if you are looking for Tamil Nadu Board Class 8 Science Chapter 9 Matter Around Us then you are at the right place. Here we are providing solutions as well as additional QA / Important Notes.
Choose the best answer.
The liquid metal used in thermometers is
- a) copper b) mercury c) silver d) gold
Which one of the following element name is not derived from planet?
- a) Plutonium
- c) Uranium
- b) Neptunium
- d) Mercury
Symbol of mercury is
- a) Ag
- b) Hg
- c) Au
- d) Pb
A form of non-metal which has high ductility is
- a) nitrogen
- b) oxygen
- c) chlorine
- d) carbon
The property which allows the metals to be hammered into their sheets is
- a) ductility
- b) malleability
- c) conductivity
- d) shining strength
The non-metal which conducts electric current is
- a) carbon
- b) oxygen
- c) aluminium
- d) sulphur
Pencil lead contains
- a) graphite
- c) aluminium
- b) diamond
- d) sulphur
[II] Fill in the blanks.
- The element which possesses the character of both metals and non-metals are called___[metalloid]
- The symbol of tungsten is____[W]
- Melting point of most metal is____than non-metal. [higher]
- Water contains_____and______element. [hydrogen and oxygen]
- _____is used as semiconductor. [silicon]
III. Match the following.
- Iron – For making wires
- Copper – Sewing needle
- Tungsten – As a fuel for ignition in rocket
- Boron – Making the filament of a bulb
Iron – Sewing needle
Copper – For making wires
Tungsten – Making the filament of a bulb
Boron – As a fuel for ignition in rocket
- Atom – Building block of matter
- Element – Atoms of different kinds
- Compound – More than one atom
- Molecule – Smallest unit of a substance
Atom – Building block of matter
Element – Atoms of the same kind
Compound – More than one kind of atom
Molecule – Smallest unit of a substance
Answer very briefly.
What is ductility?
Ductility is the property of a material, usually a metal, that allows it to be stretched into a thin wire without breaking.
Write the constituent elements and their symbols for the following compounds.
- a) Carbon monoxide
- b) Washing soda
- a) Carbon monoxide (CO):
Constituent elements: Carbon (C) and Oxygen (O)
- b) Washing soda (Na₂CO₃):
Constituent elements: Sodium (Na), Carbon (C), and Oxygen (O)
Write the symbols for the following elements.
- a) Oxygen
- b) Gold
- c) Calcium
- d) Cadmium
- e) Iron
- a) Oxygen: O
- b) Gold: Au
- c) Calcium: Ca
- d) Cadmium: Cd
- e) Iron: Fe
Which non-metal is essential for our life and all living beings?
Oxygen is essential for our life and all living beings.
Why are bells made of metals?
Bells are made of metals because metals are sonorous, meaning they produce a clear, resonant sound when struck.
What does a chemical symbol represent?
A chemical symbol represents one atom of an element and is a shorthand notation for the element’s name.
Give two examples for metalloids.
Silicon (Si) and Boron (B).
Mention any three compounds that exist in liquid state.
Water (H₂O), Ethanol (C₂H₅OH), and Acetone (CH₃COCH₃).
Write three properties of metalloids.
Metalloids have properties of both metals and non-metals.
They can act as semiconductors (e.g., Silicon and Germanium).
Metalloids are typically brittle and not as malleable or ductile as metals.
Answer briefly.
Can you store pickle in an aluminium utensil? Give reason.
No, you cannot store pickle in an aluminium utensil because pickles are acidic and can react with aluminium, leading to corrosion and the formation of harmful substances.
Tabulate the differences between metals and non-metals.
| Property | Metals | Non-Metals |
|---|---|---|
| Physical State | Solid (except mercury) | Solid, liquid, or gas |
| Appearance | Shiny (metallic lustre) | Dull (except diamond) |
| Hardness | Generally hard (except sodium, potassium) | Generally soft (except diamond) |
| Malleability | Malleable | Non-malleable |
| Ductility | Ductile | Non-ductile |
| Conductivity | Good conductors of heat and electricity | Poor conductors (except graphite) |
| Melting/Boiling Points | High | Low |
| Sonorousness | Sonorous | Non-sonorous |
Why are utensils made up of aluminium and brass?
Aluminium is used because it is lightweight, has good thermal conductivity, and is resistant to corrosion. Brass is used for its durability, attractive appearance, and resistance to corrosion.
Define Alchemy.
Alchemy is an ancient practice that aimed to transform base metals into noble metals like gold, discover a universal cure for diseases, and achieve eternal life.
Name the elements with the following symbols.
a) Na b) W c) Ba d) Al e) U
- a) Na: Sodium
- b) W: Tungsten
- c) Ba: Barium
- d) Al: Aluminium
- e) U: Uranium
Name six common non-metals and write their symbols.
Oxygen (O), Nitrogen (N), Carbon (C), Sulphur (S), Phosphorus (P), Chlorine (Cl)
Mention any four compounds and their uses.
a) Water (H₂O): Used for drinking, cleaning, and as a solvent.
b) Sodium chloride (NaCl): Used as table salt in food.
c) Carbon dioxide (CO₂): Used in carbonated beverages and fire extinguishers.
d) Ammonia (NH₃): Used in cleaning products and fertilizers.
Name the metals that are used in jewellery.
Gold (Au), Silver (Ag), Platinum (Pt), and sometimes Palladium (Pd).
Mention the uses of the following compounds.
a) Baking soda b) Bleaching powder c) Quick lime
a) Baking soda (NaHCO₃): Used in baking as a leavening agent, in cleaning, and as an antacid.
b) Bleaching powder (CaOCl₂): Used for bleaching fabrics, disinfecting water, and sanitizing surfaces.
c) Quick lime (CaO): Used in construction (cement and mortar), in the steel industry, and for soil stabilization.
Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
Aluminium foils are used to wrap food items because aluminium is non-toxic, lightweight, and a good conductor of heat. It provides a barrier to light, oxygen, moisture, and bacteria, which helps to keep food fresh and prevent spoilage.
(b) Immersion rods for heating liquids are made up of metallic substances.
Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity. They can efficiently transfer heat to the liquid, making the heating process quick and effective.
(c) Sodium and potassium are stored in kerosene.
Sodium and potassium are stored in kerosene because they are highly reactive metals, especially with water and moisture in the air. Storing them in kerosene prevents their contact with air and moisture, thus preventing potentially dangerous reactions.
(d) Mercury is used in thermometers.
Mercury is used in thermometers because it has a high coefficient of expansion and a uniform rate of expansion over a wide range of temperatures. It is also a good conductor of heat and remains in liquid form at a wide range of temperatures, making it ideal for accurately measuring temperature.
Why wires cannot be drawn from materials such as stone or wood?
Wires cannot be drawn from materials such as stone or wood because these materials lack ductility. Ductility is the property that allows materials to be stretched into thin wires without breaking. Stone and wood are brittle and lack the ability to deform plastically, making them unsuitable for being drawn into wires.
