Bonding Evaluation Information Page
Broad definition of what we are considering
We are considering the formation of bonds from either free atoms or from elements. This would include the formation of ionic or molecular covalent compounds from elements or explaining why bonds form. This boundary is set to limit the video sampling. Other kinds of electrostatic attractions (e.g., IMFs) will be investigated as separate topics.
Johnstone's Triangle Elements
Gas Law Specific Criteria
| Element | Examples |
|---|---|
| Macroscopic | Visible phenomena - difference in chemical properties for ionic and covalent compounds, physical properties (mp, bp, density, etc.). Must be a specific example - e.g., NaCl has a mp of 801 ℃ as compared with sugar with a mp of 186 ℃, can’t just generally say “ionic compounds generally have high melting points” |
| Symbolic |
A chemical equation that shows a chemical reaction that involves changes in bonding,
but some videos may show a graph of change of concentrations of reactants and
products as the reaction proceeds and how reactants get converted into products. This
may also include representations that involve the elemental abbreviations (e.g. C, H)
changing bonds (going from C-C to C=C). Lewis structure representations that show ion formation and attraction between ions (ionic bonding) or electron sharing (covalent bonding). PE well graph. |
| Particulate | Particle representations of ionic and covalent compounds (ionic lattice vs. molecules). Showing interactions between two particles (i.e. relating that to Potential Energy) |
| Connection between levels |
Videos should make explicit connections between two or more levels for this to be
coded as present. For example, they could show a particle level diagram for an ionic
lattice and connect that to physical properties of ionic compounds. |
Core Ideas
| Core Ideas Elements | ||
|---|---|---|
| Electrostatic Bonding & Interactions | Energy | Atomic/Molecular Structure & Properties |
|
Attractive and repulsive electrostatic forces govern bonding (covalent and ionic) interactions between atoms.
The attraction arises between oppositely charged ions (ionic) or protons of one atom and the valence electrons of the other atom (covalent).
Notes: If the video talks about both ionic and covalent bonds, it must address electrostatics for both types of bonding to get coded as having this CI. The strength of the attractive forces depends on the magnitude of the charges involved and the distances between them (Coulomb’s law). This last part is NOT required for the video to be coded with this CI. |
Key idea: The driving force for bond formation is forming compounds that are
lower in energy (more stable). In the formation of a chemical bond there is a
decrease in chemical potential energy. Conversely, energy is required to break bonds.
This may often be represented with a potential energy well diagram.
Note: The formation of bonds results in a release of kinetic energy to the surroundings. This is NOT required for the video to be coded with this CI. |
The macroscopic physical and chemical properties of a substance are determined by
the nature and extent of interactions between the particles that make up that substance.
Note: Must explain how bonding results in these different properties. |
Casual Mechanistic Reasoning
What drives the formation of bonds between atoms?
How:
- Both ionic and covalent bonds form as a result of electrostatic attractions between oppositely particles.
- Ionic bonding: electrostatic attractions between oppositely charged ions (ions formed from the gain or loss of electrons). Important note: ionic bonding is NOT a transfer of electrons.
- Covalent bonding: electrostatic attraction between nucleus of one atom and the valence electrons of another atom results in “sharing” of electrons between the two atoms. More accurate analogy may be a “tug of war” between two atoms for the valence electrons.
Why:
- Energy changes are associated with (and potentially drive) chemical reactions. Spontaneous reactions will result in a net decrease in energy.
- For covalent bonds, this means that the new bonds formed by sharing result in a lower energy state than having two non-interacting atoms.
- For ionic bonds, the electrostatic interactions between the newly formed ions are stronger than the original interactions between the atoms within the elemental compound. OR The formation of ionic bonds releases a great deal of energy (strong attractions) which compensates for the energy required to form ions.
- For molecular compounds, the formation of new bonds are stronger than the bonds present in the elemental form.
Must have both parts!
What determines the Relative Strengths of Iconic Bonds?
How:
- Ionic bonds are formed by the electrostatic attractions between oppositely charged ions (ions
formed from the gain or loss of electrons). Important note: ionic bonding is NOT a transfer of
electrons. - The strength of the ionic bond depends on the size and charge on the ions
Why:
- Coulomb’s Law (F∝Q1Q2/D2) relates the strength of attraction between oppositely charged particles to size of charges and distance between them
- Higher charges and smaller distances between charges result in stronger attractions which means stronger bonds
Must have both parts!
What is the relationship between different types of bonds and physical properties? (molecular vs. covalent networks, or ionic)
How:
- Different kinds of compounds can be classified or identified based on physical properties (can be implicit).
- Physical properties depend on the strength of attractive forces between individual particles in the substance OR the types of particles that make up the substance.
Why:
- Network solids require the breaking of covalent bonds, but in the case of molecular compounds, you are only breaking IMFs which are notably weaker and can be disrupted at much lower temperatures. Thus mp/bp of network compounds are generally very high whereas molecular
compounds have lower mp and bps. - Mp/bp of ionic compounds are generally high due to strong electrostatic attractions between oppositely charged ions; conductivity of liquids and solutions because ions are free to move; brittle because when you bend like charged ions get close together and will repel; solubility of many in water as water is polar and positive end of water can surround negative ions etc.
- Does not need to explain all of these but generally needs to explain some well.
Must have both parts!
Scientific Practices
We expect that the most common practices will be:
- constructing explanations and engaging in argumentation from evidence (e.g. answers one of the causal mechanistic reasoning questions)
- Developing and Using Models (e.g. using a potential well diagram or explaining molecular properties based on drawing of particulate level interactions)
- Analyzing and Interpreting Data (e.g. looking at specific data about physical properties)
- Using Mathematical and Computational Thinking (e.g. using Coulomb’s Law to explain relative strengths of ionic interactions)
| Most Frequent Science Practice |
|---|
SP 2: Developing and Using Models
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SP 4: Analyzing and Interpreting Data
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SP 5: Using Mathematics and Computational Thinking
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SP 6: Constructing Explanations and Engaging in Argument from Evidence
|
Multimedia Principles
Multimedia learning as knowledge construction: The goal of multimedia presentations is not only to present information but also to provide guidance for how to process the presented information – that is, for determining what to pay attention to, how to mentally organize it, and how to relate it to prior knowledge. We will categorize the videos along each of the following criteria (High and Low should be mutually exclusive.)
| High | Low |
|---|---|
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Example High Quality Videos
Examplar Videos
These are examples of videos that were found to provide good illustrations of some or many of the framework components for this concept. Develop a deep understanding of chemistry concepts requires multiple experiences with the material and these videos may provide one such experience.
|
Exemplar Video 1 |
Exemplar Video 2 |
Exemplar Video 3 |
|
Comments Covalent bonding is the sharing of electrons resulting from attraction of nucleus of one atom for valence electrons of another. Covers attractive and repulsive forces involved and PE curve. |
Comments This video focuses on how bonding impacts the physical properties of substances. |
Comments Video focuses on ionic bonding |
|
Strengths Up to 3:40 the video provides a focused and causal mechanistic level explanation of covalent bonding. The video clearly connects particle and symbolic representations and uses Science Practice of Developing and Using Models as it uses an animated potential energy diagram to show how the potential energy of the system changes as two hydrogen atoms approach or move away from each other. The decrease in energy when atoms come together is connected to energy release during bond formation and the requirement of energy to break bonds supporting a causal mechanistic explanation of covalent bonding. |
Strengths This video focuses on the concept of how bonding affects physical properties of substances, comparing the properties of simple molecular substances to giant covalent structures (covalent network substances). It clearly connects the macroscopic physical property of boiling points and particle pictures for bromine (Br2) and diamond. Stressing that for Br2 weaker IMFs are overcome but for diamond to boil you must break much stronger covalent bonds. This clearly connects the structure to the property (Core Idea) and provides a scientific explanation (Science Practice) at the particle level which meets the expectations for CMR. It is very focused and provides multiple features to help learners organize content. |
Strengths Makes good connections between symbolic/mathematical and particulate representations in explanation of why different compounds have different lattice energies. This is a causal mechanistic level explanation that addresses the core idea of Bonding and Interactions. The video contains a lot of the multimedia features that support learning. Good overview of content at the beginning, very focused and short video, has clear titles at the top of the screen to highlight what is being talked about, minimal text with good images to help support understanding. Closed captioning is accurate with punctuation. |
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Weaknesses After 3:40 the video moves into sigma bonds and pi bonds and then presents a table of bond energies. This material is not as focused and does not add meaningfully to the explanation from the first part of the video. |
Weaknesses The content is stepped in; however, sometimes the screens get cluttered with a lot of information which might be distracting to some learners. The video is autocaptioned meaning there is no capitalization or punctuation. |
Weaknesses The instructor is present on screen throughout the video which can be distracting to some. Though the video did explain differences in lattice energy, it could have connected this to the macroscopic property of melting points, which is more tangible to most learners. |
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