Why are the terms 'nation' and 'state' often confused?

To answer this question you have to identify what a nation is, what a state is, and why they might be thought to be the same thing. First of all you should outline that a nation is a psycho-political entity or a group of people who feel as though they share some kind of commonality. Then, in contrast, outline a state as referring to a legal and political entity usually operating within strict territorial boundaries. Once your understanding of the difference between the two terms has been made apparent, you should begin to identify reasons why they are thought to be the same. You could appeal to the success of the doctrine of liberal nationalism after WWI, which reorganised Europe such that nations and states coincided in the form of nation-states. Another paragraph could expand upon this by going into liberal nationalism in greater detail. You could identify key thinkers like J.S. Mill, President Wilson, Mazzini, Rousseau who, championing the cause of liberal nationalism, aimed to make the final culmination of national self-determination the nation-state as they believed that this would ensure that each nation could self govern. Throughout an answer like this it would be useful to use examples, where appropriate, of nations which do not have a state (Tibet/Kurdistan) and also of stats which are home to multiple nations (UK) in order to illustrate how nations have in the past (Italy/Germany) and still strive for the overlapping of nation and state. Finally, remember to bare in mind throughout this answer the difficulty of dealing with the concept of a nation because of its inherent subjectivity.