Explanation

The permanent hardness of water is due to the presence of MgSO₄ (magnesium sulfate).

Permanent hardness is caused by dissolved minerals like calcium sulfate (CaSO₄) and magnesium sulfate, which cannot be removed by boiling the water.

Explanation

The head of the femur (thigh bone) attaches to the acetabulum, a cup-like structure in the pelvis.

The acetabulum is formed by the fusion of three bones: the ilium, ischium, and pubis.

This joint is known as the hip joint or coxofemoral joint.

Explanation

The rate of evaporation can be increased by:

• Decreasing atmospheric pressure
• Increasing temperature
• Decreasing humidity
• Increasing the surface area of the liquid

Explanation

The boiling point is the temperature at which a pure liquid changes state from liquid to gas at standard atmospheric pressure.

Key Points:

• The melting point is the temperature at which a solid changes state to a liquid.
• The freezing point is the temperature at which a liquid changes state to a solid.

Explanation

The work done on an object is calculated as the product of the force applied and the distance over which the force is applied:

Work = Force x Distance

= 6 N x 2 m

= 12 J

So, the work done is 12 Joule.

Explanation

A burning candle is an example of all three states of matter:

• Solid: The wax is in a solid state.
• Liquid: The melted wax is in a liquid state.
• Gas: The vaporized wax and combustion products are in a gaseous state.

Explanation

• Your weight, as measured on Earth, will be decreased if you move to a planet or moon with a weaker gravitational field.
• Weight is the force exerted on an object by gravity.
• It depends on both the mass of the object and the strength of the gravitational field.

Explanation

The stability of a racing car is increased by lowering its center of gravity, which reduces the risk of rollover or loss of control.

This can be achieved through design elements like a lower ride height, a wider stance, or a lower seating position for the driver.

Explanation

• Noble gases are stable because their outermost energy level is full, meaning they have eight electrons in their valence shell.
• This full outer energy level gives them a stable electronic configuration, similar to that of the noble gases, and makes them unreactive.

Explanation

• The number of protons and neutrons in an atom are added together to obtain the total number of nucleons.
• It is also known as the mass number.