a. Melting butter: In this the physical property of the butter changes. That is the butter changes from solid to liquid state. This is a physical change.
b. Boiling of water: In this temperature of water changes. Simultaneously, some of the water changes from liquid state to gaseous (steam or water vapour). Both these changes are physical changes.
c. Digesting food: Digesting of food is a very complex process including changes in chemical composition of food, dissolving of nutrients in water and other fluids, and absorption of food by blood. Thus digesting of food involves combination of physical as well as chemical change.
d. Baking brownie: This process, like digesting of food is a complex process involving physical as well as chemical change. For example, some of the water in the dough gets evaporated. This is a physical process. Also some of the ingredients in the dough change their chemical composition. This is a chemical change.
e. Exploding TNT: In this process, what happens to TNT is a pure chemical change. But the accompanying impact of explosion on surroundings is a physical change.
f. Dissolving sugar: This is a purely physical change.Pleas note that dissolving of sugar is not same as converting sugar from solid to liquid state. Dissolving is a different type of physical change.
g. Burning fuel oil: This is purely a chemical change. This is primarily a result of chemical process called oxidation.
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