Nature of Science Statements

5.1 Measuring energy changes

Fundamental principle—conservation of energy is a fundamental principle of science. (2.6) Making careful observations—measurable energy transfers between systems and surroundings. (3.1)

8.4 Strong and weak acids and bases

Improved instrumentation—the use of advanced analytical techniques has allowed the relative strength of different acids and bases to be quantified. (1.8) Looking for trends and discrepancies—patterns and anomalies in relative strengths of acids and bases can be explained at the molecular level. (3.1) The outcomes of experiments or models may be used as further evidence for a claim—data for a particular type of reaction supports the idea that weak acids exist in equilibrium. (1.9)

11.3 Spectrochemical techniques

Improvements in instrumentation—mass spectrometry, proton nuclear magnetic resonance and infrared spectroscopy have made identification and structural determination of compounds routine. (1.8) Models are developed to explain certain phenomena that may not be observable—for example, spectra are based on the bond vibration model. (1.10)

21.1 Stereoscopic identification

Improvements in modern instrumentation—advances in spectroscopic techniques (IR, 1H NMR and MS) have resulted in detailed knowledge of the structure of compounds. (1.8)

18.3 pH curves

Increased power of instrumentation and advances in available techniques—development in pH meter technology has allowed for more reliable and ready measurement of pH. (3.7)

D.8 Nuclear medicine

Risks and benefits—it is important to try and balance the risk of exposure to radiation with the benefit of the technique being considered. (4.8)

D.1 Pharmaceutical drugs and drug action

Risks and benefits—medicines and drugs go through a variety of tests to determine their effectiveness and safety before they are made commercially available. Pharmaceutical products are classified for their use and abuse potential. (4.8)

8.5 Acid deposition

Risks and problems—oxides of metals and non-metals can be characterized by their acid-base properties. Acid deposition is a topic that can be discussed from different perspectives. Chemistry allows us to understand and to reduce the environmental impact of human activities. (4.8)

D.5 Antiviral medications

Scientific collaboration—recent research in the scientific community has improved our understanding of how viruses invade our systems. (4.1)

20.2 Synthetic routes

Scientific method—in synthetic design, the thinking process of the organic chemist is one which invokes retro-synthesis and the ability to think in a reverse-like manner. (1.3)

4.3 Covalent Structures

Scientists use models as representations of the real world—the development of the model of molecular shape (VSEPR) to explain observable properties. (1.10)

10.1 Fundamentals of organic chemistry

Serendipity and scientific discoveries—PTFE and superglue. (1.4) Ethical implications—drugs, additives and pesticides can have harmful effects on both people and the environment. (4.5)

D.2 Aspirin and penicillin

Serendipity and scientific discovery—the discovery of penicillin by Sir Alexander Fleming. (1.4) Making observations and replication of data—many drugs need to be isolated, identified and modified from natural sources. For example, salicylic acid from bark of willow tree for relief of pain and fever. (1.8)

2.2 Electron configuration

Developments in scientific research follow improvements in apparatus—the use of electricity and magnetism in Thomson's cathode rays.(1.8) Theories being superseded—quantum mechanics is among the most current models of the atom. (1.9) Use theories to explain natural phenomena—line spectra explained by the Bohr model of the atom. (2.2)

D.9 drug detection and analysis

Advances in instrumentation—advances in technology (IR, MS and NMR) have assisted in drug detection, isolation and purification. (3.7)

D.7 taxol - chiral auxilary

Advances in technology—many of these natural substances can now be produced in laboratories in high enough quantities to satisfy the demand. (3.7) Risks and problems—the demand for certain drugs has exceeded the supply of natural substances needed to synthesize these drugs. (4.8)

1.2 The mole concept

Concepts—the concept of the mole developed from the related concept of "equivalent weight" in the early 19th century. (2.3)

D.4 pH regulation of the stomach

Collecting data through sampling and trialling—one of the symptoms of dyspepsia is the overproduction of stomach acid. Medical treatment of this condition often includes the prescription of antacids to instantly neutralize the acid, or H2-receptor antagonists or proton pump inhibitors which prevent the production of stomach acid. (2.8)

D.3 Opiates

Data and its subsequent relationships—opium and its many derivatives have been used as a painkiller in a variety of forms for thousands of years. One of these derivatives is diamorphine. (3.1)

19.1 Electrochemical cells

Employing quantitative reasoning—electrode potentials and the standard hydrogen electrode. (3.1) Collaboration and ethical implications—scientists have collaborated to work on electrochemical cell technologies and have to consider the environmental and ethical implications of using fuel cells and microbial fuel cells. (4.5)

17.1 Equilibrium Law

Employing quantitative reasoning—experimentally determined rate expressions for forward and backward reactions can be deduced directly from the stoichiometric equations and allow Le Châtelier's principle to be applied. (1.8, 1.9)

D.6 Environmental impact of medicines

Ethical implications and risks and problems—the scientific community must consider both the side effects of medications on the patient and the side effects of the development, production and use of medications on the environment (ie disposal of nuclear waste, solvents and antibiotic waste). ( 4.8)

9.2 Electrochemical cells

Ethical implications of research—the desire to produce energy can be driven by social needs or profit. (4.5)

2.1 The nuclear atom

Evidence and improvements in instrumentation—alpha particles were used in the development of the nuclear model of the atom that was first proposed by Rutherford. (1.8) Paradigm shifts—the subatomic particle theory of matter represents a paradigm shift in science that occurred in the late 1800s. (2.3)

12.1 Electrons in atoms

Experimental evidence to support theories—emission spectra provide evidence for the existence of energy levels. (1.8)

8.1 Theories of Acids and Bases

Falsification of theories—HCN altering the theory that oxygen was the element which gave a compound its acidic properties allowed for other acid-base theories to develop. (2.5) Theories being superseded—one early theory of acidity derived from the sensation of a sour taste, but this had been proven false. (1.9) Public understanding of science—outside of the arena of chemistry, decisions are sometimes referred to as "acid test" or "litmus test". (5.5)

9.1 Oxidation and Reduction

How evidence is used—changes in the definition of oxidation and reduction from one involving specific elements (oxygen and hydrogen), to one involving electron transfer, to one invoking oxidation numbers is a good example of the way that scientists broaden similarities to general principles. (1.9)

5.2 Hess's Law

Hypotheses—based on the conservation of energy and atomic theory, scientists can test the hypothesis that if the same products are formed from the same initial reactants then the energy change should be the same regardless of the number of steps. (2.4)

3.2 Periodic Trends

Looking for patterns—the position of an element in the periodic table allows scientists to make accurate predictions of its physical and chemical properties. This gives scientists the ability to synthesize new substances based on the expected reactivity of elements. (3.1)

20.1 Types of organic reactions

Looking for trends and discrepancies—by understanding different types of organic reactions and their mechanisms, it is possible to synthesize new compounds with novel properties which can then be used in several applications. Organic reaction types fall into a number of different categories. (3.1) Collaboration and ethical implications—scientists have collaborated to work on investigating the synthesis of new pathways and have considered the ethical and environmental implications of adopting green chemistry. (4.1, 4.5)

4.2 Covalent Bonding

Looking for trends and discrepancies—compounds containing non-metals have different properties than compounds that contain non-metals and metals. (2.5) Use theories to explain natural phenomena—Lewis introduced a class of compounds which share electrons. Pauling used the idea of electronegativity to explain unequal sharing of electrons. (2.2)

13.1 First row d-block elements

Looking for trends and discrepancies—transition elements follow certain patterns of behaviour. The elements Zn, Cr and Cu do not follow these patterns and are therefore considered anomalous in the first-row d-block. (3.1)

1.3 Masses and Volumes

Making careful observations and obtaining evidence for scientific theories—Avogadro's initial hypothesis. (1.8)

1.1 Particle nature of matter

Making quantitative measurements with replicates to ensure reliability—definite and multiple proportions. (3.1)

15.1 Energy cycles

Making quantitative measurements with replicates to ensure reliability—energy cycles allow for the calculation of values that cannot be determined directly. (3.2)

11.1 Uncertainties in measurements

Making quantitative measurements with replicates to ensure reliability—precision, accuracy, systematic, and random errors must be interpreted through replication. (3.2, 3.4)

5.3 Bond enthalpies

Models and theories—measured energy changes can be explained based on the model of bonds broken and bonds formed. Since these explanations are based on a model, agreement with empirical data depends on the sophistication of the model and data obtained can be used to modify theories where appropriate. (2.2)

13.2 coloured Complexes

Models and theories—the colour of transition metal complexes can be explained through the use of models and theories based on how electrons are distributed in d-orbitals. (1.10) Transdisciplinary—colour linked to symmetry can be explored in the sciences, architecture, and the arts. (4.1)

4.4 Intermolecular forces

Obtain evidence for scientific theories by making and testing predictions based on them—London (dispersion) forces and hydrogen bonding can be used to explain special interactions. For example, molecular covalent compounds can exist in the liquid and solid states. To explain this, there must be attractive forces between their particles which are significantly greater than those that could be attributed to gravity. (2.2)

3.1 Periodic Table

Obtain evidence for scientific theories by making and testing predictions based on them—scientists organize subjects based on structure and function; the periodic table is a key example of this. Early models of the periodic table from Mendeleev, and later Moseley, allowed for the prediction of properties of elements that had not yet been discovered. (1.9)

18.2 Acid Base calcs

Obtaining evidence for scientific theories—application of the equilibrium law allows strengths of acids and bases to be determined and related to their molecular structure. (1.9)

7.1 Equilibrium

Obtaining evidence for scientific theories—isotopic labelling and its use in defining equilibrium. (1.8) Common language across different disciplines—the term dynamic equilibrium is used in other contexts, but not necessarily with the chemistry definition in mind. (5.5)

8.2 Properties of acids and bases

Obtaining evidence for theories—observable properties of acids and bases have led to the modification of acid-base theories. (1.9)

8.3 The pH scale

Occam's razor—the pH scale is an attempt to scale the relative acidity over a wide range of H+ concentrations into a very simple number. (2.7)

14.1 Further aspects of covalent bonding

Principle of Occam's razor—bonding theories have been modified over time. Newer theories need to remain as simple as possible while maximizing explanatory power, for example the idea of formal charge. (2.7)

16.1 rate expressions and mechanisms

Principle of Occam's razor—newer theories need to remain as simple as possible while maximizing explanatory power. The low probability of three molecule collisions means stepwise reaction mechanisms are more likely. (2.7)

11.2 Graphical techniques

The idea of correlation—can be tested in experiments whose results can be displayed graphically. (2.8)

14.2 Hybridisation

The need to regard theories as uncertain—hybridization in valence bond theory can help explain molecular geometries, but is limited. Quantum mechanics involves several theories explaining the same phenomena, depending on specific requirements. (2.2)

6.1 Collision theory and rates of reactions

The principle of Occam's razor is used as a guide to developing a theory—although we cannot directly see reactions taking place at the molecular level, we can theorize based on the current atomic models. Collision theory is a good example of this principle. (2.7)

15.2 Enthalpy and spontaneity

Theories can be superseded—the idea of entropy has evolved through the years as a result of developments in statistics and probability. (2.2)

16.2 Activation Energy

Theories can be supported or falsified and replaced by new theories—changing the temperature of a reaction has a much greater effect on the rate of reaction than can be explained by its effect on collision rates. This resulted in the development of the Arrhenius equation which proposes a quantitative model to explain the effect of temperature change on reaction rate. (2.5)

18.1 Lewis Acids and Bases

Theories can be supported, falsified or replaced by new theories—acid-base theories can be extended to a wider field of applications by considering lone pairs of electrons. Lewis theory doesn't falsify Brønsted-Lowry but extends it. (2.5)

20.3 Steroeisomers

Transdisciplinary—the three-dimensional shape of an organic molecule is the foundation pillar of its structure and often its properties. Much of the human body is chiral. (4.1)

10.2 Fundamentals of group chemistry

Use of data—much of the progress that has been made to date in the developments and applications of scientific research can be mapped back to key organic chemical reactions involving functional group interconversions. (3.1)

4.1 Ionic bonding and structure

Use theories to explain natural phenomena—molten ionic compounds conduct electricity but solid ionic compounds do not. The solubility and melting points of ionic compounds can be used to explain observations. (2.2)

4.5 Metallic bonding

Use theories to explain natural phenomena—the properties of metals are different from covalent and ionic substances and this is due to the formation of non-directional bonds with a "sea" of delocalized electrons. (2.2)