NCERT Solutions Class 7 Science Chapter 5 – Changes Around Us: Physical and Chemical

Change is continuous in our surroundings. Change involves melting ice, rusting of iron, baking a cake, etc. In NCERT Solutions Chapter 5 of Class 7 Science, Changes Around Us, students will learn about physical and chemical changes, what are the differences, what is the purpose of physical or chemical changes, and what is the real-life application of changes?

Recognizing these changes will encourage us not only in science but also in our exploration and awareness about the environment around us. With organized NCERT solutions to help encourage the development of strong conceptual clarity, students will be able to easily answer any question found in the textbook.

1.0NCERT Solutions Class 7 Science Chapter 5 – Changes Around Us: Physical and Chemical – Download PDF

Download the free PDF of NCERT Solutions for Class 7 Science Chapter 5 from below:

2.0Key Concepts in Chapter 5 – Changes Around Us: Physical and Chemical

Reversible and Irreversible Changes

• Reversible Change: Can be undone. Example: melting of wax; freezing of water.
• Irreversible Change: Cannot be easily undone. Example: cooking of food; burning of paper.

Physical Changes

• changes in state; shape; appearance.
• No new substance is formed.
• Most will be reversible.

Examples: stretching of a rubber band, melting ice, breaking glass.

Chemical Changes

• Creates one or more new substances.
• Usually it will create heat, light, change in color, gas released, or formation of a precipitate.
• Usually irreversible.

Examples: rusting of iron, curdling of milk, burning of wood, digestion of food.

Common Identifiers of a Chemical Change

• Gas bubbles are formed without boiling
• Unexpected temperature or color change occurs
• A solid (precipitate) is formed in a liquid.

Real-World Uses of Physical and Chemical Changes

Household Examples

Cooking- A chemical change because raw ingredients change into something new, edible and a substance.

Melting wax- A physical change, as people melt chic wax and create candles and molds.

Freezing water- A physical change, where water freezes or a change in state that can be seen in refrigerators or cold storage.

Industrial and Environmental Examples

Rust prevention- A chemical change that we avoid; we paint or galvanize some metals that we use to avoid changes in those metals over time.

Paper recycling- is an example of physical change that is a process involving pulping ingredients, and removing water to make shapes. 

Burning gasoline in a vehicle- A chemical change as we do a process of conversion, in a truck it changes gasoline to energy and exhaust gases.

Agriculture and Health

Photosynthesis- A chemical change. It is a process that converts carbon-dioxide and water into glucose and oxygen. 

Fermentation- A chemical process involving microbes to turn grape juice or grain into alcohol or acids. 

Digestion- A chemical change. A series of chemical changes that break down food, to sugars, protein, etc.

Promoting the Scientific Mindset 

This was the part of my chapter intended to promote the scientific mindset, trying to pose questions like:

• What happens when we burn a piece of paper?
• Does boiling water have a reverse process, to become cold water?
• Why does iron rust, and what can I do to prevent that from occurring?
• What is the difference between ice melting and curdling milk?

Because of observations and participation in hands-on experiments, whether we blow up balloons from the chemical reactions, and/or whether or how soap impact changes in turmeric, students are encouraged to visualize the next step in learning, hypothesize the reasons why, conduct a series of observations of example, or what they think an example may appear or what additional resources they have.

3.0NCERT Class 7 Science Chapter 5 : Changes Around Us - Physical and Chemical: Detailed Solutions

• Which of the following statements are the characteristics of a physical change? (i) The state of the substance may or may not change. (ii) A substance with different properties is formed. (iii) No new substance is formed. (iv) The substance undergoes a chemical reaction. (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iii) (d) (iii) and (iv) Ans. The correct option is (c) (i) and (iii). A physical change may or may not involve a change in state, but no new substance is formed. Formation of a new substance and occurrence of a chemical reaction are characteristics of a chemical change.
• Predict which of the following changes can be reversed and which cannot be reversed. If you are not sure, you may write that down. Why are you not sure about these? (i) Stitching cloth to a shirt (ii) Twisting of straight string (iii) Making idlis from a batter (iv) Dissolving sugar in water (v) Drawing water from a well (vi) Ripening of fruits (vii) Boiling water in an open pan (viii) Rolling up a mat (ix) Grinding wheat grains to flour (x) Forming of soil from rocks Ans. (i) Stitching cloth to a shirt - Reversible (we can un-stitch the thread). (ii) Twisting of a straight string Reversible (we can untwist it). (iii) Making idlis from batter - Cannot be reversed (We cannot recover the batter back). (iv) Dissolving sugar in water Reversible (evaporate water to get sugar back). (v) Drawing water from a well Reversible (water can be poured back). (vi) Ripening of fruits - Cannot be reversed (cannot un-ripen fruits). (vii) Boiling water in an open pan Cannot be reversed (water vapour cannot be collected back). (viii) Rolling up a mat - Reversible (we can unroll it again). (ix) Grinding wheat grains to flour Cannot be reversed (we cannot reform grains again). (x) Forming soil from rocks - Cannot be reversed (naturally irreversible process we cannot get back rocks again).
• State whether the following statements are True or False. In case a statement is False, write the correct statement. (i) Melting of wax is necessary for burning a candle. (ii) Collecting water vapour by condensing involves a chemical change. (iii) The process of converting leaves into compost is a chemical change. (iv) Mixing baking soda with lemon juice is a chemical change. Ans. (i) False Melting of wax is necessary for burning a candle. It is the vapour of wax which burns to produce flame and not just the melted wax. (ii) False Collecting water vapour by condensing involves a chemical change. Condensation is a physical change as no new substance is formed. (iii) True The process of converting leaves into compost is a chemical change. Decomposition takes place during conversion of leaves into compost, which is a new substance. (iv) True Mixing baking soda with lemon juice is a chemical change. The chemical reaction occurs between baking soda and lemon juice to produce carbon dioxide and other new substances, so it is a chemical change.
• Fill in the blanks in the following statements: (i) Nalini observed that the handle of her cycle has got brown deposits. The brown deposits are due to $\_\_\_\_$ and this is a $\_\_\_\_$ change. (ii) Folding a handkerchief is a $\_\_\_\_$ change and can be $\_\_\_\_$ . (iii) A chemical process in which a substance reacts with oxygen with evolution of heat is called $\_\_\_\_$ , and this is a $\_\_\_\_$ change. (iv) Magnesium, when burnt in air, produces a substance called $\_\_\_\_$ . The substance formed is $\_\_\_\_$ in nature. Burning of magnesium is a $\_\_\_\_$ change. Ans. (i) chemical change. (ii) physical, reversed. (iii) combustion, chemical (iv) magnesium oxide, white-coloured, chemical
• Are the changes of water to ice and water to steam, physical or chemical? Explain. Ans. Both are reversible physical changes. Water changes its state (solid $\rightleftharpoons$ liquid $\rightleftharpoons$ gas), but no new substance is formed, and its chemical composition ( ${\mathrm{H}}_2\mathrm{O}$ ) remains unchanged.
• Is curdling of milk a physical or chemical change? Justify your statement. Ans. Curdling of milk is a chemical change. New substances (curd which contains lactic acid) with different properties is formed, and the process is irreversible.
• Natural factors, such as wind, rain, etc., help in the formation of soil from rocks. Is this change physical or chemical and why? Ans. The formation of soil from rocks involves both physical and chemical changes: Physical changes: Breaking of rocks into smaller pieces due to wind, water, temperature changes, and root growth (mechanical weathering). Chemical changes: Reaction of minerals with water, oxygen, and acids (e.g., iron forming rust), changing the rock composition.
• Read the following story titled 'Ecofriendly Prithvi and tick the most appropriate option(s) given in the brackets. Provide a suitable title of your choice for the story. Prithvi is preparing a meal in the kitchen. He chops vegetables, peels potatoes, and cuts fruits (physical changes/chemical changes). He collects the seeds, fruits, and vegetable peels into a clay pot (physical change/chemical change). The fruits, vegetable peels, and other materials begin to decompose due to the actison of bacteria and fungi, forming compost (physical change/chemical change). He decides to plant seeds in the compost and water them regularly. After a few days, he notices that the seeds begin to germinate and small plants start to grow, eventually blooming into colourful flowers (physical change/chemical change). His eff orts are appreciated by all his family members. Ans. Prithvi chops vegetables, peels potatoes, and cuts fruits: Physical changes He collects seeds, fruit and vegetable peels into a clay pot: Physical change The peels decompose to form compost: Chemical change Seeds germinate and grow into flowering plants: Chemical change
• Some changes are given here. Write physical changes in the area marked 'A' and chemical changes in the area marked 'B'. Enter the changes which are both physical and chemical in the area marked ' C '. Process of burning a candle; Tearing of paper; Rusting; Curdling of milk; Ripening of fruits; Melting of ice; Folding of clothes; Burning of magnesium and Mixing baking soda with vinegar.
  
  Physical Changes (A) Tearing of paper Melting of ice Folding of clothes Chemical Changes (B) Rusting Curdling of milk Ripening of fruits Burning of magnesium Mixing baking soda with vinegar Both Physical and Chemical Changes (C) Burning of a candle (wax melts physical change, wax burns - chemical change)
• The experiments shown in Figure $\mathrm{a},\mathrm{b},\mathrm{c}$, and d were performed. Find out in which case(s) did lime water turn milky and why?
  
  (a)
  
  (b)
  
  (c)
  
  (d) Ans. Lime water turns milky in cases (a) and (d) because carbon dioxide is formed, producing calcium carbonate in lime water.

4.0Key Features of NCERT Solutions – Chapter 5 : Changes Around Us: Physical and Chemical

• Deep Conceptual Knowledge: The solutions turn complicated concepts such as oxidation and precipitation into easy-to-understand language, therefore ensuring a deep understanding.
• Complete Coverage: All conceivable textbooks questions—In-Text Exercises, Activity-based Reasoning, and HOTs questions—are all thoroughly outlined and explained.
• Transferable Thinking: Explanations contain more than just the answers—they explain the reason behind the changes, creating stronger scientific thinkers.
• Real-World Relevance: Learning is facilitated and enriched by connecting real-world instances such as rustings, baking, and freezing to classrooms.
• Exam-Ready Format: After working through step-by-step solutions using key terminology, students will have the confidence to answer any question type on class and exam tests.