ساينس الصف الأول الاعدادي – الفصل الدراسي الاول ساينس اولي اعدادي ترم اول In This part we will study : Second : Molecules and physical change of matter On heating the Solid substance : Its molecules gain thermal energy. So ; the speed of its molecules increases causing the weakness of the intermolecular force . So ; the intermolecular spaces increase and they become more freely leading to the change of matter from the solid state into the liquid state. This process is known as Melting . Melting It is the change of matter from the solid state to the liquid state by heating. On heating the liquid substance : Its molecules gain more energy. So ; the speed of its molecules increases and some of them overcome the intermolecular forces (becomes more free). So ; the intermolecular spaces increase and they escape in the form of vapor. This process is known as Vaporization . Vaporization It is the change of matter from the liquid state to the gaseous state by heating. 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