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-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

ExperimentingA. 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 experimenti. 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 resultsb. 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 experimentsa. field work does not usually include a control group, where laboratory work is usually controlled

Theories and Lawsi. Theory

a. An explanation of a natural phenomenon that is supported by a large body of evidenceb. Continual verification and refinement of a hypothesis results in a theoryc. A valid theory enables scientists to predict new facts and relationshipsd. It explains a natural phenomenone. Can change

ii. Laws or Principlesa. Certain facts of natureb. Description of a natural phenomenonc. Doesn’t change

Matter and ChangeChpt 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 substanceex. 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 actsex. 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

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.

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 & Compoundselements – 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

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