Nature and meaning of science

Correct answer: A. It helps plan a suitable investigation

A clear problem makes it easier to choose the right question and method. Distinguish the problem from the conclusion in exams.

Correct answer: B. It shows change over time

Regular measurement clearly shows changes in growth. Remember the link between time and measurement.

Correct answer: C. Check the method and measurements

When results differ the method and measurements should be checked. Compare evidence before identifying an error.

Correct answer: D. When several pieces of evidence support it

Several independent pieces of evidence increase the reliability of a scientific claim. Do not treat popularity as evidence.

Correct answer: A. To provide a basis for comparison

A control group provides a basis for comparison with the experimental group. Identify it in comparison-based questions.

Correct answer: B. The liquid is blue

“The liquid is blue” is correct because colour is a property that can be directly seen and recorded. A scientific observation states what is observed or measured, not a personal opinion. Options A and D are opinions, while option C is a prediction rather than an observation. Exam tip: Words such as “I think,” “best,” and “will” often indicate an opinion or prediction, not an observation.

Correct answer: C. Inferring from a wet road that it may have rained

A scientific inference is a possible explanation drawn from an observation. Do not confuse inference with direct observation.

Correct answer: D. Objectivity

Recording only preferred results allows personal bias to influence observations and conclusions, so objectivity is affected. In a scientific investigation, both expected and unexpected results must be recorded accurately. Curiosity means asking questions; the issue here is selectively recording data. Exam tip: Choose objectivity when a question refers to unbiased recording or honest observation.

Correct answer: A. Giving priority to evidence over personal preference

Objectivity means making decisions on the basis of evidence. Keep personal preference away from conclusions.

Correct answer: B. To show the correct meaning and standard of the measured quantity

A unit states the physical quantity and standard associated with a numerical value. For example, 5 may mean 5 m, 5 kg, or 5 s; without a unit, the number is unclear. Option A concerns appearance only, whereas the main purpose of units is to make measurements meaningful and usable. Exam tip: Always write the correct unit along with a measured value.

Correct answer: C. It becomes easier to identify the cause of change

Changing one factor makes its effect easier to identify. This principle is used in a fair test.

Correct answer: D. Measurement error may occur

If a measuring instrument is faulty or not properly calibrated, it can give a reading different from the true value. This causes measurement error and may make the experimental result unreliable. “The experiment will repeat automatically” is incorrect because an experiment must be repeated by the investigator. Exam tip: In measurement questions, a faulty instrument is usually a source of error.

Correct answer: A. Understanding regular relationships in data

Identifying patterns helps scientists notice repeated changes, regular trends, and relationships between variables in data. This can lead to questions and testable predictions for further investigation. Unusual results should not be removed without checking, because they may indicate an error or an important new finding. Exam tip: In a graph or table, look for values that increase, decrease, or repeat in a regular way.

Correct answer: B. It shows trends in data easily

The direct answer is option B: a graph shows trends in data easily. A graph changes numbers into a visual form. By reading the horizontal and vertical axes, their units, the scale, and the plotted points or bars, we can quickly see increase, decrease, equality, or a pattern. For example, a rising line may show that one quantity increases as another changes, though the graph alone does not automatically prove the cause. Option A is wrong because a graph represents the experiment’s purpose and results; it does not change the purpose. Option B is correct because visual patterns are often easier to compare than a long table of numbers. Option C is wrong because a graph displays evidence rather than removing it. Option D is wrong because making a graph does not stop measurement; measurements are collected first and then represented. Remember to read both axis labels and the scale before interpreting any graph.

Correct answer: C. बड़े समूह से अध्ययन के लिए कुछ प्रतिनिधि वस्तुएँ चुनना

Sampling means choosing a smaller set of items or individuals from a larger population so that the set represents the larger group for study. Therefore, option C is correct. Studying every item in the group is a census, not sampling. Exam tip: A representative sample is usually selected fairly or randomly to reduce bias.

Correct answer: D. It represents the group better

A large and unbiased sample can represent the whole group better. Do not select only preferred items.

Correct answer: A. Obtaining similar results using the same method

Reproducibility means similar results can be obtained by following the same method. It is linked with reliability.

Correct answer: B. It cannot be scientifically verified

The direct answer is option B: it cannot be scientifically verified. A scientific claim must be stated in a way that observation, measurement, or a suitable experiment could support or challenge it. This testability makes it possible to compare the claim with evidence and revise it when necessary. Option A is wrong because the length of a claim has nothing to do with whether it can be tested. Option B is correct because an untestable claim cannot be checked against observations, so science cannot establish how well it is supported. Option C is wrong because a picture is not required for every scientific statement; words, tables, measurements, or equations may be enough. Option D is wrong because being old or new is not the deciding condition. A claim may be old and testable or new and testable. The exam cue is: ask, “What observation or experiment could show whether this claim is supported?”

Correct answer: C. The factor deliberately changed by the investigator

The direct answer is option C: the independent variable is the factor deliberately changed by the investigator. In an experiment, a researcher changes one condition and observes whether another condition responds. The deliberately changed condition is called the independent variable. For example, if we test how the amount of sunlight affects plant growth, sunlight is changed, so it is independent; plant height is measured and is the dependent variable. The exact reasoning is: identify what the investigator controls and changes on purpose; that factor is the independent variable. Option A is wrong because the factor measured as the result is the dependent variable. Option B is wrong because a variable is not defined as something always wrong. Option C is correct because it gives the scientific definition. Option D is wrong because removing something after an experiment is not the meaning of an independent variable. Memory cue: independent means “I change it.”

Correct answer: D. The outcome that is measured or observed

An experiment usually includes a factor that the investigator changes, other conditions that are controlled, and an outcome that is observed or measured. The dependent variable is this outcome. Its value may change because of the independent variable, so it is called dependent. For example, if the amount of light is changed and plant height is recorded, plant height is the dependent variable. It is important to measure it consistently so that the results can be compared fairly.

Option D is correct because it identifies the dependent variable as the result that is measured or observed. Option A describes a controlled variable, which is kept the same to make the test fair. Options B and C are not definitions of experimental variables; an experiment’s name and the instrument’s size do not automatically represent the outcome. Therefore, the dependent variable is best understood as the measured response to a change made during the investigation.

Correct answer: A. So that the comparison is fair

Similar conditions help compare effects correctly. Controlled conditions are part of a fair test.

Correct answer: B. Qualitative observation

The word ‘shiny’ describes a property of the metal, but it gives no number or measurement. Therefore, it is a qualitative observation. Quantitative data or numerical measurement includes numbers, such as a metal having a mass of 50 g. Exam tip: A description of a property without numbers is usually qualitative.

Correct answer: C. Quantitative observation

Temperature is measured with a thermometer and expressed as a numerical value with a unit, such as 25 °C. Hence, it is a quantitative observation because it involves measurement or numbers. A qualitative observation only describes a quality, such as saying that an object feels hot or cold. Exam tip: An observation stated using a number, measurement, or unit is quantitative.

Correct answer: D. Others may not repeat the experiment correctly

The direct answer is D: others may not repeat the experiment correctly. Science depends not only on obtaining a result but also on explaining how the result was obtained. A clear method normally states the materials, measurements, conditions, sequence of steps, and relevant precautions. Step by step: a researcher performs an experiment; if the procedure is not recorded clearly, another person cannot know exactly what was done; different people may use different amounts, times, temperatures, or tools; their results may then differ; so the original finding cannot be checked properly. Option A, “the result will become correct automatically,” is wrong because unclear writing cannot improve the actual experiment or guarantee accuracy. Option B, “all instruments will improve,” is unrelated; instruments do not become better merely because a method is poorly written. Option C, “evidence will increase,” is wrong because missing procedural detail usually weakens the evidence and its reliability. Option D is correct because repeatability requires a sufficiently detailed method. Repetition also helps identify mistakes and test whether a result is dependable. Memory cue: record enough detail so another careful student can perform the same investigation.

Correct answer: A. Careful observation and collection of evidence

Natural phenomena are studied through observation and evidence. Do not accept hearsay without testing it.