CLASS 7 SCIENCE · CHAPTER 1 · STUDY NOTES
The Ever-Evolving World of Science
Connect what you know with new questions about materials, living things, light, time and Earth.
01 / EXPLORE & UNDERSTAND
Science keeps growing
An answer can lead to another question. New evidence can improve an old idea.
A familiar activity can start a science question
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1. An everyday question can start an investigation
Why does one paper plane travel farther than another? Start with something you can observe, then choose one feature to compare, such as wing width.
2. Let the evidence improve your idea
Use similar paper and the same launch place. Repeat the trials and record the distances. One lucky flight is not enough to decide. If the results differ from your guess, check the test and rethink the explanation.
A little deeper: A design can improve through evidence
If two paper-plane designs fly differently, compare what you changed and what you observed. One flight alone may not settle the question. Repeated safe observations help you separate a useful pattern from a chance result.
Your turn
Question
Why is finding an unexpected result useful?
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02 / EXPLORE & UNDERSTAND
Ask what a material can do
Different materials behave differently. We can notice and compare their properties.
The material becomes part of a circuit
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1. Ask about a property
A property is something about a material that we can observe or test. Is it hard, flexible or able to carry electricity? Wood and metal can look different and behave differently too.
2. Connect a question to a safe test
The book introduces questions about sour fruits, colour changes and electric circuits. These are different investigations. Do not taste unknown substances. For electricity activities, use only an approved low-voltage battery setup with adult guidance—never a wall socket.
Your turn
Question
Two objects look alike. Does that prove their materials have the same properties?
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03 / EXPLORE & UNDERSTAND
Connect changes, heat and water
Melting ice, ripening fruit and water moving through nature are different questions.
Follow water through the landscape
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1. Describe before and after
Ice can melt into liquid water. A raw fruit can ripen. Both are changes, but they are not the same kind. Compare what has changed before trying to explain why.
2. Follow the water, not just the picture
Water at the surface can enter the air as invisible water vapour. Energy from sunlight helps this happen. In the water cycle, water also forms droplets and returns as rain. The diagram above shows evaporation, just one part of that cycle.
A little deeper: Invisible water vapour
Water can enter the air as invisible vapour. In the drawing, blue dots stand for vapour; we cannot see real water vapour with our eyes. Later you will connect evaporation with cooling, condensation and the water cycle.
Your turn
Question
Why should you record what you saw before a change?
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04 / EXPLORE & UNDERSTAND
Growing bodies need life processes
Animals and plants stay alive through important activities inside their bodies.
Find the parts before naming their jobs
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1. Living things need more than one process
Animals take in food and breathe. Digested nutrients and oxygen need to reach different parts of the body. The book introduces these connected processes; later chapters explain how they work.
2. Plants are living too—but not little animals
Green plants make food using light, water and carbon dioxide. Plants also respire. Living things grow and change; during adolescence, human bodies go through important changes. Do not assume that every organism gets food in the same way.
Your turn
Question
Why is “plants do not need food” a poor starting assumption?
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05 / EXPLORE & UNDERSTAND
Time, light and the moving Earth connect
A shadow on the ground and day and night can both start questions about light.
One Earth, a lit side and a dark side
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1. Look at the side facing the Sun
Sunlight reaches one side of Earth at a time. That side has day; the side facing away has night. As Earth rotates, a place moves into sunlight and later out of it.
2. Keep different movements separate
Earth’s rotation explains day and night. Its journey around the Sun is a different movement. Shadows help us investigate light and time, while eclipses involve particular arrangements of the Sun, Earth and Moon. An everyday shadow is not automatically an eclipse.
Your turn
Question
Does every shadow on Earth mean an eclipse is happening?
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06 / EXPLORE & UNDERSTAND
Ask better questions; explore responsibly
Curiosity works best with care for people, living things and the environment.
Before testing a paper cover
- What changes?
- The material used as a cover.
- What stays the same?
- Paper size, amount of water and test time.
- What will you notice?
- How wet the paper is afterwards.
1. Plan before you begin
Choose a question you can investigate safely. For example, compare how two covers keep a sheet of paper dry with a little water. Decide what to keep the same and ask an adult to check the activity.
2. Care is part of good science
Listen to others, record what actually happened and avoid wasting water or materials. Do not harm plants or animals to satisfy curiosity. A useful investigation can answer one question and give you another.
Your turn
Question
The answer is “Compare both.” Suggest one interesting question that could lead to it.
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Take these ideas with you
- Questions lead to tests; evidence can change an explanation.
- Materials, changes, living things and light connect to everyday life.
- Investigate safely, honestly and with care for nature.
Use your understanding in a new situation
Question
A towel soaks up more water in one trial. What should you check before calling it the better material?
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It is daytime in one place and night in another at the same moment. Does this mean the Sun switches on and off?
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Sign inNew here? Sign up freeNCERT · Chapter source PDF, pages 2, 5, 6 · Original Learnijoy explanations and practice.