Cells are surrounded by water, and cells themselves consist of about 70 to 95% water. As a result, _____. (eText Concept 3.1)
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dissolved substances can be easily transported within a cell or between cells in multicellular organisms ,the temperature of living things tends to change relatively slowly ,waste products produced by cell metabolism can be easily removed ,a variety of nutrient molecules is readily available as dissolved solutes ,All of the listed responses are correct.
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Water is a polar molecule. This means that _____. (eText Concept 3.1)
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the opposite ends of the molecule have opposite electrical charges
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The partial charges on a water molecule occur because of _____. (eText Concept 3.1)
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the unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule
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In a group of water molecules, hydrogen bonds form between _____. (eText Concept 3.1)
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the oxygen atom in one water molecule and a hydrogen atom in another water molecule
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Which of the following accurately relates the emergent properties of water to the effects of global warming in the Arctic? (eText Concept 3.2)
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The significant increase in Arctic air temperature over the past 50 years is causing sea ice to form later in the year, to melt earlier, and to cover a smaller area each year.
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If water were not a polar molecule, how would the effects of global warming differ from what are currently observed or predicted to occur in the future? (eText Concept 3.2)
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The effects would be drastically worse because the loss of the polar nature of water would greatly reduce its specific heat and its ability to moderate temperature.
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What water-related evidence do scientists have that suggests life may exist on other planets? (eText Concept 3.2)
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In 2008, the robotic spacecraft Phoenix found ice present just under the material on Mars's surface, and detected sufficient water vapor in the Martian atmosphere for frost to form.
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The tendency of water molecules to stay close to each other as a result of hydrogen bonding _____. (eText Concept 3.2)
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provides the surface tension that allows leaves to float on water , acts to moderate temperature , keeps water moving through the vessels in a tree trunk , is called cohesion
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What do cohesion, surface tension, and adhesion have in common with reference to water? (eText Concept 3.2)
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All are properties related to hydrogen bonding.
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Most of water's unique features (for example, its versatility as a solvent, ability to moderate temperature, and cohesive behavior) result from the fact that _____. (eText Concept 3.2)
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oxygen attracts electrons more than hydrogen does
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The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are _____. (eText Concept 3.2)
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both caused by water's partial charges
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The phenomenon responsible for maintaining the upward movement of water through a vessel is _____. (eText Concept 3.2)
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cohesion
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Adhesion is best described as _____. (eText Concept 3.2)
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the clinging of one substance to another substance
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You can fill a glass of water to just slightly above the rim without it spilling over the glass. What property of water best explains this phenomenon? (eText Concept 3.2)
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surface tension
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Which action would involve the greatest transfer of heat? (eText Concept 3.2)
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condensing 5 g of steam to liquid water
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Imagine that organisms consisted of 70-95% alcohol instead of 70-95% water. Alcohol's specific heat is about half that of water. How would living things be different? (eText Concept 3.2)
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Systems for temperature regulation would have to be much more efficient.
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The amount of heat required to change the temperature of 1 g of any substance by one °C is defined as _____. (eText Concept 3.2)
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the specific heat of that substance
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The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as _____. (eText Concept 3.2)
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the heat of vaporization of that substance
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The reason that coastal climates are more moderate than inland climates is due primarily to water's high _____. (eText Concept 3.2)
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specific heat
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Sweating has a cooling effect because of water's high _____. (eText Concept 3.2)
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heat of vaporization
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Water molecules have _____ than molecules of similar size, such as ammonia and methane, reflecting its capacity to absorb large amounts of heat. (eText Concept 3.2)
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a higher boiling point
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Because molecules of water are farther apart in ice than in liquid water, _____. (eText Concept 3.2)
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ice floats
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Water is a very versatile solvent because water molecules are _____. (eText Concept 3.2)
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polar
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How does the polarity of water contribute to its ability to dissolve so many substances? (eText Concept 3.2)
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Because it is polar, water's oppositely charged ends are attracted to positively and negatively charged ions and molecules. Water molecules form a hydration shell around oppositely charged particles.
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Nonpolar molecules that cluster away from water molecules are called _____ molecules. (eText Concept 3.2)
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hydrophobic
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A molecule that has all nonpolar covalent bonds would be _____. (eText Concept 3.2)
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hydrophobic
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Hydrophobic molecules are _____ water. (eText Concept 3.2)
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repelled by
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Why are cell membranes composed primarily of hydrophobic molecules? (eText Concept 3.2)
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In order to perform their function of separating the aqueous solutions outside of cells from the aqueous solutions inside of cells, cell membranes cannot be soluble in water.
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Hydrophilic substances, but not hydrophobic substances, _____. (eText Concept 3.2)
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have charges and partial charges to which water molecules can adhere
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Some substances, such as oil and gasoline, will not dissolve in water because _____. (eText Concept 3.2)
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their molecules have no charges or partial charges to which water molecules can adhere
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Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, _____. (eText Concept 3.2)
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stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5 L
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A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution? (eText Concept 3.2)
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0.092 g
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An acid is _____. (eText Concept 3.3)
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a compound that donates hydrogen ions to a solution
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Adding acid tends to _____ of a solution. (eText Concept 3.3)
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increase the hydrogen ion concentration and lower the pH
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Which of the following dissociations is that of an acid? (eText Concept 3.3)
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HF → H+ + F
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A glass of grapefruit juice, at pH 3, contains _____ H+ as a glass of tomato juice, at pH 4. (eText Concept 3.3)
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ten times as much
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A solution at pH 6 contains _____ than the same amount of solution at pH 8. (eText Concept 3.3)
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100 times more H+
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Adding a base tends to _____ of a solution. (eText Concept 3.3)
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lower the hydrogen ion concentration and increase the pH
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When the pH of a solution shifts from 7 to 3, how has the hydrogen ion concentration changed? (eText Concept 3.3)
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it has increased by 10,000 times.
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Pure water has a pH of 7. Why does uncontaminated rainwater have a pH of 5.6? (eText Concept 3.3)
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formation of carbonic acid from carbon dioxide and water
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A substance that minimizes changes in the concentration of H+ and OH-in a solution is a _____. (eText Concept 3.3)
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buffer
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Why is the increasing amount of carbon dioxide being taken up by the oceans a cause for concern? (eText Concept 3.3)
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More carbon dioxide causes an increase in carbonic acid (H2CO3), which leads to a decrease in the concentration of carbonate ion (CO32-).
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Which of the following statements is true about acid precipitation? (eText Concept 3.3)
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It washes away some minerals that are plant nutrients, and causes some toxic minerals to accumulate.
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The absorption of human-generated CO2 by the oceans _____. (eText Concept 3.3)
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increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for calcifying organisms
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The partial charges on a water molecule occur because of _____.
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the unequal sharing of electrons between hydrogen and oxygen
Consider the nature of the type of covalent bonds found within a water molecule.
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Water molecules are known for forming hydrogen bonds between themselves and for their ability to dissolve a great variety of substances that have charges or partial charges on their molecules. These two properties are ___________.
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both caused by water's partial charges
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The attraction of unlike substances is termed _____.
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adhesion
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Surface tension involves _____.
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cohesion
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Water resists temperature change because _____.
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heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur
Hydrogen bonding makes water molecules more cohesive.
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Because the molecules of water are farther apart in ice than in liquid water, _____.
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ice floats
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Sucrose has a molecular weight of 342 daltons. To make a 2-molar (2 M) solution of sucrose, _____.
answer
stir 342 grams of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5
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A mole of ethyl alcohol weighs 46 grams. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution?
answer
0.092 g
This would produce a 2-M solution. Remember that "milli-" means thousandth
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A molecule that has all nonpolar covalent bonds would be _____.
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hydrophobic
Hydrophilic substances are polar.
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Sodium chloride (NaCl) dissolves in water because water molecules _____.
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are polar
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Some substances, such as oil and gasoline, will not dissolve in water because _____.
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their molecules have no charges or partial charges to which water molecules can adhere
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Adding acid tends to ____ of a solution.
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increase the hydrogen ion concentration and lower the pH
As the hydrogen ion concentration increases, the pH declines.
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Which of the following dissociations is that of an acid?
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HF --> H+ + F-
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An acid is _____.
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a compound that donates hydrogen ions to a solution
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Adding a base tends to _____ of a solution.
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lower hydrogen ion concentration and increase the pH
A lower pH means a higher hydrogen ion concentration.
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When pH shifts from 7 to 3, how has the hydrogen ion concentration changed?
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It has increased by 10,000 times.
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Which of the following statements is true about acid precipitation
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It has the most pronounced effect on lakes and streams in the early spring.
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In a group of water molecules, hydrogen bonds form between _____.
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the oxygen atom in one molecule and a hydrogen atom in another molecule
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The most widely effective solvent is a material that is _____.
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polar
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