A body is said to be porous, or to have porosity, because the particles of matter of which it is composed do not fill the entire volume occupied by it. The pores in bodies vary in size from those that can be seen in a sponge or a piece of charcoal, to those in stone or metal, which may be invisible even though a microscope of the highest power be used. All bodies are porous.

 The fact that a blotter will absorb ink and that a drop of oil will pass into a fine-grained piece of polished marble depends upon the porosity of the blotter and the marble.

Demonstrations. - The porosity of leather may be proved by the use of the apparatus shown in Fig.1. The funnel A has a long stem over the end of which there is securely tied a piece of stretched wash leather B. Pour mercury into the funnel, and it will pass through the pores in the leather and fall in the form of a fine rain into the jar below. As the mercury is thus freed from all mechanical impurities, the process is of practical value.

 Pour water into a glass tube about a meter long, until it is nearly half full, and then add colored alcohol until the surface is a half inch from the end of the tube. If this is done carefully, the line of division between the water and the alcohol can be clearly seen. Now place the finger over the end of the tube and invert it. The water will be seen to flow down through the lighter alcohol, and minute bubbles of air will rise through the mixed liquid. Invert the tube two or three times, and the length of the liquid column will be half an inch or more less than before. What does this demonstration teach?

The existence of spaces that are not occupied by the molecules of a liquid can be illustrated by filling three glasses, one with smooth round peas, one with fine shot, and one with water. Let the first be level full, then pour shot upon the peas and shake down, being careful that the surface of the peas is not raised. When no more shot can be put in, pour in water until it comes to the top of the peas.

اخر الاخبار

اخبار العتبة العباسية المقدسة

الحزام الأخضر الجنوبي الأول يستضيف وفدًا شبابيًّا من محافظة المثنى

قسم شؤون المعارف الإسلامية يحتفي بإرث الأديب الراحل علي أنكيل ويتسلم مكتبته الشخصية

سماحة السيد الصافي يدعو إلى توثيق الأفكار والأحداث لحماية الإرث العراقي من الاندثار بغية نقله سليمًا للأجيال القادمة

قسم التطوير يقدم محاضرة ثقافية حول كتاب نهج البلاغة لملاكاته

المزيد

الآخبار الصحية

أول إرشادات غذائية قائمة على الأدلة لمعالجة الإمساك المزمن

صباح بلا إفطار؟.. صحتك في خطر!

هل يمكن للجلد أن يكشف عن صحتك العقلية؟.. دراسة حديثة تجيب

السر في مطبخك.. 6 أطعمة تمنح عظامك قوة الشباب

المزيد

الآخبار التكنلوجية

ناسا تكشف: كوكب الأرض أصبح أقل لمعانا خلال العقود الماضية

دراسة: الوقت الذي تستخدم فيه هاتفك قد يفضح حالتك النفسية

الهنغاري لاسلو كراسناهوركاي يفوز بجائزة نوبل للآداب 2025

رسميا.. إعلان الفائز بجائزة نوبل للسلام لعام 2025

المزيد

مواضيع ذات صلة

الزمان من وجهة نظر ليبنتس

Inertia

Divisibility

Indestructibility

Compressibility

Impenetrability

General and Specific Properties

Physics

Experiments

Kinetic Theory of Matter.

States of Matter

Size of Molecules