Hindi
Study Word- Meanings and Question-Answers of
Lesson-15 for a review on Tuesday, 29/3/16
Science
Save the following content and answer the questions that follow.
Waterborne diseases are
caused by pathogenic microorganisms that most commonly are transmitted in
contaminated fresh water. Infection commonly results during bathing, washing,
drinking, in the preparation of food, or the consumption of food thus infected.
The term
"waterborne disease" is reserved largely for infections that
predominantly are transmitted through contact with or consumption of infected
water.
Microorganisms
causing diseases that characteristically are waterborne, prominently include
protozoa and bacteria, many of which are intestinal parasites, or invade the tissues
or circulatory system through walls of the digestive tract. Various other waterborne
diseases are caused by viruses.
Water
purification is the removal of contaminants from raw
water to produce drinking water that is pure enough for human consumption or
for industrial use.
When the
solute dissolves in the solvent, a solution is formed.
Solute: the substance that is dissolved in another substance
Solvent: The liquid in which a solute is dissolved
to form a solution.
Solution: Mixture of Solute and Solvent.
Removal
of insoluble impurities
Insoluble
impurities present in water may be removed by sedimentation.
Sedimentation: The act or process of depositing sediment. It done to separate particulates from a
liquid by allowing the solids to settle to the bottom of the mixture and
pouring off the particle-free part of the liquid.
The
process by which insoluble substances which are heavier than water are
separated is called sedimentation
Removal
of soluble Impurities
Soluble impurities
may be removed by evaporation and by distillation.
Evaporation: During evaporation the soil is kept in a dish and heated. When
all the water evaporates, the solute is left over.
Distilled
water is the purest form of water. It is generally used in car batteries, in
science experiments and in medicines.
Distillation
is a method which gives us both the solute (impurities) and the
solvent (water) separately. On heating the solution, the water evaporates. It
enters the condenser which is kept cool by the cold water circulating around
it. On entering the cool condenser, the hot steam changes into water again,
which collects in the flask below. This water is totally pure and free from any
impurities. It is called distilled water.
Filtration: After sedimentation the water is filtered through a clean sand bed
to remove finer suspended particles and bacteria.
Chlorination: water is then disinfected with a very small quantity of chlorine
gas to that kills bacteria.
Q1. How
are water borne diseases transmitted?
Q2. What
is a solute, solvent and a solution? Explain with examples.
Q3. What
is distillation. Explain the same with a diagram.
Q4. What
is chlorination?
