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Across 4. a record of the past 6. things becoming different over time 8. 365 days 9. north, south, east, and west 12. material that can burn to produce heat 13. a set of steps necessary to do scientific investigations 16. a line marked off in periods of time that shows events in order 17. a person who is an expert on the past 19. a way we learn about our world 20. anything that has mass and takes up space

Down 1. northeast, northwest, southeast, southwest 2. a symbol that shows cardinal and intermediate directions 3. a person who tries to explain how and why things happen 5. to keep from harm 7. an important object that has been saved and passed down to others 10. things staying the same over time 11. a tall cylindar-shaped tool used to measure volume 14. the first person to do something 15. a tool used to measure mass 18. to decay or spoil because of exposure to oxygen