Name________________________________________ Period__________ Scientific Concepts Big Idea: The scientific method is a systematic approach to answering questions about the world we live in. Laws, hypotheses, and theories are scientific statements about the phenomena we observe. 1. Recall an example of how you used the scientific method to solve a problem this past week. The Scientific Method Researchers use the scientific method to answer questions and explore ways to solve problems. The scientific method was established to prove hypotheses via observations, measurements, and experimentation. It has since been used as a guide for scientists in their quest for knowledge. Although sometimes condensed or broken into more parts, the scientific method consists of steps organized in a logical manner. This makes it easier to follow and repeat. Figure 1: The scientific method. Step 1: Make an observation and ask a question. Step 2: Gather background information and form a hypothesis that answers the question. Step 3: Perform an experiment and collect data. Repeat the experiment to verify the data. Step 4: Analyze the data. Step 5: Conclude whether to accept or reject the hypothesis. If rejected, go back to step 2. Step 6: Share the information with others. Even if you are not a scientist, you use many of these steps to solve everyday problems of your own. For example, if you observed that your TV remote stopped working, you would likely hypothesize that the batteries were dead. You would then test your hypothesis by replacing the batteries and checking if the remote worked. If it didn’t, you would reject your hypothesis and try something different. In this way, you’ve used the scientific method without even thinking about it. 2. Explain what we learn from a hypothesis that has been rejected. 3. Imagine you are a chef working on a new recipe. What would occur during the experiment and result phase? Did you know? 4. Identify two characteristics of a good hypothesis. The scientific method is not attributed to any one person. Instead, it grew from the methods of multiple well-known scientists dating back to the 4th century B.C. From Aristotle, to Francis Bacon, to Galileo, to Isaac Newton, the scientific method has evolved over time. Law, Hypothesis, and Theory There are three main types of scientific statements that are classified by the information they explain. A hypothesis is a possible explanation for an observation. A valid hypothesis must be testable. If the evidence collected does not support the hypothesis, it can be rejected, and a new hypothesis can be formed. Most hypotheses are written as “If…then…” statements. They are sometimes referred to as “educated guesses,” but a hypothesis is never uninformed. Rather, scientists rely on prior knowledge to form a hypothesis. 5. Hypothesize how placing a plant under only green light might affect its growth. Bad hypothesis: Smoking causes lung cancer. Good hypothesis: If smoking causes lung cancer, then people who smoke will have a higher rate of developing lung cancer than those who do not. Good hypothesis: People who smoke will have a higher rate of developing lung cancer. Scientific laws are statements about observations of phenomena under certain conditions. Laws tell us what happens, but do not explain why it happens. Scientific laws are accepted as truth because they are observed to always work. Most scientific laws are mathematical equations. Some examples include the Law of Gravity, Boyle’s Gas Laws, and the Law of Conservation of Energy. A scientific theory is a well-substantiated explanation that includes related facts, laws, and verified hypotheses. Theories must be able to explain past events and predict new observations. They are supported by data and evidence. Over time, theories evolve and can be replaced as new evidence is acquired. In general, theories are backed by enough information that scientists consider them correct and highly reliable. Some examples of famous theories include the Theory of Evolution, the Cell Theory, and Atomic Theory. 6. Identify the main difference between a scientific theory and law. The Experimental Process When designing an experiment to test a hypothesis, scientists use an independent and dependent variable. The independent variable is what is changed or controlled during the experiment. The dependent variable is what is being tested and measured. As the independent variable is changed, the effects on the dependent variable are measured and recorded. A good hypothesis will state both the independent and dependent variables. Look at the following experiment: 7. Create a hypothesis and underline the independent variable. 8. Determine from the following hypothesis the dependent and independent variables. If you drink coffee before bed, then it will take more time to fall asleep. Good experiments have both an experimental and control group. An experimental group receives the independent variable, while a control group does not. In the end, the two groups are compared to determine if there is a difference. It is important to note that both the control and experimental group should be similar in all other aspects. This ensures that only the independent variable can make the difference. The data that is collected during an experiment can be qualitative or quantitative. Qualitative data is not a numerical measurement. Instead, it is a description. By contrast, quantitative data is a quantity or measurement. For example, if the height of a plant is described as “tall,” it is qualitative data. If instead the height is measured as 15.5 inches, then it is quantitative data. Qualitative It smells like cherries. The color is red. It tastes sour. It is short. Quantitative 6 foot 3 inches 145 lbs 98.6oF 0.45 meters 9. Describe your classroom using qualitative data. Scientific Concepts Review Mixed Review: 1. Identify the following as either a good hypothesis (G) or bad hypothesis (B). a. If a hermit crab is given a choice between shells, then it will pick the most colorful shell. b. If there are clouds, then it might rain. c. The height of the plant is not affected by temperature. d. If sugar is added to cold water, then it will not dissolve as well as if it were added to warm water. e. The football team will do better this year. f. My dog is smarter than your dog. g. If I drink caffeinated tea at night, then then it will take longer to fall asleep. 2. Determine if the following is a theory (T), law (L), or hypothesis (H). a. Force equals the mass multiplied by the acceleration. b. If leaf color is affected by temperature, then lowering the temperature will cause a green leaf to change color. c. Evolution states that species of organisms change over time because of changes in inherited physical or behavioral traits. d. For a fixed amount of an ideal gas kept at a fixed temperature, the pressure and volume are inversely proportional. e. With the development of the microscope, scientists found that all organisms are composed of cells and all cells come from other cells. f. If I add salt to water, then the boiling point will lower. 3. For the upcoming science fair, you want to determine if a white or colored candle takes longer to melt down. Create a hypothesis and underline the independent and dependent variable. Describe the experimental design that will test your hypothesis. 4. Change the following statements into a good hypothesis. Adding salt to the soil may affect the growth of grass. Plants will grow better in soil than in just water. Cinnamon oil can help repel mosquitos. Temperature affects how quickly bread molds. 5. Pick a hypothesis from question #4 and identify the independent and dependent variables. What would be your control and experimental group?
