Changes Around Us Physical and Chemical Study Notes

Key concepts from this chapter

• Physical changes involve change in state or form without creating a new substance.
• Chemical changes result in the formation of new substances and are usually irreversible.
• Physical changes are often reversible, like melting ice turning back to solid ice.
• Chemical changes show signs like change in color, smell, temperature, or gas formation.
• Examples of physical changes: melting ice, boiling water, cutting vegetables, dissolving sugar in water, warming a bottle of water, freezing water into ice, evaporation of water, condensation of steam into water, breaking glass, stretching rubber band, mixing sand and salt, folding paper, crushing paper, boiling water to steam, freezing water into ice cubes, dissolving sugar in tea, cutting fruits, tearing paper, bending metal wire, dissolving salt in water, melting butter, chopping vegetables, mixing oil and water (physical mixture). Examples of chemical changes: rusting of iron, cooking food, ripening of fruits, burning paper, digestion of food, photosynthesis in plants, fermentation of grapes to make wine, burning candle, baking a cake, souring of milk, burning wood, formation of curd, combustion of fuels, ripening of banana, corrosion of metals, digestion of food in stomach, burning coal, formation of new substances during chemical reactions, change in smell or color during chemical reactions, release or absorption of heat during chemical changes.