Hello. You did not inform the experiment to which this question refers, which makes it impossible for it to be answered accurately. However, I will try to help you in the best possible way.
Specific heat is the term that refers to the amount of thermal energy needed to affect the temperature of 1 gram of a homogeneous material, that is, a material that is composed entirely of the same substance. In this case, if we imagine an experiment that evaluates the specific heat of different materials, we can consider that the presence of impurities in that material can alter the specific heat, causing errors in the experiment. The intensity of thermal energy can also cause this change, as well as the presence of water in the tested materials because the water has a very high specific heat, which can interfere in the experiment.