"Tofautisha katika nishati joto na nishati mwendo."
Translation:Compare thermal energy and kinetic energy.
Yup, but I think that the audio is correct Swahili (kati ya), whereas the written text is wrong (katika). One example on Glossbe:
Ikiwa ni vigumu kwetu kutofautisha kati ya vitu tunavyotaka na mahitaji halisi... -> 'If we have difficulty distinguishing between what we want and what we truly need...'
There are many more examples there using kati ya, and only one with katika.
I've seen people mention that the content and structure of Duolingo courses are sometimes influenced by the volunteers that create the courses. Swahili was initially spearheaded by Peace Corps Tanzania, which has a lot of volunteers teaching secondary math and science (including Physics).
Thanks for this Science bit.....enjoying it. Not so talented with language so along with numbers time etc this makes it so more interesting. The Swahili speaker does it all very fast. Wide open ears help a lot but while learning the language slow speaking audios might be helpful.