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Objective 1.2

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Objective 1.2

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    1. Objective 1.2 Scientific Method, Data Presentation and Analysis, Safety and Procedures

    2. What is a valid hypothesis? When an hypothesis is valid, it must be able to be tested in an experiment. Only one variable is being changed. All other factors are being controlled. The result must be observable and/or measurable.

    3. Example Question As temperature drops to the dew point, clouds form in the atmosphere, and dew forms on ground surfaces. A scientist proposes that adding more water molecules to the atmosphere will change the dew point. This proposal is — F an invalid observation G a valid hypothesis H an invalid problem J a valid conclusion

    4. What if the data doesn’t support the hypothesis? Some very important discoveries occurred when the scientist was actually looking for something else. For example, some antibiotics like penicillin were discovered that way.

    5. When the hypothesis doesn’t fit 1. Make a new hypothesis, based on the observations. 2. Make an inference. What could the data be showing, even if it is not DIRECTLY OBSERVABLE?

    6. Taks Hint

    7. A scientist has hypothesized that the existence of life on Mars is likely because the atmosphere is 95% carbon dioxide.

    8. Variables – MIX Manipulated or Independent Variable is the one you are purposely changing and is first in a data table and plotted on the X-axis of the graph.

    9. Variables - DRY Dependent or Responding variable is listed in the second column in a data table, and plotted on the Y-axis of a graph.

    10. A Control Group vs. Controlled Variables Control or control group is one that participates in the experiment without the change being tested. (Receives a placebo, or grown under the same conditions.) Controlled Variables are the other factors in an experiment that might affect the results but are kept constant to prevent them from affecting the outcome. (Amount of water, sunlight, strength of the drug, food.)

    12. TAKS HINT In a question where a data table or a graph is given READ the graph or data table before you read the question. Look carefully at lines in the graph, or numbers in a data table, are they increasing? decreasing? staying the same? As one line or data column changes, what is happening to the others? Is there a pattern? Compare slopes of the lines.

    13. Reading Graphs Always read the title. Read the x- & y-axis labels & UNITS. What is happening? As the pressure of oxygen increases, the % saturation is increasing.

    14. Graph Types – Pie and Bar

    15. Graphs – Line or Curves Line Graphs show continuous data like distance vs. time, acceleration, or plant growth over 6 weeks

    16. Data Trends Direct relationship means as one variable changes, the other changes in the same way.

    17. 3. According to the data in the table, about how far can a spring be expected to stretch if a force of 3.92 N is applied? A. 10.5 cm B. 13.6 cm C. 14.0 cm D. 17.3 cm

    18. Tools for Measurement

    19. Measuring Units – System Internationale (SI) Mass is in? Volume in? Length in? Grams Liters or cubic measures such as cm3 Meters

    21. Is it accurate? Is it precise? Accuracy depends on how close the measurement tool is to the actual. If the equipment has been properly calibrated and cared for it is usually accurate. Precision is repeatability and usually depends on the amount of estimating that has to be done. The smaller the measurement markings on the tool, the more precise it is.

    22. 13 Four lab groups measured the volume of acid required to neutralize a standard solution of sodium hydroxide base. Which of the groups measured the volume with the highest precision?

    23. What equipment is used to measure volume? In A, they are using two flasks. Not very precise markings! B is better, at least they are using a graduated cylinder. C is a bad choice, since most test tubes have no markings for volume. D is the best choice as the small volume markings on the burette gives the most precise measurement.

    25. 5. Objects of the same mass but of different sizes and shapes were dropped from a given height. Their rates of free fall were measured and recorded. Which of the following is most likely the question this experiment is designed to answer. A. How does height affect the force of gravity? B. How does gravity affect objects of different densities? C. How do mass and weight affect falling objects? D. How do size and shape affect an object’s rate of free fall?

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