Explain why the extrapolated temperature is used to determine the maximun temperature of the mixture rather than the highest recorded temperature

The extrapolated temperature is used to define the maximum temperature of the mixture relatively than the highest recorded temperature in which the conclusion will effect in a higher specific heat value. Heat is bound to escape from whatever apparatus is using, therefore it is needed to account for the loss of the heat that does not go into increasing the temperature of the mixture. 

Answerigneous bedrock of the oceanic crust;