policies ry Resources 2. Life as we know it could not exist without water. All t
ID: 90632 • Letter: P
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policies ry Resources 2. Life as we know it could not exist without water. All the chemical reactions of life occur in aqueous solution. Water molecules are polar and are capable of forming hydrogen bonds with other polar or charged molecules. As a result, water has the following properties: A H20 molecules are cohesive: they form hydrogen bonds with each other. B. H20 molecules are adhesive; they form hydrogen bonds with polar surfaces. C. Water is a liquid at normal physiological (or body temperatures. D. Water has a high specific heat. E. Water has a high heat of vaporization. Water's greatest density occurs at 4°C. Complete the table below. illustrating how these properties of water above are related to the phenomena listed below. More than one property may be used to explain a given phenomenon. You also need to explain how each property is responsible for each phenomenon. Property Phenomenon (e.g. A, B, Brief Explanation During the winter, air temperatures in the northern United States can remain below 0°C for months; however, the fish and other animals living in the lakes Many substances, for example, salt (NaC) and sucrose, dissolve quickly in When you pour water into a 50-ml graduated cylinder, a meniscus forms at the top of the water column. Sweating and the evaporation of sweat from the body surface help reduce a human's body temperature.Explanation / Answer
1.F .All liquids have a boiling point and a freezing point. When water boils at a certain temperature it turns into steam. When it is cooled to a certain temperature it freezes and becomes ice. Water boils at 100 degree Celsius (100 °C) and freezes at 0 °C. When the outside temperature falls below the freezing point of water, lakes and rivers get frozen.However, only the top layer of the lake or river freezes. Underneath the frozen upper layer, the water remains in its liquid form and does not freeze. Also, oxygen is trapped beneath the layer of ice. As a result, fish and other aquatic animals find it possible to live comfortably in the frozen lakes and ponds.
2.B.The polarity of water molecules enables water to dissolve many ionically bonded substances. Salt (sodium chloride) is made from positive sodium ions bonded to negative chloride ions.Water can dissolve salt because the positive part of water molecules attracts the negative chloride ions and the negative part of water molecules attracts the positive sodium ions.
3.A,B .When liquid is placed on a smooth surface, the relative strengths of the cohesive and adhesive forces acting on that liquid determine the shape it will take (and whether or not it will wet the surface). If the adhesive forces between a liquid and a surface are stronger, they will pull the liquid down, causing it to wet the surface. However, if the cohesive forces among the liquid itself are stronger, they will resist such adhesion and cause the liquid to retain a spherical shape and bead the surface.
4.E.Water molecules are very good at forming hydrogen bonds, weak associations between the partially positive and partially negative ends of the molecules. Hydrogen bonding explains both the effectiveness of evaporative cooling (why sweating cools you off) and the low density of ice (why ice floats).
5.A. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids would be approximately spherical.
6.A,B. Colored water molecules rises up due to capillary action.This occurs due to cohesive and adhesive forces of water.The polar water is attracted to the polar walls of the capillaries, and to itself.Thus the water rises up.
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