My vision for Algebra I (part 1)

What are the big ideas in Algebra I? I'm not 100% sure of my sequencing but I know I want to weave the following questions into each unit.

Big Questions:

1. What is a solution? How do you find them?

2. What is rate?

3. What does it mean to be a function?

4. Why is equivalency important? (this one bothers me - not sure how to word it)

I'm hoping to keep record of students' understanding of these big ideas along with their algebra skills.