1 Chapter 1 Chemistry: An Introduction

2 What is Chemistry?  The study of the matter, its composition, properties, and the changes it undergoes.  Applied Chemistry is the using chemistry to attain certain goals, in fields like medicine, agriculture, and manufacturing  Pure chemistry gathers knowledge for knowledge sake

3 Types of Chemistry  Analytical Chemistry studies composition of substances.  Inorganic Chemistry substances without carbon  Organic Chemistry compounds containing carbon  Biochemistry- Chemistry of living things  Physical Chemistry studies behavior of substances

4 Chemistry is  A natural science.  a language with its own vocabulary.  a way of thinking.

5 Scientific Method  A way of solving problems or answering questions.  Starts with observation- noting an recording facts  Hypothesis- an educated guess as to the cause of the problem or answer to the question.

6 Scientific Method  Experiment-  Experiment- designed to test the hypothesis  only  only two possible answers –hypothesis –hypothesis is right is wrong  Generates  Generates data observations from experiments.  Modify  Modify hypothesis hypothesis - repeat the cycle

7 Observations Hypothesis Experiment  Cycle repeats many times.  The hypothesis gets more and more certain.  Becomes a theory  A thoroughly tested model that explains why things behave a certain way.

8  Theory can never be proven.  Useful because they predict behavior  Help us form mental pictures of processes (models) Observations Hypothesis Experiment

9  Another outcome is that certain behavior is repeated many times  Scientific Law is developed  Description of how things behave  Law - how  Theory- why Observations Hypothesis Experiment

10 Law Theory (Model) Prediction Experiment Modify Observations Hypothesis Experiment

11 Experiment  Scientists use an experiment to search for cause and effect relationships in nature.  In other words, they design an experiment so that changes to one item cause something else to vary in a predictable way.

12 Variables  Variables:changing quantities in experiment  An experiment usually has three kinds: independent, dependent, and controlled.  The independent variable is the one that is changed by the scientist.  Experiment has only one independent variable. Independent variable are changed to observe what happens.

13  Dependent variable changes in response to the change maked to the independent variable.  The new value of the dependent variable is caused by and depends on the value of the independent variable.  For example, if you open a faucet (the independent variable), the quantity of water flowing (dependent variable) changes in response--the water flow increases.

14  Controlled variables are quantities that a scientist wants to remain constant, and he must observe them as carefully as the dependent variables.  For example, if we want to measure how much water flow increases when we open a faucet, it is important to make sure that the water pressure (the controlled variable) is held constant. That's because both the water pressure and the opening of a faucet have an impact on how much water flows.