ساينس الصف الثاني الاعدادي – الفصل الدراسي الاول ساينس تانية اعدادي – ترم اول In This part we will study : 1. Weakness of water ionization Ionization It is the process of converting the molecules of some covalent compounds into ions. 2. Water has a neutral effect on litmus paper : ionization Water has a neutral effect on litmus paper (red and blue) because when it is ionized, it gives equal numbers of : • Positive hydrogen ions (H+), which are responsible for the acidic property. • Negative hydroxide ions (OH-) , which are responsible for the basic property . 3. Resistance of water to decomposition : ionization – Water doesn’t decompose into its elements (oxygen and hydrogen) under normal conditions or even by the effect of heat. – This property helps to keep the aqueous solutions inside the cells of living organisms . water can be decomposed electrically – The acidified water decomposes by electricity into : • Oxygen gas evolves at the anode (because oxygen ions are negatively charged) . • Hydrogen gas evolves at the cathode (because hydrogen ions are positively charged) . – The ratio between the produced hydrogen gas and oxygen gas is about (2 : 1 ) by volume because water molecule (H2O) is composed of two hydrogen atoms and one oxygen atom. Give Reason for … 1 . During electrolysis of acidified water by Hofmann’s Voltameter, oxygen gas evolves at the anode, while hydrogen gas evolves at the cathode. Because oxygen ions are negatively charged so, oxygen gas evolves at the anode , while hydrogen ions are positively charged so , hydrogen gas evolves at the cathode. 2. Adding few drops of dilute sulphuric acid to water during its electrolysis by Hofmann’s voltameter. Because pure water is a bad conductor of electricity, but acidified water conducts electricity. Water Pollution It is the addition of any substance to the water which causes continuous gradual change in water properties affecting the health and the life of living creatures . لمتابعة مستر احمد الباشا وكل ما يخص الساينس : جروب الفيس بوك http://bit.ly/2Of1mcN صفحة الفيس بوك http://bit.ly/2Gq5xMo بالتوفيق مستر احمد الباشا