Water Properties and Cycle (PDF)

Water has unique properties that support life. Water can dissolve many chemicals and can exist in three states of matter: solid, liquid, and gaseous, within the temperature range known on Earth. Water is essential for life on Earth. All life forms have a membrane that separates the organism from its...

Water has unique properties that support life. Water can dissolve many chemicals and can exist in three states of matter: solid, liquid, and gaseous, within the temperature range known on Earth. Water is essential for life on Earth. All life forms have a membrane that separates the organism from its environment. Water passes from the environment into the living cell through this membrane, carrying the materials needed to produce energy and also to remove waste to the outside. WATER %70 and LAND 30% 97% of water is salt and 2% fresh water exist in ice state in polar region and glaciers and the remain percentage is liquid in rivers, lakes and underground The hydrosphere distinguishes Earth from the other planets in the solar system. Water vapor (water in the gaseous state) is considered one of the components of the atmosphere. There is also the cryosphere, which refers to frozen water in the polar regions and the mountain and glacier sections. Egypt is distinguished by the diversity of its aquatic environments, which include the Nile River, the Gulf of Suez, the Gulf of Aqaba, the Red Sea, the Mediterranean Sea, and many salt and freshwater lakes. Water cycle in nature Water exists on or near the Earth\'s surface in a state of constant change between its three states. Water is constantly moving from one place to another through many different pathways that form a nearly closed system called the water cycle in nature or the hydrological cycle. The water cycle as a system is capable of changing the Earth\'s surface physically, chemically and biologically. The water cycle in nature mainly includes the sea process that contributes to the formation of clouds and the process of rain or snow falling. In addition to other processes such as biological processes such as transpiration in plants and respiration in plants and animals, and the processes of water seepage through the pores of soil and rocks. Sedimentary to form groundwater. Water vapor in clouds may react chemically with compounds in the air, forming acids that fall as acid rain, which dissolves rocks. Water is composed of two elements, hydrogen and oxygen, in a ratio of 2:1 volumes respectively, while oxygen represents 88.89 of the mass of a water molecule and hydrogen represents 11.11. The two hydrogen atoms are linked to the oxygen atom by two covalent bonds, between which an angle measuring about 104.50 is confined. Chemical properties of water: Water does not exist on the surface of the Earth in a pure form, as it contains many ions and substances The chemical elements that interact with it in different ways, and we will review three of the main properties of water: Polarity of water: H2O The oxygen atom is characterized by its higher electronegativity than the hydrogen atom, so the bonding electrons are attracted towards the oxygen atom, forming a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom, which is known as the polarity of the water molecule. The polarity of water molecules results in their connection with other water molecules in what are called hydrogen bonds or polar molecules of other materials, which gives water the ability to dissolve many salts and break them down into dissociated ions. the ability of water molecules to form Hydrogen bonds between them are a major reason for The boiling point of pure water, which reaches 100 H under normal atmospheric pressure, is higher than that of H H Boiling of compounds similar to it in composition, such as hydrogen sulfide, which boils at 61-. Hydrolysis (hydration): A small percentage of water molecules are in the form of hydrogen ions (H) and hydroxide ions (OH), and as a result of chemical reactions with various compounds, some salts present in natural waters are hydrolyzed, which affects the balance of these ions, causing the acidity or basicity of the water. Practical example When table salt (NaCl) is added to water, it dissociates into sodium ions (Na) and sodium ions (Na). sodium bicarbonate of hydroxide ions (OH), in the case of sodium bicarbonate, salt in solution Chloride (CI), and ions remain Without binding to water ions, which makes the solution neutral because the concentration of hydrogen ions (H) equals the concentratioدث salt (NaHCO), hydrolysis leads to a decrease in the concentration of hydrogen ions (H) and an increase in the concentration of hydroxide ions (OH), which makes the salt solution basic. The opposite occurs when ammonium chloride salt concentration of besic. (NHCI) is dissolved in water, which decomposes and causes a decrease in the hydroxide ions and an increase in the concentration of hydrogen ions, which makes the salt solution The salt solution is acidic. The acid-base balance in water depends on the relationship between the concentration of hydrogen ions (H) and hydroxide ions (OH). This pH is a measure of the acidity or basicity of water. Seawater The pH value of seawater generally ranges between 7.5 and 8.4 depending on the area in which the sea is located and the surrounding environmental factors. Fresh water rivers and lakes have a pH value that varies and usually naturally ranges between 6.5 and 8.5. Pure water: Has a pH value of about 7 because it is free of most of the impurities and ions that contribute to the acidity or alkalinity of other natural water sources. Groundwater The pH value of groundwater varies from one region to another depending on several factors, the most important of which is the rock composition in the region. Groundwater is either neutral or basic, and its pH value varies due to exposure to calcium carbonate rocks or Magnesium carbonates. The pH of clouds is generally slightly acidic, with values ranging from 4.5 to 5, due to the presence of carbon dioxide and other acidic gases dissolved in the water droplets.