Lesson 2 – Matter: its classification and properties

Matter - is “anything that has mass and occupies space”, we were taught in school. True enough, but not very satisfying. A more complete answer is unfortunately far beyond the scope of this course, but we will offer a hint of it in the later section on atomic structure. For the moment, let’s side-step definition of matter and focus on the chemist’s view: matter is what chemical substances are composed of. But what do we mean by chemical substances? How do we organize our view of matter and its properties? These will be the subjects of this lesson.

Matter - is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume. However, different fields use the term in different and sometimes incompatible ways; there is no single agreed scientific meaning of the word "matter".

Observable properties of matter

The science of chemistry developed from observations made about the nature and behavior of different kinds of matter, which we refer to collectively as the properties of matter.

The properties we refer to in this lesson are all macroscopic properties: those that can be observed in bulk matter. At the microscopic level, matter is of course characterized by its structure: the spatial arrangement of the individual atoms in a molecular unit or an extended solid.

The study of matter begins with the study of its properties

By observing a sample of matter and measuring its various properties, we gradually acquire enough information to characterize it; to distinguish it from other kinds of matter. This is the first step in the development of chemical science, in which interest is focused on specific kinds of matter and the transformations between them.

Extensive and Intensive properties

Intensive - Properties that do not depend on the amount of the matter present.

·         Color

·         Odor

·         Luster - How shiny a substance is.

·         Malleability - The ability of a substance to be beaten into thin sheets.

·         Ductility - The ability of a substance to be drawn into thin wires.

·         Conductivity - The ability of a substance to allow the flow of energy or electricity.

·         Hardness - How easily a substance can be scratched.

·         Melting/Freezing Point - The temperature at which the solid and liquid phases of a substance are in equilibrium at atmospheric pressure.

·         Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid (generally atmospheric pressure).

·         Density - The mass of a substance divided by its volume

Extensive - Properties that do depend on the amount of matter present.

·         Mass - A measurement of the amount of matter in a object (grams).

·         Weight - A measurement of the gravitational force of attraction of the earth acting on an object.

·         Volume - A measurement of the amount of space a substance occupies.

·         Length

Classify each of the following as an extensive or intensive property.

1.             The volume of beer in a mug

2.             The percentage of alcohol in the beer

3.             The number of calories of energy you derive from eating a banana

4.             The number of calories of energy made available to your body when you consume 10.0 g of sugar

5.             The mass of iron present in your blood

6.             The mass of iron present in 5 mL of your blood

7.             The electrical resistance of a piece of 22-gauge copper wire.

8.             The electrical resistance of a 1-km length of 22-gauge copper wire

9.             The pressure of air in a bicycle tire

Classification of Matter

Matter Anything with mass and volume.
Substance  Matter with constant composition		Mixture Matter with variable composition
Element Substance made up of only one type of atom	Compound Two or more elements that are chemically combined	Heterogeneous Mixture Mixtures that are made up of more than one phase	Homogeneous Mixtures Also called solutions.  Mixtures that are made up of only one phase
Examples - gold, silver, carbon, oxygen and hydrogen	Examples - water, carbon dioxide, sodium bicarbonate, carbon monoxide	Examples - sand, soil, chicken soup, pizza, chocolate chip cookies.	Examples - salt water, pure air, metal alloys, seltzer water.

Operational and conceptual classifications

Since chemistry is an experimental science, we need a set of experimental criteria for placing a given sample of matter in one of these categories. There is no single experiment that will always succeed in unambiguously deciding this kind of question. However, there is one principle that will always work in theory, if not in practice. This is based on the fact that the various components of a mixture can, in principle, always be separated into pure substances.

Consider a heterogeneous mixture of salt water and sand. The sand can be separated from the salt water by the mechanical process of filtration. Similarly, the butterfat contained in milk may be separated from the water by a mechanical process known as centrifugation, which depends on differences in density between the two components. These examples illustrate the general principle that heterogeneous matter may be separated into homogeneous matter by mechanical means. Turning this around, we have an operational definition of heterogeneous matter: if, by some mechanical operation we can separate a sample of matter into two or more other kinds of matter, then our original sample was heterogeneous.

To find a similar operational definition for homogeneous mixtures, consider how we might separate the two components of a solution of salt water. The most obvious way would be to evaporate off the water, leaving the salt as a solid residue. Thus a homogeneous mixture can be separated into pure substances by undergoing appropriate changes of state— that is, by evaporation, freezing, etc. If a sample of matter remains unchanged by carrying out operations of this kind, then it could be a pure substance.

Some common methods of separating homogeneous mixtures into their components are outlined below.

Ø  Distillation. A liquid is partly boiled away; the first portions of the condensed vapor will be enriched in the lower-boiling component.

Ø  Fractional crystallization. A hot saturated solution of a solid in a liquid is allowed to cool slowly; the first solid that crystallizes out tends to be of higher purity.

Ø  Liquid-liquid extraction. Two mutually-insoluble liquids, one containing two or more solutes (dissolved substances), are shaken together. Each solute will concentrate in the liquid in which it is more soluble.

Ø  Chromatography. As a liquid or gaseous mixture flows along a column containing an adsorbant material, the more strongly-adsorbed components tend to move more slowly and emerge later than the less-strongly adsorbed components.

    Physical and chemical properties

Physical Changes	Chemical Changes
Changes in matter that do not alter the identity of the matter itself	Changes that do alter the identity of a substance.
Ø  Size Ø  Shape Ø  State - solid  liquid  gas Ø  Dilutions	Ø  Iron rusting Ø  Wood burning Ø  Copper turning to brass
Common Errors Ice melting, water freezing, water evaporating, and steam condensing are all examples of a state change. These are physical changes, not chemical. Diluting a solution is a physical change, even if the color becomes fainter.

Classify each of the statements as a physical or chemical property, and explain the basis for your answer.

Chlorine is a greenish-yellow gas at room temperature.
Liquid oxygen is attracted by a magnet.
Gold is highly resistant to corrosion.
Hydrogen cyanide is an extremely poisonous gas.
Sugar is a high-energy food.

Introduction to Chemistry

Chemistry is such a broad subject and one so full of detail that it is easy for a newcomer to find it somewhat overwhelming, if not intimidating. The best way around this is to look at Chemistry from a variety of viewpoints:

• How Chemistry relates to other sciences and to the world in general
• What are some of the fundamental concepts that extend throughout Chemistry?
• What are some of the major currents of modern-day Chemistry?

The Scope of Chemical Science

Chemistry is too universal and dynamically-changing a subject to be confined to a fixed definition; it might be better to think of chemistry more as a point of view that places its major focus on the structure and properties of substances— particular kinds of matter— and especially on the changes that they undergo.

In some ways, physics might be considered more "fundamental" to the extent that it deals with matter and energy in a more general way, without the emphasis on particular substances. But the distincion can get pretty fuzzy; it is ultimately rather futile to confine any aspect of human endeavour to little boxes.

CHEMISTRY: The central science

The real importance of Chemistry is that it serves as the interface to practically all of the other sciences, as well as to many other areas of human endeavor. For this reason, Chemistry is often said (at least by chemists!) to be the "central science".

Chemistry can be "central" in a much more personal way: with a solid background in Chemistry, you will find it far easier to migrate into other fields as your interests develop.

Research or teaching not for you? Chemistry is so deeply ingrained into so many areas of business, government, and environmental management that some background in the subject can be useful (and able to give you a career edge as a team member having special skills) in fields as varied as product development, marketing, management, computer science, technical writing, and even law.

History of Chemistry

Ø  Egyptian alchemy [3,000 BCE – 400 BCE], formulate early "element" theories such as the Ogdoad.

Ø  Greek alchemy [332 BCE – 642 CE], the Macedonian king Alexander the Great conquers Egypt and founds Alexandria, having the world's largest library, where scholars and wise men gather to study.

Ø  Islamic alchemy [642 CE – 1200], the Muslim conquest of Egypt; development of alchemy by Jābir ibn Hayyān, al-Razi and others; Jābir modifies Aristotle's theories; advances in processes and apparatus.^[15]

Ø  European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry.^{[citation needed]} From the 12th century, major advances in the chemical arts shifted from Arab lands to western Europe.^[15]

Ø  Chemistry [1661], Boyle writes his classic chemistry text The Sceptical Chymist.

Ø  Chemistry [1787], Lavoisier writes his classic Elements of Chemistry.

Ø  Chemistry [1803], Dalton publishes his Atomic Theory.

Ø  Chemistry [1869], Dmitri Mendeleev presented his Periodic table being the framework of the modern chemistry

So what is CHEMSITRY?

Ø  Alchemy (330) – the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos).

Ø  Chymistry (1661) – the subject of the material principles of mixed bodies (Boyle).

Ø  Chymistry (1663) – a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection (Glaser).

Ø  Chemistry (1730) – the art of resolving mixed, compound, or aggregate bodies into their principles; and of composing such bodies from those principles (Stahl).

Ø  Chemistry (1837) – the science concerned with the laws and effects of molecular forces (Dumas).

Ø  Chemistry (1947) – the science of substances: their structure, their properties, and the reactions that change them into other substances (Pauling).

General Definition

• Chemistry is the science of matter, especially its chemical reactions, but also its              composition, structure andproperties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds.
• Chemistry is sometimes called "the central science" because it connects physics with other natural sciences such as geology and biology.
• Chemistry is a branch of physical science but distinct from physics.