Introduction to Chemistry Chpt 1

What is chemistry? The study of the composition of matter and the changes it undergoes Matter is anything that has mass and takes up space Everything!! 5 traditional areas of study Organic – carbon based Inorganic – not carbon based Biochemistry – living things Analytical - composition of matter Physical – mechanisms, rate & energy transfer that accompany changes in matter

Pure chemistry – pursuit of knowledge for its own sake Applied chemistry – how can the knowledge be applied to society technology

Scientific Method Common steps that scientists use to gather information and solve problems They are not fixed steps, but generally involve the following: Observe, Hypothesize, Experiment, Collect and Analyze Data, Drawing Conclusion, Reporting, Revision and Verification

Observe – watch, take note of, pay attention to Hypothesis Observe – watch, take note of, pay attention to Hypothesis -A testable explanation for a question or problem -An educated guess as to the answer to a question or problem -Scientists may test a hypothesis by conducting an experiment *either disprove or support the hypothesis

Experimenting A. An experiment is a procedure that tests a hypothesis by the process of collecting information under controlled conditions. B. A controlled experiment i. Some experiments involve 2 groups: a. The control group: The standard for comparison, the group that is not tested on b. The experimental group: The test group in which all conditions are kept the same except for the single condition being tested

Designing an experiment. i Designing an experiment i. In a controlled experiment only one condition is changed at a time a. We only change one condition so we know which condition caused the results b. the condition in the experiment that the experimenter changed is the independent variable ii. While changing the independent variable, the scientist observes a second condition that results from the change. This condition is the dependent variable. a. changes in this variable depend on changes in the independent variable iii. Not all investigations are controlled experiments a. field work does not usually include a control group, where laboratory work is usually controlled

Theories and Laws i. Theory a. An explanation of a natural phenomenon that is supported by a large body of evidence b. Continual verification and refinement of a hypothesis results in a theory c. A valid theory enables scientists to predict new facts and relationships d. It explains a natural phenomenon e. Can change ii. Laws or Principles a. Certain facts of nature b. Description of a natural phenomenon c. Doesn’t change

Matter and Change Chpt 2

Properties of Matter Extensive – depends on the amount of matter present (ex. mass or volume) Intensive – depends on the type of matter present (ex. conductivity, malleability, flammability Physical property - a property that can be determined without changing the nature of the substance -characteristics of the substance ex. Color, state, texture, melting point, boiling point, density, hardness, etc Chemical property– a property that describes a substances ability to participate in chemical reactions -describes how a substance acts ex. Reactivity, flammability, combustibility

States of Matter all matter is made of particles, the type and arrangement of particles in a sample determine the properties of that matter matter comes in 3 common states (there are other states, but not used in general chemistry): -solid - fixed volume and shape, particles held tight and rigid (usually close together), don’t compress or expand much

States of Matter -liquid – fixed volume but not shape, particles not held as tightly together as solids, particles can slip past one another, therefore liquids can flow and take the shape of their containers, not very compressible but expand slightly -gas – neither fixed volume nor shape, particles are weakly attracted, they move independently of one another, particles move at high speed, will fill any container they occupy, easily compress and expand *vapor – gas form of a substance that is usually solid or liquid at room temperature

a pure substance is one thing 2 types of pure substances a pure substance is a sample of matter that has a definite composition, and definite chemical and physical properties a pure substance is one thing ex. Gold, salt, sugar, water, hydrogen, etc. 2 types of pure substances Elements and compounds

Physical Changes -physical changes – the identity of the substance doesn’t change *the arrangement, location, and speed of the particles may change *ex. change of state, ripping paper, dissolving sugar in tea, crushing chalk

Mixtures Mixtures matter that is made up of two or more pure substances they are not chemically bonded, and they are not in a specific ratio they can be separated into their pure substances by physical means ex. Filtration, distillation, evaporation, etc.

heterogeneous – the pure substances are not evenly distributed 2 types of mixtures homogeneous – the pure substances are evenly distributed giving the mixture a uniform structure and composition the different parts cannot be seen even under a microscope also referred to as solutions heterogeneous – the pure substances are not evenly distributed you can see the different parts different regions have different properties

Elements & Compounds elements – contain only kind of atom *a substance that cannot be separated or broken down into simpler substances by chemical means *all atoms of the same elements have the same structure each element has its own unique set of physical and chemical properties *each element has its own symbol, and they are listed on the periodic table (ex. C)

some elements exist as single atoms, they are called monatomic elements some elements exist in groups of atoms, if they come in twos we call them diatomic elements (there are 7 common ones: Br, I, N, Cl, H, O, F) some elements have more than one form, they are called allotropes ex. Oxygen can come as O2 or O3 the different forms have different properties

represented by a formula using symbols (ex. H2O) compounds – made of more than one type of atom chemically bonded in a specific ratio represented by a formula using symbols (ex. H2O) if there is only one atom of a certain type, we use no subscript several types of formulas molecular formulas, structural formulas , ball and stick models , space filling compounds can be further classified by their type of bond or what elements they are made of ex. Ionic/covalent or organic/inorganic can only be separated into its elements by chemical means

Chemical Changes chemical changes – the identity of the substance(s) changes and a new substance is formed -even though the substances are changed, the atoms that make them up are just rearranged, atoms are not created or destroyed just rearranged

evidence of chemical changes production of a gas formation of a precipitate change in energy color change -these are all possible indicators that a chemical change is occurring, some of these may occur during a physical change as well, the more that are occurring the more likely it is a chemical change

Substance vs mixture Flow chart p.44

Periodic Table Intro Elements are organized in a special arrangment in the periodic table Rows are called periods Columns are called groups or families

Law of conservation of mass – matter is neither created nor destroyed it just changes forms Law of conservation of energy – energy is neither created nor destroyed it just changes forms