Introduction to Chemistry

What is Chemistry? Chemistry is the study of matter and its changes Matter is anything that has mass and occupies space Because all physical things are composed of matter, chemistry affects all aspects of life and natural events

Areas of Study Organic chemistry Inorganic chemistry Biochemistry Analytical chemistry Physical chemistry

Pure vs. Applied Chemistry Pure chemistry involves development of new chemical knowledge without a specific application in mind Applied chemistry is directed toward a particular goal or practical application The practice of chemistry usually involves both pure and applied chemistry

1.2 Chemistry Far & Wide Chemistry involves many areas of our lives such as Developing new materials Energy use Medicine & Biotechnology Agriculture The Environment The Universe

1.3 Thinking Like a Scientist Alchemists laid the groundwork for chemistry –Developed techniques for separating mixtures –Only made observations Experimental approach to science –Lavoisier was one of the first to use measurements in science –Showed that oxygen was required for burning

Scientific Method A way of logical thinking and problem solving Involves collaboration and communication

Experiments: Testing Hypotheses Experiments are tests to determine if a hypothesis is correct Experiments must be controlled to yield meaningful results Variables are the factors that are relevant to the experiment A controlled experiment means that all variables are controlled except for one

Controlled Experiments Yield meaningful data because only one variable is tested at a time. Independent variable vs. dependent variable Manipulated variable vs. responding variable Independent variable is normally on the x- axis.

Manipulated and Responding Variables When the effect of salt on the freezing point of water was studied, the following results were recorded Salt AddedFreezing Point 5 g-4.8 C 10 g-9.7 C 15 g-15.1 C 20 g-15.0 C

Manipulated and Responding Variables Which is the manipulated variable? Which is the responding variable? Explain. Would it be important to have the same volume of water in each trial? Why? Salt AddedFreezing Point 5 g-4.8 C 10 g-9.7 C 15 g-15.1 C 20 g-15.0 C

Graphing Data How would you graph this data? Which are the manipulated (dependent) and responding (independent) variables What would you put on the x- and y- axes? Construct a graph of the data Salt AddedFreezing Point 5 g-4.8 C 10 g-9.7 C 15 g-15.1 C 20 g-15.0 C

Concluding Statements A concluding statement is used to summarize the results of an experiment Evaluate this conclusion. –“When salt is added to water, the temperature decreases.” Salt AddedFreezing Point 5 g-4.8 C 10 g-9.7 C 15 g-15.1 C 20 g-15.0 C

Hypothesis, Theory, Law Hypothesis: a preliminary explanation or idea concerning an observation –contingent Theory: An explanation based upon much testing and evidence –contingent Law: A description of a phenomenon, often expressed as an equation