Chemistry Midterm Review Part 1

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Across
  1. 5. The smallest unit of matter that retains the properties of an element.
  2. 8. A pure substance made of two or more elements chemically combined.
  3. 9. A chemical equation where the number of atoms for each element is the same on both sides of the reaction.
  4. 12. Elements in Group 1 of the periodic table; they are soft shiny and highly reactive.
  5. 13. How close a measurement is to the actual or true value.
  6. 16. A reaction that releases energy (feels warm).
  7. 18. The energy change when an atom gains an electron.
  8. 20. A negatively charged particle in an atom that orbits the nucleus.
  9. 21. The minimum energy needed to start a chemical reaction.
  10. 23. A positively charged ion (an atom or molecule that has lost electrons).
  11. 24. Elements in Group 2 of the periodic table; they are less reactive than alkali metals but still reactive.
  12. 25. A process where substances change into new substances with different properties.
  13. 27. A pure substance made of only one type of atom.
  14. 28. A written representation of a chemical reaction using symbols and formulas.
  15. 31. The energy needed to break a chemical bond.
Down
  1. 1. Numbers placed in front of chemical formulas in a chemical equation to balance it.
  2. 2. The size of an atom measured from its nucleus to the outermost electrons.
  3. 3. The number of protons in an atom which determines the element.
  4. 4. A chemical reaction where two compounds swap parts to form new compounds.
  5. 6. A repeating pattern of atoms or ions in a solid.
  6. 7. A negatively charged ion (an atom or molecule that has gained electrons).
  7. 10. A reaction that absorbs energy (feels cold).
  8. 11. A measure of how strongly an atom attracts electrons in a bond.
  9. 14. A substance that speeds up a chemical reaction without being used up.
  10. 15. A characteristic that describes how a substance reacts with other substances.
  11. 17. A molecule made of two atoms like oxygen (O₂).
  12. 19. A pair of electrons shared between two atoms in a covalent bond.
  13. 22. Changes that create new substances with different properties.
  14. 25. The study of matter and how it changes.
  15. 26. A chemical bond formed when two atoms share electrons.
  16. 29. The ability to do work or cause change.
  17. 30. The average mass of an atom based on the number of protons and neutrons in the nucleus.