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Chemistry. Dr. Michael P. Gillespie. Chemistry. Chemistry is the study of matter, its chemical and physical properties, the chemical changes it undergoes, and the energy changes that accompany those processes.
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Chemistry Dr. Michael P. Gillespie
Chemistry • Chemistry is the study of matter, its chemical and physical properties, the chemical changes it undergoes, and the energy changes that accompany those processes. • Matter is anything that has mass and occupies space. The changes that matter undergoes always involve either gain or loss of energy. • Energy is the ability to do work to accomplish some change.
Chemistry • The study of chemistry involves matter, energy, and their interrelationship. • Matter and energy are at the heart of chemistry.
Scientific Method • The scientific method is a systematic approach to the discovery of new information. • It is a way of gaining information (facts) about the world by forming possible solutions to questions. • Rigorous testing is employed to determine if the proposed solutions are supported.
Basic Assumptions In Science • There are specific causes for events observed in the natural world. • The causes for events in nature can be identified. • There are general rules or patterns that describe what happens in nature.
Basic Assumptions In Science • Repeated events probably have the same cause. • What one person observes can be observed by others. • The same fundamental rules apply, regardless of when or where they occur.
Cause and Effect • Some events are correlated (happen together). • Some events have a cause and effect relationship (an event is a direct result of a previous event).
Components of the Scientific Method • Observation • Hypotheses • Openness to new information and ideas • Willingness to submit ones ideas to the scrutiny of others
Observation • Observations are made using our senses or an extension of our senses. • Observations are careful, thoughtful recognition of an event.
Questioning and Exploration • Optimal questions lend themselves to experimentation. • Explore other sources of knowledge relevant to the question.
Hypothesis • A hypothesis is a statement that provides a possible answer to a question or an explanation for an observation that can be tested.
Characteristics of a Good Hypothesis • Logical • Account for all relevant information • Predict future events • Testable • Use the simplest hypothesis with the fewest assumptions
Einstein • “Make everything as simple as possible, but not simpler.”
Testing a Hypothesis • A good hypothesis is testable. • It can be either supported or disproved. • If a hypothesis cannot be disproved, confidence in it increases. • New information can encourage scientists to reformulate an hypothesis.
Methods for Testing a Hypothesis • Collect relevant information. • Make additional observations. • Devise an experiment.
Experiment • An experiment is a re-creation of an event or occurrence in a manner that allows the scientist to support or disprove a hypothesis.
Variables • Variables are individual factors that help determine the outcome of an event.
Controlled Experiment • A controlled experiment is one in which only one variable is present. • Two groups: • Control group – no manipulation of the variable. • Experimental group – a group in which one variable is manipulated.
Variables • Independent variable – is manipulated in the experiment by the scientist. • Dependent variable – will change as a result of manipulation of the independent variable. • There should be only one independent variable in an experiment. • Be careful not to introduce additional variables into the experiment.
Development of Theories and Laws • If new evidence consistently and repeatedly supports the original hypothesis and other related hypotheses, we begin to see patterns emerge. • Scientific theories and laws come into existence.
Inductive Reasoning • The process of developing general principles from the examination of many specific facts is known as inductive reasoning or induction.
Deductive Reasoning • The process of using general principles to predict the specific facts of a situation is called deductive reasoning or deduction.
Scientific Theory • A theory is a widely accepted, plausible, general statement about fundamental concepts in science that explain why things happen. • A theory is a very broad statement, which is the result of years of observation, questioning, experimentation, and data analysis.
Theory Vs. Hypothesis • A hypothesis provides a possible explanation for a specific question; whereas a theory is a broad concept that shapes how scientists look at the world and how they frame their hypothesis.
Scientific Law • A scientific law is a uniform or constant fact of nature that describes what happens in nature.
Theory Vs. Law • Theory • Describes why things happen • Examined repeatedly • Independently verified • Excellent predictors of how nature behaves • Law • Describes what happens in nature • Examined repeatedly • Independently verified • Excellent predictors of how nature behaves
Properties of Matter • Properties are characteristics of matter and are classified as either physical or chemical.
States of Matter • Three states (phases) of matter: • Solid state • Liquid state • Gaseous state.
States of Matter • The phases of matter are determined by the following: • The amount of kinetic energy molecules have. • The strength of the attractive forces between molecules. • The arrangement of molecules.
Solid • A solid consists of molecules with strong attractive forces and low kinetic energy. • The molecules vibrate in place and are at fixed distances from one another.
Liquid • A liquid has molecules with enough kinetic energy to overcome the attractive forces that hold the molecules together. • The molecules are still strongly attracted to one another, but they are slightly farther apart.
Liquid • The molecules can slide past one another. • Liquids change shape, but they maintain their volume. • Liquids flow and are called fluids.
Gas • A gas is made of molecules that have a great deal of kinetic energy. • The attraction of the molecules to one another is overcome by the speed with which the individual molecules move.
Gas • The molecules collide against one another and push each other apart. • Therefore, gases expand to fit their container. • Vapor is the gaseous form of a substance that is usually in a liquid phase.
Water • Water is the most common example of a substance that can exist in all three states over a relatively small temperature range.
Physical Change • A physical change produces a recognizable difference in the appearance of a substance without causing any change in its composition or identity. • Conversion of water from one state to another constitutes a physical change.
Physical Properties of Matter • A physical property can be exhibited, observed or measured without changing the composition or identity of a substance.
Physical Properties • A practical application of this concept is in the separation of materials based upon their physical properties.
Chemical Properties of Matter • Chemical properties can be observed only through chemical reactions and result in a change in the composition of the material. • The substances internal structure must be affect to observe chemical properties.
Chemical Reaction • A chemical reaction is a process that produces a change in matter by rearranging, removing, replacing, or adding atoms to produce new substances. • This is achieved by either forming or breaking chemical bonds. • A chemical reaction involves atoms interacting with other atoms to fill their outermost energy shell.
Chemical Reaction • The interacting atoms become attached or bonded to one another. • Two types of bonds: • Ionic • Covalent
Ionic Bonds • A positively or negatively charges atom or molecule is called an ion. • Ionic bonds are formed after atoms transfer electrons to achieve a full outermost energy level. • Electrons are donated or received during the transfer to form positive or negative ions (ionization).
Covalent Bonds • A covalent bond is a chemical bond formed by the sharing of electrons. • A covalent bond in which a single pair of electrons is shared is called a single covalent bond (single bond). • Double bond – two pairs of electrons are shared. • Triple bond – three pairs.
