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ATI TEAS 7 CHEMISTRY STUDY GUIDE
Cohesion Cohesion is the tendency of particles of the same kind to stick to each other and is an important property to consider when looking at states of matter. This image describes the various phase changes and how it either absorbs or releases energy. Please see chart. What phase changes require energy to be added to the system because the substance has more energy at the end of the phase change? The phase changes are melting , vaporization (boiling) , and sublimation. What phase changes require energy to be released to the system because the substance has more energy at the end of the phase change? These phase changes are freezing , condensation , and deposition. Matter Matter is anything that takes up space and has mass. A golf ball contains more matter than a table-tennis ball. The golf ball has more mass. The amount of matter that an object contains is its mass. Mass Matter is anything that takes up space and has mass. A golf ball contains more matter than a table-tennis ball. The golf ball has more mass. The amount of matter that an object contains is its mass.
substance A substance is matter that has a uniform and definite composition. Lemonade is not a substance because not all pitchers of lemonade are identical. physical property A physical property is a quality or condition of a substance that can be observed or measured without changing the substance’s composition. chemical property Chemical properties are observed only when a substance undergoes a change in composition, which is a chemical change. extensive properties extensive properties do depend on the amount of a sample that is present. A good example of the difference between the two types of properties is that mass and volume are extensive properties, but their ratio (density) is an intensive property. Notice that mass and volume deal with amounts, whereas density is a physical property. Intensive properties Intensive properties do not depend on the amount of matter that is present. Intensive properties do not change according to the conditions. They are used to identify samples because their characteristics do not depend on the size of the sample. Deposition Deposition is a gas changing into a solid without going through the liquid phase. It is an uncommon phase change. Melting Melting is the change of a solid into a liquid.
If the two atoms share electrons equally, the bond is classified as nonpolar covalent. This occurs if the two atoms have similar electronegativities, which means that neither atom pulls significantly harder on the shared electrons than the other. solution A solution is a type of homogeneous mixture that is formed when a solute dissolves in a solvent. heterogeneous A heterogeneous mixture is when the substances mix unevenly and it is possible to see individual components. mixture A mixture is when elements and compounds are physically, but not chemically, combined. what is the difference between a saturated and an unsaturated solution? The concentration of a solution is the amount of a substance in a given amount of solution. An unsaturated solution has the ability to dissolve more solute and a saturated solution has already reached the limit of solute it can dissolve. activated complex In every reaction, an activated complex must form between reactants. This complex can also be referred to as a transition state because it is required to convert, or provide a transition between, the reactants and products. activation energy The activation energy is the amount of energy required to transform the reactants into the activated complex, which then breaks apart to form the products. Acids Acids and bases exhibit unique properties when dissolved in water. Acids donate protons (in the form of hydrogen ions) and bases accept protons (or hydrogen ions) in solution. Acids generally taste sour, turn litmus paper red, and act corrosive. bases Acids and bases exhibit unique properties when dissolved in water. Acids donate protons (in the form of hydrogen ions) and bases accept protons (or hydrogen ions) in solution. Bases generally taste bitter, turn litmus paper blue, are very corrosive, and will be slippery in solution.
pH Researchers can determine the strength of an acid or a base by measuring the pH of a solution. The pH value describes how acidic or basic a solution is. On pH scale, shown below, if the number is less than 7 the solution is acidic. A pH greater than 7 means the solution is basic. When the pH is exactly 7, the solution is neutral. deprotonates The strength of a base is determined by how readily it removes a hydrogen ion from a molecule, or deprotonates. neutralization reactions In an aqueous solution, a base increases the hydroxide concentration (OH–), while an acid increases the hydrogen ion (H+) concentration. Sometimes, neutralization reactions also occur. This type of reaction happens when an acid and a base react with each other to form water and salt. What is a Lewis Acid and Lewis base? The last theory about acids and bases is called the Lewis theory. This theory is based on electron movement during an acid-base reaction. A Lewis acid accepts a pair of electrons, while a Lewis base donates an electron pair.
