Isomers+chemistry+lessons

= Chemistry lessons =

**1. “Isomers” (presented on 29th July 2011)**

Today I’m going to help you to understand a new meaning and a new word, that is the very abstract concept of isomer. You couldn’t clearly understand this concept by definition: “isomeric substances are different substances that have the same formula”… (maybe somebody can? Who can? Wow! Great! So what are isomers? Oh! Well. So, for what the two substances with the same formula are different? Don’t worry if you don’t know: this is the target of this class) Like the most other important concepts of chemistry you will learn this one by practicing and thinking about it. In order to do that you need first to practice and learn some dictionary and lexicon.

**Activity 1** Collaborating with your peer, match names and definitions with images in the diagram. You can do this by numbering diagram’s boxes, for shortness. Then try to pronounce the corresponding words to him/her at your best, with the help of the phonemic symbols (transcription). (type and copy from [] ) []

Activity 1 was tried just for pronouncing terms and then was assigned as homework.
 * **IMAGES** || **Nouns – phonetic symbols** || **Meanings** ||
 * ? || 9. ISOMER \ˈaɪ-sə-mər\ || 9. different substance with the same formula ||
 * [[image:Water_molecule.png width="70" height="80"]] ||  ||   ||
 * [[image:Compound_of_five_tetrahedra.png width="259" height="152"]] ||  ||   ||
 * H2O ||  ||   ||
 * [[image:element.jpg width="130" height="80"]] ||  ||   ||
 * || [|Mol. formula formula] || C12H22O11 ||
 * [|Molar mass] || 342.30 g/mol  ||
 * Appearance || white solid  ||
 * [|Density] || 1.587 g/cm3, solid  ||
 * [|Melting point] || 186 °C decomp.  ||
 *  [|Solubility] in [|water]  || 2000 g/L (25 °C)  ||   ||   ||   ||
 * [[image:substance.jpg width="250" height="127"]] ||  ||   ||
 * [[image:atom.png width="130" height="120"]] ||  ||   ||
 * [[image:sf6-molecule-structure.jpg width="114" height="108"]] ||  ||   ||
 * //List of words/phonetic//** (1-8 by Collins, 9 from Merriam Webster’s, [|www.merriam-webster.com]. Syllabication by a.t.)
 * 1) Atom, [\ ˈ æ-t <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ə <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">m\]
 * 2) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Compound, [\ <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ˈ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">k <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɔ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">m-paund\]
 * 3) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Element, [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\ <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">ˈɛ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-l <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">ɪ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-m <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">ə <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">nt\]
 * 4) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Formula, [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\'f <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɔː <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-mju-la\]
 * 5) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Molecule, [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\'m <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɔ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-l <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɪ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-kju <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ː <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">l\]
 * 6) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Property set, [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\'pr <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɔ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-p <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ə <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">t <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɪ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\ \s <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɛ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">t\]
 * 7) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">(molecular) Structure, [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">(\'m <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɔ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-l <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ɪ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">-kju <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ː <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">l <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">əʳ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\) \ <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ˈ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">str <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ʌ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">k-t <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ʃəʳ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\ ]
 * 8) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Substance [ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">\ <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ˈ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">s <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ʌ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">b-st <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">ə <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">ns\]
 * 9) <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Isomer [ <span style="color: black; font-family: 'Segoe UI',sans-serif; font-size: 12pt;">\ˈaɪ-sə-mər\ <span style="color: black; font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">]


 * //<span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">List of meanings: //**
 * 1) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">The family of atoms having the same and definite number of protons in their nuclei (e.g. carbon family’s atoms have six protons in all their nuclei)
 * 2) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">The 3D-model of the geometrical arrangement of the atoms and their connections in a molecule.
 * 3) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Describes a substance that is formed by the combination of two or more elements.
 * 4) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">Says how many atoms and which elements are in one molecule.
 * 5) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">A portion of matter with constant – uniform composition.
 * 6) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">The smallest piece of an element, it is made of smallest subparticles as protons neutrons in a nucleus and electrons moving around the nucleus.
 * 7) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">A list of data that identifies a substance unambiguously (identity card)
 * 8) <span style="font-family: 'Trebuchet MS',sans-serif; font-size: 12pt;">A number of atoms grouped and linked to each other.
 * 9) different substance with the same formula

Each student draw this grid with six boxes and write in the boxes six words from your homework list of nine. <span style="font-family: Calibri,sans-serif; font-size: 18px; line-height: 27px;">The teacher draw out names but, instead of telling them, he reads the definitions aloud giving their list numbers. Each time the students recognize the names, they tick them off on the grid writing close the definitions’ numbers (without telling the ticked names). The first student who complete a row says “BINGO” and will be checked by the others for correct matching of the six names. In case of errors the peer who has singled out the error will continue the game, by reading the remaining listed definitions, otherwise the teacher will continue until all the definitions will be read.
 * BINGO! A quick way to check homework-study **

**Explanation** **Was given through a CmapTools step presentation of this cmap**



Substances are made up of molecules (and molecules are made of atoms). Different molecules cause substances to be different. That means that two different substances will have at least some different properties, such as melting temperature or density etc. So you should ask to yourselves as could two different molecules be different. The most obvious way to make two molecules differing is that they are made up of different kind or number of atoms, or elements (eventually recall the element definition from the table). So CH2O, H2O and H2O2 represent different molecules of the three completely different substances: formic aldheyde, water, hydrogen peroxide. Despite the similarity between molecules (and formulas), the three corresponding substances are very different. But there is another way to get different molecules without changing type or number of atoms, that is: //changing structure// //by// //maintaining the same atoms//. This is not always possible. As an example, even if in principle you can **connect atoms** in water as H-O-H and **in a different way**: H-H-O, only molecules corresponding to the former scheme exist. Nature is not always respectful of our creativity. But we have the same an important idea: connecting the same atoms in different ways. In organic chemistry, it is often possible (almost always) to invent changed structures that correspond to really existing molecules and substances. Maybe this is the reason why 99,99 % of known substances are organic and why most of chemists researches work as organic chemists. As an example, try to connect four carbon atoms and ten hydrogen atoms with the **following rules**: Each carbon atom © //must// be bonded to four atoms (C s “tetravalent”) Each hydrogen atom (H) //must// be single-bonded (H is “monovalent”). The task is to find //really// different molecules (structures) having formula C4H10 with the aforesaid rules, as described in the following.

**Activity 2**… 1. Connect FOUR carbon atoms and TEN hydrogen atoms to give a molecular formula C4H10
 * Each carbon atom (C) must be bonded to 4 atoms
 * Each hydrogen atom (H) must be single-bonded

Build up at least three DIFFERENT STRUCTURES.

WARNING: don’t show your masterpieces to the other groups!

2. Describe one structure at a time, with only **allowed terms**, **//without showing it//** to the others.

3. Every group listen at the description and check if it has a structure that correspond to the description. The molecules from the groups that corresponded to the description are collected also if they have different shapes.

(referred to CONNECTIVITY) ||  TABOO WORDS (referred to SHAPE) || tobeconnectedto To bond (reg. tr. verb) Nouns and adjectives: Sameatom Hydrogenatom(s); carbonatom(s) End(s), Neighbour, Nearby, next, Main chain or carbonbackbone Un-branched / branched Ring or cyclic (adjs) ||  ORIENTATION termsas the following Up, Down Left, right ARE BANNED SHAPE terms are BANNED Angle, right angle, Line or linear Step-shaped U-shaped or C-shaped L-shaped T-shaped ||
 * ALLOWED WORDS
 * Verbs

The following is a possible discussion. // Ok. Is there anybody that have found more than two structures? Yes? OK! Now we are going to reduce them to the **two** that are the only “really” different. The true 3D models would have less structural variables and more freedom of changing shape than the flat models we have used for our comfort. So we have to focus on the connectivity, that doesn’t depend on the space dimensions and doesn’t change with the internal movement of the atoms in real molecules. // // To group your outcomes in just two different kinds of connectivity, you have to compare them describing one structure without using words that can refer to the shape, while the other team will identify and confirm whether has got the same kind of connectivity or not. // // When describing the structures, the group members have to strictly use the following terms and verbs that refer to the **connectivity** and not other terms as up, down, left or right, flat angle or right angle, step-shape, U shape, T shape, L shape, etc. that can be referred to the structure’s **shape**. //


 * // After the experiment in the course, I think that after constructing the structures the connectivity descriptions should be helped by some questions (instead of using allowed terms, that was a too much demanding task): //**

1. Draw lines connecting and passing through the centre of every carbon atom. The segments form a broken line that could be linear or not-linear.

2. If the line has not "T-crosses" say that the structure is "unbranched". Say that in your structure all carbons are chained forming a skeleton structure with two ends

3. How many **//consecutive//** carbon atoms are in this structure? If there are only three say that your structure is "branched", and carbon skeleton has three ends.

4. Ask the other if they have a branched/unbranched as yours and collect them in two groups.

(if someone has got a cyclic structure, a square, ask him/her to number the hydrogen atoms) You should get four apparently different shapes for the //unbranched// structure and a single T shaped structure that is //branched//. Based on the two different connectivity you have only two different structures: branched and unbranched. With bigger molecules ( > 4 C atoms) the branched molecules, having different connectivities, will be more.

**Metacognition** So, we were successful in solving a complicate problem: //discover how many C4H10 hydrocarbons should exist in nature (and indeed they exist)//. We obtained more than two structures, but only two had most striking differences that result also in **//different kinds of connectivity//**. Has someone got any doubt about this? I would wonder if not! There are plastic 3D-molecular models that are more similar to the real molecules, but if we had used them, we had obtained only the two real structures straightaway, but renouncing to a so neat concept of connectivity, that is very useful in describing molecules.
 * 1) How is this point related to the reality?
 * 2) Why are the linear, C, U, and step shapes interchangeable but not the T-shape?
 * 3) Are there any other assumptions that are necessary to understand what the atoms in molecules can do or cannot do?

4. Why it was impossible to everybody to make a cyclic (ring) structure? 5. What should we left apart to make such a molecule? Cyclobutane: remember this name. It is important, not only because it corresponds to an existing hydrocarbon.

**Follow up:** These two different molecules, having the same formula, correspond to two different substances-hydrocarbons, having different properties and even different names: butane (the linear or **unbranched** one) and isobutane (the **branched** one). So, finally, we can easily understand what isomers are. Butane and isobutane (the substances and the molecular structures) are isomers, as to say, two substances with the same formula. We can say the same with an adjective: butane and isobutane are two //isomeric// substances. If you use the singular “//isomer”// for a substance it is to mean that that substance has no isomers, as in saying: “ethane, C2H6, is formed by a //single isomer//”; or even to stress the “isomeric” relationship: “isobutane is the //only// //isomer// of butane”. This is a question to verify true understanding. Do you remember cyclobutane? Who can say why we mustn’t consider this as a further isomer of butane and isobutane? In English, please. Another question: why we haven’t any isomers of propane (C3H8)? Answer in English please. Now I’m going to show you a propane molecule with a 3D Blu-Tack – toothpicks model. Who wants build up that molecule?

OK. Why we haven’t a linear and a angled structure, but just one? You will answer at this question in English, while doing your homeworks.

**Homeworks**: how many hydrogen atoms would be necessary for the pentane-C5 hydrocarbons, for structures without rings? How many isomeric structures could be made with that formula?