NCERT Solutions for Curiosity Chapter 5 Changes Around Us: Physical and Chemical
Updated on 2026-09-05
About this chapter
A physical change alters only physical properties such as shape, size or state. No new substance is formed — folding paper, crushing chalk, melting ice. A chemical change forms one or more new substances through a chemical reaction , which can be written in short as a chemical equation . Blowing air into lime water, vinegar + baking soda, rusting and burning are chemical changes. Lime water turning milky is the standard test for carbon dioxide . Calcium hydroxide + Carbon dioxide → Calcium carbonate (insoluble, white) + Water. Combustion is a reaction with oxygen that gives out heat and/or light . It needs three things — the fire triangle : a combustible substance (fuel), oxygen , and enough heat to reach the ignition temperature . One process can involve both kinds of change . In a burnin
- Chapter opener
- Table 5.1: Some changes observed around us
- .1 A Substance May Change in Appearance but Remain the Same!
- .3.2 Combustion
- Is the Presence of Air Enough for Combustion?
- .5 Are Changes Permanent?
- Table 5.2: Can changes be reversed?
- .6 Are All Changes Desirable?
- .7.1 Weathering of rocks
- .7.2 Erosion
Exercises
- Chapter opener — In-text Questions Page 57
- Table 5.1: Some changes observed around us — Activity 5.1: Let us think and reflect Page 58
- .1 A Substance May Change in Appearance but Remain the Same! — Activity 5.2: Let us create and discuss Page 595
- .2 A Substance May Change in Appearance and Not Remain the Same! — Activity 5.3: Let us explore Page 605
- .2 A Substance May Change in Appearance and Not Remain the Same! — Activity 5.4: Let us experiment Page 615
- .3.2 Combustion — In-text Questions Page 625
- .3.2 Combustion — Activity 5.5: Let us investigate Page 625
- .3.2 Combustion · Science and Society · Is the Presence of Air Enough for Combustion? — In-text Questions Page 635
- Is the Presence of Air Enough for Combustion? — Activity 5.6: Let us investigate Page 64
- .4 Can Physical and Chemical Changes Occur in the Same Process? — Activity 5.7: Think, pair, and share Page 655
- .5 Are Changes Permanent? — In-text Questions Page 665
- Table 5.2: Can changes be reversed? — Activity 5.8: Let us think Page 66
- .6 Are All Changes Desirable? — In-text Questions Page 665
- .7.1 Weathering of rocks — In-text Questions Page 675
- .7.2 Erosion — In-text Questions Page 685
- Chapter-end exercise, Questions 1–10 — Let Us Enhance Our Learning Page 69
- Projects and investigations at the end of the chapter — Exploratory Projects Page 71