How do scientists know when substances change?

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Across
  1. 2. substance that dissolves
  2. 5. solid substance breaks into tiny, invisible pieces and spreads out evenly in a liquid
  3. 6. reaction when something burns, reacting with oxygen to make heat and light
  4. 10. liquid that does the dissolving
  5. 11. substances that are present at the beginning of a chemical reaction
  6. 14. liquid, like water, heats up and changes into a gas called water vapor, rising into the air
  7. 15. how hot or cold something feels, measured by a thermometer
  8. 16. changes substances mix and create a completely new substance with different properties
  9. 21. changes when something looks or feels different (like its shape, size, texture, or state of matter) but is still the exact same substance
  10. 22. reaction a chemical change that happens when a substance absorbs energy from light, like sunlight, making its molecules get excited and rearrange to form new substances
  11. 24. substances combine to make another substance
Down
  1. 1. reaction a compound splits into two or more elements or simpler compounds
  2. 3. the new substance formed at the end of a chemical reaction
  3. 4. when invisible water vapor (a gas) in the air gets cold and changes back into tiny liquid water droplets
  4. 7. a type of matter (stuff) that has its own special properties
  5. 8. pushing or pulling force spread out over a certain area
  6. 9. how much solute is mixed into a liquid (like water) to make it strong or weak
  7. 12. a chemical that tastes sour, feels slippery, can burn or dissolve things (like strong cleaners), makes blue litmus paper turn red, and gives away tiny particles called hydrogen ions (H+)
  8. 13. new mixture that forms
  9. 17. scale a number line from 0 to 14 that measures how acidic (sour) or basic/alkaline (bitter/soapy) a liquid is
  10. 18. of conservation of mass matter can't be created or destroyed, it just changes form, so the total amount of stuff stays the same before and after an event like melting ice or mixing ingredients
  11. 19. reaction when substances (called reactants) mix and rearrange their atoms to form brand new substances (called products) with different properties
  12. 20. anything that takes up space (has volume) and has weight (mass)
  13. 23. a substance that feels slippery (like soap), tastes bitter, has a pH above 7, and can accept tiny particles called hydrogen ions (protons) from acids