Exams

Saudi Arabia is the country in the world to have no cinema theaters.

With the exception of one IMAX theater in Khobar by Khalid, there were no cinemas in Saudi Arabia from 1983 to 2018, although there was occasionally talk of opening movie theaters, and in 2008 conference rooms were rented to show the comedy Mennahi.

USB - Universal Serial Bus is a secondary type of storage device which is used in all computers, laptops, mobiles...

It is a plug-and-play portable storage device that uses flash memory and is lightweight enough to attach to a keychain.

Hardness can be removed by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column.

Hardness in water is caused by dissolved magnesium ions and calcium ions. These can get into the water when it comes into contact with limestone and other rocks that contain calcium compounds. This can happen, for example, when rainwater flows over these rocks on its way to a reservoir.

Hardness in water is of two types. They are :

1. Temporary hardness

2. Permanent hardness

1. Temporary hardness:: Temporary hardness is caused by dissolved calcium hydrogen carbonate.

2. Permanent hardness:: Permanent hardness is caused by dissolved calcium sulfate. Unlike temporary hardness, it is not removed by boiling the water.