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Introduction

Elements compound and mixture of Class 8

About Elements compound and mixture

All developments in chemistry are based on scientific approach. A scientist is always very keen to perform experiments, make observations and draw inferences from the observations. In order to achieve correct results, he has to rely upon the various skills connected with the measurements. Chemistry is the science of molecules and their transformations which deals with the study of matter, its composition, the changes that matter undergoes and the relation between changes in composition and changes in energy. Chemistry plays a central role in science and is often intertwined with other branches of science. Chemistry plays an important role in meeting human needs for food, health care products. In this chapter we will understand how matter and elements are related and what is compound and mixture.

MATTER

Matter is everything around you. Matter is anything made of atoms and molecules. Matter is anything that has a mass. Even though matter can be found all over the universe, you usually find it in just a few forms.

Elements:

The primary stuff present in all the substance is known as element, whose smallest unit known as atom.

Elements are further divided into metals, non-metals and metalloids.

(a) Metals: These are generally solids and have characteristics such as hardness, malleability, ductility, high tensile strength, lustre and ability to conduct heat and electricity. Some common examples are ; Copper, iron, aluminium, silver, zinc, etc.

(b) Non-metals: These are generally, non-lustrous, brittle, poor conductors of heat and electricity. Some common examples are ; Sulphur, phosphorus, nitrogen, hydrogen, oxygen, etc.

(c) Metalloids. These elements have characteristics common to metals as well as non-metals. Some common examples are ; Arsenic, tin, bismuth and antimony.

Compound :

A compound may be defined as a pure substance which can be decomposed into simpler substances by some suitable chemical method. A compound is formed by combination of two or more elements in a definite proportion by mass.

Classification of compounds: These compounds are further classified broadly into two categories :

  • Organic compounds: Carbon element is the essential constituent of these compounds. They are originally obtained from living sources, i.e., animals and plants. Some examples are oils, fats, protiens etc.
  •  Inorganic compounds: These compounds find their origin from non-living sources such as minerals and rocks. Common salt, marble, gypsom, etc., are some examples.

Mixture

Mixtures are the aggregate of more than one type of pure substance whose chemical identity remains maintained even in mixtures. Their constituent ratio may vary unlike compound.

For example - Sugar + Water = Sugar syrup, Gun Powder – 75% KNO3, 10% Sulphur + 15% Carbon.

There are two types of mixture.

  • Homogeneous 
  • Heterogeneous
  • Homogeneous Mixtures are those whose composition for each part remains constant. For example aqueous and gaseous solution.
  • Heterogeneous Mixtures are those whose composition may vary for each and every part. For example soil, concrete mixture.To score More in your class 8 refer NCERT solutions for class 8 .

 

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