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? SolidLiquidGas

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 oC = 273.15 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. 21-22 (11-20)