Answers and suggestions for the NOC-based activities
The scientific method
Activity 1 - The scientific method:
- Try to suggest key terms such as observation, hypothesis, prediction, testing, confirm, falsify.
- Hopefully some parts of your flowchart match with those in the scientific method.
- Repeatability: Hopefully, to confirm your hypothesis you watched a number of turns (repeated outcomes) to add strength to your suggestion. Ideally you might ask students in a different class to also confirm it. Falsification: The strength of our hypothesis can be better tested by actively looking to disprove it.
- In science, there is no one to tell us whether or not our hypotheses are 100% correct or not so we can never be completely certain.
Activity 2 - Ways of knowing in the natural sciences
- Rutherford's gold foil experiment (17.50-25.00): Sense perception - Required to collect data of the marks seen on the zinc sulfide detection screen; intuition - asking the research assistant to move the detection screen to the same side as the radioactive source suggests Rutherford's may have had a feeling that they were not seeing the full picture; Reason - Rutherford used logic to suggest an explanation for his experimental results e.g. as only a very small percentage of the alpha particles were reflected, the thing they are hitting (the nucleus) must take up very little space in the material.
- Mendeleev's predictions of the missing elements: Reason - Finding evidence of atoms with a large range of number of protons indicated that there would likely be atoms with all numbers of protons (up to around 100 at that time). This would be an example of inductive reasoning; Faith - Some scientific knowledge in Mendeleev's day relied on the belief that these gaps would one day be filled.
- Kekulé's dream about the structure of benzene: Intuition - If the claim about the dream was true, it may suggest that Kekulé's prior work with chemical structure may have given him unconscious insight; Imagination - dreaming might indicate the role of imagination and divergent thinking in solving scientific problems.
- Fritz Haber's work on chemical weapons: Emotion - Haber was driven to this research via his patriotic sentiment although this gas would be later used on his fellow Jewish citizens.
- Organic nomenclature: Language - Given the immense range of organic compounds, an internationally agreed use of language to describe them is essential.
Activity 3 - The scientific method
A linear example of a scientific methodology is used below but in reality, the process is often nonlinear and may require many iterations.
Observation and inference
Activity 1 - Tricky tracks
Teacher guidance can be found in the RSC document here.
Teacher guidance can be found in the RSC document here.
Activity 2 - Mystery machine
Questions to discuss:
1. How did you identify the patterns? (lead to understanding of inductive reason as specific data → general pattern; underlying assumption that there is a pattern)
2. Was their prediction accurate?
3. How certain can they be? How could they increase their certainty? (repeating with the same and other shapes)
4. Can we ever be 100% certain? (not without an infinite amount of data)
Questions to discuss:
1. How did you identify the patterns? (lead to understanding of inductive reason as specific data → general pattern; underlying assumption that there is a pattern)
2. Was their prediction accurate?
3. How certain can they be? How could they increase their certainty? (repeating with the same and other shapes)
4. Can we ever be 100% certain? (not without an infinite amount of data)
Evidence, modelling and predictions
Activity 1 - Mystery box
- -
- Likely a lot of sense perception (holding/listening), reason and imagination. Language, intuition and memory also may play a significant part. Emotion and faith may be less important.
- Not necessarily. Depends on the use of the box. The model may be better for predicting the behaviour of the box.
- Weighing, use of magnet, float testing, x-ray.
Activity 2 - Modelling the atom
1a.
a. The earliest model of the atom is of a single, solid balls as the smallest possible units of matter. Possibly put forward by Democritus.
b. The plum pudding model describes the atom as a number of negative electrons stuck in a larger, positively-charged ball.
c. Rutherford suggested that electrons are orbiting a small, dense, positively-charged nucleus.
d. Bohr's model places electrons in quantifiable energy levels around the nucleus.
e. The cloud model suggests that electrons are found in probability clouds of different shapes around the nucleus.
1b.
Observation 1: Model a's simplicity would be very useful here as solid balls of matter would surely not be able to pass through one another. With some understanding of electrostatic repulsion, the other models might also help explain the phenomenon.
Observation 2: This observation would require a model which identifies electrons as independent particles. Perhaps models b, c and d would be most useful.
Inference 1: This inference (made by Rutherford) requires a model with a significant portion of empty space. Perhaps models c, d and e would be most useful.
Inference 2: This inference (made by Bohr) requires a model that has clear and quantifiable energy levels such as d and possibly c depending on the description of the orbits.
1a.
a. The earliest model of the atom is of a single, solid balls as the smallest possible units of matter. Possibly put forward by Democritus.
b. The plum pudding model describes the atom as a number of negative electrons stuck in a larger, positively-charged ball.
c. Rutherford suggested that electrons are orbiting a small, dense, positively-charged nucleus.
d. Bohr's model places electrons in quantifiable energy levels around the nucleus.
e. The cloud model suggests that electrons are found in probability clouds of different shapes around the nucleus.
1b.
Observation 1: Model a's simplicity would be very useful here as solid balls of matter would surely not be able to pass through one another. With some understanding of electrostatic repulsion, the other models might also help explain the phenomenon.
Observation 2: This observation would require a model which identifies electrons as independent particles. Perhaps models b, c and d would be most useful.
Inference 1: This inference (made by Rutherford) requires a model with a significant portion of empty space. Perhaps models c, d and e would be most useful.
Inference 2: This inference (made by Bohr) requires a model that has clear and quantifiable energy levels such as d and possibly c depending on the description of the orbits.
Activity 3 - Modelling mass spectrometry
1. Sketch might look something like this --> 2. The larger ball would likely be less affected by the magnetic attraction so the path would remain the straightest. The smallest ball with the lowest mass would do the opposite. 3. The curved line would become more exaggerated. 4. The curves would become straighter. 5. Larger ions would be less affected by the magnetic field and the smaller ions more affected. 6. This may help with understanding how we a mass spectrometer provides information about mass/charge ratio. 7. Possibilities for weaknesses include: metal balls are not actually charged like the ions would be; we are only modelling one part of the process. |
Theories and paradigm shifts
Activity 1: Phlogiston theory
1a. Possible deductions:
ii. Increasing evidence that opposes a theory would decrease its validity.
iii. The demo shows that when a candle is burning, the volume of gas in the container decreases. This causes the liquid level to rise. Phlogiston theory suggests the air absorbs phlogiston when an object is burning but does not identify whether phlogiston possesses a volume. Therefore, technically, the demo does not support or oppose the theory.
1c. i. A paradigm shift in the natural sciences is a complete change in the way we approach or understand the natural world. In this case, our understanding of combustion shifted dramatically from a substance losing an element (phlogiston) to the surrounding air, to a substance combining with oxygen from the air.
ii. In a similar manner, flat-earth theory became redundant as we obtained new contradictory evidence that pointed towards a different explanation. Eventually, round earth theory was proposed to fit this new evidence.
iii. A valid theory must be supported by empirical evidence. The more supporting evidence, the more valid the theory. A theory always has the potential to be replaced. If we begin to find contradictory evidence then we have to reconsider our explanation.
iv.
1a. Possible deductions:
- The candle has run out of phlogiston ('dephlogisticated').
- Wood contains more phlogiston than coal.
- The plant contained 6 g phlogiston.
ii. Increasing evidence that opposes a theory would decrease its validity.
iii. The demo shows that when a candle is burning, the volume of gas in the container decreases. This causes the liquid level to rise. Phlogiston theory suggests the air absorbs phlogiston when an object is burning but does not identify whether phlogiston possesses a volume. Therefore, technically, the demo does not support or oppose the theory.
1c. i. A paradigm shift in the natural sciences is a complete change in the way we approach or understand the natural world. In this case, our understanding of combustion shifted dramatically from a substance losing an element (phlogiston) to the surrounding air, to a substance combining with oxygen from the air.
ii. In a similar manner, flat-earth theory became redundant as we obtained new contradictory evidence that pointed towards a different explanation. Eventually, round earth theory was proposed to fit this new evidence.
iii. A valid theory must be supported by empirical evidence. The more supporting evidence, the more valid the theory. A theory always has the potential to be replaced. If we begin to find contradictory evidence then we have to reconsider our explanation.
iv.
- A theory is a proposed explanation for phenomena that is supported by empirical evidence.
- A law is a statement (often mathematical) that describes a phenomena and is supported by all available evidence. It does not explain.
Activity 2: Paradigm shifts in atomic theory
There is no correct order here. The focus is just to highlight some of the factors that can cause a paradigm shift. (In the context of atomic theory, I might put technology at the top given that without those advances, even the most brilliant of geniuses would not have been able to hypothesise the consequent models)
There is no correct order here. The focus is just to highlight some of the factors that can cause a paradigm shift. (In the context of atomic theory, I might put technology at the top given that without those advances, even the most brilliant of geniuses would not have been able to hypothesise the consequent models)
Cause and effect
Activity 1: What causes the Sun to rise?
1. Is he correct? No (certainly not according to all the other evidence we have).
2. What kind of logic is he using - inductive or deductive? Inductive logic - this is identification of a pattern from many single pieces of data.
3. His daughter wants to scientifically investigate this claim. How might she do it? The independent variable she would need to change is the rooster's noise - so perhaps she could place the rooster in a soundproof box for a number of mornings and record her observations of the sunrise. She would need to control other variables such as the position of the rooster to ensure a fair test.
4. Challenging: What does this example suggest about the temporal relationship between cause and effect? One thing happening after another is often an indication of a causal relationship but we must be careful to investigate those claims to ensure that it is.
1. Is he correct? No (certainly not according to all the other evidence we have).
2. What kind of logic is he using - inductive or deductive? Inductive logic - this is identification of a pattern from many single pieces of data.
3. His daughter wants to scientifically investigate this claim. How might she do it? The independent variable she would need to change is the rooster's noise - so perhaps she could place the rooster in a soundproof box for a number of mornings and record her observations of the sunrise. She would need to control other variables such as the position of the rooster to ensure a fair test.
4. Challenging: What does this example suggest about the temporal relationship between cause and effect? One thing happening after another is often an indication of a causal relationship but we must be careful to investigate those claims to ensure that it is.
Accuracy, validity and reliability
Activity 1: Precision in scientific constants
Task A - Precision in a calculated value
i: When talking about an individual value, precision refers to the number of decimal places. The Google value has the most decimal places so is considered the most precise.
ii. When using Avogadro's constant, the number of decimal places, and hence the number of significant figures in the value, is limited by other values used in the calculation. When making measurements in IB Chemistry, we will rarely see values with more than 3 significant figures, so having more in Avogadro's number will make no difference as we have to round up our final value to 3 significant figures according to scientific convention.
Task A - Precision in a calculated value
i: When talking about an individual value, precision refers to the number of decimal places. The Google value has the most decimal places so is considered the most precise.
ii. When using Avogadro's constant, the number of decimal places, and hence the number of significant figures in the value, is limited by other values used in the calculation. When making measurements in IB Chemistry, we will rarely see values with more than 3 significant figures, so having more in Avogadro's number will make no difference as we have to round up our final value to 3 significant figures according to scientific convention.
Task B - Precision in measurement
Reason and imagination
Activity 1 - What role does reason play in the natural sciences:
- C.
- See reasoning here.
- This is inductive reasoning - the formation of a general trend or pattern from a range of individual points.
- The natural sciences produce knowledge by identifying patterns from empirical evidence. We can test the reliability of these patterns by making predictions and then testing them experimentally.
- Unless we have 100% of the data, we can never be 100% sure that a pattern exists. Practically speaking, collected an infinite number of data points is impossible.
Activity 2 - What if?
Observation set A
Observation set A
- Perhaps, as Thomson suggested, the atom is like a positive cake with electrons dotted inside it. This 'positive cake' might explain why all the positive alpha particles were reflected.
- Perhaps the gold atoms are more like 2-dimensional structures that are a 50:50 patchwork of positive and negative areas. This might explain why only half the alpha particles pass through.
- Perhaps this would suggest an area of dense negative charge in the atom that has enough charge to attract and hold the alpha particles that hit it.
Activity 3 - Invalid deductive reason:
a. Homer has not realised that other factors can also cause the lack of bears. For example, the fact that no bears live in the area anyways! b. Premise 1: Lisa has a rock. Premise 2: There are no tigers present in the town. Conclusion: The rock must keep the bears out of the town. c. See Venn diagrams right --> |
Bias and the role of humans in science
Activity 1 - Ego and lies
This real-life example might provoke thinking around other motivators of scientists:
This real-life example might provoke thinking around other motivators of scientists:
- Money
- Fame
- Prestige
- Respect
- Competition
Other areas of knowledge
Activity 1 - Natural science v religion
- What kind of knowledge does it produce? NS: Descriptions and proposed explanations for how the natural world works. R: Meaning around why we are here and frameworks for how we should live our lives; some religions may suggest explanations for how we got here.
- What kind of evidence is used? NS: Empirical evidence - Data collected from experiments (sense perception important here). R: Interpretation of religious texts and experiences. Perhaps some physical evidence such as the Dead Sea scrolls.
- What might certainty mean? NS: May relate to closeness of theory to empirical evidence; may connote the accuracy of predictions; may relate to success in peer review process. R: May relate to an individual's intuitive senses; may relate to agreement between religious scholars: may relate to literal truth of religious texts.
- What is considered reliable knowledge? NS: Knowledge that is replicable and cannot be falsified; predictive accuracy. R: Knowledge that is agreed upon by many.
- Who would be considered an expert in it? NS: A scientist; editor of scientific media R: A religious scholar or leader.