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We have in LO.8 Chemistry G10
First: the Concepts
•1. Pure substance.
• 2. Solution.
• 3. Solute.
• 4. Solvent.
• 5. Colloid.
• 6. Tyndall Effect.
• 7. Suspension.
Second: the References
Zumdahl: CH.1 SEC.10
CH.11 SEC.1,8
Active Chemistry: CH.2 SEC.3
Third: the Videos links
Fourth: Skills
1. Separate mixtures by evaporation and filtration.
2. Use laboratory techniques to differentiate colloids from true solutions.
3. Differentiate suspension, solution, colloid.
4. Explain how particle size influences physical and chemical properties.
Fifth: the materials as PPT., DOCX., and PDF
In the Drive from this link
Few Notes:
Classification of Matter
Before we can hope to understand the changes we see going on around us—the growth of plants, the rusting of steel, the aging of people, the acidification of rain—we must find out how matter is organized. Matter, best defined as anything occupying space and having mass, is the material of the universe. Matter is complex and has many levels of organization
. In this section we will introduce basic ideas about the structure of matter and its behavior. We will start by considering the definitions of the fundamental properties of matter. Matter exists in three states: solid, liquid, and gas. A solid is rigid; it has a fixed volume and shape. A liquid has a definite volume but no specific shape; it assumes the shape of its container. A gas has no fixed volume or shape; it takes on the shape and volume of its container.
In contrast to liquids and solids, which are only slightly compressible, gases are highly compressible; it is relatively easy to decrease the volume of a gas. Molecular-level pictures of the three states of water . The different properties of ice, liquid water, and steam are determined by the different arrangements of the molecules in these substances. the states of some common substances at 208C and 1 atmosphere pressure. Most of the matter around us consists of mixtures of pure substances. Wood, gasoline, wine, soil, and air all are mixtures. The main characteristic of a mixture is that it has variable composition. For example, wood is a mixture of many substances, the proportions of which vary depending on the type of wood and where it grows. Mixtures can be classified as homogeneous (having visibly indistinguishable parts) or heterogeneous (having visibly distinguishable parts).
A homogeneous mixture is called a solution. Air is a solution consisting of a mixture of gases. Wine is a complex liquid solution. Brass is a solid solution of copper and zinc. Sand in water and iced tea with ice cubes are examples of heterogeneous mixtures. Heterogeneous mixtures usually can be separated into two or more homogeneous mixtures or pure substances (for example, the ice cubes can be separated from the tea).
Mixtures can be separated into pure substances by physical methods. A pure substance is one with constant composition. Water is a good illustration of these ideas. As we will discuss in detail later, pure water is composed solely of H2O molecules, but the water found in nature (groundwater or the water in a lake or ocean) is really a mixture. Seawater, for example, contains large amounts of dissolved minerals.
Boiling seawater produces steam, which can be condensed to pure water, leaving the minerals behind as solids. The dissolved minerals in seawater also can be separated out by freezing the mixture, since pure water freezes out. The processes of boiling and freezing are physical changes. When water freezes or boils, it changes its state but remains water; it is still composed of H2O molecules. A physical change is a change in the form of a substance, not in its chemical composition.
A physical change can be used to separate a mixture into pure compounds, but it will not break compounds into elements. One of the most important methods for separating the components of a mixture is distillation, a process that depends on differences in the volatility (how readily substances become gases) of the components. In simple distillation, a mixture is heated in a device. The most volatile component vaporizes at the lowest temperature, and the vapor passes through a cooled tube (a condenser), where it condenses back into its liquid state.
For example, a mixture of water and sand is easily separated by boiling off the water. Water containing dissolved minerals behaves in much the same way. As the water is boiled off, the minerals remain behind as nonvolatile solids. Simple distillation of seawater using the sun as the heat source is an excellent way to desalinate (remove the minerals from) seawater. However, when a mixture contains several volatile components, the one-step distillation does not give a pure substance in the receiving flask, and more elaborate methods are required. Another method of separation is simple filtration, which is used when a mixture consists of a solid and a liquid.
The mixture is poured onto a mesh, such as filter paper, which passes the liquid and leaves the solid behind. A third method of separation is chromatography. Chromatography is the general name applied to a series of methods that use a system with two phases (states) of matter: a mobile phase and a stationary phase. The stationary phase is a solid, and the mobile phase is either a liquid or a gas. The separation process occurs because the components of the mixture have different affinities for the two phases and thus move through the system at different rates.
A component with a high affinity for the mobile phase moves relatively quickly through the chromatographic system, whereas one with a high affinity for the solid phase moves more slowly. One simple type of chromatography, paper chromatography, uses a strip of porous paper, such as filter paper, for the stationary phase. A drop of the mixture to be separated is placed on the paper, which is then dipped into a liquid (the mobile phase) that travels up the paper as though it were a wick. This method of separating a mixture is often used by biochemists, who study the chemistry of living systems. It should be noted that when a mixture is separated, the absolute purity of the separated components is an ideal. Because water, for example, inevitably comes into contact with other materials when it is synthesized or separated from a mixture, it is never absolutely pure. With great care, however, substances can be obtained in very nearly pure form.
Pure substances are either compounds (combinations of elements) or free elements. A compound is a substance with constant composition that can be broken down into elements by chemical processes. An example of a chemical process is the electrolysis of water, in which an electric current is passed through water to break it down into the free elements hydrogen and oxygen. This process produces a chemical change because the water molecules have been broken down.
The water is gone, and in its place we have the free elements hydrogen and oxygen. A chemical change is one in which a given substance becomes a new substance or substances with different properties and different composition. Elements are substances that cannot be decomposed into simpler substances by chemical or physical means.
We have seen that the matter around us has various levels of organization. The most fundamental substances we have discussed so far are elements. As we will see in later chapters, elements also have structure: They are composed of atoms, which in turn are composed of nuclei and electrons. Even the nucleus has structure: It is composed of protons and neutrons. And even these can be broken down further, into elementary particles called quarks. However, we need not concern ourselves with such details at this point.
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