Basic Concepts of Chemistry Chapter 1

1.1 Chemistry and Its Methods Scientific Method Hypotheses Laws Theories

Hypotheses, Laws, & Theories Hypothesis: a tentative explanation or prediction based on experimental observations Law: a concise verbal or mathematical statement of a behavior or a relationship that is consistently observed in nature without contradiction Theory: a well-tested unifying principle that explains a body of facts and the laws based on them

Types of Observations Qualitative versus Quantitative

1.2 Classifying Matter How do the three states of matter differ?  Solid  Liquid  Gas

Kinetic-Molecular Theory All matter consists of tiny particles in constant motion. Movement of particles depends upon the state of matter. Higher temperatures increase movement.  Energy of motion = kinetic energy  Increasing temperature corresponds to faster and faster motions of atoms and molecules.

Macroscopic and Particulate Levels Macroscopic  observations and experimentation such as color, conductivity, dissolution, combustibility Particulate (or submicroscopic)  use models and represent atoms and molecules that cannot be seen – how chemists “think” about chemistry

Pure Substances and Mixtures Pure substance  unique properties  cannot be separated into two or more different pure substances by physical means Heterogeneous mixture  uneven texture  different samples yield different properties Homogeneous mixture or solutions  uniform at the particulate level  one or more substances in the same phase

Purification Mixtures can be purified into separate components.  Multi-step procedures leading to increased levels of purity; such as water treatment.

1.3 Elements and Atoms An atom is the smallest particle of an element retaining properties of that element, and elements are made up of only one type of atom. Symbols and other information about elements are found in the periodic table.

1.4 Compounds and Molecules Pure substances composed of two or more different elements are chemical compounds.  What are the chemical and physical differences between the elements sodium and chlorine, and their compound, sodium chloride?  Remember the Physical and Chemical Properties lab in regular chemistry…

Compounds and Molecules Compounds may be composed of ions or molecules, the smallest unit that retains the characteristics of the compound.  How do the compounds salt and sugar differ in their chemical composition? A chemical formula is used to represent a compound.

1.5 Properties of Matter Physical versus Chemical Properties What are some examples of each? Is density a physical or chemical property, and how do you know?

Temperature Temperature is the property that determines whether heat energy can be transferred from one object to another and the direction of that transfer. Celsius and Kelvin Temperature Scales What is the conversion between the two?  0 o C = K

Extensive and Intensive Properties Extensive properties depend on the amount of a substance present, such as mass and volume. Intensive properties do not depend on the amount, such as melting point or boiling point. Is density extensive or intensive? tricky – intensive; size doesn’t matter!

1.6 Physical and Chemical Change What’s the difference? Chemical reactions are the result of chemical change, wherein reactants are changed into different substances (products). Reactions are represented by chemical equations.

Homework Chapter 1 After reading Chapter 1, you should be able to do the following problems… pp (11-20)