Properties of Matter Help (page 2)
Chemistry is defined as the study of matter and the way it reacts in different situations. But, what is matter?
At first, people thought matter only included things that could be seen and measured, like salt, grain, and olive oil. Everyone used their senses to define what they saw, heard, tasted, touched, and smelled. Anything that could not be sensed simply did not exist or belonged in the realm of myths and legends. Most people only believed in what they saw for themselves. They doubted everything until they had experienced it for themselves, usually by seeing it “with their own eyes.”
With the beginning of the scientific era, the search for exactly what makes up the “stuff” of the universe became more intense.
Matter is defined as anything that has mass and occupies space.
We now know that even in the unseen world matter exists that is too small to be seen or measured except with very complex machines and sometimes not even then. Sometimes all scientists can do is observe the effects of matter, even though the actual matter cannot be obtained.
Around 495 , a Greek philosopher named Democritus wondered if substances could be divided into smaller and smaller parts indefinitely. He thought that eventually particles would be reached that could no longer be divided. He called these smallest particles atoms (from the Greek word atomos , which means “not divided”). The great philosophers Aristotle and Plato thought matter was continuous, fluid, and could not be divided into individual particles.
In 100 , another forward thinker named Lucretius wrote a long, descriptive poem called De Rerum Natura (The Nature of Things), praising early ideas that leaned toward an atomic theory of matter. Since few people could read and most gained information through story telling, the poem helped people to understand the basic nature of matter. The invention of the Gutenberg printing press in 1452, which used olive oil ink with a screw-type wine press, helped to spread the knowledge of the time.
The De Rerum Natura poem was one of the first texts set in print. This fact helped the atomic theory survive. Along with religious texts and Bibles of the time, the poem was one of the few things available to read.
Once the first seeds of the atomic theory spread, scientists began thinking about matter in particle form. Experiments were performed and measurements taken to discover how compounds could be further divided, rearranged, and combined.
In the late 1700s, Antoine Lavoisier, the father of modern chemistry, insisted on precise measurements to better compare results and explain the properties of matter. Unfortunately, though a brilliant scientist, he was also associated with French taxation and the ruling governmental class. In 1794, his research was cut short by the guillotine and the French Revolution.
Since then, modern scientists have discovered particles that are smaller than an atom. These subatomic particles, which exist in the core of an atom, are called protons with a positive charge, and neutrons which are neutral and have no charge. Electrons orbit the nucleus like untamed satellites that are attracted by the forces of electromagnetism.
Figure 3.1 shows how the core of an atom might look if a model were made of the subatomic particles.
In 1968, quarks were discovered. Quarks are particles of matter that are constituents of neutrons and protons. So far, six different types of quarks have been identified. These will be discussed more in later chapters.
Solids, Liquids, And Gases
Chemistry and the study of matter focus on the forms of matter. Scientists describe the three basic forms of matter as: solid, liquid , and gas . Figure 3.2 illustrates these three different forms that matter can take.
Solids include things like boulders, metals, crystals, and glass. They are fixed in shape and rigid with a measurable volume. To change shape in a major way, a strong outside force like fire or heavy impact is needed.
Liquids such as water, oil, and alcohol have been known for centuries. They have a measurable volume, but are bendable and can change shape. Liquids are easier to study since they fill the shape of their container and flow from one place to another. They do not require force to change shape, but are affected by heat.
Gases are a different story. They have neither form nor volume and expand to fill the entire container into which they are placed. At times they are visible and then disappear. They seem to come from nothing and leave to go nowhere. Ancient alchemists’ ideas of transmutation seem to better describe the mystery of gases.
To make things even more interesting, some liquids like water can take on all three modes (water, ice, and steam) at different times. Scientists wanted to understand how this happened. Through much experimentation, it was discovered that matter had specific properties .
The unique character or the way an element reacts is said to be its properties . These properties are grouped into two classes, physical and chemical .
Physical properties are special characteristics that make up the physical composition of a sample. Physical properties include: color, form, density, thermal and electrical conductivity, and melting and boiling points. Physical properties can be seen without any change in form or dimension. For example, barium is commonly silvery white in color, a solid, melts at 727°C (1341 °F) and burns green at a wavelength of 554 nanometers. Even melted, it is still barium, but in a different form than when it was solid.
Chemical properties are those characteristics that focus on a substance’s behavior when mixed with another element or compound. For example, copper when exposed to oxygen turns green on the surface, but doesn’t dissolve in water. The reaction that causes the surface to turn green forms a very thin layer (copper carbonate or copper sulfate) that actually protects the surface from further corrosion.
Iron is abundant in the Earth’s crust and was one of the first refined metals. However, it is never found in its pure form, but as an oxide (combined with oxygen). Iron chemically reacts with air and water to form rust, a porous crumbling material that sticks loosely to the iron’s surface. When rust crumbles and falls away, a new place on the iron’s surface is exposed; eventually the entire sample will rust away.
Practice problems for these concepts can be found at - Properties of Matter Practice Test