Question Discussion & Solution

The correct answer is Energy.

• Energy can neither be created nor be destroyed.

Key Points

• First Law of Thermodynamics:
  • It is also known as the Law of Conservation of Energy and states that energy cannot be created or destroyed in an isolated system.
  • Thermodynamics was discovered by Ludwig Boltzmann.
  • Albert Einstein also said that "Energy cannot be created or destroyed. It can only be changed from one form to another."

Additional Information

• Force is that external cause which when acts on a body, changes or tries to change the initial state of the body.
  • Force = mass × acceleration
  • Its S.I. unit is Newton (kg. m s-2)
• Momentum is the property of a moving body and is defined as the product of mass and velocity of the body.
• It is a vector quantity.
  • Its SI unit is kg m/s.
• The rate of doing work is called power.
  • SI unit of power is watt or Joule Per second named as a respect to the scientist James Watt.
  • It is a scalar quantity.

Bleaching powder:

• Calcium hypochlorite is known as bleaching powder.​
• It is a pale yellowish powder having a strong smell of chlorine.
• It is soluble in cold water.
• Bleaching powder reacts with dilute acids to produce chlorine.
• When bleaching powder is treated with an excess of a dilute, all the chlorine present in it is liberated.
• It is used in bleaching clothes in the laundry due to its oxidizing property.

Formula- CaOCl₂ 

Additional Information

• Washing powder: The chemical name of washing soda is Sodium carbonate Decahydrate and the chemical formulae is Na_2​CO3​.10H_2​O.
• Baking powder: Sodium hydrogen carbonate is the chemical term for the baking powder with chemical formulae NaHCO₃.
• Soda ash: Anhydrous Sodium carbonate is known as Soda ash with chemical formulae Na₂CO₃.

Statement 1 and 2: correct

• OS allows the computer to manage its own resource such as memory, keyboard and printer

Statement 3: correct

• OS provides the user an easy to work user interface, so the user doesn’t have to learn a different UI every time.

Statement 4: correct

Concept-

• The transparent curved surface which is used to refract the light and make an image of any object placed in front of it is called a lens.
• The lens whose refracting surface is upside is called a convex lens.
• The convex lens is also called a converging lens.
• The lens having refracting surface inward is called a concave lens.
• The concave lens is also called a diverging lens.

Explanation-

As we can see below, The concave lens is also called a diverging lens.

Hence option 2 is correct among all

• The blue litmus paper will turn red when it comes into contact with an acidic solution.
• When a litmus paper is put in a solution, depending on what the solution is, the indicator will react with the solution and will change its colour.
• On the other hand, red litmus paper reacts to alkaline substances by turning blue.
• Note: Acid will turn red litmus paper to red only.No change.