Which statement is true about physical changes and chemical changes? a. chemical changes are not observable. b. chemical changes always produce new substances. c. physical changes can change physical and chemical properties. d. physical and chemical changes cannot happen at the same time.

Asmall electric heater, immersed in 80g of water in a calorimeter of 40j/k raises the temperature from 10.5 degree celsius to 25 degree celsius in 12 minutes. using the same apparatus with 50g of oil instead of water, it is found that the temperature of oil rises from 7 degree celsius to 27 degree celsius in 10 minutes. find specific heat capacity of the oil.