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Exploring the Investigative World of Science: questions with answers

Class 8 Science, Chapter 1 (NCERT). 15 questions by concept. Open “Show answer” for the answer and why.

How to teach this chapter · Common misconceptions & worked visual for this chapter

What investigation means in Grade 8

Question 1

A student wonders why a phulka swells when put directly on the flame. The student then says this is not a science question, because it is only about cooking at home. Name the reason this is still a science question.

  1. (a)A question about food belongs to cooking rather than to science
  2. (b)Only the bigger mysteries of Earth and beyond are worth an investigation
  3. (c)Even your kitchen at home is a wonderful place to observe and ask questions
  4. (d)A question is worth asking only once its answer can be looked up
Show answer

(c) Even your kitchen at home is a wonderful place to observe and ask questions

The chapter answers this directly: it says that even your kitchen at home is a wonderful place to observe and ask questions. A question is worth investigating when it can be observed and tried, not when its answer is already known or the subject sounds grand.

Question 2

A student asks another question after finding an answer, then investigates it. What does this show about how science works?

  1. (a)Careful observation matters only when special apparatus is available.
  2. (b)Science begins with wonder, grows through new questions, and uses investigation and observations to improve understanding
  3. (c)Wonder should be left behind once investigation begins.
  4. (d)Science is mainly about collecting more facts.
Show answer

(b) Science begins with wonder, grows through new questions, and uses investigation and observations to improve understanding

Science begins with wonder and questions. Each answer can lead to another question. Investigation uses focused questions, simple experiments and observations. Observations can improve understanding.

Science is everywhere: no fancy laboratory required

Question 3

A student wonders why a batura puffs up when placed in hot oil and wants to try it out at home. Give the reason that a kitchen at home can be a place for a science investigation.

  1. (a)An experiment counts only when it is done in a laboratory with proper apparatus
  2. (b)Cooking can be watched but must never be changed on purpose
  3. (c)A fancy laboratory is not needed, and a kitchen at home is a wonderful place to observe and ask questions
  4. (d)Science is about the sky and the stars, not about what happens in a kitchen
Show answer

(c) A fancy laboratory is not needed, and a kitchen at home is a wonderful place to observe and ask questions

You do not need a fancy laboratory to do simple experiments. The chapter works its whole method through on a kitchen question, why a puri puffs up in hot oil. Apparatus does not make something science, and a subject does not have to be far away to be worth investigating. A kitchen at home is a wonderful place to observe and ask questions.

Question 4

Why a puri puffs up when it is fried is not completely understood by scientists even today. A student concludes that the question must therefore be dropped. What is the right conclusion?

  1. (a)That the answer will be found only once better instruments exist
  2. (b)That the question stands, and that being unanswered is exactly what leaves something to find out
  3. (c)That it is not a scientific question at all, since science has no answer for it
  4. (d)That everyone who cooks already understands it, so there is nothing left to find out
Show answer

(b) That the question stands, and that being unanswered is exactly what leaves something to find out

Being unanswered does not stop something from being a good scientific question. It is exactly what leaves something to find out. The chapter says the puffing of a puri is not really completely understood by scientists today, and it still shows its whole method on that very question. Nor is the puffing already understood by everyone who cooks.

What we can change, and what we can observe or measure

Question 5

In the puri experiment a student times how long each puri takes to puff up. The student says that whether the puri puffs up is not one of the things we observe. The reason given is that there is no number to write down. Is the student right?

  1. (a)No. It counts only because we can see it happen; a smell of smoke would not count
  2. (b)No. A yes or no answer is something we observe, just as a measured number is
  3. (c)Yes. Whether it puffs up is really one of the things we can change, not one of the things we observe
  4. (d)Yes. Only something that can be measured as a number counts as an observation
Show answer

(b) No. A yes or no answer is something we observe, just as a measured number is

A yes or no answer is a result, not a lesser one. The chapter says some of these may have just yes or no answers. It adds that in some cases there might be a number we can measure. Both kinds are listed together as things we can observe or measure. So rejecting a yes or no answer is wrong, and counting it as an observation is right. It is also not one of the things we can change: it is not set before the trial. It is what the trial gives back. The chapter also asks us to note everything we see and sense, so a smell of smoke counts as well.

Question 6

We want to find out why a puri puffs up on one side and stays flat on the other. Which explanation correctly shows why whether the dough is slid in at an angle or dropped straight down is something we can control?

  1. (a)Only quantities with a number or scale are controllable; a chosen way of putting dough into oil is not
  2. (b)We choose whether the dough is slid in at an angle or dropped straight down before frying and can choose it differently in the next trial
  3. (c)Only the dough and flour can be changed; how the frying is done cannot
  4. (d)It is a result that we wait to see after the frying is finished
Show answer

(b) We choose whether the dough is slid in at an angle or dropped straight down before frying and can choose it differently in the next trial

A thing we control is chosen before frying and can be changed from one trial to the next. This includes both measured settings and chosen actions, such as how the dough is put into the oil. A result is what we observe afterwards.

Changing only one thing at a time

Question 7

A student tests what difference the temperature of the hot oil makes. The other conditions are held the same from one trial to the next, but the way the rolled dough is dropped into the oil also changes. Is this a fair comparison?

  1. (a)Yes, because the way the rolled dough is dropped into the oil is not connected to the temperature of the hot oil
  2. (b)No, because one more thing changed as well: the way the rolled dough is dropped into the oil
  3. (c)Yes, because most of the conditions were held, and one more makes little difference
  4. (d)No, because the temperature of the hot oil should have been held the same in every trial too
Show answer

(b) No, because one more thing changed as well: the way the rolled dough is dropped into the oil

Only the thing being tested may change from one trial to the next. Everything else must be held the same, even a condition that seems to have nothing to do with it. Here the way the rolled dough is dropped into the oil changed as well, so the puffing cannot be traced to the test.

Question 8

To see what difference the thickness of the rolled dough makes, a student fries three puris. In all three, the dough is rolled to the same thickness and size. The same flour is used. The oil is at the same temperature, and the dough is put in the same way each time. What is wrong with this set of trials?

  1. (a)Three trials are too few; the student should have run many more
  2. (b)Nothing is wrong. Every condition was kept the same in all three trials, and that is how a careful test is run
  3. (c)The student should have written down the expected result before starting
  4. (d)Across all trials, the thickness of the rolled dough stayed the same, so its effect on puffing cannot be compared.
Show answer

(d) Across all trials, the thickness of the rolled dough stayed the same, so its effect on puffing cannot be compared.

Repeating the same setup can show whether the results vary, but it cannot test the effect named in the aim. To test that factor, the student must change it while keeping the other conditions the same.

Keeping notes, and letting the results raise the next question

Question 9

A student is timing how long each puri takes to puff up, and also notices that the oil smoked. What should the student write in the notes?

  1. (a)The puffing time and the smoke, because both are observations
  2. (b)Only the smoke, since the planned time can be recalled later from memory
  3. (c)The puffing time alone, since that is the one thing chosen to be measured
  4. (d)The puffing time alone, because only measurements written as numbers are observations.
Show answer

(a) The puffing time and the smoke, because both are observations

Choosing what to observe does not narrow what to record. The chapter asks for notes of everything you see and sense, and it gives splattering, smell and smoke as its own examples. So the notes hold the puffing time and the smoke together. A smell is an observation even though it cannot be written as a number, and the timing is not left to memory either.

Question 10

A student fries puris, changing one thing at a time and keeping the other conditions the same. After this round of experiments, the student asks: What happens if I prick a hole in the puri before frying? What kind of question is that?

  1. (a)A question for professional scientists, not something an investigation like this one can answer
  2. (b)A question that is not really scientific, since nobody has answered it yet
  3. (c)A further question raised by the first round of experiments, and the next thing to try with the puri
  4. (d)A sign that the first round of experiments went wrong and has to be done again
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(c) A further question raised by the first round of experiments, and the next thing to try with the puri

One round of experiments normally ends with fresh questions like this one. It names the next thing to try. Nobody has answered it yet, and that is what makes it worth investigating. The chapter says all scientific experiments, from simple to the most complicated, are done this way, so a kitchen investigation can take it up.

From electric current to the phases of the Moon: how this year's physical topics lead into one another

Question 11

Everything around us is made of tiny particles. Think about the tiny particles inside a piece of something solid. How much can these particles move?

  1. (a)They can move a little, but they cannot move much
  2. (b)They can move around as freely as the particles in a gas
  3. (c)A solid has no particles inside it, so there is nothing to move
  4. (d)They cannot move at all, because a solid itself stays still
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(a) They can move a little, but they cannot move much

The whole difference is in one word. The chapter says that in materials that are solid these particles cannot move MUCH. Cannot move much is not the same as cannot move at all, so the particles in a solid still move a little. A solid looks perfectly still from outside, which is why the stronger claim seems safe. In a gas the particles can move around freely.

Question 12

Light falls on a surface that is not polished. What happens to that light?

  1. (a)It is reflected, even though a surface that is not polished is not a mirror
  2. (b)It is reflected only after the surface bends it, the way a lens bends light
  3. (c)It is not reflected at all, because only a mirror or a polished surface reflects light
  4. (d)It is not reflected; the surface gives out light of its own instead
Show answer

(a) It is reflected, even though a surface that is not polished is not a mirror

Light does not bounce back only from a polished mirror. Rough surfaces reflect light as well, and so does the Moon, which is why we can see it.

Roots and kites: grounded observation balanced with free thinking

Question 13

A science book contains facts, questions and activities. What is the main purpose of learning science?

  1. (a)To collect and memorise more facts each year
  2. (b)To develop and test explanations about the world
  3. (c)To learn only about discoveries made in laboratories
  4. (d)To find answers that never need checking again
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(b) To develop and test explanations about the world

Learning science involves asking questions, using evidence and testing explanations about the world. Remembering more facts alone does not achieve this purpose.

Question 14

A student observes carefully, but never lets curiosity fly towards new ideas. What does this student still need, if the investigation is to work well?

  1. (a)The student needs a longer list of facts learnt by heart, because knowing more answers is what makes an investigation work
  2. (b)The student needs creative thinking as well, balanced with the careful observation they already have
  3. (c)The student needs nothing further, because the two ways of working belong to two kinds of scientist and each may keep one
  4. (d)The student needs a firmer hold on knowledge that is already settled, because science asks us not to depart from it
Show answer

(b) The student needs creative thinking as well, balanced with the careful observation they already have

The root stands for a solid foundation of knowledge and the kite for curiosity taking flight to explore the unknown. The chapter asks for both: stay grounded in real observations while allowing your ideas to soar towards new horizons. A student who keeps only one of them is left with half the method.

From a drop of water to a planet that is just right for life

Question 15

A student says air around the planet explains by itself why Earth supports life. What is missing from this explanation?

  1. (a)Earth must have no changes in temperature.
  2. (b)Nothing: an atmosphere alone makes a planet suitable for life.
  3. (c)Earth also has conditions that allow water to remain liquid.
  4. (d)Earth must have no sunlight.
Show answer

(c) Earth also has conditions that allow water to remain liquid.

An atmosphere helps life, but it is not the whole explanation. Earth also lies at a distance from the Sun where water can remain liquid.

Common misconception in Exploring the Investigative World of Science

Open full misconception guide →

Does a difference in one trial establish a reliable effect?

Wrong

Setup B always evaporates more water because it lost 5 mL while setup A lost 4 mL in the first trial.

Why it feels right. I treat one pair of measurements as typical.

Right

Repeat each trial to see whether a difference holds up against ordinary variation.

Worked example

Both setups have two readings of 4 mL and one of 5 mL.
  1. Repeat both setups under the same conditions.
  2. A loses 4, 5 and 4 mL.
  3. B loses 5, 4 and 4 mL.
  4. The averages are equal, so these trials do not support the claim that B evaporates more.