Changing Entity Framework consumed classes after the DB has been created and deployed

Question

Assume we have an ASP.NET MVC3 Web site that makes use of Entity Framework Code First approach to working with database.

The system is now working in test environment.

If the part of the DbContext is the following:

public DbSet<Incident> Incidents { get; set; }

will it cause DB-Code collaboration problems, if I, for example, add Properties to an Incident class?

Or will the framework just update the Database tables automatically, and will treat the older records, that were created without new properties as if they are null?