Update 2_debye_model.md - typo

src/2_debye_model.md

@@ -32,8 +32,8 @@ _(based on chapter 2.2 of the book)_
     Before the start of this lecture, you should be able to:
 
     - Describe how atoms are modeled in the Einstein model 
-    - Describe the low-temperature behaviour of the Einstein heat capacity per atom 
-    - Describe how the frequency of a sound wave depends on the wavenumber $k=2\pi/\lambda$ of the soundwave, where $\lambda$ is the wavelength.
+    - Derive the low-temperature behaviour of the Einstein heat capacity per atom 
+    - Describe how the frequency of a sound wave depends on the wavenumber $k=2\pi/\lambda$, where $\lambda$ is the wavelength.
     - Formulate a volume integral in spherical coordinates
     
 !!! summary "Learning goals"