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Q: As per the kinetic-molecular theory, in what direction do the molecules and ions of liquids move? Read this paragraph and choose the correct option from the provided answers: We discussed earlier some basic principles about the behavior of gases called the kinetic-molecular theory. Among other things, this theory suggests that gas molecules are in constant motion, and the average speed of the individual gas particles is dependent upon temperature the higher the temperature, the faster the molecules move. It is not just gas particles that are in constant motion. The molecules and ions that make up liquids and solutions are also continually moving in nearly random directions. As a result, molecules and ions in a solution will collide with one another fairly frequently. As with gases, a temperature increase will produce an increase in the average particle speed. Choices: - alter directions - opposite direction - same direction - random directions A:
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random directions

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Q: What helps pumice float in water? Read this paragraph and choose the correct option from the provided answers: Some extrusive igneous rocks cool so rapidly that crystals do not develop at all. These form a glass, such as obsidian. Others, such as pumice, contain holes where gas bubbles were trapped in the lava. The holes make pumice so light that it actually floats in water. The most common extrusive igneous rock is basalt. It is the rock that makes up the ocean floor. Shown below are three types of extrusive igneous rocks ( Figure below ). Choices: - high density - large mass - gravity - gas bubble holes A:
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gas bubble holes

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Q: Technetium is named after the greektechnikos, meaning "artificial," because all its isotopes are what? Read this paragraph and choose the correct option from the provided answers: Group 7 (Mn, Tc, and Re) Continuing across the periodic table, we encounter the group 7 elements (Table 23.5 "Some Properties of the Elements of Groups 6 and 7"). One group 7 metal (Mn) is usually combined with iron in an alloy called ferromanganese, which has been used since 1856 to improve the mechanical properties of steel by scavenging sulfur and oxygen impurities to form MnS and MnO. Technetium is named after the Greektechnikos, meaning "artificial," because all its isotopes are radioactive. One isotope, 99mTc (m for metastable), has become an important biomedical tool for imaging internal organs. (For more information on biomedical imaging, see Chapter 20 "Nuclear Chemistry", Section 20.5 "Applied Nuclear Chemistry". ) Because of its scarcity, Re is one of the most expensive elements, and its applications are limited. It is, however, used in a bimetallic Pt/Re catalyst for refining high-octane gasoline. All three group 7 elements have seven valence electrons and can form compounds in the +7 oxidation state. Once again, the lightest element exhibits multiple oxidation states. Compounds of Mn in oxidation states ranging from 3 to +7 are known, with the most common being +2 and +4 (Figure 23.5 "Compounds of Manganese in Oxidation States +2 to +7"). In contrast, compounds of Tc and Re in the +2 oxidation state are quite rare. Because the electronegativity of Mn is anomalously low, elemental manganese is unusually reactive. In contrast, the chemistry of Tc is similar to that of Re because of their similar size and electronegativity, again a result of the lanthanide contraction. Due to the stability of the half-filled 3d5 electron configuration, the aqueous Mn3+ ion, with a 3d4 valence electron configuration, is a potent oxidant that is able to oxidize water. It is difficult to generalize about other oxidation states for Tc and Re because their stability depends dramatically on the nature of the compound. Consistent with higher oxidation states being more stable for the heavier transition metals, reacting Mn... Choices: - rare - plastic - neutral - radioactive A:
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radioactive