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7.1: Prelude to Introduction to Chemical Reactions
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Although yeast has been used for thousands of years, its true nature has been known only for the last two centuries. Yeasts are single-celled fungi. About 1,000 species are recognized, but the most common species is Saccharomyces cerevisiae, which is used in bread making. Other species are used for the fermentation of alcoholic beverages. Some species can cause infections in humans.
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7.2: Laws of Conservation : A Review
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One scientific law that provides the foundation for understanding in chemistry is the law of conservation of matter. It states that in any given system that is closed to the transfer of matter (in and out), the amount of matter in the system stays constant. A concise way of expressing this law is to say that the amount of matter in a system is conserved. The amount of matter in a closed system is conserved.
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7.3: Evidence of a Chemical Reaction
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In a chemical change, new substances are formed. In order for this to occur, the chemical bonds of the substances break, and the atoms that compose them separate and rearrange themselves into new substances with new chemical bonds. When this process occurs, we call it a chemical reaction. A chemical reaction is the process in which one or more substances are changed into one or more new substances.
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7.4: Chemical Equations
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A chemical reaction is the process in which one or more substances are changed into one or more new substances. Chemical reactions are represented by chemical equations. Chemical equations have reactants on the left, an arrow that is read as "yields", and the products on the right.
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7.5: How to Write Balanced Chemical Equations
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In chemical reactions, atoms are never created or destroyed. The same atoms that were present in the reactants are present in the products - they are merely reorganized into different arrangements. In a complete chemical equation, the two sides of the equation must be present on the reactant and the product sides of the equation.
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7.6: Aqueous Solutions and Solubility - Compounds Dissolved in Water
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When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process represents a physical change known as dissociation. Under most conditions, ionic compounds will dissociate nearly completely when dissolved, and so they are classified as strong electrolytes.
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7.7: Precipitation Reactions
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A precipitation reaction is a reaction that yields an insoluble product—a precipitate—when two solutions are mixed. Thus precipitation reactions are a subclass of exchange reactions that occur between ionic compounds when one of the products is insoluble. Because both components of each compound change partners, such reactions are sometimes called double-displacement reactions.
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7.8: Writing Chemical Equations for Reactions in Solution- Molecular, Complete Ionic, and Net Ionic Equations
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Precipitation is a process in which a solute separates from a supersaturated solution. In a chemical laboratory it usually refers to a solid crystallizing from a liquid solution, but in weather reports it applies to liquid or solid water separating from supersaturated air.
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7.9: Acid–Base and Gas Evolution Reactions
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A gas evolution reaction is a chemical process that produces a gas, such as oxygen or carbon dioxide.
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7.10: Oxidation-Reduction Reactions
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Oxidation-reduction (redox) reactions involve the transfer of electrons from one atom to another. Oxidation numbers are used to keep track of electrons in atoms. There are rules for assigning oxidation numbers to atoms. Oxidation is an increase in oxidation number (loss of electrons); reduction is a decrease in oxidation number (gain of electrons).
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7.11: Classifying Chemical Reactions
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Chemical reactions are classified into types to help us analyze them and also to help us predict what the products of the reaction will be. The five major types of chemical reactions are synthesis, decomposition, single replacement, double replacement, and combustion.
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7.12: The Activity Series- Predicting Spontaneous Redox Reactions
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Metals and halogens are ranked according to their ability to displace other metals or halogens below them in the series. The activity series is a list of elements in decreasing order of their reactivity. Since metals replace other metals, while nonmetals replace other nonmetals, they each have a separate activity series.