Why does the Temperature Decrease?

![enter image description here](https://i.stack.imgur.com/8sF7Z.png)


This is from a calorimetry lab. $50\ \mathrm{ml}$ of acid and base were mixed. Why does the temperature keep decreasing after 1 minute and why isn't at a constant rate?


Is it because heat is lost to the surroundings?




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Source: <https://fronter.com/uio/links/files.phtml/1520337012>$477794732$/Lab/Laboppgaver+-++Prelab++-+Rapportmal/Oppgave+2+all.pdf


This for a Lab Report Hand-IN at my University. Blindern University of Oslo. 


