CHAPTER 4 Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII SUBSTANCE  DEFINITION Substance is something occupying the room and has mass. According to the particle theory, substance consists of particle that its size is very small, related, and keep moving on.  THE CHARACTERISTIC OF SUBSTANCE BASED ON ITS FORM SUBSTANCES Solid Gas Liquid

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII SUBSTANCE  Solid is a substance that has a constant form and volume.  Liquid is a substance that has a constant volume, but the form changes following the place where it is.  Gas is a substance that both its form and volume are inconstant. Table : characteristic of solid, liquid, and gas characteristicSolidLiquidGas form Volume Compressibility Specific Mass Streaming constant uncompressed Generally has high specific mass Not streaming Follow the place constant Hard to be compressed Medium specific mass Streaming Follow the place Depending on the place Easy to be compressed Very low specific mass Streaming

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII THE FORM OF SUBSTANCE Based on the form, the substances could be divided into 3 kinds, solid, liquid, and gas. Each of them has its own characteristic, either physical or the composer particles, as follows : A. Gas The inter-particle space changes almost without any force each other.

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII THE FORM OF SUBSTANCE B. Liquid Example : water, oil, lubricating oil, etc.  Its molecules are relatively closed if compared with gas, but not as close as solid.  The movement of its molecules are free,  The molecules are able to move, but not easy to be separated with their colony, because they are pulled each other,  The form is easy to change, but the volume is constant. The inter-particle space is constant and somewhat distantly spaced. The force of attraction is weaker if compared with solid, and its particles are livelier and can move from one to another place

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII THE FORM OF SUBSTANCE  Its molecules are very closed and tidy.  The inter-molecule force is very strong, so the molecules movement is not free.  The movement of its molecules are limited, they only vibrate and rotate.  The molecules are very hard to be separated, so that the shape is constant.  Example : wood, stone, iron, etc. C. Solid The particles occupies the constant position and the inter-particle force of attraction is very strong. The particles movement is vibrating on its position

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII ADHESION Adhesion Adhesion is the force among the molecules that are different. Example :  Ink can stick on the paper  Chalk / ink can stick on the whiteboard  Cement can glue the stone and the sand  Paint can stick on the wall

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII COHESION Cohesion Cohesion is the force among the molecules that are same. Example :  The force among the molecules of wood form a wood  The force among the molecules of chalk form a bar of chalk  The force among the molecules of sugar form the grain of sugar

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII MENISCUS AND CAPILLARITY The effect of adhesive and cohesive force causes phenomenon as follows : A. Concave and Convex Meniscus In our daily life, we can easily find the adhesion and cohesion, for instance, when a drop of water drop on a leaf, it would form a water-ball. It is because of the cohesive force is bigger than the adhesive force.

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII MENISCUS AND CAPILLARITY B. CAPILLARITY

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII The process of capillarity in our daily life :  The absorption of oil through the wicking in primus stove  The absorption of oil through the wicking in the gasoline blow- lamp  The absorption of oil to the leaf through the filter vessel  The drop of water on clothe inside the slender bucket MENISCUS AND CAPILLARITY

Electindo.com PHYSICS FOR JUNIOR HIGH SCHOOL VII MEASUREMENT If it is found a capillary pipe in an interconnected-container or the diameter of the pipes are significantly different, the liquid surface in the smaller pipe will be higher than in the bigger pipe, so that the law of interconnected- container will not occur. C. THE INVALIDITY OF THE INTERCONNECTED-CONTAIINER LAW

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