Part I

Classification of Matter

What is Chemistry?

Chemistry is the study of the structure, function, and properties of matter and the changes it undergoes.

What are Chemicals?

Chemicals are any substances with a definite composition.

What is a Chemist?

• a scientist trained in the study of chemistry.

• Careers that involve chemistry include:– Marketing– Lab Technologist or Instrumentation

Specialist – Clinical or Medicinal Chemists – Chemical Patent Attorney

Matter and its Properties

Matter is anything that has mass and volume.

Example: A piece of chalk has matter but

sunlight does not.

Mass is a measure of the amount of matter in an object.

Volume is the amount of space occupied by an object.

Classification of Matter

Substances-are either mixtures or pure substances

Elements- are pure substances made of only one type of atom.Example: Gold, Silver, Sodium, Fluorine

Elements cannot be broken down by chemical reactions. (only by nuclear reactions)

An atom is the smallest particle of a chemical element that retains its properties.

Compounds are substances composed of atoms of two or more elements chemically bonded in a specific ratio.

Example: Water is always H2O.

Compounds can be broken down into simpler compounds or elements by a chemical change.

Example:

Carbon is an element & carbon dioxide is a compound.

Carbon dioxide can be decomposed into carbon and oxygen by chemical change.

A molecule is the smallest particle of a chemical compound that retains its

properties.

Example: A sample of methane is composed of CH4 molecules.

Classification of Matter

Substances are either elements or compounds.

Elements cannot be broken down by chemical reactions.

Compounds can be broken down to simpler compounds or elements by a

chemical change.

Example:

Water can be broken into hydrogen and oxygen gas with electrolysis.

MixturesMixtures contain more than one substance.

Their composition may vary from sample to sample. Mixtures can generally be separated by a physical change.

Methods for Classifying Matter

1. If the substance is listed on the

periodic table, then it is an element.

2. If you put an “and” in the substance’s

name, then it is a mixture.

example: peanut butter and jelly

3. If the substance has more than one

type of atom, then it is a compound.

Heterogeneous Mixtures

Heterogeneous Mixtures are mixtures without uniform composition. You can see the different components that make up the mixture

Homogeneous Mixtures

Homogeneous mixtures or solutions are mixtures with uniform composition.

Methods for Separating MixturesDifferent methods can be used to separate the parts of a mixture. Most of these methods utilize physical properties.

One method would be filtration.

Distillation

Crude oil goes through fractional distillation which utilizes differences in boiling points to separate the different

petroleum products.

Distillation of Petroleum Products

Classification of Matter

Properties are characteristics of matter that can be observed.

Example: Water boils at 1000C

and vinegar reacts with baking soda to form carbon dioxide.

Physical properties can be observed without changing the composition of the

substance.

Example: Boiling point, Odor, and Density

Properties cont.

• Intensive – Do not depend on the amount of matter present.

• Melting point, boiling point, density

• Extensive – Depends on the amount of matter present.

• Volume, mass, amount of energy

Physical changes do not change the identity of the substance.

Example: Cutting a board in half is a physical change.

State (phase) changes are physical changes from one state to another.

Endothermic change is a change in which energy is absorbed. The

substance takes in energy and the particles move faster as a result.

Which processes are exothermic?

Exothermic change is a change in which energy is released. The

substance loses energy and the particles move slower as a result.

Chemical PropertiesChemical properties can be observed as

a substance changes into a different substance.

In a chemical change, a new substance will be formed.

A chemical change usually involves a chemical reaction taking place.

Chemical Change

Chemical changes are chemical reactions.

During a chemical reaction one substance is changed into another substance.

Signs of a Chemical Reaction

1. Heat is given off or absorbed.

2. Light is given off.

3. Gas or precipitate formed

4. Color Change not due to moisture loss or gain.

5. Odor change.

6. Change is not easily reversed.

States of matter include solid, liquid, gas, and plasma.

Solids have a definite shape and volume. They are closely packed, have strong attractive forces, and vibrate around fixed points. They have low compressibility, because they are tightly packed.

Liquids have a definite volume and an indefinite shape. They are close together

but can move past each other. The attractive forces in a liquid are weaker

and can be overcome allowing liquids to flow.

Gases have indefinite shape and volume. They move randomly, are far from each

other, and have little attraction. They have higher compressibility, because the

particles are far apart.

Plasma is a high energy state in which electrons have been knocked off the

atoms.Example: Plasma is found in fluorescent

light tubes and in the sun.

State of Change ChartProcess Change Particle

Motion

Heat

Change

Example

Melting Solid to liquid

Speeds up

Endothermic Ice → Water

Freezing Liquid to solid

Slows

down

Exothermic Water → Ice

Vaporization Liquid to gas

Speeds

up

Endothermic Water Boiling

Condensation Gas to liquid

Slows

down

Exothermic Dew Forming

Sublimation Solid to gas

Speeds

up

Endothermic Dry Ice

Deposition Gas to solid

Slows down

Exothermic Frost

Forming

Phase Change Diagram is a graph of temperature versus energy that shows how energy added or removed from a substance affects its state. During a state change, composition does not change.

Law of Conservation of Energy-states that in any chemical or physical process, energy is neither created nor destroyed. It may only be converted from one form to another.

Energy- is the ability of an object to do work.

Work-is the ability to move an object against a force (W = F x d).

Kinetic Energy- is the energy of an object due to its motion.

Example- Gas particles are moving faster than solids or liquids and, therefore, have more kinetic energy.

Potential Energy- is the energy of an object due to its position or internal structure.

Chemical Energy- is the potential energy released during a chemical reaction. Matter has potential energy since energy is absorbed to break a chemical bond (endothermic) and energy is released when a chemical bond forms (exothermic).

Example- When hydrochloric acid reacts with zinc, energy is released in the form of heat.

Thermal Energy or Heat is the energy transferred as a result of a temperature

difference.

Left undisturbed, energy will flow from objects of _____ temperature to objects of _____ temperature until the objects have

equal temperature.

Unit – Joules (J) or Calories (cal)

• Temperature- is a measure of the average kinetic energy of the particles in a sample of matter.

Unit- Kelvin (K) or Celsius (ºC)

Instrument- Thermometer

Methods of Heat Transfer

Conduction: energy transfer by direct contact. Conduction occurs between particles of solids, liquids, or gases.

Example: Heat energy is transferred from the electric heating element in your stove to the pan resting on it.

Methods of Heat Transfer

Convection: energy transfer by movement. Convection occurs only between fluid particles (liquids or gases).

Example: Heat energy is transferred within a pan of water by currents resulting from density differences. Hotter water is less dense and rises to the top while colder, denser water falls to the bottom creating currents.

Methods of Heat Transfer

Radiation: is energy transfer by electromagnetic waves. Radiation does not require particles of any kind.

Example: Heat energy is transferred from the sun to the earth via electromagnetic waves.