integrated science.pdf

Theme Sustainability of life (1) in ecosystems 1  Chapter 1 Aquatic Ecosystem Every time you drink a glass of water ,have you thought about the chemical reactions that take place inside this vital liquid ? Water it is a clear liquid in which many chemical...

Theme Sustainability of life (1) in ecosystems 1  Chapter 1 Aquatic Ecosystem Every time you drink a glass of water ,have you thought about the chemical reactions that take place inside this vital liquid ? Water it is a clear liquid in which many chemical compounds may react What are results of chemical reactions that occur in water? 1-quality of water is affected. 2-health of organisms that depend on water is affected. unique properties of water that support life 1- Water can dissolve many chemical substances 2- Water exists in the three states of matter solid, liquid and gaseous, within the known range of temperature on the Earth's surface. 3- Water is necessary for continuity of life on the earth( Give reasons) Because a) Water passes from the environment into the living cell through cell membrane carrying the materials needed to produce energy. b) Water passes from the living cell to the environment through cell membrane to remove wastes to the outside. 2  types of spheres on Earth Hydrosphere Atmosphere Cryosph ere Hydrosphere Distinguishes Earth from the other planets refers to water in a liquid state. covers about 70% of the Earth's surface where : 97% Salty water found in oceans, seas and salt lakes as salt water, 3% fresh water found in rivers Fresh lakes and groundwater. Atmosphere It contains and Water vapor (water in the gaseous state) Cryosphere It refers to the frozen water in the polar regions, the mountain range, and glaciers. Note Egypt is characterized by the diversity of its aquatic environmentssuch as the Nile River, the Gulf of Suez, and the Gulf of Aqaba. the Red Sea, the Mediterranean Sea, and many salt lakes and freshwater lakes 3  Water cycle( hydrological cycle) in nature it is a closed system in which Water is moving from one place to another through many different paths The water cycle in nature mainly includes 1-the evaporation process that causes the formation of clouds 2- biological processes such as transpiration in plants and respiration in plants and animals. 3- rain or snow falling, process of 4- leakage of water processes through the pores of soil and sedimentary rocks to form underground water. Give reasons for the formation of underground water Note Water vapor in clouds can react chemically with compounds in the air, forming acids that fall as acidic rains which dissolves rocks Chemical structure of water: (H2O) Water consists of of two elements, Hydrogen and oxygen in a ratio of: a) 2:1 by volume. b) 1:8 by mass where hydrogen represents 11.11% of the mass of the water molecule and oxygen represents 88.89% of the mass of the water molecule 4 c) The two hydrogen atoms are joined to the oxygen atom by two single covalent bonds, the angle between them is (104.5º) Chemical properties of water water is not existed on the surface of the earth in the pure form (why?) because it contains many ions and chemical materials. Some of the main properties of water. 1-Polarity of water 2-Hydrolysis (hydration) 3-Acid-base balance 1- Polarity of water The oxygen atom is charcterized by its higher electronegativity than the hydrogen atom, therefore the electrons of the bond are attracted to the oxygen atom, forming : a)a partial negative charge on the oxygen atom b)a partial positive charge on the hydrogen atom, which is known as the polarity of the water molecule. Note The polarity of the water molecule. Causes a) water molecules to link other water molecules by hydrogen bonds b) water molecules to link other polar molecules of other materials(such as salts) therefor water can dissolve many salts and break them down into their hydrated ions 5 Example soulibility of sodium chloride in water Nacl(S)+ H2O(L) Na+(aq) + cl - (aq) Give reasons the boiling point of water(100 oC) is higher than the boiling point of hydrogen sulphide H2S (- 61 oC). 6 7 8 9 10 11 12 13 14 15