ACT Science Vocab List: Updated 2017-2018

The following ACT science vocab list includes scientific terms that have appeared on previously released ACT exams. Although the ACT Science section is not a test of scientific knowledge -- more scientific reasoning -- getting comfortable with the scientific terminology is a good idea. 

 If the ACT Science vocab terms below seem relatively easy, that is great, because you have a head start, but you will still need to study  the scientific reasoning elements of the exam. If you would like help on the ACT test, in general, read my recommendations for "Best Books for ACT" for some great test prep resources.

ACT Science Vocab 

PDF of ACT Science Vocab

ACT Science Vocab Set #1

  1. absolute zero: lowest-possible temperature, approximately -273 degrees
  2. acceleration:  the rate of change of velocity
  3. acid: compound with a pH less than 7
  4. alloy: a substance composed of two or more metals (synonym: amalgam)
  5. aerobic respiration:  The breakdown of glucose in the body of an animal to supply muscles with oxygen 
  6. alkalinity:  Having a pH greater than 7 ( contrast with basic, which meaning having PH less than 7) 
  7. antigen:  A substance such as a toxin or enzyme that is capable of eliciting an immune response 
  8. asteroids:  Small celestial bodies that revolve around the sun
  9. barometer: an instrument used to measure atmospheric pressure
  10. biomass:  Total mass of all living matter within a given area 
  11. boiling point: the temperature at which additional thermal energy causes a substance to change from liquid to vapor
  12. carbohydrate: an organic compound like sugar or starch that contains carbon, hydrogen, and oxygen at a ratio 1:2:1; also the main source of energy for humans
  13. carcinogen: cancer-causing agent
  14. catalyst: a substance that speeds up a chemical reaction without being changed by the reaction
  15. chlorophyll: the main pigment in plants that captures light energy during photosynthesis
  16. compound: a substance composed of two or more chemically bonded elements
  17. compressibility:  The ease at which pressure can alter the volume of matter
  18. conductor: a material that allows heat or electricity to flow through it with minimal resistance
  19. control: a sample in which no variables are tested, thus serving as a basis for comparison
  20. control variable: a variable that stays constant in an experiment, allowing the effect of another variable to be measured
  21. diffusion time:  The time that it takes for material to spread from one area to another
  22. ecological succession: a sequence of changes in the plant or animal life of a region or habitat
  23. ecology: The field of science that concentrates on relationships between organism and their environments 
  24. electron: a negatively charged fundamental atomic particle
  25. emulsion:  A state in which one liquid is suspended in another because the liquids will not dissolve in one another

Best ACT Science Books

ACT Science Vocab Set #2

  1. erosion: wearing away, typically by running water or wind
  2. evaporation: the changing of liquid into gas
  3. equilibrium: a state of balance
  4. experimental Variables: Elements of an experiment that are changed (distinguished from constants), which are held the same in order to produce significant results
  5. fahrenheit: A temperature scale in which the boiling point of what is 212 degrees and the freezing point is 32 degrees 
  6. fermentation: The chemical process of breaking down an organic substance into simpler substances, such as a fermentation of sugar to alcohol 
  7. friction: the force resistant to motion
  8. habitat: the area of the ecosystem where a plant or animal naturally lives
  9. herbivore: an animal that eats only plants
  10. hormone: a chemical substance secreted by a gland of the body that affects change on other parts of the body
  11. humidity: the amount of water vapor in the air
  12. Hydrogen bonding:  The chemical bonding of hydrogen atom with another electronegative atom 
  13. Indigenous:  Native to or naturally existing in a certain area
  14. Intracellular:  Fluid in cells
  15. infrared radiation: electromagnetic waves whose wavelength is longer than that of visible light
  16. insulator: a substance that blocks the flow of heat or electricity
  17. ion: a molecule or atom that has become charged by either gaining or losing an electron
  18. isotope: a type of element with the same number of protons per atom but different number of neutrons
  19. kinetic energy: the energy of an object in motion
  20. lipid: An oily or waxy organic compound that cannot be dissolved in water
  21. lithosphere: A substance (such as air) that possesses the quality of indefinite expansion
  22. manometer
  23. melting point: the temperature at which a substance changes from solid to liquid state
  24. molecular weight:  The weight of all the atoms in a molecule
  25. neutron: an atomic particle that has no charge

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As I said above, many students and parents do not realize that the ACT is copyrighted material, so test prep materials from companies, like Princeton or Kaplan, cannot publish "real" ACT practice tests in their test prep materials, just approximations of the real ones. If you can only afford one book, buy this one. It is the most important of the bunch.

So many students could benefit from an inexpensive timer, a necessary test prep tool. In my office, I always have at least three timers on my desk. So many students use cell phones as timers, but the cell phone can be a big distraction when studying for the test. 

ACT Science Vocab Set #3

  1. organic matter:  matter that is derived from living or formerly living organisms
  2. osmosis: the movement of liquid through a membrane
  3. parasite: an organism that invades another organism and feed off that organism
  4. pH: a scale from 1-14; represents the acidity or alkalinity of a solution; low values are acidic, 7 is neutral, high values is alkaline
  5. photosynthesis: the process in which plants use the sun's energy to convert carbon dioxide and water into glucose
  6. pigmentation: coloration
  7. protein:  A compound that consist of amino acids and plays various structural, mechanical and nutritional roles within the organism 
  8. proton: a positively charged atomic particle
  9. radioactive decay:  A natural process by which an atom of a radioactive isotope spontaneously decays into another element 
  10. specific gravity:  The ratio of the weight of one substance to the weight of another substance 
  11. starch: a complex carbohydrate found in many vegetables
  12. ultraviolet radiation: electromagnetic waves with wavelength shorter than that of visible light
  13. vapor: the gaseous for of liquid
  14. velocity: speed of motion
  15. viscosity: a liquid resistant to flow
  16. wavelength: the distance between repeating crests of a wave

PDF of ACT Science Vocab

Best ACT Prep - Advanced

Caution: In general, Barron's test preparation materials tend to be very intensive and the practice problems and practice tests are often more difficult than the actual exam. My general rule is to save this book for students who already are scoring 29+ on the ACT exam and need to focus on the more difficult concepts to improve their ACT score. Most students will want to start with the books mentioned above and work up to the "ACT 36" book. 

If you need the test dates for 2017-2018, please click here. Test dates typically correspond to the school year, rather than calendar year, but every year, the test are offered six times: February, April, June September, October, and December. Most colleges will take test scores from any test taken before December of the senior year (and some schools may also take the December ACT test too). 

NoteThe test dates listed below are for test takers in the United StatesIf you plan to take the exam outside of the United States, be sure to check the exact ACT test dates 2017-2018 for International ACT testing.

Are you taking the SAT Subject Tests? If you are not sure if you need to take them, then read "Do I Need to Take the SAT Subject Tests?". If you know you are applying to colleges that recommend or require them, read my recommendations for best SAT prep book for for the Math 2 Subject Test.