Chapter 2 – Chemistry Flashcard
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| Name two categories used to classify properties of matter. |
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| Extensive or intensive. |
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| Explain why all samples of a given substance have the same intensive properties. |
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| Because every sample has the same composition. |
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| Name three states of matter. |
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| Solid, liquid, and gas. |
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| Describe the two categories used to classify physical changes. |
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| Reversible or irreversible. |
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| How are mixtures classified? |
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| Heterogeneous or homogeneous mixtures, based on the distribution of their components. |
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| What type of properties can be used to separate mixtures? |
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| Differences in physical properties can be used to separate mixtures. |
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| How is a compound different from an element? |
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| Compounds can be broken down into simpler substances by chemical means, but elements can not. |
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| How can you distinguish a substance from a mixture? |
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| If the composition of a material is fixed, the material is a substance. If the composition may vary, the material is a mixture. |
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| What are chemical symbols and chemical formulas used for? |
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| Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds. |
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| How does a chemical change affect the composition of matter? |
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| During a chemical change, the composition of matter always changes. |
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| Name four possible clues that a chemical change has taken place. |
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| A transfer of energy, a change in color, the production of gas, or the formation of a precipitate. |
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| In a chemical reaction, how does the mass of the reactants compare with the mass of the products? |
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| The mass of the products is always equal to the mass of the reactants. |
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| How do measurements relate to experimental sciences? |
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| Measurements are fundamental to the experimental sciences. |
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| How are accuracy and precision evaluated? |
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| To evaluate accuracy, the measured value must be compared to the correct value. To evaluate precision, you must compare the values of repeated measurements. |
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| Why must a given measurement always be reported to the correct number of significant figures? |
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| Calculated answers often depend on the number of significant figures in the values used in the calculation. |
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| Why must a given measurement always be reported to the correct number of significant figures? |
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| Calculated answers often depend on the number of significant figures in the values used in the calculation. |
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| How does the precision of a calculated answer compare to the precision of the measurements used to obtain it? |
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| In general, a calculated answer cannot be more precise than the least precise measurement from which it was calculated. |
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| Which five S1 base units are commonly used in chemistry? |
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| The meter, kilogram, kelvin, second and mole. |
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| What happens to the numerical value of a measurement that is multiplied by a conversion factor? What happens to the actual size of the quantity? |
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| Multiplying by a conversion factor does not change the actual size of a measurement. |
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| What determines the density of an object? |
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| Density is an intensive property that depends only on the composition of a substance. |
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| How does density vary with temperature? |
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| The density of a substance generally decreases as its temperature increases. |
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| Why did Rutherford's atomic model need to be replaced? |
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| Rutherford's planetary model could not explain the chemical properties of elements. |
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| What do two sublevels of the same principal energy level differ from each other? |
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| The quantum mechanical model determines the allowed energies an electron can have and how likely it is to be found in various locations around the nucleus. |
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| How are wavelength and frequency of light related? |
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| The wavelength and frequency of light are inversely proportional to each other. |
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| Describe the cause of atomic emission spectrum of an element. |
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| When atoms absorb energy, electrons move into higher energy levels. These electrons then lose energy by emitting light when the electrons drop back to lower energy levels. |
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| How is the change in electron energy related to the frequency of light emitted in atomic transitions? |
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| The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron. |
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| How are elements arranged in the modern periodic table? |
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| In the modern periodic table, elements are arranged in order of increasing atomic number. The elements within a group in the table have similar properties. |
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| Into what four classes can elements be sorted based on their electron configurations? |
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| Elements can be sorted into noble gases, representative elements, transition metals, or inner transition metals based on their electron configurations. |
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| Compare the size of ions to the size of the atoms from which they form. |
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| Cations are always smaller than the atoms from which they form. Cations are always larger than the atoms from which they form. Anions are always larger than the atoms from which they form. |
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| Atoms of which elements tend to gain electrons? Atoms of which elements tend to lose electrons? |
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| Atoms of metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetallic elements tend to gain electrons to achieve a complete octet. |
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| How can you describe the electrical charge of an ionic compound? |
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| Although they are composed of ions, ionic compounds are electrically neutral. |
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| Why are alloys more useful than pure metals? |
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| Alloys are important because their properties are often superior to those of their component elements. |
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| What information does a molecular formula provide? |
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| A molecular formula shows how many atoms of each element a molecule contains. |
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| List three ways in which the octet rule can sometimes fail to be obeyed. |
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| The octet rule is not satisfied in molecules with an odd number of electrons, and in molecules where an atom has less, or more, than a complete octet of valence electrons. |
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| List three ways in which the octet rule can sometimes fail to be obeyed. |
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| The octet rule is not satisfied in molecules with an odd number of electrons, and in molecules where an atom has less, or more, than a complete octet of valence electrons. |
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| How are atomic and molecular orbitals related? |
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| Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole. |
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| Explain how the VSEPR theory can be used to predict the shapes of molecules. |
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| According to VSEPR theory, the repulsion shapes to adjust so that the valence-electron pairs stay as far apart as possible. |
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| How is orbital hybrization useful in describing molecules? |
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| Orbital hybridization provides information about both molecular bonding and molecular shape. |
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| What happens when polar molecules are between oppositely charged metal plates? |
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| Polar molecules between oppositely charged metal plates tend to become oriented with respect to the positive and negative plates. |
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| Compare the strengths of intermolecular attractions to the strengths of ionic bonds and covalent bonds. |
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| Intermolecular attractions are weaker than either an ionic or covalent bond. |
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| Explain why network solids have high melting points. |
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| Melting a network solid requires breaking covalent bonds throughout the solid. |
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| What are the five types of chemical reactions? |
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| The five general types of reactions are combination, decomposition, single-replacement, and combustion. |
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| What are the keys to predicting the products of the five general types of reactions? |
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| The number of elements and/or compounds reacting is a good indicator of possible reaction type and thus possible products. |
