How many minutes should 750 ml of water take to boil?

Heat require to boil 750 g water from 25 C0to 100 C0

Q = m s dT

= 750 g * 4.2 cal /g /K * (100 - 25)

= 236.25 * 103 J

If stove is supplying 1000 W power then time required is:

Q = P *t

236.25 * 103 = 1000 * t

t = 236.25 s

Thus 236.25 s is required by a 1000 W power supplying stove to boil 750 mL water

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e