حصريا : شرح درس Matter - علوم لمدارس اللغات للصف الاول الاعدادى

تاريخ التسجيل : 30/03/2010

Introduction

Matter is anything which has a mass and volume, each matter is recognized by its color, smell and taste.
Objectives:

Recognize the structure of matter.
Explain the change in the state of matter by heat.
Recognize the melting and evaporation processes.

Matter's definition and its structure

Matter's definition

Matter is anything which has a mass and volume.
Each matter has its own distinctive properties such as color, smell or taste, for example:

You can identify copper from silver from gold by color.
You can identify water from milk from honey by taste.
You can identify chalk from naphthalene by smell.
Some substances have no color, taste nor smell like water.
The common states of matter are three: solid, liquid and gaseous state.
Matter may change from one state to another by heating or cooling, like when heating a piece of solid ice, it melts into liquid water.

The structure of matter:

The brick is the building unit of any building and the living cell is the building unit of any living organisms.

Activity:

To learn what is the building unit of matter, do the following activity:

Click Here

Spray some perfume some where in a room.
Move to another side of the room.

What do you observe?

You smell the perfume at the new place

From this activity we conclude that:

The ability to recognize the perfume at the new place and at any other place inside the room indicates that the perfume has been divided ultimately into small units called molecules.
These units (molecules) which maintain the smell and the characteristics of the perfume are the building units from which this perfume is composed.

The molecule:

Is the smallest unit of matter which can individually exist and still maintain the characteristics of the matter.
The molecules of the same matter are the same but molecules of different matters are different.
The molecule itself is made up from smaller building units called atoms, for example a molecule of:
- Oxygen is made up from the combination of two similar oxygen atoms.
- Hydrogen is made up from two hydrogen atoms.
- Water is built up from the combination of two hydrogen atoms with one atom of oxygen.
- Table salt (sodium chloride) is made up from one sodium atom and one chlorine atom.

Melting and Evaporation

Melting:

Is the change of matter from the solid state to the liquid state by heat.
The solid substances are characterized by short intermolecular distances and strong intermolecular forces, therefore the molecules are relatively fixed in their positions which makes the solid substances maintain their volumes and have invariant shapes.

Explanation of the melting process:

When the solid substance is heated, some molecules overcome the intermolecular forces and become not confined to their positions, hence the substance changes from the solid to the liquid state in what is known as melting.

Evaporation:

Is the change of matter from the liquid state to the gaseous state.
The molecules of liquids are in a state of continuous motion, but this motion is not enough to overcome the intermolecular forces among the molecules.

Explanation of the evaporation process:

When the liquid is heated to its boiling point, some molecules overcome the intermolecular forces and escape during the boiling in the form of vapor in what is known as evaporation.