CBSE Class 10 Chemistry | Chemical reactions | Introduction

Physical and Chemical Changes

Change in Matter

Change in matter can be studied in two major ways. The two types of changes are as follows:

 

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Difference between Physical Change And Chemical Change

 

Physical Change

Chemical Change

(i) Those changes in which no new substances are formed are called physical changes.

(i) Those changes in which the original substances lose their chemical nature and identity and form new chemical substances with different properties are called chemical changes.

(ii) It is a temporary change

(ii) It is a permanent change.

(iii) It is easily reversible

(iii) It is usually irreversible.

(iv) In a physical change the mass of substance does not alter.

(iv) In a chemical change the mass of the substance does alter.

CBSE Class 10 Biology | Reproduction | Population Control and Reproductive Health

Population Control/Birth Control

 

The population of our country is expanding very quickly. Large families and frequent pregnancies not only affect mother’s health but also lead to shortage of resources and more over a small family is a happy family. So, family planning can be done by practicing birth control measures to prevent pregnancy.

 

BIRTH CONTROL METHODS

 

The prevention of pregnancy in a woman is called contraception. Any device or chemical which prevents pregnancy is called a contraceptive. All the birth control methods are divided into

1. Barrier methods

2. Chemical methods

3. Intra uterine contraceptive device (IUCD)

4. Surgical methods

 

Barrier methods

 

These are the physical devices to prevent the entry of sperm so that it does not reach the egg. e.g. condoms can be used to cover the penis. Condoms also protect against STD’s (Sexually transmitted disease). Coverings like diaphragm worn in the vagina can serve the same purpose.

 

Chemical methods

 

(a) Oral pills: They are hormonal preparations. They act by changing the hormonal balance of the body, so that eggs are not released & fertilization cannot occur. They are taken orally, therefore commonly called oral contraceptives (OC).

(b) Vaginal pills: They contain spermicides and therefore they kill the sperms.

 

Intra-uterine contraceptive device (IUCD)     

 

They are contraceptives such as a loop or the copper-T placed in the uterus. They prevent implantation in the uterus.

Surgical methods

(a) Vasectomy: In males, a small portion of vas deferens (sperm duct) is cut and the cut ends are then ligated (tied). This prevents the sperms from coming out.

(b)
Tubectomy: In females, a small portion of fallopian tubes is cut & the cut ends are then ligated (tied). This prevents the egg to enter the fallopian tube.

 

Reproductive Health And Sexually Transmitted Diseases

Reproduction is an important biological process like nutrition, respiration, transportation etc.

The reproductive life of human begins at puberty and continues throughout the life in males and upto menopause in females.

Like the physical fitness, mental fitness and social fitness, the human beings need fitness of reproductive life as well.

Diseases are caused by bacteria, viruses, protozoa, fungi & other kinds of pathogens. These infectious diseases are spread by air, water and food. Similarly, there are some diseases which are spread by sexual contact with an infected person. Such diseases are called sexually transmitted diseases (STD).

 

For example:

  1. Gonorrhea (bacterial disease)
  2. Syphilis (bacterial disease)
  3. Warts (viral infection)
  4. AIDS (viral infection)

 

AIDS: It is caused by HIV- Human immuno deficiency virus. This disease weakens the body’s immune system so that body becomes weak & cannot protect itself against infection. AIDS is transmitted to a healthy person by

(i) Sexual contact with infected person.

(ii) Use of contaminated needles and syringes.

(iii) Use of contaminated razors.

(iv) Transfusion of infected blood.

(v) Mother to the baby during pregnancy and lactation.

 

This disease can be prevented by educating people about its transmission.