Free HSC Investigating Science Flashcard Review

Robin Warren saw curved (spiral) bacteria in biopsies of inflamed stomach lining. This conflicted with the accepted view that the acidic stomach was sterile and that ulcers were caused by stress and excess acid.

Attempts to infect animals had failed, so he tested on himself whether the bacterium could cause disease in a healthy stomach. He developed gastritis, supporting a causal link, although a single self-experiment is weak evidence on its own.

Clinical trials showed that ulcers treated with antibiotics to eradicate the bacterium recurred far less often than those treated only with acid-reducing drugs. Marshall and Warren received the 2005 Nobel Prize in Physiology or Medicine.

That a plant gains its mass from the soil. The tree gained about 164 pounds in five years while the dried soil lost only about 2 ounces, so the hypothesis was rejected.

He concluded the tree's mass came from water alone. He did not consider the air; we now know most of a plant's dry mass comes from carbon dioxide fixed in photosynthesis.

He used quantitative measurement of mass before and after, dried the soil to remove water's mass, and covered the pot to stop dust adding mass, which improved validity.

While working near an operating radar magnetron in the mid-1940s, he noticed a confectionery bar in his pocket had melted. He then deliberately tested food such as popcorn kernels in the microwave beam.

Investigations can be initiated by an unexpected observation, by questioning an accepted idea, or by applying new technology. They rarely follow a single fixed 'scientific method'.

To estimate the circumference of the Earth, using the angle of the Sun's rays at two places and the distance between them.

At noon on the summer solstice the Sun was overhead at Syene, while a vertical gnomon at Alexandria cast a shadow at about 7.2° (1/50 of a circle). The cities were about 5000 stadia apart, giving about 250 000 stadia.

That the Sun's rays reaching Earth are parallel and that the Earth is a sphere. He also assumed Syene was due south of Alexandria and exactly on the line where the Sun is overhead, which was only approximately true.

That the observed frequency of a wave depends on the relative motion of the source and the observer: higher when they approach and lower when they move apart. He applied it to the colour of light from double stars.

Buys Ballot had musicians play a sustained note on a moving train while trained listeners beside the track judged the pitch. The pitch was heard higher as the train approached and lower as it moved away.

After some days the air could again support a flame (and a mouse). He concluded plants 'restore' air injured by burning or breathing.

He used few trials and some repeats failed, probably because plants release oxygen only in light, a variable he did not control. His explanations also relied on the phlogiston theory.

A fixed sequence: observation, question, hypothesis, experiment, analysis, conclusion. It is a useful teaching outline but rarely describes how real science proceeds.

Results can lead back to a revised question or method, chance observations open new lines of inquiry, and technology, funding and collaboration shape what can be tested. Steps are revisited many times.

Marshall and Warren's work began with an unexpected observation, needed repeated failed culturing attempts (success came after cultures were accidentally left over a long weekend), and included a self-experiment before formal clinical trials.

It predicts a relationship between an independent and a dependent variable that can be measured, and it can be shown false by data. For example, 'If salt concentration increases, the germination rate of mung beans will decrease.'

A focused question that guides an investigation and identifies what is to be found out, for example 'How does water temperature affect the time for a tablet to dissolve?'