be drawn into shells (For information on how to place electrons into orbitals please read more in Atomic Structure).

Each shell can take up a number of different electrons, but for the intents of this chapter the first shell takes in 2 electrons, the second shell takes in 8 electrons, the third shell takes in 8 electrons and the in the fourth shell the maximum number of electrons that will be put in it is going to be 2 electrons.

For example:

Oxygen has 8 electrons, therefore these will be placed in shells as 2 in the first shell, and 6 in the second shell, being written as 2, 6.

Calcium has 20 electrons, therefore these will be placed in shells as 2 in the first shell, 8 in the second shell, 8 in the third shell and the final 2 in the fourth shell, being written as 2, 8, 8, 2.

In order to draw these atoms with electrons around them, one should draw the nucleus, either as the letter of the element or the number of protons and neutrons, and shells around it. The electrons are then depicted as either dots or crosses.

Putting Electrons in Shells

Diagonal relationship

A relationship within the periodic table by which certain elements in the second period have a close chemical similarity to their diagonal neighbours in the next group of the third period. This is particularly noticeable with the following pairs.

Lithium and magnesium:

(1) both form chlorides and bromides that hydrolyse slowly and are soluble in ethanol;

(2) both form colourless or slightly coloured crystalline nitrides by direct reaction with nitrogen at high temperatures;

(3) both burn in air to give the normal oxide only;

(4) both form carbonates that decompose on heating.

Beryllium and aluminium:

(1) both form highly refractory oxides with polymorphs;

(2) both form crystalline nitrides that are hydrolysed in water;

(3) addition of hydroxide ion to solutions of the salts gives an amphoteric hydroxide, which is soluble in excess hydroxide giving beryllate or aluminate ions [Be(OH)₄]²⁻ and [Al(OH)₄]⁻;

(4) both form covalent halides and covalent alkyl compounds that display bridging structures;

(5) both metals dissolve in alkalis.

Boron and silicon:

(1) both display semiconductor properties;

(2) both form hydrides that are unstable in air and chlorides that hydrolyse in moist air;

A polymer is a material made of long, repeating chains of molecules. The material would have unique properties, depending on the type of molecules being bonded and how they are bonded.

Some common polymers are:

• polyethene: This is the most popular plastic in the world. This is the polymer that makes grocery bags, shampoo bottles, children’s toys, and even bulletproof vests. For such a versatile material, it has a very simple structure, the simplest of all commercial polymers.

• polyvinylchloride (PVC): PVC is used in construction for pipe and in profile applications such as doors and windows.

• polytetrafloroethene (PTFE): PTFE is used as a non-stick coating for pans and other cookware.

Addition Polymerisation

An addition polymer is a polymer that forms by the linking of individual monomers without the generation of other by-products.

This is formed when the double bond opens up reacting with a second monomer, giving each Carbon 4 single bonds instead of 2 single bonds and 1 double bond each.

Plastics and the environment

During addition polymerisation a new Carbon to Carbon bond is being created. Such bonds are very strong and therefore these would be difficult to break down. This means that any material created in such a reaction would take a very long time to degrade, as is the case with plastics, which makes such polymers detrimental to the environment.

Questions about polymers

MATSEC May 2011 Paper 1 Question 11 d

The hydrocarbon, C3H6, undergoes addition polymerisation.

1. Explain the term addition polymerisation.
2. Another compound which undergoes addition polymerisation is vinyl chloride. Draw two repeating units of the polymer, PVC, which is formed from vinyl chloride.
3. Some polymers are environmentally friendly. Is PVC considered as environmentally friendly. Explain.
4. Give one use of PVC.

MATSEC May 2012 Paper 2 Question 13 b

A typical reaction that alkenes undergo is polmerisation, as in the case of polyethene, PTFE and PVC.

1. Explain briefly was is meant by the term polymerisation.
2. The polymers polyethene, PTFE and PVC are produced through an addition polymerisation reaction. Considering one of these three polymers, outline the polymerisation reaction that takes place for ONE of these polymers.

 

 

A transition metal is a metal that can have at least one oxidation state with an electron in the d-orbital. According to this definition Scandium and Zinc are not transition metals because both Sc³⁺ and Zn²⁺ do not have electrons in their d orbitals.

General Properties

Size

The size of the transition metals is more or less the same. This is due to the fact that the last shell is actually the s orbital which is being shielded by the d electrons. The increase in the electron count in the d-orbital is counteracted with an increase in the positive charge in the nucleus, and therefore the effect of the nuclear charge on the outer electrons found in the s-orbital would be more or elss constant. This would result in a similar atomic radius for all the transition metals in the same period.

• Atomic radius remains more or less constant, increasing in size only slightly.
• Ionisation energy decreases by a marginally small amount due to the constant atomic radius.

Metallic character

Transition metals are metals, and therefore they have metallic bonding, giving them similar properties as all metals:

• High melting point and boiling point
• High densities
• High electrical and thermal conductivities
• High tensile strength
• Good mechanical properties

Oxidation state

All transition elements lose the 2 electrons found in the s orbitals to produce a 2+ ion. Apart from this they can also lose electrons from the d-orbital, since these would have similar ionisation energies. Normally it is easier to lose unpaired electrons, although the most stable oxidations states are the +3 for the transition metals on the left and the +2 for the transition elements on the right. Manganese can have a maximum oxidation state of +7 since it is 4s² 3d⁵ and therefore it has 5 unpaired electrons in the d-orbitals.

Catalytic properties

Heterogeneous catalysts

A heterogenous catalyst is a catalyst that is in a different state to the reactants, for example a solid in a solution mixture. This normally offers an adsorption surface where the reaction can take place, just like Iron in the preparation of ammonia.

Homogenous catalysts

A homogenous catalyst is one which is in the same state as the reaction mixture. In this case transition metals can use their variable oxidations states. One such reaction is the reaction between iodide ions and thiosulfate.

Complexes

Complex compounds are produced between transition metals or ions by receiving electrons from a ligand via a dative bond. The ligand can be a neutral molecule or a negatively charged ion.

There are two types of ligands:

Monodentate: can only form 1 dative bond with the metal ion

Polydentate: can form more than one dative bond with the metal ion

Writing the formula

The formula is written in a specific order:

1. Symbol of metal ion
2. Formula of negatively charged ligands
3. Formula of neutral ligands.
4. If there is an overall charge the complex is written inside a square bracket.

Naming complexes

A complex should be named as follows:

1. Ligands in alphabetical order
2. Name of metal
   1. Normal name if complex is positive or netural
   2. Latin name ending in –ate of compound is negative
3. Oxidation number of the metal

Shapes

Complexes can have a co-ordintion number of 2, 4 or 6. A co-ordination number of 2 would give rise to a linear molecule, a co-ordination number of 4 can be either tetrahedral or square planar while co-ordination number of 6 gives rise to an octahedral complex.

Isomerism

Cis/trans isomerism

Chirality

Ligand groups and anions

Chromium(III) chlorides display the somewhat unusual property of existing in a number of distinct hydrates, forming a series of [CrCl_3−n(H₂O)_n]^z+. The main hexahydrate can be more precisely described as [CrCl₂(H₂O)₄]Cl^.2H₂O. It consists of the cation [CrCl₂(H₂O)₄]⁺and additional molecules of water and a chloride anion in the lattice. Two other hydrates are known, pale green [CrCl(H₂O)₅]Cl₂^.H₂O and violet [Cr(H₂O)₆]Cl₃.

Coloured compounds

When transition metals form ligands the overlapping of the orbitals do not remain degenerate, producing 2 different energy states. This is due to the interaction between the orbitals of the ligands with the d-orbital of the transition metal.

Electrons can be excited from the lower energy state to the higher energy state, and when the electron de-excites itself a wavelength is given off which corresponds to the wavelengths of visible light. The colour given off depends on the energy difference between the two states, which in turn depends on:

• The central metal or ion
• The ligands.

Chromium

General Properties

Electronic configuration: [Ar] 4s¹ 3d⁵

Oxidation states: +2, +3, +6

Amphoteric properties

Chromium can react with both acids and bases

Cr + 2HCl → CrCl₂ + H₂

Cr + OH^– → 2[Cr(OH)₄]^– + 3H₂

The reaction of Chromium with sulphuric acid is a redox reaction in which the sulphuric acid produces SO₂ while the chromium is oxidised to the +3 oxidation state.

2Xr + H₂SO₄ →Cr₂(SO₄)₃ + 6H₂O + SO₂

On the other hand it will not react with nitric acid since this will passivate the emtal, making it unreactive.

Cr³⁺

Chromium burns in air to produce the oxide.

2Cr + 3O₂ → 2Cr₂O₃ (green solid)

This oxide dissolve in hydrochloric acid to give the hexaquachromium (III) with the chloride ions as the balancing anions (giving rise to the isomerism as discussed previously)

These compounds can be differentiated by the amount of AgCl that is precipitated on the addition of AgNO₃. The Cl^– in the complex will not be precipitated.

The hexaaquachromium (III) is acidic since the Chromium will pull the electrons towards it making one of the waters to lose an H⁺

Cr⁶⁺

Chromium (III) can be oxidised to Chromium (VI) using a strong oxidising agent like the peroxide. Chromate are mostly known for their ability to act as oxidising agents, in which they are reduced to chromium (III).

Chromium (VI) can exist in two forms, CrO₄^2- of Cr₂O₇^2- with the former being found in alkaline conditions and the latter being found in acidic conditions.

Oxide

The oxide is prepared by the action of concentrated sulfuric acid on the salt.

K₂Cr₂O₇ + 2H₂SO₄ → 2KHSO₄ + 2CrO₇ + H₂O

This oxide can then react with hydrochloric acid to create CrO₂Cl₂ which is an oxidising agent for the reaction of methylbenzene to benzaldehyde.

CrO₃ + 2HCl → CrO₂Cl₂ + H₂O

Manganese

General Properties

Electronic configuration: [Ar] 4s² 3d⁵

Oxidation states: +2, +3, +6

Reaction with acids

The metal reacts with acids to for the Mn²⁺ ion. The ion produced then forms very stable hexaaqua complexes, which are slightly pink in colour. This is a very stable complex.

Mn + HCl → MnCl₂ + H₂

Mn²⁺ + 6H2O → [Mn(H₂O)₆]²⁺

Reaction with halogens

Reacting Manganese with halogens gives the Mn²⁺ ion.

Mn + Cl₂ → MnCl₂

Oxide

The oxide of managanese produced in combustion with air depends on the amount of Oxygen produced.

The reaction pathway goes like this:

Mn + O₂ → MnO              black solid

4MnO + O₂ → 2Mn₂O₃    brown solid

2Mn₂O₃ + O₂ → 4MnO₂  brown solid

With the Mn (IV) being the most stable)

Mn⁴⁺

MnO₂ can act as both an oxidising agent and a reducing agent,m since it can be oxidised to Manganese (VII) while it can also be reduced to Mn²⁺.

Oxidising agent:

MnO₂ → Mn²⁺

Cl^– à Cl₂

 

Reducing agent:

MnO₂ → MnO₄^2-

ClO₃^– àCl^–

 

MnO₂ is also oxidised by heating in alkali in contact with air.

Mn⁶⁺

The manganite (VI) ion disproportionates to give Manganese (VII) and Manganese (IV)

MnO₄^2- → MnO₂

MnO₄^2- → MnO₄^– _

 

Mn⁷⁺

Manganese (VII) is a very good oxidising agent being itself reduced to Manganese (II)

Iron

General Properties

Electronic configuration: [Ar] 4s² 3d⁶

Oxidation states: +2, +3

Rust

Rust is the reaction of iron, water and oxygen. All 3 are needed in order for rust to take place.

Mixed oxide

When iron is reacted with oxygen on heating or steam the mixed oxide is formed.

3Fe + 2O₂ → Fe₃O₄

3Fe + 4H₂O → Fe₃O₄ +4H₂

Reaction with acid

Iron reacts with acids to form Iron(II) compounds since these are not very strong oxidising agents.

Fe + HCl → FeCl₂ + H₂

Fe + H₂SO₄ → FeSO₄ + H₂

Both of these salts are hydrated. Preparation of the anhydrous chloride by heating is not possible, while preparation of the sulphate is. This is due to the fact that the chloride would actually react with the hydroxide.

FeCl₂.6H₂O → FeOHCl + 5H₂O + HCl

Fe²⁺

FeS

Prpared by direct synthesis

Fe + S → FeS

This happens because S^2- is a strong reducing agent and it will reduce Fe³⁺ to Fe²⁺.

Fe(OH)₂

Prepared by the addition of OH^– to any Iron(II) salt.

Fe + OH^– → Fe(OH)₂ green

FeX₂

All the halides can be produced by the reaction of the iron with the acid.

Fe + 2HCl → FeCl₂ + H₂

The bromide and the iodide can also be produced direct combination.

Fe + Br₂ → FeBr₂

The iron should be in excess to ensure that no FeBr₃ is formed.

FeCO₃

Iron is acidic and dissolution of iron carbonate in water would give rise to iron hydroxide and the hydrogencarbonate.

[Fe(H₂O)₆]²⁺ + 2CO₃^2- à [Fe(OH)₂(H₂O)] + 2HCO₃^–

FeSO₄

Iron(II) sulphate is prepared by the reaction of iron with sulfuric acid.

The hydrated crystals are green and turn white when the water of crystallisation is removed.

On strong heating iron (III) oxide is produced together with a mixture of SO₂ and SO₃

2FeSO₄ → Fe₂O₃ + SO₂ + SO₃

Brown ring test

This is a test for nitrates.

NO₃^– + FeSO₄ + H₂SO₄ → brown ring

NO₃^–  + 4H⁺ 3e^{– →} NO + 2H₂O

Fe²⁺ → Fe³⁺ + e^–

NO₃^– + 4H⁺ + 3Fe²⁺ → NO + 2H₂O +3Fe³⁺

NO can act as a ligand and it will displace one of the water ligands on the iron, and this would form the brown ring visible in the test.

[Fe(H₂O)₆]²⁺ +NO → Fe(H₂O)₅NO]²⁺ + H₂O

Fe³⁺

Oxide

The oxide os prepared by the decomposition of Iron (II) sulphate or by the reaction of iron (III) with hydroxide ions.

2FeSO₄ → Fe₂O₃ + SO₂ + SO₃

Fe³⁺ + OH^– → Fe(OH)₃ → Fe₂O₃.xH₂O

Halides

The chloride and bromide are prepared by direct combination with the halogens. These are both collected and purified by sublimation.

2Fe + 3Cl₂ → 2FeCL₃

2Fe + 3Br₂ → 2FeBr₃

It is noted that Bromine has to be in excess in order to ensure that FeBr₃ is formed.

Thiocyanate

Thiocyanate and Fe³⁺ can form a complex with a deep blood red colouring. The thiocyanate will displace a water molecule to form the complex.

[Fe(H₂O)₆]³⁺ + SCN^– → Fe(SCN)(H₂O)₅]²⁺  + H₂O

Copper

General Properties

Electronic configuration: [Ar] 4s¹ 3d¹⁰

Oxidation states: +1, +2

Reactions of Copper

It reacts with strong oxidising agents such as HNO₃ and H₂SO₄ (both concentrated) to give nitrogen dioxide and sulfur dioxide respectively.

Cu + 4HNO₃ → Cu(NO₃)₂ + 2H₂O + NO₂

Cu + 4H₂SO₄ → CuSO₄ + 2H₂O + SO₂

Cu²⁺

Copper (II) oxide can be prepared from the decomposition of copper carbonate, coipper nitrate or copper hydroxide.

2Cu(NO₃)₂ → 2CuO + 4NO₂ + O₂

This oxide is basic and therefore it can be used to produce salts by reacting with the respective acids.

CuO + H₂SO₄ → CuSO₄ + H₂O

Cu⁺

Less stable then copper (I)

Copper (I) disproportionates to give copper and Copper (II)

2Cu⁺ –> Cu + Cu²⁺

Iodine and Iodide only form the copper (I) salts.

Cu + I₂ → CuI

2Cu²⁺ + 4I^– → 2CuI + I₂