In other words, why should we be interested in the research problem or issue that you want to address?
The types of motivation that may drive your dissertation will vary depending on the subject area you are studying, as well as the specific dissertation topic you are interested in.
It is not sufficient to simply state what the problem or issue is.
Whilst the motivation component of your purpose statement explains why the reader should care about your dissertation, the significance component justifies the value of the dissertation. Even though dissertations are rarely "ground-breaking" at the undergraduate or master's level (and are not expected to be), they should still be significant in some way.
However, the research questions that you set out indicate the specific intent of your dissertation.
In other words, your research questions tell the reader exactly what you intend to try and address (or answer) throughout the dissertation process.
It may: When writing your purpose statement, you will need to explain the relationship between the motivation driving your dissertation and the significance of the research you plan to carry out.
These two factors - motivation and significance - must be intrinsically linked; that is, you cannot have one without the other.
In other words: What contribution will the dissertation make to the literature? This component of the Introduction chapter, which follows the motivation section, should explain what this significance is.
In this respect, your research may be significant in one of a number of ways.