Part a theme 1: The position of an element on the periodic table tells a story of that element’s bonding capabilities, and we consider these properties when writing formulas and naming chemical compounds. Part B



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Theme 1: Atoms, Elements and Bonding

Part A

Theme 1: The position of an element on the periodic table tells a story of that element’s bonding capabilities, and we consider these properties when writing formulas and naming chemical compounds.


Part B

The essential questions that arise from these Specific Learning Objectives are:




  1. How does an element’s position on the periodic table relate to its combining capacity (valence)?

  2. Using the periodic table, explain how and why elements combine in specific ratios to form compounds?

  3. How do we write formulas and names of binary ionic compounds?

  4. How do we write formulas and names for covalent compounds using prefixes?


Part C

Theme 1 covers the first four Specific Learner Outcomes (SLO’s) in the Chemistry in Action Unit.


Students will…

S2-2-01 Relate and element’s position on the periodic table to its combining capacity (valence).


S2-2-02 Explain, using the periodic table, how and why elements combine in specific ratios to form compounds.
S2-2-03 Write formulas and names of binary ionic compounds.
S2-3-04 Write formulas and names of molecular compounds using prefixes.
Part D

There are some misconceptions that students can have coming into this theme. Some of these misconceptions I believe may still exist if they were not properly addressed at the S1 General Science level. These misconceptions can be found at http://edu.queensu.ca/~science/main/concept/chem/c07/C07CDTL1.htm



(Note: The proper concept (to date of course) is explained at the bullet under the misconception.)

Misconceptions about Atoms:


  1. Atoms can be seen with a microscope.

  • Atoms cannot be seen with a microscope. The extent of an atom’s small size is often not well understood. (E.g. the width of a human hair contains about one million atoms, not hundreds of thousands as guessed by students.

  1. Atoms are alive (because they move).

  • Atoms vibrate because they all possess thermal energy and do not possess the characteristics of living things (i.e. needing energy to survive, producing wastes, reproduction, etc.)




  1. Atoms have electrons circling them like planets around a star.

  • For visualization purposes, the nucleus has been compared to the sun and the electrons compared to the planets for Bohr’s model.

  • Electrons do not follow a simple pattern around the nucleus.




  1. The electron cloud is like a rain cloud, with electrons suspended in it like droplets of water.

  • Electrons are not suspended motionless in an electron cloud. They are actually constantly moving throughout the cloud that is not made of any other matter.




  1. The electron shell is there to protect the nucleus, like an eggshell and a yolk

  • Again electron shells have been compared to an eggshell for visualization purposes in different texts.

  • Shells are not physical shells like eggshells and they are not thin or hard. Instead they are just regions around the nucleus where the electrons can be found.




  1. Atoms “own” their electrons.
  • There are not different kinds of electrons for different atoms. All electrons are the same and can be transferred from one atom to another. Atoms do not possess their specific electrons.



Misconceptions about Molecules:

  1. Molecules are basic, simple, indivisible entities.

  • Molecules are really made up of smaller entities called atoms. Therefore molecules are divisible.




  1. Molecules expand when heated.

  • Molecules themselves do not expand. When a substance is heated they appear to expand because the heat cause the molecules to move faster and further apart.


Misconceptions about Chemical Bonds:

  1. Molecules are glued together.

  • Molecules are held together by forces of attraction, not glue.




  1. The chemical bond is a physical thing made of matter.

  • Chemical bonds are not made of a separate form of matter but are held together by the forces of attraction and the electrons that are shared.




  1. Electrons know where they come from.



  1. Atoms know who owes them an electron.

  • See No. 6 of Misconceptions about Atoms



Part E

See the diagnostic tool (Chemistry in Action: Atoms and Elements) following this section that tests students’ pre-instructional views at the beginning of this theme.


Part F

Some considerations teachers should take into account when planning and implementing lessons from this theme:



  • Re: Student’s views of Atoms and Elements. Prior to starting this outcome the student’s S1 knowledge, like all good teaching, should be checked. The atomic structure and Bohr model should be reviewed. Their knowledge of how the periodic table is designed should also be checked.





  • When discussing the formation of compounds with the students the focus should be on the reasons “why” atoms lose/gain/share electrons to obtain a full valence electron arrangement before the “how”.




  • Re: Writing formulas and naming ionic compounds. In this outcome students will only learn about compounds containing two elements. Compounds involving polyatomic ions (e.g., sodium nitrate, NaNO3) will be examined in Senior 3 Chemistry. Students may also have difficulty determining the Stock system name from the chemical formula. Therefore students must be provided with plenty of opportunities to practice and understand this system.




  • Re: Naming molecular compounds. Prefixes should be memorized by the student for instant recall.


Assessing Student Knowledge in Chemistry: Atoms, Elements and Bonding
This is not a test. There are no right or wrong answers. Please answer all of the questions to the best of your ability because I want to know what you think about atoms, elements, the periodic table, and how different elements combine.


  1. At the atomic level, how could you explain the differences between Helium and Magnesium?




  1. What is the simplest and purest form of “matter” on earth?




  1. What is the overall charge of an atom and explain why.




  1. Atomic theory states that atoms are made up of certain main particles. What are these main particles and what is their charge?




  1. In an atom with more than two electrons, how are all of the electrons located relative to the nucleus?


  1. Define the general properties of a Metal, Metalloid, and a Non-Metal and provide an example of each specifying its chemical symbol?





  1. Create a small diagram illustrating how electrons really rotate around the nucleus of an atom.




  1. What are the main elements that make up the human body?




  1. What elements are the names and the chemical symbols for the coinage metals?




  1. Fill in the below chart as required.




Name of Compound

Compound or Element?

Chemical Formula

Names of Elements Present in Formula?

How Many Atoms of Each Element?

Water










2 atoms H

1 atom O


Carbon Dioxide













Propane




C3H8







Nitrogen











Oxygen
















  1. Explain why the element Argon is not very reactive with other elements.




  1. What parts of an atom are involved in chemical bond formation? Explain.




  1. How does an element’s location in the periodic table affect its reactivity with other elements?




  1. When elements combine together to form a chemical bond, what is it that holds them together?

Theme 2: Conservation of Mass

Part A

Theme #2: During any of the five chemical reaction types, mass is conserved and all atoms involved can be accounted for.


Part B

Essential Questions that relate to this theme:




  1. What is the Law of the Conservation of Mass and how does it apply to chemical reactions?

  2. How does the above Law influence the behavior of elements at the atomic level during chemical reactions?

  3. Why is it necessary to “balance” chemical equations?

  4. In what ways may chemical reactions be represented?

  5. How are the five reaction types distinguished from one another?


Part C

SLO’s related to this theme:


Students will…

S2-2-05 Investigate the Law of Conservation of Mass and recognize that mass is conserved in chemical reactions.

S2-2-06 Balance Chemical Equations. Include: translation of word equations to balanced chemical reactions, and balanced chemical equations to word equations.

S2-2-07 Investigate and classify chemical reactions as synthesis, decomposition, single displacement, double displacement, or combustion.
Part D

Pre-instructional Views Regarding Theme 2:


Common misconceptions of students may be directly related to the outcomes involving theme number two or they be linked to concepts that theme two builds on (i.e. the nature of matter, phase changes etc.) Some of the common misconceptions can be outlined as follows:


  • If students perceive gases to be “weightless” then learners will be less likely to conserve mass in reactions that produce a gas or have gases as reactants. This may be linked to students’ false perceptions that conclude gases to be free of mass since they generally are thought to be free floating in air.




  • Similarly, when compounds or components of compounds are made to disappear during reactions, it is common for students to think that the matter that has disappeared no longer has mass.




  • The concept of “mass” may be influenced more by the outward physical appearance of a substance than its properties at the atomic level. For example, students may think that a bulky piece of material has more mass because it is massive.




  • Students may conclude that materials gain or lose (weight) mass during phase changes. If a substance like water changes from liquid to gas state, students could believe that water vapour has less mass than liquid water.




  • Problems in understanding may result simply from vocabulary problems and the way that certain terms are introduced or used interchangeably. Attention should be given to the usage of the following terms.
    • “Properties” is a term used to compare characteristics of new and old substances during reactions, but students are more accustomed to the use of this word in the context of “pieces of lands”.


    • Mass

    • Chemical change

    • “pure” substances

    • mixtures




  • Students may commonly equate the phrase “chemical change” to refer to changes in physical state. Most students at this level are more likely to encounter physical changes of state.




  • When it comes to accounting for individual atoms during chemical changes, students may think that elements simply “disappear.” An example of this is the reaction (combustion) that involves gasoline while driving. Students may view these fuels and their components as simply “vanishing”.




  • When chemical reactions result in the formation of certain compounds that were not present as reactants, students may think of them as somehow being present “within” the starting materials. For example, if water is a product it is possible that it could have been “in” the acid and/or base during neutralization reactions.




  • When new products are formed students may think that the resulting products are the result of a transformation and not the rearrangement of atoms into new compounds.




  • Students may not perceive chemical reactions as being reversible since they are more dramatic at the macroscopic level.




  • Students may perceive elements or substances as being necessary for a reaction to occur (for example, oxygen in a combustion reaction) but not directly taking part in the reaction.



  • Failure to relate substances as being made up of tiny pieces called atoms. These atoms may be seen as having the same properties individually as they do when combined. For example, students may believe Aluminum or Copper atoms to be malleable since these two substances are malleable in a macroscopic sense.





  • Students may conclude that atoms, due to their extremely small size, have negligible mass.


Part E

The diagnostic tool (What Happens When Materials React?) that has been created specifically for the purpose of assessing student’s prior knowledge of this subject follows this section.



Part F

Some teacher considerations about this theme:


1. Teachers need to make the abstract concepts as concrete as possible.
The concepts related to the conservation of mass are very abstract ideas. Not all students may be able to make connections between the macroscopic changes that are taking place right before their eyes (i.e. gas formation, color changes etc.) and the way that these changes relate to the changes at the microscopic (i.e. atomic) level. In order to accommodate the abstract nature of theme 2 objectives, teachers should try to incorporate teaching techniques that are visual and provide students with activities that mirror the changes going on between atoms at the microscopic levels.
2. The role of first hand experiences.
The specific learning outcomes related to theme 2 call for students to take part in science activity. They may not need to be lab specialists, but it is vital to include investigation as the core of Theme 2 teaching methodology. The curriculum outcomes specifically say that students will “investigate” the Law of Conservation of mass and that they will follow this study by “investigating” the five types of chemical reactions. Without providing first hand experiences to students in the lab, the teacher is not being true to the intent behind this part of the unit.
3. The trouble with balancing.

Teachers may want to consider introducing word and chemical equations early on in the unit in order to prepare students for the introduction of balancing later on. Teachers may wish to consider teaching students to balance equations throughout the course of the unit and continue to give them practice on balancing equations even after formal instruction about surrounding the conservation of mass has ended. Providing ample practice, visual examples and a variety of instructional techniques will help to make balancing less of a chore for students. Teachers should also be careful to help students continue to keep the concept of conservation and the ability to balance connected to each other.


Assessing Students’ Pre-instructional Views about the Law of Conservation of Mass, Chemical Changes, and Accounting for Atoms at the Particle Level.

Introduction and Rationale

The following diagnostic tool was designed to aid teachers in their approach to the Chemistry in Action cluster from the Manitoba S2 Science Curriculum. The reader is asked to refer to the misconceptions outlined in Part A of this report as background for the administration of this diagnosis tool.


In using this tool one should also keep in mind that the following diagnostic tool is only one way to measure students’ concepts as they relate to theme two of this report specifically:
During any of the five chemical reaction types, mass is conserved and, theoretically, all atoms involved can be accounted for.
The open response questionnaire format was chosen because it gives a more accurate idea of exactly what, if anything, students believe is happening during chemical reactions. The collaborative approach with a part is used so that the completion of the questionnaire can also serve as an activation activity.

Procedure

The teacher should ask the students to find partners. Each member of the group is responsible to answer questions 1-8 individually with the teacher assisting by reading out the questions one at a time. After they have completed the questions individually students take turns offering their answers to their partner. Space is given so that students can record their partner’s responses.

After sharing answers, the students decide together on an appropriate answer that may combine their ideas together or are one of their original answers. The teacher can assess student learning by evaluating the responses of students and how well they match the learning outcomes. These responses can help form the basis for future instruction and a springboard for teaching strategy.

The teacher may opt to use the same tool after the completion of the unit as an indicator of change in student perceptions regarding the conservation of mass law, reaction types and the foundational concepts that these concepts are built upon.

What Happens When Materials React?


Instructions:
1. On your own, read each of the following 8 statements and answer the question in point form on the space provided.
2. After completing each question, take turns sharing your answers to each question with a partner. Record your partner’s answers in the space provided.
3. Turn in your papers after you and your partner have each shared all your answers and recorded what you both agree best answers the question in the “our new answer” section.

Question 1: What happens to gasoline when it is burned as fuel in automobiles?
My answer:

My partner’s answer:

Our new answer:

Question 2. What is gas made of?
My answer:

My partner’s answer:

Our new answer:

Question 3. When water is boiled does the water vapour have more or less mass than the liquid water?
My answer:

My partner’s answer:

Our new answer:

Question 4. Scientists know that Hydrogen gas is invisible. Does hydrogen have any mass?
My answer:

My partner’s answer:

Our new answer:


Question 5. When Iron and Oxygen are made to react, the result is a compound called Iron Oxide. Since oxygen is a gas, will the Iron Oxide weight more (have more mass than) the Iron? Explain your answer.
My answer:

My partner’s answer:

Our new answer:

Question 6. When elements react to form “new” compounds, where do the “new” compounds come from?

My answer:

My partner’s answer:

Our new answer:

Question 7. What has more mass: a kilogram of Iron, a kilogram of water or a kilogram of nitrogen gas? Explain your answer.
My answer:

My partner’s answer:

Our new answer:
Question 8. Describe the difference between a chemical and a physical change. Give an example of each.
My answer:

My partner’s answer:

Our new answer:

Theme 3: Acids and Bases



Part A

Theme 3: Acids and bases are chemicals we are in contact with and use everyday, have distinct and different properties and react differently with other compounds.


Part B

Essential Questions about the acids and bases theme:

1. What are the differences between acids and bases?


  1. How can we recognize acids and bases in our everyday products?

  2. What happens when acids and bases are mixed together?


Part C

There are three SLO’s which govern this theme:


Students will…
S2-2-08 Experiment to classify acids and bases using their characteristic properties.
S2-2-09 Discuss the occurrence of acids and bases in biological systems, industrial processes, and domestic applications.
S2-2-10 Explain how acids and bases react together to form a salt and water in the process of neutralization.

Part D

There are several misconceptions that students have about acids and bases before, during and even after they’ve studied them in class. Coming into the unit, it’s likely that most students will be familiar, in passing, with acids, but not necessarily with bases. The Acids and Bases theme in the Chemistry in Action Unit strives to shed light on some definitions of acids and bases, their properties and what makes them different.

Some of the common misconceptions students might have about acids and bases:
All acids eat material away.

When students see an acid reacting with another substance, they incorrectly assume that the acid is eating the other compound away. This is mainly because the piece of material disappears. What they don’t realize is that the acid is actually reacting with the substance to form new products (a gas, an aqueous solution, etc).


All acids will burn you.

While it is true that there are acids that will harm your skin and should be handled very carefully, students do not realize that there are other acids out there that are safe to use without protection (e.g. vinegar, citric acid). Strong acids and some acids in high concentrations can be dangerous or hazardous to your health, but this fact is not true for all kinds of acids.


There is only one test for an acid: see if it eats something away.

There are many tests that can be conducted to see if an acid is present – the most common being a pH test, where the presence and strength of an acid can be determined.
Strong acids can “eat away” faster than weak acids.

Students think of strength in terms of stronger, faster, higher rather than of power and the application of that power on another object. So just as a strong man can lift more weight than a weak man can, they assume a stronger acid will consume more in a shorter amount of time than a weak acid will.


Acids reacting with metals is not a property of an acid, it’s just as test for an acid.

This misconception deals more with students inability to define the term “property” as it is used in Science. Students perceive acids reacting with metals as just another example of an acid “eating something away”, and don’t realize that it is a characteristic that is unique to an acid.

There is no difference between “acid strength” and “acid concentration.”

Students believe that the more acid you have, the stronger it must be. This is most likely because they have limited experience with using the pH scale as a measure of acid strength independent of how much acid is present in solution. The term concentration might also confuse students, as it is unlikely a term they have used in this context before.

Acids are chemicals with ‘H’ atoms in their formula, and bases are chemicals with ‘OH’ in their formula.

Once students finally begin to examine acids and bases in more depth, they will quickly pick up on the pattern in the chemical formulas of most common acids and bases as they are presented in class, and will try and to relate it to any new Chemistry concepts they are introduced to later on in their education. (Most especially, if they go on to study Organic Chemistry.)

Bases are what make up acids.

This misconception most likely arises due to students’ lack of experience with bases prior to their Science education. They see the terms acids and bases together and probably assume they are more closely related than they actually, in that bases are the “base” from which an acid is formed, or that an acid is the product of a base reacting with another chemical.


When acids and bases are mixed together, the result is always neutral.

If students have been introduced to acids and bases (as a unit) before – perhaps in an informal environment – they were probably given the glib explanation “acids and bases are opposites”. Thus they believe that an acid and a bases together in the same vessel will automatically cancel each other out.


Acids are stronger than bases.

Acid typically show their reactivity in more dramatic, visual ways than bases do, and some students will automatically equate this observation with chemical strength.

Acids have a higher pH than bases.

As they begin to learn more about acids and bases, it is not uncommon for some students to assume that acids have a higher pH because their hydronium ion concentration is higher in acids than in bases. They should be reminded that pH has a reciprocal relationship with concentration.


Part E

Diagnostic Tool for Testing Students’ Misconceptions About Acids and Bases.

The following activity specifically tests for the misconceptions listed above and should be implemented at the beginning of the theme in order to better plan preceding lessons to try and mend some of the false assumptions. This tool can also be implemented at the end of the theme to test how successful the lessons were as well as see where the work still needs to be done.


True or False Quiz

*Note: This activity is not for marks, and serves only as formative assessment for the teacher.


Directions: After each statement, indicate whether you think it is True (T) or False (F). Be truthful and answer to the best of your knowledge. Good luck!


  1. All acids will “eat away” at many materials or substances.

  2. All acids should be considered dangerous because they will burn your skin.

  3. There is only one test for an acid: to see if it “eats” something away.

  4. Strong acids “eat away” faster than weak acids.

  5. Acids are made using bases.

  6. Acids typically taste sour, while bases typically taste bitter.

  7. All chemicals with ‘H’ atoms in their formula are acids, and all chemicals with ‘OH’ in their formula are bases.

  8. Acids are stronger than bases.

  9. The strength of acids and bases can be recorded using the pH scale.

  10. Acids have a lower pH than bases.

  11. The concentration of an acid or a base tells you how strong that acid or base is.

  12. Acids and bases always cancel each other out.

Part F

Considerations when teaching this theme:




  • Stay away from the advanced definitions of acids and bases in Senior 2, and instead encourage the development of student-derived definitions of acids and bases based on their properties.




  • Allow for as much “hands on” student discovery as possible. It’s the best way to get students to investigate the properties of acids and bases and promotes reform in their perceptions about acids and bases (i.e. helps to fix their misconceptions).



  • When introducing the pH scale, keep it simple. Use the pH scale as a tool used to record acid and bases strength. Try to stay away from relating pH to H+ and OH- ion concentrations this early in their study of acids and bases, as it might just confuse the students.





  • Try to keep the examples of acids and bases in biological systems, industrial processes and domestic applications as simple as possible. That is, limit the discussion to the occurrence and role of acids and bases in different settings.




  • Always emphasize safety in all investigative settings.

Theme 4: Chemistry and STE
Part A

Theme 4: The effects of chemistry on society, technology and the environment.


Part B

There is one Essential Question in this theme:


What role does chemistry actually have in our everyday life, often stated as “Why do we have to learn this stuff anyway? I’ll never need it.”
[On the contrary young __________. You see chemistry does play a role in biological, industrial, and domestic settings in your life and mine, and it is more prevalent then you think.]
Part C

The two SLOs associated with this theme are:


Students will…
S2-2-11 Describe the formation and environmental impact of various forms of air pollution.
S2-2-12 Investigate technologies that are used to reduce emission of potential air pollutants.

Part D

There are a few common misconceptions that should be addressed within this theme:




  1. How often are we going to be dealing with chemicals, we do not see them in regular everyday life. (Everything is chemical by nature.)




  1. Chemicals are harmful. (That depends on what you are looking at, is a tree harmful when you are looking at it.)


  1. Everything that is natural is better for us. (Once again it depends, is poison ivy good for us if we eat it, or if we rub it all over our bodies.)



Part E

As with all the other themes in this unit, student misconceptions should be addressed at the beginning of this theme, to help with the planning and implementation of lessons.


Ten Questions

1. Give an example of a material that contains chemicals, and a material that does not?


2. Products that are acidic and basic by nature surround us on a daily basis. Why are acidic products dangerous for us?
3. a) Ingestion or consumption of chemicals will make us sick and possibly kill us. True or false. Justify your answer.
b) In particular note the following:

Dihydrogen monoxide:



  • is known as hydroxyl acid, and is the major component of acid rain.

  • contributes to the "greenhouse effect."

  • may cause severe burns.

  • contributes to the erosion of our natural landscape.

  • accelerates corrosion and rusting of many metals.

  • may cause electrical failures and decreased effectiveness of automobile brakes.

  • has been found in excised tumors of terminal cancer patients.

3. b) continued.

Would you agree in supporting a ban on a substance that causes so much damage to us and environment?

4. Breathing in clean air will allow us to live longer, healthier lives. It is when chemicals exist in the air that it becomes dirty, and we can begin to get sick from breathing the air. True or false. Justify your answer.

5. Natural medicines are better for us because they contain no chemicals. True or false. Justify your answer.


6. Because of the increased use of chemicals in society our quality of life has gone down, and our life spans are getting shorter. True or false. Justify your answer.

7. McDonald's hamburgers are made with 100% pure beef. This means that there are no additives or chemicals in the beef. True or false. Justify your answer.

8. Explain why it is better to drink bottled water and not tap water.
9. Americans predominantly use ketchup when they eat French fries. This is in part due to the finding that in mixing French fries with acetic acid during preparation for consumption many people were becoming sick. Express your thoughts on whether we as Canadians should ban this method of preparation for French fries.
10. It is because the air within a fridge is purified that food does not spoil. True or false. Justify your answer.
Part F

Considerations for this theme:


Obviously the first consideration will be safety. The opportunity to discuss WHMIS with students is excellent for their learning and for their overall safety and awareness that they will be able to take with them when they leave the classroom. Teachers must consider the particular community that they are living in. If for instance you are in a community where a chemical company is a major employer, you will need to be sensitive in your approach to negative effects of chemistry in industry. It is also good practice regardless because it ensures that you teach in a balanced manner.

Resources


These are a few of the resources we consulted while thinking about and putting together this unit.
Curriculum Documents

Manitoba Education and Youth

Science 2: A Foundation for Implementation

Revised, 2003


Websites

Queen’s University, Faculty of Education

Chemistry Misconceptions

http://edu.queensu.ca/~science/main/concept/chem/c07/C07CDTL1.htm
Arizona State University

“Students Preconceptions and Misconceptions in Chemistry.” http://www.daisley.net/hellevator/misconceptions/misconcepions.pdf

2001

Kevin Lehmann, Dept of Chemistry, Princeton University, NJ.

“Bad Chemistry.”


http://www.princton.edu~lehmann/BadChemistry.html

1996
Joe O’Connell

“Salt Myths and Urban Legends.”

http://www.scbbqa.com/myths/Salt.html

2001
Oklahoma State

“Common Student Misconceptions.”

http://www.okstate.edu/jgelder/acidPage25.html#Com
Eric Werna

“Everything you’ve always wanted to know about what your students think they know but were afraid to ask.”



http://www.mrs.org/microworld/werwa.pdf

2000
Science Hobbist

“Children’s Misconceptions about Science”

http://www.amasci.com/miscon/opphys.html

1998
Vanessa Barker, Royal Society of Chemistry in London, England.

“Chemistry Misconceptions”

http://www.chemsoc.org/pdf/LearnNet/rsc/miscon.pdf
Websites (cont’d)

Winnipeg School Division

Teaching Science

http://www.wsd1.org/PC_Science/for_teachers.htm
Ron Bannister, K-S4 Science Consultant, Wpg. SD

http://wsd1.org/PC_Science/
Coalition to Ban Dihydrogen Monoxide

http://www.netreach.net/~rjones/no_dhmo.html

Books/Textbooks

Driver, et al.

Making Sense of Secondary Science

Routledge, New York

2000


Eric Grace, et al.

Science, Technology, Society, Environment.

McGraw-Hill Ryerson Limited, Toronto

2001

Ted Gibb, et al.

Science 10: Concepts and Connections.

Nelson Thomson Learning, Toronto

2002




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