What is spontaneos and explosive combustion.

The conditions for combustion are

there is combustible materia.

theupply of is continius supply of oxygen.

The temperature of combustible material should be above its ignition temperature.

On the basis of above mention line

please tell me the meaning of this line

If any one of the obove condition is not satisfied,the combustion will not take place . It is this principle , which is used in fire fighting.

In this line Iam not understand the the meaning of “It is this principle,which is used in fire fighting.

please answer in easy and understandable wordings

I want  complete notes on the chapter friction 

In my book subtopics are:

Friction 

Types of friction 

Factors affecting friction 

Methods of reducing friction 

Methods of increasing friction 

Advantages and disadvantages of friction 

Some real life based situation where friction is applied.

How to make a monomer into polymer if it is an addition polymer example

This planet, _______ is yellowish in colour and has many rings and satellites.

A. Uranus

B. Jupiter

C. Neptune

D. Saturn

Pasteurized milk does not need to be boiled. Why?

Write the $pH$ value of the

1. Saliva (before meal)

2. Saliva (after meal)

3. Lemon juice

4. Colourless aerated drink

5. Carrot juice

6. Coffee

7. Tomato juice

8. Tap water