Two different liquids are mixed together. which observation indicates that an exothermic chemical reaction has taken place?
a. an increase in volume
b. a decrease in volume
c. a rise in temperature
d. a drop in temperature

The  observation  which indicate  that an exothermic reaction  has taken place when two different  liquid are mixed  together is  a rise  in temperature  (answer C)

Explanation

 Exothermic reaction  is a   chemical reaction which releases  energy  in form of heat  or light.

  Examples  of   exothermic reaction is  a combustion reaction,  for instance combustion of methane which occurs as below.

CH4 +O2→  CO2 + 2H2O + heat

other  examples  of exothermic reaction is   neutralization reaction,  rusting of iron  and reaction between water and calcium  chloride.

the answer is a

photosynthesis

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."