The Ever-Evolving World of Science – Case-based Questions with Answers
CBSE Class 7 Science – Chapter Wise Study Materials (NCERT Based)
Class: 7
Subject: Science
Chapter: 1 – The Ever-Evolving World of Science
CBSE Board Examinations – Systematic Preparation
These NCERT-based Case-Based Questions for Class 7 Science are designed to strengthen concepts and improve exam readiness for:
- Class 7 Annual / Term-End School Examinations
- Class Tests, Periodic Tests and Internal Assessments
- Olympiads and Science Talent Search Exams (Class 7 level)
- Foundation preparation for higher classes (Class 8–10)
Chapter 1 – “The Ever-Evolving World of Science” introduces students to the nature, scope and importance of science in everyday life. It also highlights how scientific inquiry works through observation, questioning, experimentation and logical thinking.
The following 20 Case-Based Questions with Answers are prepared strictly as per the NCERT syllabus for Class 7 Science. Each case study is linked to key concepts of this chapter and provides exam-style practice for CBSE Class 7 standard.
Note for Students: Read each case carefully, understand the situation, and then answer the
questions in your own words. This will help you develop scientific thinking, reasoning and application skills.
Topic 1: Nature and Scope of Science
Case Study 1 (Q1): Science in a Village Fair
During a village science fair, students put up different stalls. One group explains how electricity
lights their homes, another shows how farmers use improved seeds, and a third stall displays models of
the solar system. Visitors realise that science is connected to farming, lighting, communication and space
research. Their teacher tells them that science is not limited to laboratories, but is present in almost
every aspect of life.
- What does this fair show about the scope of science?
- Give two examples from the case which show that science is used in everyday life.
- Why does the teacher say that science is not limited to laboratories?
Answers for Q1:
- The fair shows that the scope of science is very wide and covers many fields like agriculture, electricity, communication and space research.
- (i) Use of electricity to light homes (ii) Use of improved seeds by farmers are two examples of science in everyday life.
- Because scientific ideas and inventions are used in homes, farms, transport, medicine and many other places outside laboratories.
Case Study 2 (Q2): Riya’s Curiosity about Rainbows
Riya loves to watch rainbows during the rainy season. One day she wonders, “Why do rainbows appear
only when it rains and the Sun is out?” She asks her teacher, reads her science textbook and also
searches for videos that explain rainbows. She learns that rainbows are formed due to refraction, reflection
and dispersion of sunlight by water droplets in the atmosphere.
- Which quality of a scientist does Riya show in this case?
- How does this case show that science helps us to understand natural phenomena?
- What is the importance of asking questions in science?
Answers for Q2:
- Riya shows curiosity and the habit of asking questions, which are important qualities of a scientist.
- She uses scientific explanations (refraction, reflection and dispersion) to understand the natural phenomenon of a rainbow.
- Asking questions leads to investigation, learning and discovery of new facts and explanations in science.
Topic 2: Scientific Inquiry – Observation, Hypothesis, Experimentation
Case Study 3 (Q3): The Wilting Plant
In the school garden, a potted plant near the wall looks weak and wilted, whereas another plant of the same
type placed in the open is healthy and green. Ansh observes this carefully. He guesses that the first plant
may not be getting enough sunlight. To test his idea, he shifts the wilted plant to a sunnier spot and waters
both plants equally for a week. After a few days, he notices that the shifted plant becomes healthier.
- What was Ansh’s hypothesis about the wilted plant?
- Name the step of scientific inquiry illustrated when he shifted the plant to a sunnier spot.
- What conclusion can he draw from the result of his activity?
Answers for Q3:
- Ansh’s hypothesis was that the wilted plant was not getting enough sunlight.
- Shifting the plant to a sunnier spot is the experiment to test his hypothesis.
- He can conclude that sunlight is necessary for the healthy growth of that plant.
Case Study 4 (Q4): Melting Ice Cubes
Two friends, Meera and Kabir, are doing a simple activity with ice cubes. Meera keeps her ice cube on a
metal plate, while Kabir keeps his on a thick book. They both start at the same time. After a few minutes,
Meera’s ice cube has melted more than Kabir’s. They observe this carefully, note the time and record their
results in a table. Their teacher then explains the role of different materials in transferring heat.
- What is the observation made by Meera and Kabir?
- How did they record their findings scientifically?
- What scientific skill is being developed when they compare the melting of ice on different surfaces?
Answers for Q4:
- They observed that the ice cube on the metal plate melted faster than the one on the book.
- They recorded the time taken and results in a table, which is a scientific way of recording data.
- They are developing the skills of observation, comparison and data recording in scientific inquiry.
Topic 3: Science in Our Daily Life
Case Study 5 (Q5): Morning with Science
On a school day, Arjun wakes up to the alarm on his digital clock, brushes his teeth with a fluoride
toothpaste, takes a warm bath using a geyser, and has breakfast cooked on an LPG stove. On his way to school,
he uses a bus fitted with GPS. During the day, he uses a computer and projector in his classroom. In the
evening, he video-calls his grandparents who live in another city.
- Mention any three ways in which science and technology are used in Arjun’s daily routine.
- How does science help in improving communication in this case?
- Why can we say that science has made life more comfortable for Arjun?
Answers for Q5:
- Examples: digital alarm clock, geyser for warm water, LPG stove for cooking, GPS-fitted bus, computer and projector, video-calling.
- Science has helped to develop devices like mobile phones and internet-based video calling, which allow him to see and talk to his grandparents instantly.
- Because scientific inventions provide comfort (warm water, quick cooking), save time (transport, alarms) and improve learning (computer, projector).
Case Study 6 (Q6): Science in the Kitchen
Sanya observes her mother working in the kitchen. Her mother soaks dry peas to make them soft, uses a
pressure cooker to cook food faster, and stores leftover food in the refrigerator so that it does not spoil.
When Sanya asks why these steps are important, her mother explains that science helps us understand soaking,
pressure, heat and preservation.
- Which two scientific ideas are used when her mother soaks dry peas and uses a pressure cooker?
- How does a refrigerator help in food preservation?
- Why can the kitchen be called a “small science laboratory”?
Answers for Q6:
- Soaking dry peas shows absorption of water and softening; using a pressure cooker shows that higher pressure and temperature make cooking faster.
- A refrigerator slows down the activity of microorganisms by keeping food at a low temperature, which helps in preserving it for longer.
- Because many scientific processes like heating, boiling, freezing, mixing and preserving happen in the kitchen.
Topic 4: Science, Society and Environment
Case Study 7 (Q7): Clean Energy for a Village
In a remote village, electricity cuts are very common. To solve this problem, the village panchayat installs
solar panels on the roofs of the school and community hall. Now the school gets light even during power cuts,
and mobile phones can be charged at the community centre. The villagers also learn that solar energy is a
clean and renewable source of energy that does not pollute the environment.
- Which form of energy is being used by the village in this case?
- Mention any two benefits of using this form of energy.
- How does this example show that science can help society and the environment together?
Answers for Q7:
- The village is using solar energy.
- It is renewable (comes from the Sun) and does not cause air pollution. It can also provide electricity during power cuts.
- Solar energy solves the villagers’ electricity problem (social benefit) and reduces pollution (environmental benefit), showing how science can help both.
Case Study 8 (Q8): Plastic-Free Campaign
A Class 7 section starts a “Plastic-Free Week” campaign. They learn from their science teacher
that plastic does not decompose easily and can harm animals and soil. The students design posters explaining
the harmful effects of plastic and suggest alternatives like cloth bags and steel bottles. They present their
work in the morning assembly and encourage others to reduce plastic use.
- Which environmental problem is highlighted in this case study?
- How do the students use their scientific knowledge to create awareness?
- Suggest one more environmentally friendly habit that the students can promote.
Answers for Q8:
- The problem of plastic pollution and non-biodegradability of plastic is highlighted.
- They use scientific facts about plastic harming animals and soil to make posters and presentations for the assembly.
- They can promote habits like proper waste segregation, planting trees or using bicycles instead of motorbikes for short distances.
Topic 5: Safety and Ethics in Science
Case Study 9 (Q9): Safety in the Science Lab
During a science practical, students are heating a liquid in test tubes. Their teacher instructs them to wear
safety goggles, tie long hair, and never point the mouth of the test tube towards anyone. One student ignores
the instructions and holds the test tube with bare hands and towards his friend. The teacher quickly stops
him and explains the importance of lab safety rules.
- Mention any two safety rules that were followed in the lab.
- What was the unsafe act done by the student?
- Why are safety rules important while doing scientific activities?
Answers for Q9:
- Wearing safety goggles and tying long hair are two safety rules followed.
- He held the test tube with bare hands and pointed its mouth towards his friend, which is unsafe.
- Safety rules prevent accidents, burns and injuries and make scientific work safe for everyone.
Case Study 10 (Q10): Fair Testing
A group of students wants to test which brand of seeds grows faster. They decide to plant seeds of two
different brands in separate pots. One student suggests watering one pot more than the other to “help”
his favourite brand grow better. The teacher explains that for a fair test, all conditions like water,
sunlight and soil must be kept the same for both brands.
- What is the aim of the students’ experiment?
- Why was the suggestion of watering one pot more incorrect scientifically?
- What do we call such an experiment where only one factor is changed and others are kept the same?
Answers for Q10:
- The aim is to find out which brand of seeds grows faster.
- Because then the test would not be fair; extra water would affect the growth, and the difference would not be only due to the seed brand.
- It is called a fair test or controlled experiment.
Topic 6: Careers and Contributions in Science
Case Study 11 (Q11): Science Career Day
On Science Career Day, professionals visit a school to talk about their work. A doctor explains how she uses
medical science to treat patients. An engineer talks about building bridges and machines using physics and
mathematics. A meteorologist explains how he studies weather patterns to predict storms and rainfall. Students
are surprised to see how different careers are related to science.
- Name any two careers mentioned in the case that are based on science.
- How does the meteorologist use science in his work?
- Why is it useful for students to know about science-related careers at an early age?
Answers for Q11:
- Doctor and engineer (meteorologist is also a science-based career).
- He studies weather data and uses scientific instruments and models to predict storms and rainfall.
- It helps them understand how science is used in real life and may inspire them to choose science-related careers in the future.
Case Study 12 (Q12): Inspiration from Scientists
Neha reads about great scientists like Marie Curie, C. V. Raman and A. P. J. Abdul Kalam. She learns that
these scientists worked hard, faced difficulties and still continued their experiments. She notices that they
were curious, honest about their results and worked for the benefit of humanity. Neha feels motivated to
develop similar qualities.
- Mention any two qualities of scientists that Neha observes.
- How do these qualities help in scientific progress?
- Why is it important for students to learn about the lives of scientists?
Answers for Q12:
- Qualities: curiosity, hard work, honesty, perseverance, working for the benefit of humanity.
- These qualities help scientists to keep trying, accept true results and make useful discoveries.
- Because such stories inspire students, teach good values and show how science can be used for the betterment of society.
Topic 7: Scientific Attitude and Logical Thinking
Case Study 13 (Q13): Superstition vs Science
In a village, some people believe that an eclipse brings bad luck, so they close their doors and windows.
However, a group of students, after studying their science textbook, knows that an eclipse is a natural
astronomical event. They conduct a small session in the community hall using charts and models to explain how
eclipses occur. Slowly, some villagers start understanding the scientific explanation and stop fearing eclipses.
- What wrong belief (superstition) is shown in this case?
- How do the students show a scientific attitude?
- Why is it important to replace superstitions with scientific explanations?
Answers for Q13:
- The belief that an eclipse brings bad luck is a superstition.
- They study the scientific reason behind eclipses and explain it logically to others using charts and models.
- Because scientific explanations are based on facts and evidence, and they help people make correct decisions without fear.
Case Study 14 (Q14): The Rumour about a New Medicine
A message spreads in a town that a new herbal syrup can cure all diseases. Many people rush to buy it without
checking if it is tested or approved by doctors. Ananya’s family decides not to believe the rumour. They
consult a doctor, who explains that any medicine must be tested scientifically for safety and effectiveness
before use. The herbal syrup, he says, has not been properly tested.
- What mistake are many people in the town making?
- How does Ananya’s family apply scientific thinking?
- What lesson do you learn from this case about health-related information?
Answers for Q14:
- They are blindly believing a rumour and using a medicine that is not scientifically tested.
- They do not accept the claim without proof, and they consult a doctor (expert) to find out the truth.
- We should not trust unverified health information and should always rely on scientific testing and expert advice.
Topic 8: Science and Technology – Benefits and Limitations
Case Study 15 (Q15): Online Learning and Screen Time
During a period of heavy rains, schools shift to online classes. Students attend lessons on laptops and
smartphones. While this helps them continue learning, some students start spending extra time watching videos
and playing games. A teacher explains that technology is useful, but too much screen time can cause eye
strain, headaches and reduced physical activity.
- What advantage of technology is shown in this case?
- What problem arises due to overuse of screens?
- Write one way students can balance the use of technology in their daily life.
Answers for Q15:
- Technology allows students to attend online classes and continue learning even when schools are closed.
- Overuse of screens can cause eye strain, headaches and less physical activity.
- They can fix a limited time for entertainment on screens and include time for outdoor play or exercise.
Case Study 16 (Q16): Machines in a Factory
A visit to a factory shows students how big machines can cut, shape and pack products very quickly. The guide
explains that machines help to produce goods on a large scale. However, he also mentions that too much
dependence on machines can reduce the need for some types of manual labour, affecting certain jobs.
- How do machines in the factory show the benefit of science and technology?
- What limitation or problem is also mentioned?
- Why is it important to use machines in a balanced and responsible way?
Answers for Q16:
- Machines help to cut, shape and pack products quickly, allowing large-scale production.
- Too much dependence on machines can reduce the need for some types of manual labour, affecting jobs.
- Balanced use ensures that we enjoy the benefits of efficiency while also caring for workers and society.
Topic 9: Ever-Evolving Nature of Scientific Knowledge
Case Study 17 (Q17): Changing Models of the Solar System
In their science class, students learn that long ago people believed that the Earth was at the centre of the
universe. Later, scientists like Copernicus and Galileo gave evidence that the Sun is at the centre of the
solar system. Over time, more planets and dwarf planets were discovered. Even the definition of a planet was
changed when Pluto was called a dwarf planet.
- What does this case tell us about scientific ideas over time?
- Why was Pluto reclassified as a dwarf planet?
- How does this example show that science is “ever-evolving”?
Answers for Q17:
- Scientific ideas can change when new evidence is found. Old models can be replaced by better ones.
- Because new information and a new definition of a planet showed that Pluto did not fit as a main planet.
- It shows that science develops continuously. As we collect more data, scientific knowledge is updated.
Case Study 18 (Q18): From Traditional Remedies to Modern Medicine
In earlier times, people used only traditional home remedies for illnesses. Some were helpful, while others
did not work well. Today, modern medicine is developed through careful scientific research and testing. Many
useful traditional remedies have also been studied scientifically, and some have become part of modern
treatments after being tested.
- How has the understanding of medicines changed with time?
- What is the role of scientific testing in accepting traditional remedies?
- Why is it important to combine useful traditional knowledge with modern scientific methods?
Answers for Q18:
- Earlier, medicines were used mainly based on experience and belief. Now, modern medicines are based on scientific research and testing.
- Scientific testing checks if a remedy is safe and effective before it is widely used.
- Because it preserves useful traditional practices and makes them safer and more reliable through scientific proof.
Topic 10: Role of Science in Shaping the Future
Case Study 19 (Q19): Preparing for Natural Disasters
A coastal city often faces cyclones. Scientists use satellites and weather radars to track storms and give
early warnings. Based on this information, the government evacuates people from risky areas and provides safe
shelters. Schoolchildren are taught safety drills and the importance of listening to weather forecasts.
- How does science help in predicting cyclones in this case?
- What is the benefit of getting an early warning?
- Why should students learn about disaster preparedness in their science classes?
Answers for Q19:
- Scientists use satellites and weather radars, which are scientific tools, to track cyclones.
- Early warning gives time to evacuate people, save lives and reduce damage.
- Because it helps them understand natural phenomena and teaches them how to stay safe during disasters.
Case Study 20 (Q20): Science for a Better Tomorrow
A school organises a Science for Future exhibition. Students present models of water purifiers, low-cost
houses, robots for difficult rescue operations and ways to recycle waste. Teachers explain that future
scientists and engineers will have to solve problems like shortage of clean water, pollution, diseases and
natural disasters using science and technology.
- What kinds of future problems are mentioned in this case?
- How can science help in solving these problems?
- Why is it important for today’s students to develop an interest in science?
Answers for Q20:
- Problems like shortage of clean water, pollution, diseases and natural disasters.
- Science can help by developing new methods of water purification, medicines, cleaner technologies and better disaster management tools.
- Because they are the future citizens and scientists who will use scientific knowledge to improve the world.