THEORIES vs. LAWS SC.6.N.2.2: Explain that scientific knowledge is durable because it is open to change as new evidence or interpretations are encountered. SC.7.N.3.1: Recognize and explain the difference between theories and laws and give several examples of scientific theories and the evidence that supports them.

Bell Ringer 1. Chemists once believed that an atom was made of negative electrons dispersed inside a positive mass like raisins in pudding. An experiment with radiation and gold foil demonstrated that most of an atom was made of empty space. After this experiment, they adopted a new model of the atom that showed the electrons orbiting the nucleus of the atom from a distance. Which of the following statements about the new model is true? The new model is perfect and will not change. The new model is a wrong model and will not last. The new model fits the data worse than the old model. The new model fits the data better than the old model. *

The Scientific Method Observe an event. Ask a Scientific Question 3. Develop a Hypothesis ( which makes a prediction). 4. Test the hypothesis. 5. Observe/Analyze the results. 6. Draw conclusions. Revise the hypothesis if needed. Repetition/Replication as needed. A successful hypothesis might become a Scientific Theory. model test

Law vs. Theory A law summarizes what happens. A scientific law is a statement that describes what scientists expect to happen every time under a particular set of conditions. A scientific law describes an observed pattern in nature without attempting to explain it. A theory (model) is an attempt to explain why it happens. A scientific theory is a well-tested explanation for a wide range of observations or experimental results. A scientific theory connects large sets of related observations by one explanation.

THEORIES Scientific knowledge changes as a result of new evidence or new interpretations of existing evidence. For example, thousands of years went by with people thinking the sun revolved around the Earth. To them, it made sense with information they had. The sun would rise on one side of the sky, move across the sky, and set on the opposite side. A scientific theory connects large sets of related observations by one explanation. Examples of scientific theories include the atomic theory and the cell theory. The atomic theory states that all substances are made up of tiny particles called atoms. The cell theory states that cells are the basic units of structure and function in living things. Cell Theory Atomic Theory Theory of Plate Tectonics

LAWS For example, the law of gravity states that all objects in the universe attract each other. Unlike a theory, a scientific law describes an observed pattern in nature without attempting to explain it. Both scientific theories and scientific laws are developed slowly through repeated observation and experimentation. Law of Universal Gravitation Law of Conservation of Mass Law of Conservation of Energy

Theories and Laws Fill in the table below focusing on the difference between what makes something a theory or a law. Theories and Laws Brief Description Why is it a theory or a law?  Law of Universal Gravitation   Theory of Plate Tectonics Atomic Theory  Law of Conservation of Mass Cell Theory Law of Conservation of Energy 

Exit Ticket Explain the difference between a scientific theory and a scientific law. Explain why theories may be modified, but rarely discarded.