Chapter 6 – Metals and Non-metals

Selina Concise Chemistry 2023 solutions for class 7 Chemistry. Chapter 6 – Metals and Non-metals is provided here with simple step-by-step explanations. These solutions for Metals and Non-metals (6th Chapter) are extremely popular among class 10 students. The Metals and Non-metals solution is handy for quickly completing your homework and preparing for exams.

EXERCISE

Question 1

Name a metal

1. that is most malleable
2. that is brittle
3. as precious as gold
4. that can be cut with a knife
5. used in making electric cables
6. used as a thermometric liquid
7. that is the best conductor of electricity

Answer

1. Pure gold
2. Zinc
3. Platinum
4. Sodium
5. Copper
6. Mercury
7. Silver

Question 2

Name a non-metal that is :

1. a good conductor of heat and electricity
2. hardest naturally occurring substance
3. used to kill germs in water
4. lustrous
5. used for filling into electric bulbs
6. used for cancer therapy
7. liquid at room temperature

Answer

1. Graphite (Carbon)
2. Diamond (Carbon)
3. Chlorine
4. Iodine
5. Argon
6. Radon
7. Bromine

Question 3

Mention two uses of the following metals and non-metals

1. Iron
2. Aluminium
3. Gold
4. Oxygen
5. Iodine

Answer

(a) Iron

• It is used to make pipes, tanks, railings, etc.
• It is used in the construction of power transmission towers.

(b) Aluminium

• It is used to make electric wires.
• It is used to make utensils, cans, window frames, etc.

(c) Gold

• It is used for making ornaments and coins.
• It is used in the manufacture of electronic devices like computers, telephones, home appliances, etc.

(d) Oxygen

• It is used by all living beings for breathing.
• It is important for combustion.

(e) Iodine

• It is used in photographic films in the form of potassium iodide.
• It is added to salt to make it iodized salt which is necessary for the growth of the human body.

Question 4

Give reasons :

1. Magnesium is used in fireworks.
2. Aluminium is used in making aircraft.
3. Copper is used in making electric cables.
4. Graphite is used in the leads of pencils
5. Impure diamond is used to cut glass
6. Gold is mixed with copper and nickel.
7. Tungsten is used in electric bulbs.

Answer

1. Magnesium is used in fireworks because it bums with a dazzling light.
2. Aluminium is used in making aircraft because it is light and strong. It is mixed with other metals to make it stronger.
3. Copper is ductile and a very good conductor of heat and electricity. This is the reason that copper is used in making electric cables.
4. Graphite turns paper black which is why it is used in the leads of pencils.
5. Impure diamond is used to cut glass because it is the hardest substance and can easily exert force required for cutting.
6. Pure gold is a very soft metal. It cannot be moulded into ornaments so it is mixed with copper and nickel so that it becomes harder and a bit cheaper also.
7. It is a shiny grey metal, in a solid state at room temperature. It can withstand high temperatures because it has the highest melting point among metals. Hence, it is used in electric bulbs.

Question 5

Name the metals present in the following alloys

1. Brass
2. Bronze
3. Duralumin
4. Stainless steel

Answer

Question 6

Give four differences between metals and non-metals with reference to their

1. Melting point and boiling point,
2. The conductivity of heat and electricity,
3. Malleability
4. Solubility

Answer

Question 7

What are metalloids?

Answer

Metalloids are the elements which show some properties of metals and some properties of non-metals. They all are solids. They are silicon, boron, arsenic, antimony, germanium, tellurium and polonium.

Question 8

Give two uses of

1. Silicon  
2. Antimony 
3. Tungsten
4. Germanium

Answer

(a) Silicon:

• Used in the production of semiconductors and computer chips
• Used in the manufacturing of glass, ceramics, and solar cells.

(b) Antimony:

• Used as a flame retardant in plastics, textiles, and other materials.
• Used in the production of lead-acid batteries and semiconductor materials.

(c) Tungsten:

• Used in the production of filaments for incandescent light bulbs.
• Used in high-speed cutting tools, drill bits, and other industrial applications.

(d) Germanium:

• Used in the production of semiconductors and transistors.
• Used in the manufacturing of fiber optic cables and infrared night vision devices.

OBJECTIVE TYPE QUESTIONS

Question 1

Fill in the blanks :

1. The most ductile metal is ____.
2. A metal stored in kerosene oil is ____.
3. Tungsten metal is a poor conductor of ____.
4. ____ gold is a soft metal.
5. ____ carbide is the hardest compound known to us.
6. A non-metal used to purify water is ____.
7. A metal that gives a dazzling effect to crackers when they explode is ____.
8. A chemical compound that makes up the striking heads of match sticks is ____.

Answer

1. silver
2. potassium
3. heat
4. Pure
5. Silicon
6. phosphorus
7. magnesium
8. sulphur

Question 2

Match the following

Answer

Question 3

Write ‘true’ or ‘false’ for the following statements :

1. Silver is used to making electric cables
2. Iodine acts as an antiseptic in the form of a tincture of iodine
3. Sodium can be cut with a knife
4. Antimony is a metal
5. Sand is an oxide of silicon

Answer

1. False
2. True
3. True
4. False
5. True

MULTIPLE CHOICE QUESTIONS

Question 1

The noble gas used in advertising signboards is

1. Helium
2. Neon
3. Argon
4. Krypton

Answer

Neon

Explanation

Neon is the noble gas commonly used in advertising signboards. This is because when an electric current is passed through a tube filled with neon gas, it emits a bright reddish-orange glow that is highly visible in the dark.

Question 2

A metal with a melting point of less than 50°C is

1. Gallium
2. Iron
3. Gold
4. Aluminium

Answer

Gallium.

Explanation

Gallium is a soft, silvery-white metal with a melting point of only 29.76°C (85.57°F), which is one of the lowest melting points of any metal. This means that gallium is a liquid at room temperature and will melt in your hand, which makes it a fun and interesting element to play with.

Question 3

A metal which is neither ductile nor malleable is

1. Copper
2. Silver
3. Zinc
4. Aluminium

Answer

Zinc.

Explanation

Zinc is a bluish-white, lustrous metal that is brittle at room temperature and has a crystalline structure. It is not malleable, which means it cannot be easily shaped or hammered into thin sheets like other metals such as copper or silver. It is also not ductile, which means it cannot be easily drawn into wires.

Question 4

Rust is a hydrated oxide of iron which is

1. Reddish brown
2. Green
3. White
4. Black

Answer

Reddish-brown in colour.

Explanation

Rust is formed when iron or steel reacts with oxygen and water, in a process called oxidation. The hydrated oxide of iron that forms as a result of this reaction is commonly referred to as rust. Rust is typically reddish-brown in color, which is why it is also called “iron oxide.”

Question 5

Aluminium is not used to make :

1. Foils
2. Wires
3. Fireworks
4. Utensils

Answer

fireworks

Explanation

Fireworks are typically made from a mixture of chemicals, including metal powders such as magnesium, which burn brightly when ignited. While aluminium powder can also be used to make fireworks, it is not as commonly used as magnesium powder because it burns less brightly and can also create more smoke. Therefore, magnesium is a more popular choice for creating bright flashes of light in fireworks displays.

Question 6

A metalloid used in the manufacture of microchips used in computers is :

1. Antimony
2. Germanium
3. Silicon
4. Arsenic

Answer

Silicon.

Explaination

Silicon is a metalloid with atomic number 14 and is widely used in the semiconductor industry to produce microchips used in computers, smartphones, and other electronic devices. Silicon has unique electrical properties that make it an ideal material for the production of semiconductors.

Question 7

A metalloid used to make glass :

1. Sulphur
2. Germanium
3. Silicon
4. Antimony

Answer

Silicon.

Explanation

Silicon is a metalloid with atomic number 14 and is widely used in the manufacturing of glass due to its unique physical properties. Silicon dioxide, also known as silica, is the primary component of glass, and it is obtained from the mineral quartz, which is a natural source of silicon.