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2C BIO If 10 meters of wire needs 50 volts to maintain 1.5 amps, 8 x 10 = 80m of wire and 8 x 50 = 400 volts The graph shows how the voltage needed to maintain a constant current of 1.5 amps through a wire conductor varies with the length of the wire. If the trend continues, what is the most likely voltage needed to maintain a 1.5-amp current through 80 meters of the wire? A B C D 10 volts 18 volts 250 volts 400 volts D 11/06 2C BIO B 11/05 A researcher determined the percentage of electrical energy transformed into different forms of energy by a toaster. The best way to communicate these results is to display the data using a --- A B C D histogram circle graph line graph box-whisker graph Average Radius of Trees in a Forest Age of trees (years Average Radius (cm) 1 2.2 2 2.6 2C BIO C 10/06 3 4 5 6 4.4 The data table shows how the thickness of tree trunks in a certain forest is related to tree age. Use these data to plot points on a graph. Draw a straight line to show a linear relationship for the data. According to these data, what is the most likely average radius of 4-year-old trees in this forest? A. 3.0 cm B. 3.3 cm C. 3.6 cm D. 3.9 cm 2C BIO C 10-04 According to the graph, about how much hemoglobin would be saturated at an O2 pressure of 7.3 kPa? A B C D 32% 67% 89% 92% On the TAKS test, you will be tested over your knowledge of how to design and carry out a scientific experiment. So what are the steps in planning and implementing a valid experiment? Dictionary Help: VALID means acceptable, or legitimate, trustworthy. Dictionary Help: IMPLEMENTING means doing the experiment, taking the steps to make it happen. Asking questions: Can you look at an experimental set-up and figure out what question the scientist was trying to answer? Look for clues in the drawing or paragraph! What are they measuring? What does the data tell you? The diagram shows an experimental setup. Which of these questions was this experiment designed to answer? A Does water boil when exposed to air? B Will fire turn a gas into a liquid? C Does air expand when heated? D Will heat turn a gas into a solid? Heat Formulating Testable Hypothesis Can you recognize a valid hypothesis? Can you create one? Is it a statement that you can prove with data? What question Is it testable? might these students be trying to answer? What hypothesis might these students write to test their question? Is the experiment valid? Factors affecting the validity (trustworthiness) of the experiment • A control group is used • The hypothesis has measurable variables (“Flowers grown indoors will have the ‘best’ smell,” is not a measurable variable!) • Sample size is large enough. You have to run lots of test over and over again to get reliable results • Only one variable is tested at a time! “Will limiting sunlight and water effect plant growth?” is not a valid question! Your teacher has given you two unknown white solids. Your task is to mass out a sample of each compound for each test and determine the following: Procedure Equipment Procedure Equipment Procedure Equipment 1. Melting Point 2. Conductivity of solution 3. Solubility Variables • The dependent variables (the ONES THAT ARE CHANGING) • The independent variables (the MANIPULATOR – CAUSE THE CHANGE) The picture shows an experiment using different colors of light with elodea Wavelength (Color of light) plants. Sunlight Green Red Blue Dependent variable: What is being changed? Question answered in this experiment: Hypothesis: Control Group: Independent Variables: What is causing Controlled Variables: the changed? What is the manipulator? mL of Oxygen Produced in 10 minutes 20 3 18 16 READ CAREFULLY! 30. The table shows the time it took trees of the same type and size to drop all of their leaves after being grown in different atmospheres. For the experiment to be valid, which of these must be a constant for all the trees? Dependent variable F The height of all the trees during the entire experiment All of the independent variables but one (gases added) must remain constant for the experiment to be valid. G The amount of water available to all trees during the experiment Dependent variable H The mass of fallen leaves collected from each tree Dependent variable J The rate of photosynthesis in all trees during the experiment Selecting the correct procedure and equipment: Sometimes you will be asked to select correct equipment or the correct procedure from a particular lab set-up. Which procedure is best to use when determining the density of a rock? F Place the rock in a water-filled beaker and find the height at which the rock floats above the water. G Use a ruler to measure the rock’s dimensions and then find its mass using an analytical balance. H Measure the mass of the rock on a balance and then find the volume of water it displaces in a graduated cylinder. J Place the rock in three liquids with different known densities and observe which liquid the rock floats in. Formula Chart to the RESCUE!!!!