Chapter 1: The Ever-Evolving World of Science
An invitation to be curious, ask bold questions, and explore the beautiful world we live in.
✨ Curiosity • Questions • Experiments • Discovery
🧭What this chapter is about
- Science isn’t just facts—it's a way of thinking that welcomes curiosity.
- We observe, question, test, and learn from the world—tiny cells to distant stars.
- Asking deeper questions: How do things work? Why do events happen? What patterns do we notice?
🦋Let your learning take flight
Just as a butterfly flutters and a paper plane soars, learning takes flight when curiosity leads. Simple ideas—like paper planes—have inspired real scientific explorations of flight!
Try: Observe ✍️ → Wonder 🤔 → Test 🔬 → Explain 💡
🧩Science is connected
Physics, chemistry, biology, and earth science are like puzzle pieces—ideas in one field spark discoveries in another.
Materials
Heat & Changes
Water Cycle
Life Processes
Time & Motion
Light & Shadows
Earth–Moon–Sun
Sustainability
🗺️A quick journey through the book
Materials Around Us — Why are some fruits sour? Why does a haldi stain behave oddly on washing? Which materials make a lamp glow?
Metals & Non-metals — Classify materials by properties like conduction and luster.
Changes Around Us — Reversible vs. irreversible: ice → water (reversible), fruit ripening (mostly irreversible), batteries running out (irreversible), rocks to pebbles.
Heat Flow & Water — Melting ice in a glass vs. melting glaciers; evaporation, condensation, and rainfall—parts of the water cycle.
Growing Bodies & Life Processes — Eating, breathing, circulation in animals; how plants make/get food; breathing in plants.
Measuring Time — From shadow clocks to watches: how do we know how fast things happen?
Light & Shadows — Seeing the world, reading at night, and exploring nature of light; eclipses as giant shadows.
Earth–Moon–Sun Dance — Earth’s rotation (day & night), Moon around Earth, Earth around Sun, and their effects on life.
🧪Science is what you do
- Step out of the book—observe the world.
- Do hands-on experiments and record what you see.
- Spot patterns and use them to explain and predict.
- Be ready to change your mind when evidence says so.
🌍Discovery with responsibility
Human activities affect nature and society. Science helps us understand problems and build a more sustainable world.
- Use resources wisely.
- Think about long-term effects.
- Design solutions that help people and the planet.
📌Core ideas to remember
- Curiosity leads to learning—questions power discovery.
- Everything is connected—ideas jump across topics.
- Changes can be reversible or not—identify which and why.
- Heat drives change—from melting ice to the water cycle.
- Life processes keep organisms alive—nutrition, breathing, circulation, growth.
- Time & measurement help us compare speeds and durations.
- Light & shadows explain how we see and phenomena like eclipses.
- Earth–Moon–Sun motions shape days, nights, and seasons.
- Evidence first—experiments may raise new questions (that’s good!).
🎯1.1 Happy Exploring! — Activity 1.1: Question the Answer
In science, great thinkers don’t just answer questions—they ask amazing ones. Create fun, curious questions that could lead to the given answers.
| Answer | Your Creative Question |
|---|---|
| Because the cat’s teeth were crooked. | |
| Just add some milk. | |
| Don’t panic, I have my towel. | |
| 42 |
Pro-Tip: Avoid obvious questions like “What is 32+10?” Be imaginative and connect to real-life situations!
🧠Quick Self-Check
- Give two examples of reversible and two of irreversible changes around you.
- How does heat influence the water cycle?
- Why do eclipses happen? Use the words light and shadow.
- List three life processes common to animals. How do plants handle similar needs?
- What simple methods did people use to measure time before watches?
🗝️Key Terms
Observation Hypothesis Experiment Evidence Reversible Change Irreversible Change Conduction Evaporation Condensation Eclipse Rotation Revolution Sustainability
Chapter 1 Practice: The Ever-Evolving World of Science
Fully-solved practice in five sections • Perfect for revision and self-study
🔬 Ask • 🔎 Explore • 🧠 Explain • 🌍 Act
🗝️Section 1 — 20 Key Words (Simple Meanings)
| Word | Meaning (in simple words) |
|---|---|
| Curiosity | Wanting to know more; asking questions. |
| Observation | Noticing things carefully using our senses. |
| Hypothesis | A smart, testable guess to explain something. |
| Experiment | A planned test to check our hypothesis. |
| Evidence | Facts/data from observations and experiments. |
| Variable | Something that can change in an experiment. |
| Control | The part kept the same for fair comparison. |
| Reversible change | A change that can be undone (like ice → water → ice). |
| Irreversible change | A change that cannot be easily undone (like burning paper). |
| Conductor | Material that lets electricity pass (like metals). |
| Insulator | Material that does not let electricity pass (like plastic, rubber). |
| Evaporation | Liquid turning into gas by heating. |
| Condensation | Gas turning back to liquid by cooling. |
| Water cycle | Water moving as evaporation, condensation and rain. |
| Photosynthesis | Plants making food using sunlight, air and water. |
| Respiration | Releasing energy from food (needs oxygen in most living things). |
| Rotation | Earth spinning on its axis (causes day and night). |
| Revolution | Earth moving around the Sun (affects seasons). |
| Eclipse | When one space body blocks light to another, making a shadow. |
| Sustainability | Using resources wisely so future life is safe and happy. |
🎯Section 2 — One-Word Answers (10)
Answer in one word only. Fully solved
1) Plants make their own food by ________.
Photosynthesis
2) A change that can be undone is ________.
Reversible
3) Day and night are caused by Earth’s ________.
Rotation
4) Earth going around the Sun is called ________.
Revolution
5) Liquid turning to gas is ________.
Evaporation
6) Gas turning back to liquid is ________.
Condensation
7) A device that uses a shadow to tell time: ________.
Sundial
8) When one space body blocks another’s light: ________.
Eclipse
9) A material that lets electricity flow: ________.
Conductor
10) A material that stops electric flow: ________.
Insulator
✍️Section 3 — Very Short Answers (10) • 2–3 lines each
1) Why do we say science is a way of thinking?
Because science begins with curiosity and questioning. We observe, form a hypothesis, test it, and use evidence to explain the world—ready to change ideas if results disagree.
2) Give two reversible and two irreversible changes.
Reversible: melting ice, inflating a balloon. Irreversible: burning paper, ripening of fruit. In the first set we can get the original form back, in the second we cannot.
3) How does heat affect changes?
Heat speeds particle motion, so many changes happen faster—ice melts, water evaporates, butter softens. In nature, extra heat can also melt snow and glaciers.
4) Explain evaporation and condensation in the water cycle.
Water evaporates from oceans and lakes to form water vapour. High up, it cools and condenses into clouds; later it falls as rain.
5) How did people measure time before clocks?
They used the Sun’s shadow in a sundial, watching how it moves because Earth rotates. They also used hourglasses and water clocks.
6) How do plants and animals get energy differently?
Plants make food by photosynthesis and then respire to release energy. Animals eat food and respire to get energy—they cannot make their own food.
7) Why are conductors and insulators useful in a circuit?
Conductors (like copper) carry current to light a bulb. Insulators (like plastic) cover wires for safety so electricity doesn’t pass through our bodies.
8) What causes day and night?
Earth spins on its axis (rotation). The side facing the Sun has day; the opposite side has night, repeating roughly every 24 hours.
9) What is an eclipse in simple words?
It’s a big shadow event in space—one body blocks light to another. In a solar eclipse, the Moon blocks sunlight to Earth; in a lunar eclipse, Earth’s shadow falls on the Moon.
10) What does sustainability mean for young scientists?
Using resources carefully, reducing waste and pollution, and choosing solutions that help people and nature—so future generations also live well.
🧩Section 4 — Mixed Concept Practice (Fully Solved)
Covers materials & changes, heat & water, life processes, light & shadows, and Earth–Moon–Sun.
🧠 A) Fill in the Blanks
1) A fair test changes only one ________ at a time.
Variable
2) The part kept the same for comparison is called the ________.
Control
3) Metals are good electrical ________.
Conductors
4) ________ turns liquid water into water vapour.
Evaporation
5) The Moon’s shadow on Earth causes a ________ eclipse.
Solar
6) Earth’s ________ around the Sun affects seasons.
Revolution
🔎 B) Classify the changes as Reversible (R) or Irreversible (IR)
7) Melting chocolate
R — can solidify again by cooling.
8) Rusting of iron
IR — new substance (rust) forms; hard to get iron back.
9) Freezing water
R — can melt back to water.
10) Burning a candle wick
IR — burning makes new substances (ash, gases).
✅ C) True or False (Correct if false)
11) Condensation changes liquid into gas. (T/F)
False. Condensation changes gas → liquid.
12) All shiny materials conduct electricity. (T/F)
False. Many shiny plastics don’t conduct; metals usually do.
13) Day and night happen due to Earth’s revolution. (T/F)
False. They happen due to rotation.
14) Plants and animals both respire. (T/F)
True. Both use respiration to release energy from food.
📝Section 5 — Long Answer Type (10) • 3–4 lines each
1) Explain how curiosity leads to scientific understanding.
Curiosity makes us observe and ask “why/how?”. We suggest a hypothesis, test it by experiments, and collect evidence. If results support it, we build explanations; if not, we rethink—this cycle grows knowledge.
2) Compare rotation and revolution of Earth with their effects.
Rotation is Earth spinning on its axis once in ~24 hours—causing day and night. Revolution is Earth’s yearly path around the Sun—affecting seasons and the apparent position of stars over months.
3) Differentiate reversible and irreversible changes with examples.
Reversible changes can be undone (ice ↔ water, stretching a spring). Irreversible changes form new substances or permanent changes (burning paper, baking a cake, rusting iron).
4) Describe how heat drives parts of the water cycle.
Sunlight heats water, causing evaporation. Warm, moist air rises and cools, leading to condensation into clouds. When droplets grow heavy, they fall as rain—completing the cycle.
5) Explain why a bulb glows with some materials but not others.
The bulb glows only if current completes a circuit. Metals (copper, aluminium) are conductors so they allow current. Materials like plastic or wood are insulators; they block current so the bulb stays off.
6) How do plants and animals meet basic life processes?
Plants make food by photosynthesis, exchange gases through stomata, and transport materials via vessels. Animals eat food, breathe using organs (lungs/gills), and circulate nutrients through blood.
7) Connect light, shadows, and eclipses to everyday observations.
A shadow forms when light is blocked—like your hand near a lamp. In space, the same idea scales up: if the Moon blocks sunlight to Earth, we see a solar eclipse; if Earth’s shadow falls on the Moon, it’s a lunar eclipse.
8) Outline a fair test to check which materials conduct electricity.
Make a simple circuit with a cell, bulb, and gap for a test piece. Keep cell and bulb the same (control), change only the test material (variable). If the bulb lights, the material is a conductor; if not, an insulator.
9) What is sustainability and how can students practice it daily?
Sustainability means using resources without harming the future. Students can save electricity and water, reduce plastic, reuse notebooks, plant trees, and prefer public transport or cycles.
10) Why is evidence important in science?
Evidence—measurements and observations—lets everyone check claims. It reduces personal bias, allows repeatable results, and helps us accept, modify, or reject ideas fairly.