Properties of Water Answer Key

Name: _________________________________________________ Period: ___________ Date: ________________ Properties of Water Assignment ANSWERS I. MULTIPLE CHOICE. Select the best answer. 1. All of the following are from the properties of water except __________. a) It shows no reaction on both red and blue litmus paper. b) It has a low surface tension c) It increases in volume on heating. d) It is a polar compound. 2. There are _______________ bonds between the water molecules a) hydrogen b) covalent c) ionic d) metallic 3. A liquid boils at 100°C, which of the following is another property which will confirm the liquid is pure water? a) Sugar dissolves in it. b) When it freezes, its density decreases. c) Neutral on both litmus paper. d) It evaporates on heating. 4. When the temperature of water drops below 4°C, _______________. a) it expands. b) it shrinks. c) it doesn't change. d) its density increases. 6. The molecular shape of a water molecule is called __________________. a) pyramidal b) A-shaped c) triangle d) bent Name: _________________________________________________ Period: ___________ Date: ________________ Properties of Water Assignment II. Explain the following. 1. The presence of hydrogen bonds between water molecules. Hydrogen bonds exists between the oxygen atom on one water molecule and the hydrogen atom on another water molecule. These bonds form due to the difference in electronegativity between these atoms (oxygen being partially negative and hydrogen partially positive). 2. Pure water doesn't affect litmus paper dye. When water ionizes (splits apart), the positive H ions produced are equal in concentration to the negative OH ions. 3. Although sugar is a covalent compound, it dissolves in water. The sugar molecules dissolve in water due to the formation of hydrogen bonds between the water molecules and the sugar molecules. 4. Water has high melting and boiling point. The abnormality of the boiling point and melting point of water is due to the presence of the hydrogen bonds. The hydrogen bonds require extra heat energy to be broken. This happens before the molecules themselves gain heat energy. Once these bonds are broken, there is an increase in space between the water molecules and a change of state from ice to water (melting) or from water to steam (boiling) occurs. III. Two equal masses of pure water, one of them is at 20°C and the other is at 2°C. Which of them has the larger volume? Why? The water at 2°C has larger volume than the water at 20oC .This because at 4°C, the density of water starts to decrease. The molecules of water lose heat energy and start to move slowly, making it easier for them to form hydrogen bonds. Their crystalline shape now is open and hexagonal which increases their volume. IV. Explain why water is essential to life Water is required for many processes which are necessary for life such as digestion and circulation. Without water the chemical reactions which facilitate these processes would not occur. V. Water is made up of two hydrogen atoms bonded to an oxygen atom. 1. Name the type of bonds which exist between the atoms in a water molecule. Covalent bonds Name: _________________________________________________ Period: ___________ Date: ________________ Properties of Water Assignment 2. Describe why this bond forms These bonds form due to the partially complete valence shells of the hydrogen and oxygen atoms. 3. Explain the arrangement of electrons which form this bond. Oxygen requires two additional valence electrons to complete its outer shell, while each hydrogen atom requires one. Each hydrogen atom shares their single valence electron with oxygen and oxygen shares one of its valence electrons with hydrogen. This allows each atom to have a complete valence shell and be more stable than it would be as a single atom. VI. Explain why water is called the universal solvent. Water is able to dissolve many solutes which are both polar and covalent compounds.