Question

ses, write in the blank whether the process is a chemical change or a physical change: a. A sheep eats grass and produces a coat of wool. b. A sheep is sheared and the wool is used to make a suit. c. Flour, baking powder, sugar, eggs, milk, shortening, and apples are used to bake an apple turnover. d. A pan full of ice is heated until the ice becomes water and then steam. An entrepreneur harvests silk from a spider and manufactures a new pillowcase e.

Answer 1

A physical change is the one where the substance does not lose its identity and remains the same even after the change whereas the chemical change is the one where the substance loses its identity and change into something new thereby giving altogether a new substance.

a) chemical change ( grass ------> wool)

b) Physical change [wool -------suit (made up of wool)]

c) chemical change ( Flour, baking powder etc -------> apple turnover)

d) Physical change [ ice (H₂O)--------> water (H₂O) -----------> steam (H₂O) ]

e) Physical change [silk ---------> pillow (silk)]

2. Addition of acid to sodium bicarbonate releases CO₂ thereby making it a chemical change because here sodium bicarbonate decomposes to form CO₂ and since sodium carbonate is converted into CO₂, therefore, this is a chemical change whereas dry ice is solid CO₂ which when sublimes turns into gas and thus this is a physical change since before and after the change, CO₂ remains as CO₂ and does not change into another substance.