Tell a hypothesis, a theory and a law apart

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Sorting card with three boxes

   Hypothesis, Theory, Law. Statement to sort: "Energy cannot be created or destroyed in a living cell, only changed from one form to another."

2. 1.

   Ari sorts a statement from a biology poster. Which box does it go in, and why?

   • A hypothesis: nobody has tested it yet, so it is only an idea
   • A theory: it covers more evidence than a law, so it ranks above one
   • A law: it states a pattern found in every measurement, without saying why
   • A theory: it explains why energy changes form inside a cell

3. Use this

   Lab plan line. "If warmth speeds up the reactions inside bean seeds, then seeds at 25 °C should sprout in fewer days than seeds at 15 °C."

4. 2.

   Bo reads a line in a lab plan. Which kind of statement is it?

   • A prediction: a result expected if the hypothesis about warmth is right
   • A law: it states a pattern that holds each time seeds are tested
   • A hypothesis: it explains why warmth should matter to the seeds
   • A theory: it explains how seeds sprout, based on many tests
5. 3.

   Notes line. "In the second generation, 705 plants had violet flowers and 224 had white flowers." Esme reads a line from Mendel's pea notes. Which kind of statement is it?

   • A hypothesis: it offers a reason for the white flowers
   • A law: it states the pattern found in each pea cross
   • An observation: a recorded result, with no explanation attached
   • A theory: it explains how flower color is passed on
6. 4.

   Jun checks four sentences for the word hypothesis. Which uses it the science way?

   • A hypothesis is any guess, so a test is not needed to make one
   • Brighter light may make plants taller because leaves make more sugar, which three lamps can test
   • A hypothesis is a fact that has been proven many times, so it needs no further tests of any kind
   • Once a hypothesis passes two tests it is renamed a theory
7. 5.

   Kira checks four sentences for the word theory. Which uses it the science way?

   • A theory is a statement of a pattern, with no explanation of why
   • A theory becomes a law after enough tests have been run on it
   • Cell theory is a well-tested explanation that predicts what new tissue samples will show
   • My theory about the late bus is a guess that has not been checked yet, so a theory is a hunch
8. 6.

   Luz checks four sentences for the word law. Which uses it the science way?

   • The law of conservation of mass describes what happens to mass in every reaction, not why
   • A law is a theory that has finally collected enough proof to be promoted
   • A science law is a rule that stays fixed, whatever we later find
   • A law explains why mass is conserved in a reaction, so a law does exactly the same job as a theory
9. 7.

   Milo's friend says evolution is "just a theory", so it is a guess. Which reply fits science?

   • Right, an idea like that stays a guess until enough tests finally turn it into a proper law
   • Evolution is proven, so it cannot be changed by new evidence
   • Right, theories are hunches that scientists have not tested
   • A theory is an explanation backed by many lines of evidence, such as fossils and DNA
10. 8.

    Noah finishes a test of a hypothesis, and the results match the prediction. Which sentence is best science writing?

    • The results turn the hypothesis into a theory, since it passed a test
    • The results prove the hypothesis, so it is now a fact for good
    • The results support the hypothesis but cannot prove it, and more tests could change that
    • The results show the hypothesis was a wild guess that happened to work out well this time
11. 9.

    Pia compares a school rule with a science law. Which sentence about science laws is right?

    • A science law explains why a pattern happens, as a theory does
    • A science law is a rule that nothing in nature is allowed to break
    • A science law is a theory that has passed so many tests that it was finally promoted to a law
    • A science law describes a pattern in nature and can be revised when exceptions turn up
12. 10.

    Zee bakes bread. Which statement is a hypothesis that a test could check?

    • Warmth may speed up yeast because its reactions run faster when warm
    • Any wild guess counts as a hypothesis, like "yeast likes jazz", since a guess needs no reasons
    • Living things, yeast included, are made of cells
    • The dough in the warm kitchen rose 3 cm in an hour