科學方法、探究問題與變因：練習題

When using a Bunsen burner, which type of flame is known as the safety flame because it is bright and easy to see?

A group of students is investigating the relationship between the concentration of a sugar solution and the change in mass of potato strips due to osmosis. They use five different concentrations of sucrose solution: \(0.0\text{ M}\), \(0.2\text{ M}\), \(0.4\text{ M}\), \(0.6\text{ M}\), and \(0.8\text{ M}\). They immerse three identical potato strips in each solution for \(60\text{ minutes}\).

Which of the following describes the most appropriate way to determine the dependent variable to ensure high precision and reliability in this inquiry?

A student investigates the relationship between the concentration of a reactant, \([A]\), and the initial rate of a reaction, \(r\). The student hypothesizes that the rate is directly proportional to the concentration squared (\(r \propto [A]^2\)). After conducting four trials, the following data is collected:

\(\begin{array}{|c|c|c|} \hline \text{Trial} & [A] \text{ (mol/L)} & \text{Initial Rate (mol/L/s)} \\ \hline 1 & 0.10 & 0.02 \\ 2 & 0.20 & 0.08 \\ 3 & 0.30 & 0.18 \\ 4 & 0.40 & 0.30 \\ \hline \end{array}\)

Based on the scientific method and inquiry, which of the following is the most valid evaluation of the student's hypothesis and the data set provided?

When a scientist makes a statement that can be tested through experimentation or observation to explain a natural phenomenon, which step of the scientific method and inquiry are they performing?

In an investigation measuring how the length of a wire affects its resistance, the student uses a voltmeter and an ammeter to calculate resistance (\(R = V/I\)). If the student wants to improve the reliability of the data, which action is most appropriate?

In a scientific context, what is the main difference between a qualitative observation and a quantitative observation?

A student observes the data shown in the graph below regarding the relationship between the temperature of a gas and its volume. Based on the scientific method, what conclusion can be drawn about the relationship between these two variables, and what should be the next step if the student wants to verify the reliability of these results?

In an investigation measuring the effect of different light wavelengths on the growth rate of a specific algae species, a researcher ensures all tanks have the same CO\(_{2}\) levels, nutrient concentration, and initial algae mass. However, the researcher notices that the tanks closest to the laboratory window grow faster regardless of the light wavelength being tested. Explain the role of this confounding variable and how it compromises the validity of the inquiry.

A student is investigating the effect of temperature on the activity of the enzyme amylase. The amylase breaks down starch into maltose. The student sets up five water baths at temperatures of \(10^{\circ}\text{C}\), \(20^{\circ}\text{C}\), \(30^{\circ}\text{C}\), \(40^{\circ}\text{C}\), and \(50^{\circ}\text{C}\).

(a) Identify the independent variable and the dependent variable in this inquiry.
(b) Name one controlled variable that must be kept constant to ensure the results are valid.
(c) State one way the student could improve the reliability of the results.

A researcher is studying the relationship between the concentration of a fertilizer and the height of pea plants. The researcher uses five different concentrations of fertilizer (\(0\%\), \(5\%\), \(10\%\), \(15\%\), and \(20\%\)). Each concentration is applied to 10 plants of the same species and age, grown in identical soil under the same light conditions. After 4 weeks, the average height of the plants in each group is recorded.

(a) Explain why the researcher included a group with 0% fertilizer.
(b) Why did the researcher use 10 plants for each concentration instead of just one?
(c) If the researcher finds that the plants with \(10\%\) fertilizer grew the tallest, but several plants in that group died due to a localized fungal infection, evaluate whether the data for that group is valid for drawing a final conclusion.