NGSS
MS-PS1-1
4 lessons teach this standard. Every lesson is interactive, and every one prints as a worksheet with a separate answer key.
Grade 8 Science · Chapter 1 · Lesson 1
A model is only worth having if it explains something.
Grade 8 Science · Chapter 1 · Lesson 2
About a hundred kinds, and everything else is combinations.
Grade 8 Science · Chapter 3 · Lesson 1
He left gaps, and said what would fill them.
Grade 8 Science · Chapter 3 · Lesson 2
One idea explains three groups.