Asia-Pacific Forum on Science Learning and Teaching, Volume 5, Issue 1, Article 3 (Apr., 2004) Daniel Kim Chwee TAN and Kim Seng CHAN An analysis of two textbooks on the topic of intermolecular forces Previous Contents Next

Results and Discussion

The results of analysis of the two textbooks based on the propositional knowledge identified by Tan and Chan (2003) are given in Table 1 and discussed in the following sections below.

Table 1. Analysis of two textbooks based on the propositional knowledge statements identified by Tan and Chan (2003) on the topic of ionisation energy

	Propositional knowledge statements	HH	R
Nature of intermolecular forces
1.	Intermolecular forces or van der Waals' forces are electrostatic attractions.	N	Y
2.	The electrostatic attraction is between simple discrete molecules.	Y	Y
3.	Intermolecular forces are very much weaker compared to conventional bonds (e.g., ionic, covalent and metallic) because the molecules involved are further apart and have weaker electrical dipoles.	N	Y1
4.	Intermolecular forces influence the physical properties (e.g., hardness and phase changes) of simple covalent compounds.	Y	Y
5.	Exothermic phase changes (e.g., condensation and solidification) involve the formation of intermolecular forces.	N	Y2
6.	Endothermic phase changes (e.g., melting and boiling) involve the overcoming of intermolecular forces.	Y	Y2
7.	Intermolecular forces account for the non-ideality in gases because they account for a greater decrease in volume with a pressure increment, i.e., the ideal gas equation, pV = nRT, is not obeyed.	Y3	Y4
8.	At high temperatures, the particles of a gas have greater kinetic energy and move faster and more randomly, thus minimizing the effect of intermolecular forces.	Y5	N
9.	At low pressures, the particles of a gas are further apart, thus minimizing the effect of intermolecular forces.	Y5	N
Polarity of a bond/molecule
10.	The type of van der Waals' forces present between molecules depend on whether the molecules involved have net dipole moments, m.	N	N
11.	Differences in electronegativity between two atoms cause the displacement of the shared electrons between them.	Y	Y6
12.	Displacement of the shared electrons between two atoms results in the formation of a polar bond.	Y	Y6
13.	A polar bond has a dipole moment, m.	N	N
14.	The vector sum of dipole moments gives the resultant net dipole moment of a molecule.	N	N
15.	The net dipole moment of a molecule depends on its structural geometry.	N	N
16.	The structural geometry of a molecule can be determined using the VSEPR theory.	N	Y7
17.	The electronegativity of an atom is related to its effective nuclear charge.	N	N
18.	The effective nuclear charge of an atom is dependent on its nuclear charge and the shielding of its nucleus by the inner core electrons.	N	Y8
19.	The effective nuclear charge of an atom affects the availability of any lone pair of electrons for hydrogen bonding.	N	N
Permanent dipole-permanent dipole interaction
20.	If the net dipole moment of a molecule is not zero, it is known as a polar molecule.	N9	N
21.	Permanent dipole-permanent dipole interactions are present between polar molecules.	Y	Y
22.	Permanent dipole-permanent dipole interactions are important in aldehyde, ketone, ether, acyl chloride, ester and alkyl halide.	Y	Y10
Hydrogen bonds
23.	Hydrogen bonding is a type of permanent dipole-permanent dipole interaction.	Y	N
24.	Hydrogen bonding is defined as the attraction of an electron deficient hydrogen atom, bonded to oxygen, fluorine or nitrogen atom of a molecule, for a lone pair of electrons on another oxygen, fluorine or nitrogen atom.	Y	Y11
25.	The availability of the lone pair(s) of electrons for hydrogen bonding follows the trend: H-N---H-N > H-O---H-O > H-F---H-F (in decreasing order from left to right).	N	N
26.	The bond polarity between a hydrogen atom covalently bonded to oxygen, fluorine or nitrogen follows the trend: H-F---H-F > H-O---H-O > H-N---H-N (in decreasing order from left to right).	N	N
27.	The strength of hydrogen bonding follows the trend: H-F---H-F > H-O---H-O > H-N---H-N (in decreasing order from left to right), since bond polarity plays a greater part in hydrogen bonding compared to the availability of lone pair(s) of electrons.	N	Y12
28.	The extensivity of hydrogen bonding depends on the number of sites available on the molecules involved.	Y	Y13
29.	More extensive hydrogen bonding in water results in it having a higher boiling point than hydrogen fluoride.	Y	N
30.	Hydrogen bonding can be intermolecular or intramolecular in nature.	N	Y
31.	Intramolecular hydrogen bonding can exist when functional groups capable of hydrogen bonding are in close proximity.	Y14	N
32.	Presence of intramolecular hydrogen bonding limit number of sites available for intermolecular hydrogen bonding, and this may result in lower boiling point or melting point.	N	N
33.	Hydrogen bonding results in dimerisation of simple carboxylic acid molecules.	Y	Y
34.	Hydrogen bonding is present in structures of proteins, carbohydrates and nucleic acid.	Y	Y
35.	Hydrogen bonding results in ice having an open structure.	Y	Y
Instantaneous dipole-induced dipole interaction
36.	If the net dipole moment of a molecule is zero, it is known as a non-polar molecule.	N	N
37.	Non-polar molecules possess instantaneous dipole-induced dipole interactions.	Y	Y
38.	Polar molecules also possess instantaneous dipole-induced dipole interactions.	Y15	N
39.	The strength of instantaneous dipole-induced dipole interactions depends on the surface area of molecules involved.	Y16	Y17
40.	The greater the surface area of contact between molecules, the more extensive would be the instantaneous dipole-induced dipole interactions between the molecules involved.	Y	Y17
41.	The strength of instantaneous dipole-induced dipole interactions depends on the number of electrons in the molecules involved.	Y	Y
42.	The greater the number of electrons a molecule has, the greater the polarisability of its electron cloud, and hence the greater its electrical dipoles.	N	Y
43.	The surface area of a molecule can be a more influential factor than the number of electrons it has.	N	N
44.	Instantaneous dipole-induced dipole interactions can be stronger than hydrogen-bonding.	N	N

Note:

1 During the discussion of H-bonding.

2 In a diagram.

3 The non-ideality of real gases was ascribed to "existence of cohesive forces between non-polar molecules". (p. 116)

4 In the chapter on "Gases"

5 It was presented as a question "Why does this real gas equation reduce to pV=nRT at low pressure and high temperature?" (p.116)

6 In the discussion of intermediate bond types.

7 In the chapter on "he Shapes of Molecules".

8 In the section on "Ionic Bond".

9 Polar was defined as "positive charge center and negative charge center do not coincide".

10 In Organic Chemistry.

11 The "attraction to the lone pair" part was not mentioned.

12 In a question to compare the boiling point of CH₃CH₂NH₂ and CH₃CH₂OH.

13 In a question at the end of the chapter.

14 In a diagram on hydrogen bonding in the coiled helical structure of proteins

15 In the example on estimating the strength of hydrogen bonds in water, "Remember, however, that molecules which are hydrogen bonded will also be attracted by van der Waals' forces." (p. 121)

16 The term "contact" was used.

17 The term "shape" was used.

 

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