ساينس الصف السادس الإبتدئي الفصل الدراسي الاول ساينس سادسة ابتدائي – ترم أول In This part we will study : Manganese dioxide, works as a catalyst as it remains without change. Catalyst: A chemical substance that accelerate the chemical reaction and remains without any change in its quantity and properties after the chemical reaction. Properties of Oxygen: 1. Oxygen is a colorless, tasteless and odorless gas. 2. Oxygen scarcely dissolves in water. 3. Oxygen does not burn, but helps in burning. 4. Oxygen is heavier than the air as it replaces the air (G.R). 5. Oxygen has a neutral effect on litmus paper. 6. Oxygen has the ability to react with most elements forming oxides. Oxidation It is a slow reaction (combination) between oxygen and element in presence of moisture (water). Example: Iron rusting Burning It is a rapid reaction between oxygen and element to produce heat and light. Example: Burning a piece of cleansing wire. ► The Importance of Oxygen: 1. Formation of water, as the water consists of 2 Hydrogen atoms and 1 Oxygen atom. 2. Important for Respiration process. 3. Important for food combustion inside the cell to produce energy necessary for vital processes. 4. Formation of Ozone layer (O3). (This protects the earth from the harmful radiation coming from the sun). 5. Oxygen is compressed in iron cylinders and used in: 1. Mechanical Ventilation for patients who suffer from breathing difficulties. 2. Sterilizing during surgeries. 3. Breathing during diving and climbing mountains. As it is hard to breath at high mountains due to lack of oxygen. 4. Producing Oxy-acetylene flame for cutting and welding metals. When it is combined with acetylene gas to produce Oxy-acetylene flame whose temperature is 3500 ° C 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