Introduction to Chemistry

Chemistry

• “central science”

• important to so many other fields of scientific study

• deals with the identification of the substances of which matter is composed

Three Levels of Understanding or Perspectives on the Nature of Chemistry

• Macroscopic

• Microscopic

• Symbolic

Matter

anything that has mass and can be observed

Two Types of Changes

• Physical Change

• Chemical Change

Physical Properties

variables that we can measure without changing the identity of the substance being observed

Mass

measured by comparing the object given and some standard, using a balance

Density

ratio of mass to volume

Examples of Physical Properties

• Color

• Viscosity

• Hardness

• Temperature

• Heat capacity

• Boiling point

• Melting point

• Volatility

Chemical Properties

• associated with the types of chemical changes that a substance undergoes

• can be determined only by observing how a substance changes its identity in chemical reactions

Phases of Matter

• Solid

• Liquid

• Gas

Solid

hard and does not change their shapes easily

Liquid

adapt to the shape of the container in which they are held

Gas

expands to occupy the entire volume of its container

Atoms

unimaginably small particles that cannot be made any smaller and still behave like a chemical system

Molecules

groups of atoms held together so that they form a unit whose identity is distinguishably different from the atoms alone

Accuracy

indicates how close the observed value is to the “true” value

Precision

spread in values obtained from the measurement

Random Error

make the measurement either too high or too low and is associated with the limitations of the equipment with which the measurement is made

Systematic Error

makes measurements consistently either too high or too low. This type of error is often associated with the existence of some unknown bias in the measurement apparatus.

Inductive Reasoning

begins with a series of specific observations and attempts to generalize to a larger, more universal conclusion

Deductive Reasoning

takes two or more statements or assertions and combines them so that a clear and irrefutable conclusion can be drawn

Model

refers to a largely empirical description

Theory

refers to an explanation that is grounded in some more fundamental principle or assumption about the behavior of a system

Derived Units

combination of base units

Mass

defined as a measure of the amount of matter in an object

Weight

measure of the force of gravitational attraction between the object and the Earth

Temperature scales

arise from the choice of two standard reference points that can be used to calibrate temperature with the use of a thermometer

Scientific Notation

writing numbers factoring out all powers of ten

Significant Figures

indicate the amount of information that is reliable when discussing a measurement