HESI A2 Exam: Water
• What are the five main functions of water?
• _______ involves movement of the solute from areas of higher concentration to lower concentration
• What is the difference between the latent heat of fusion and the latent heat of vaporization?
• Compare and contrast sublimation and deposition.
• Water is both cohesive and adhesive. Explain.
In a water molecule, there are two atoms of hydrogen and one atom of oxygen (H2O).
A water molecule, abbreviated as H2O, is an example of a polar covalent bond. The electrons are unequally shared, with the oxygen atom spending more time with electrons than the hydrogen atoms. Since electrons spend more time with the oxygen atom, it carries a partial negative charge. A non-polar bond, on the other hand, involves electrons being shared equally with a molecule.
A covalent bond occurs within water molecules between hydrogen and oxygen. Hydrogen bonds occur between water molecules. Water molecules form a hydrogen bond (a type of intermolecular force) with electronegative oxygen atoms of other water molecules.
Molecules that are polar will dissolve in a polar solvent like water. Glucose has many polar OH groups that can form hydrogen bonds to water. The water molecules are attracted to the glucose as strongly as they are to each other. Glucose can easily get between the water molecules, so glucose dissolves in water. A molecule like cholesterol consists almost entirely of nonpolar C-C and C-H bonds. Gasoline and methane are also non polar and will not dissolve in water.
The five main functions of water are cell life, transport, chemical reactions, temperature regulation, and waste excretion.
Blood is 92 percent water. The human body is 60 percent water.
Diffusion involves movement of the solute from areas of higher concentration to lower concentration while osmosis involves movement of the solvent from low to high concentration. Osmosis is a specific type of diffusion, it involves migration of the solvent rather than the solute, and it is a process utilized by the kidneys to maintain proper water balance.
The amount of energy needed to melt the ice after it has reached the melting point is called the latent heat of fusion.
The amount of energy needed to boil all of the water into steam is called the latent heat of vaporization.
Water has a high heat of vaporization because hydrogen bonds form readily between the oxygen of one molecule and the hydrogens of other molecules. These bonds hold the molecules together. To get water to vaporize, you must increase the temperature to make the molecules move faster. The fact that water requires more energy to raise its temperature is a reference to its high heat capacity, but not high heat of vaporization
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Water has a high heat capacity, meaning it takes a lot of energy to change its temperature. This makes releasing warm water the perfect way to cool off - that's why you sweat. When the water evaporates, it takes its stored heat with it. It also makes it harder for the environment to cause your core body temperature to change.
During sublimation, a solid that is at a temperature and pressure below its triple point (the point at which temperature and pressure reach an equilibrium so that the solid, liquid, and gas of a substance can all exist at the same time) turns directly into a gas when enough heat energy is applied.
Deposition is the opposite of sublimation. A gas that is at a temperature and pressure below its triple point turns immediately into a solid when heat energy is removed.
Polar molecules, such as sugar, and ionic compounds, such as salt, can both dissolve in water. Both of these mix well with water because they have positive and negative charges which are attracted to the negative and positive ends of the water molecules.
Transport is how oxygen and food make it through our bodies. It is also how blood flows through our veins and arteries to take those nutrients to where they are needed.
Hydrogen, not water, is the most abundant chemical substance in the universe. A water molecule (two hydrogen atoms and one oxygen atom) is polar. Since polar molecules are attracted to each other, water is cohesive. This means it holds together very well. Consequently, water does not require much energy to be pumped from one place to another. Water is adhesive because the polar molecules of other substances in water are attracted to water molecules.
Cohesion is the tendency of similar particles to cling to one another.
Adhesion is the tendency of non similar particles to cling to one another.
Cell life is based on the fact that cells have water inside them. Water is used to transport nutrients to cells and within cells (intracellular). If cells don't get nutrients including vitamins, minerals, and sugars, they die.
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