Science: Matter in Our Surroundings: Elements, Compounds and Mixture (For CBSE, ICSE, IAS, NET, NRA 2022)

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Elements

A chemical element is a pure substance and it consists of one type of atom distinguished by its atomic number . e. g. helium, carbon, iron, gold, silver, copper, aluminum, hydrogen, oxygen, nitrogen, Sulphur. A chemical element is a basic form of matter that cannot be chemically broken down into simpler substances.

Compounds

A compound can be defined as a pure substance made from two or more elements chemically combined together in a definite proportion by mass. . For example, water (a compound) is made up of elements – hydrogen and oxygen but properties of water are different from those of hydrogen and oxygen. Glucose, Hydrochloric acid , phenol, sulphuric acid are some Compounds.

Mixture

  • In our everyday life we deal with a large number of substances but majority of them are not pure substances (elements or compounds) . They are mixtures of two or more pure substances.
  • The relationship among elements, compounds and other categories of matter are summarized in Fig.
Surroundings: Mixture

Homogeneous Materials

Are those that have the same composition and same properties throughout the sample . For example, if you take water in a glass and add salt to it and stir it. It will result Information of a mixture that has same properties and uniform composition (that is no distinct layers are seen) . They mix thoroughly. If you take sample from any part of that mixture, it will show similar properties.

Heterogeneous Materials

are those that have different composition and different properties in different parts of the sample. For example, if we take sand in water, then we will see that Inspite of stirring, it does not dissolve in water. It will settle at the bottom of the container and few particles will be seen floating in the water. If you take a sample from any part of it, it will show different properties.

  • A solution (a homogeneous mixture) is formed when one or more substances (the solute) are completely dissolved in another substance (the solvent) .
  • A solution made of solid dissolved in a liquid has two parts: the solid that dissolves is called the solute, the liquid, in which the solid is dissolved, is called the solvent.
  • The substance which is present in bigger quantity is normally taken as solvent and substance which is present in smaller quantity is normally taken as solute.
  • When a substance dissolves in a solvent it is said that that particular solute is soluble in that particular solvent. If it does not dissolve, then it is insoluble. Water is a commonly used solvent as it dissolves a large number of substances. Because of this property water is called a universal solvent.

Concentration of a Solution

  • Concentration of a solution is defined as the mass of solute present in a definite volume of a solution. A solution of 10 % glucose by mass means that 100 grams of the solution contains 10 gram of glucose. This means 10 grams of glucose is dissolved in 90 grams of water.
  • .
  • The concentration of a solute in a saturated solution at a definite temperature is called solubility of that solute in that particular solvent.

Suspensions

There are large numbers of substances which do not mix with each other. There are some solids that do not dissolve in water or other liquid solvents and there are liquids that do not mix with each other. The size of particles in suspension is over 1000 nanometers. When flour is added to water it does not dissolve but forms a slurry, which we call a suspension.

Surroundings: Suspension

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