Observed Properties of Matter

The three representations that are referred to in this study are (1) macroscopic representations that describe the bulk observable properties of matter, for example, heat energy, pH and colour changes, and the formation of gases and precipitates, (2) submicroscopic (or molecular) representations that provide explanations at the particulate level in which matter is described as being composed of atoms, molecules and ions, and (3) symbolic (or iconic) representations that involve the use of chemical symbols, formulas and equations, as well as molecular structure drawings, models and computer simulations that symbolise matter (Andersson, 1986 Boo, 1998 Johnstone, 1991, 1993 Nakhleh Krajcik, 1994 Treagust Chittleborough, 2001). 

Chemists and physicists have used the observed properties of matter to develop models of the individual units of matter. These models collectively make up what we now know as the atomic theory of matter. 

An activity which illustrates this general point in relation to particle theory (the topic of Chapter 2) is included in a publication available from SEP (the Science Enhancement Programme, details of which are given in the Other resources section at the end of this introduction). The first of two group-work tasks in this activity Judging models in science asks students to consider two types of particle models - particles like tiny hard billiard balls particles as molecules with soft electron clouds - and to consider which model better explains a range of evidence based on the observable properties of matter. Students will find that each model is useful for explaining some phenomena, but neither fits all the evidence - and of course both models are stiU found useful in science. 

Molecular dynamics techniques have been used with considerable success during the past two decades to probe the often subtle relationships between the motion of individual molecules and the observable properties of matter. Most of the molecular dynamics studies carried out thus far have dealt with systems containing structureless spherical particles. Recently, there has been growing activity in the simulation of assemblies of anisotropic molecules. 

For many years, scientists believed in the existence of atoms based primarily on the successful use of the atomic theory to explain the observed properties of matter. Direct visual evidence of atoms, however, eluded scientists until 1970, when an electron microscope, which uses electron beams instead of light, obtained images that showed the locations of large, heavy atoms of thorium and uranium. 

The kinetic molecular theory provides reasonable explanations for many of the observed properties of matter. An important factor in these explanations is the relative influence of cohesive forces and disruptive forces. Cohesive forces are the attractive forces associated with potential energy, and disruptive forces result from particle motion (kinetic energy). Disruptive forces tend to scatter particles and make them independent of each other cohesive forces have the opposite effect. Thns, the state of a substance depends on the relative strengths of the cohesive forces that hold the particles together and the disruptive forces tending to separate them. Cohesive forces are essentially temperature-independent because they involve interparticle attractions of the type described in Chapter 4. Disruptive forces increase with temperature because they arise from particle motion, which increases with temperature (Postulate 4). This explains why temperatnre plays such an important role in determining the state in which matter is fonnd. 

The macroscopic level refers to how we perceive matter with our eyes, through the outward appearance of objects. The microscopic level describes matter as chemists conceive of it—in terms of atoms and molecules and their behavior. In this text, we will describe many macroscopic, observable properties of matter, but to explain these properties, we will often shift our view to the atomic or molecular level—the microscopic level. 

Not all observations are summarized by laws. There are many properties of matter (such as superconductivity, the ability of a few cold solids to conduct electricity without any resistance) that are currently at the forefront of research but are not described by grand laws that embrace hundreds of different compounds. A major current puzzle, which might be resolved in the future either hy finding the appropriate law or by detailed individual computation, is what determines the shapes of big protein molecules. Formulating a law is just one way, not the only way, of summarizing data. 

Chemistry is concerned with the properties of matter, its distinguishing characteristics. A physical property of a substance is a characteristic that we can observe or measure without changing the identity of the substance. For example, a physical property of a sample of water is its mass another is its temperature. Physical properties include characteristics such as melting point (the temperature at which a solid turns into a liquid), hardness, color, state of matter (solid, liquid, or gas), and density. A chemical property refers to the ability of a substance to change into another substance. For example, a chemical property of the gas hydrogen is that it reacts with (burns in) oxygen to produce water a chemical property of the metal zinc is that it reacts with acids to produce hydrogen gas. The rest of the book is concerned primarily with chemical properties here we shall review some important physical properties. 

Why this is so cannot be explained. Egually inexplicable is the trend towards the more-complex structures and systems observed in evolution. Even if we conclude from this that life in its beginning had to be relatively simple, it was still not primitive. Manfred Eigen (Nobel Prize 1967) in particular pointed out that one property of matter must have played a decisive role the ability to self-assemble. From there he postulated that "Life comes into existence when the conditions for it are suitable". Could a different life have come into existence had the conditions been different We don t know. Instead, we know a lot about life that we can observe and investigate. 

In talking about thermodynamics and the properties of chemical equilibrium constants it is very difficult for chemists to avoid attempts to include the influence of forces between molecules on the magnitude of the equilibrium constant and differences between observed equilibrium constants. For the purpose of this chapter, it is convenient to talk first about the equilibrium constant and the macroscopic properties of matter which affect it first. Next, the reader will be introduced to the concept of forces between molecules, their relative magnitude and influence is separations. 

We hope that this brief review will help to link advanced theoretical research in physics of extremely dense matter with observational properties of compact objects. 

You can view many things in chemistry on both the macroscopic level (the level that we can directly observe) and the microscopic level (the level of atoms and molecules. Many times, observations at the macroscopic level can influence the theories and models at the microscopic level. Theories and models at the microscopic level can suggest possible experiments at the macroscopic level. We express the properties of matter in both of these ways. 

The essential differences between the properties of matter when in bulk and in the colloidal state were first described by Thomas Graham. The study of colloid chemistry involves a consideration of the form and behaviour of a new phase, the interfacial phase, possessiug unique properties. In many systems reactions both physical and chemical are observed which may be attributed to both bulk and interfacial phases. Thus for a proper understanding of colloidal behaviour a knowledge of the properties of surfaces and reactions at interfaces is evidently desirable. 

Using the four qualities of matter and four elements as a starting point, Aristotle developed logical explanations to explain numerous natural observations. Both the properties of matter and the changes in matter could be explained using Aristotle s theory. 

STATISTICAL MECHANICS. One major problem of physios involves the prediction of the macroscopic properties of matter in terms of the properties of the molecules of which it is composed. According to the ideas of classical physics, this could have been accomplished by a determination of the detailed motion of each molecule and by a subsequent superposition or summation of their effects. The Heisenberg indeterminacy principle now indicates that this process is impossible, since we cannot acquire sufficient information about the initial state of the molecules. Even if this were not so, the problem would be practically insoluble because of the extremely large numbers of molecules involved in nearly all observations. Many successful predictions can be made, however, by considering only the average, or most probable, behavior of the molecules, rather than the behavior of individuals. This is the mediod used in statistical mechanics. 

Chemistry is an experimental science concerned with the composition and properties of matter. The relation of the observed facts to one another forms the basis for the construction of generalized mental pictures, concepts, or models of matter into theories, which ideally should be as simple as possible, so that one can talk conveniently about the multitude of specific facts in a logical manner. Theories can be used to predict the outcome of new experiments. The test of any theory, however, lies in how well these predictions agree with the observed facts. 

Science attempts to understand and explain our observations in nature and the universe, Chemistry, a branch ot science, studies the chemical and physical properties of matter. Chemistry plays a fundamental role in understanding particular concepts of biology, physics, astronomy, geology, and other disciplines of science. Arguably, chemistry is the central science. 

Matter comprising biomolecules has distinct physical and chemical properties, which can be measured or observed. However, it is important to note that physical properties are distinct from chemical properties. Whereas physical properties can be directly observed without the need for a change in the chemical composition, the study of chemical properties actually requires a change in chemical composition, which results from so-called chemical reactions. Chemical reactions encompass processes that involve the rearrangement, removal, replacement or addition of atoms to produce a new substance(s). Properties of matter may be dependent (extensive) or independent (intensive) on the quantity of a substance, for example mass and volume are extensive properties of a substance. 

What does this equation mean We have simply specified that A and k are constants. What values can these constants have Note that if they could assume any values, this equation would lead to an infinite number of possible energies—that is, a continuous distribution of energy levels. However this is not correct. For reasons we will discuss presently, we find that only certain energies are allowed. That is, this system is quantized. In fact, the ability of wave mechanics to account for the observed (but initially unexpected) quantization of energy in nature is one of the most important factors in convincing us that it may be a correct description of the properties of matter. 

A world of difference exists between partial derivative and total derivative. Yet, the environmental engineering literature seems not able to distinguish the difference between the two. In a given instance of use of the term, either partial derivative or total derivative is employed when, actually, only one version should be used— not either. To illustrate the difference, first define the word property. Property is an observable quality of matter. For example, consider water. Water may contain sodium and chloride ions, and their concentrations are an observable quality. Thus, the concentration of the sodium and chloride ions are properties of water. Water, of course, has temperature, and temperature is an observable quality therefore, temperature is also a property of water. If the water is flowing, it will have velocity and velocity is an observable quality. Hence, velocity is also a property of water. In other words, to repeat, property is an observable quality of matter. 

The phenomena can influence the properties of matter and radiation either indirectly, say, changing of the cosmological equation of state, or via direct interaction with matter and radiation. In the first case only strong phenomena are relevant, in the second case even weak phenomena are accessible to observational data. The detailed analysis of sensitivity of cosmological data to various phenomena of new physics are presented in [2],... 

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