Chemistry is the science that investigates and explains the structure and properties of matter. Matter is the stuff that’s all around you: the metal and plastic of a telephone, the paper and ink of a book, the glass and liquid of a bottle of soda, the air you breathe, and the materials that make up your body. A more formal definition of matter is anything that takes up space and has mass. Chapter 1: Introduction to Chemistry

Branches of Chemistry BranchArea of Emphasis Examples Organic chemistry most carbon-containing chemicalspharmaceuticals, plastics Inorganic chemistry in general, matter that does not contain carbon minerals, metals and nonmetals, semi- conductors Physical chemistry the behavior and changes of matter and the related energy changes reaction rates, reaction mechanisms Analytical chemistry components and composition of substances food nutrients, quality control Biochemistrymatter and processes of living organisms metabolism, fermentation

Why Study Chemistry? What materials & products did you use today? How did you get to school? What do you consume to stay alive? Everything that keeps you alive and makes your life “better” has come from our understanding of chemistry.

Scientific Methods A scientific method is a systematic approach to answer a question or study a situation. It is both an organized way for scientists to do research and a way for scientists to verify the work of other scientists.

Scientific Methods A typical scientific method includes: making observations, forming a hypothesis, performing an experiment, and arriving at a conclusion.

Scientific Methods Often, a scientist will begin with qualitative data—information that describes color, odor, shape, or some other physical characteristic that relates to the five senses. Chemists also use numerical quantitative data. A hypothesis is a possible explanation for what has been observed. An experiment is a set of controlled observations that test a hypothesis.

Scientific Methods The variable that is changed in an experiment is called the independent variable. The variable that you watch to see how it changes as a result of your changes to the independent variable is called the dependent variable.

Scientific Method Many experiments also include a control, which is a standard for comparison. A conclusion is a judgment based on the data obtained in the experiment. If data support a hypothesis, the hypothesis is tentatively affirmed. Hypotheses are never proven; they are always subject to additional research.

Scientific Methods Over time, data from many experiments can be used to form a visual, verbal, and/or mathematical explanation—called a model—of the phenomenon being studied. A theory is an explanation that has been supported by many experiments. Theories are always subject to new experimental data and are modified to include new data.

The first step to solving a problem, such as what makes up matter, is observation. Hypotheses Scientists use their senses to observe the behavior of matter at the macroscopic level.

Hypotheses They then come up with a hypothesis, which is a testable prediction to explain their observations. To find out whether a hypothesis is correct, it must be tested by repeated experiments.

Hypotheses, Theories Scientists accept hypotheses that are verified by experiments and reject hypotheses that can’t stand up to experimental testing.

Hypotheses, Theories A theory is an explanation based on many observations and supported by the results of many experiments.

Hypotheses, Theories As scientists gather more information, a theory may have to be revised or replaced with another theory.

Hypotheses, Theories, and Laws A scientific law is simply a fact of nature that is observed so often that it becomes accepted as truth. A law can generally be used to make predictions but does not explain why something happens. In fact, theories explain laws.

Scientific Methods A scientific law describes a relationship in nature that is supported by many experiments and for which no exception has been found.

Scientific Research Pure research is done to gain knowledge for the sake of knowledge itself. Applied research is undertaken to solve a specific problem.

Assessment Questions Identify the dependent variable and the independent variable in the following experiments. Question 1

A student tests the ability of a given chemical to dissolve in water at three different temperatures. independent variable: temperature; dependent variable: ability to dissolve in water Answer 1a Question 1a Assessment Questions

A farmer compares how his crops grow with and without phosphorous fertilizers. independent variable: presence of phosphorous fertilizer; dependent variable: crop growth Answer 1b Question 1b Assessment Questions

Classify each kind of research as either pure or applied. Question 2 Assessment Questions

A scientist studies plants in a rain forest in search of chemicals that might be used to treat AIDS. applied Answer 2a Question 2a Assessment Questions

A researcher studies the effects of hormones on the brain of a worm. pure Answer 2b Question 2b Assessment Questions

A researcher tries to develop cleaner burning fuels to help reduce air pollution. applied Answer 2c Question 2c Assessment Questions