Question Discussion & Solution

Concept:

Matter

• The thing which occupies space is called matter.
• The matter is made up of particles and based on the arrangement of particles matter has been classified into different states.
• The matter has 5 states, Solid, liquid, glass, Plasma, Bose - Einestine condensate.
• Solid, Liquid, and Gas are states of matter that we observe across our surroundings.
• The following table defines these three states.
   

The arrangement of particles in solid, liquid, and gas is shown in this diagram.

Explanation:

• The state of matter with a definite volume but no definite shape is liquid.
• The liquid gets itself in the shape of its container. This can be easily observed.
  • If we keep liquid in the jug it will be according to its shape.
  • The shape will change if the same liquid is poured into a glass.
• Though the volume of the liquid does not change. It will remain the same.

Therefore the correct option is liquid.

The computer has evolved from a large-sized simple calculating machine to a much smaller machine capable of multiple functionalities. Each generation of computer is designed based on the hardware technology used leading to better, cheaper and powerful computers that are faster and efficient than their predecessors.

Hence, it can be concluded from the table that vacuum tubes were used by the first generation computers.

Let Rahul’s age be x.

Let Rita’s age be y.

Let Ekta’s age be z.

⇒ x = y + 3

⇒ y = 4z – 3

⇒ x = 4z – 3 + 3

⇒ x = 4z

⇒ x/z = 4

⇒ x ∶ z = 4 ∶ 1

The correct answer is Nichrome.

Key Points

• Nichrome 
  • It is a metal alloy made up of around 20 percent of chromium and 80 percent nickel.
  • The key to the workings of an electrical heating element is the role of the nichrome in it.
  • Nichrome has fast emerged as the leading alloy to be used in terms of electrical heating elements.
  • For an electric iron heater element should have higher resistance, high melting point, and high specific heat.
  • An element should have high resistance so that it can hold its configuration in a high voltage current. It should have a high melting point such that it can sustain high temperatures.
  • Nichrome is used as a heating element in electric iron which is an alloy consisting 80% of Nickel and 20% of Chromium melting point of this element is 1400 degrees Celsius with high resistance which makes this element best for use as a heating element. Hence, Option 1 is correct.
  • The reason which makes the Nichrome best for heating elements is when it is heated in the air it develops an outer layer of chromium oxide which makes it stable in air and this chromium layer helps the element from oxidizing further during heating. 

Additional Information

• Copper
  • It is a chemical element with the symbol Cu and atomic number 29.
  • It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity.
  • A freshly exposed surface of pure copper has a pinkish-orange color.
• Silver
  • It is a chemical element with the symbol Ag and atomic number 47.
  • A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal.
• Lead
  • It is a chemical element with the symbol Pb and atomic number 82.
  • It is a heavy metal that is denser than most common materials.
  • Lead is soft and malleable, and also has a relatively low melting point.
  • When freshly cut, lead is silvery with a hint of blue it tarnishes to a dull gray color when exposed to air.

The correct answer is Calcium carbonate.

Important Points

• Calcium carbonate and its forms:
  • In nature, calcium carbonate occurs in the forms of chalk, limestone, and marble.
  • Formation:
    • ​The skeletal remains of dead sea animals sink to the seabed. Over millions of years, layer build-up and pressure from the top layer changes the bottom layer into chalk. 
  • Earth movements due to earthquake lift the layer of chalk to the Earth's surface. 
  • The earth's movements can also cause the layers to sink further. Thus, high pressure and heat cause the chalk to turn into much harder limestone. 
  • The limestone deposit may stay below the Earth for a longer time and due to higher pressure and temperature, the limestone turns to marble.