Chapter 1 Introduction to Chemistry 1 1 The

Chapter 1: Introduction to Chemistry

1. 1 The Stories of Two Substances

—Chemistry is the study of matter and the change that it undergoes o Applicable to our everyday lives

—The Ozone Layer o Overexposure to ultraviolet radiation is harmful to both plants and animals o A substance, or chemical, is matter that has a definite and uniform composition o Ozone, which is made up of oxygen, is a substance in the atmosphere that absorbs most harmful radiation before it reaches Earth’s surface. § Ultraviolet radiation from the Sun causes some oxygen gas (O 2) to break into individual particles of oxygen (O) which combine with oxygen gas to form ozone (O 3) o The ozone layer is thinning over Antarctica

—Chlorofluorocarbons o Chlorofluorocarbon (CFC) is a substance that consists of chlorine, fluorine, and carbon § Nontoxic and stable § Used in refrigerators, air-conditioning, plastic foams, solvents, and propellants in spray cans § Increasing concentration in the atmosphere

1. 2 Chemistry and Matter

—Matter and its Characteristics o Matter, anything that has mass and takes up space, and takes many different forms o Mass is a measurement that reflects the amount of matter o Mass and Weight § Weight is a measure not only of the amount of matter but also of the effect of Earth’s gravitational pull on that matter. • Weight varies depending on where an object is

o Structure and observable characteristics § Much of matter and its behavior is macroscopic • Do not need a microscope to see it § Atoms are submicroscopic, so small they cannot be seen with optical microscopes

§ The structure, composition, and behavior of all matter can be explained on a submicroscopic level – or the atomic level. § All that we observe about matter depends on atoms and the changes they undergo § A model is a visual, verbal, or mathematical explanation of experimental data • Can be used to represent matter

o Branches in the field of chemistry § A basic understanding of chemistry is central to all sciences § Chemistry can be broken down into branches that focus on specific areas – organic, inorganic, physical, analytical, biochemistry, environmental, industrial, polymer, theoretical, and thermochemistry.

1. 3 Scientific Methods

—A Systematic Approach o A scientific method is a systematic approach used in scientific study § An organized process used by scientists to do research § Provides a method for scientists to verify the work of others

o Observation § An observation is the act of gathering information § Qualitative data is information that describes color, odor, shape, or some other physical characteristic • Relates to the five senses § Quantitative data is numerical data • Tells how much, how little, how big, how tall, or how fast • Measurements of temperature, volume, quantity, etc.

o Hypothesis § A hypothesis is a tentative, testable statement or prediction about what has been observed • Meaningless unless there are data to support it

o Experiments § An experiment is a set of controlled observations that test the hypothesis § The scientist must carefully plan and set up one or more laboratory experiments in order to change and test one variable at a time

• A variable is a quantity or condition that can have more than one value o Independent variable = the variable that you plan to change o Dependent variable = changes in response to a change in the independent variable; variable you don’t control the change of • A control is a standard for comparison

o Conclusion § A conclusion is a judgment based on the information obtained § When the data support a hypothesis this indicates that the hypothesis might be true § If evidence does not support a hypothesis it can either be discarded or modified

o Theory and Scientific Law § A theory is an explanation of a natural phenomenon based on many observations and investigations over time • States a broad principle of nature that has been supported over time • All theories are still subject to new experiential data and can be modified § A scientific law is a relationship in nature that is supported by many experiments with no exceptions

1. 4 Scientific Research

—Types of Scientific Investigations o Pure research seeks to gain knowledge for the sake of knowledge itself o Applied research is research undertaken to solve a specific problem o Some scientific discoveries are made unexpectedly

—Students in the Laboratory o When you work in the chemistry laboratory, you are responsible for your safety and the safety of the people working nearby o It is important that everyone practice safe laboratory procedures o Table 2 “Safety in the Laboratory”

—The Story Continues o The Montreal Protocol was signed in 1987, and this agreement phased out the use of CFCs and place restrictions on future use o CFC concentrations did not decline immediately o The ozone hole forms each year over Antarctica during the spring o The chlorine reacts with the ozone, causing ozone depletion

—Benefits of Chemistry o Chemists are involved in finding cures or vaccines for diseases o Almost every situation that you can imagine involves a chemist o Advances in technology are possible because of the study of matter