Samacheer Kalvi 8th Science Solutions Chapter 9 Pdf
Tamilnadu Board Samacheer Kalvi 8th Science Solutions Chapter 9: Tamilnadu State Board Solution Class 8 Science Chapter 9 – Matter Around Us.
Samacheer Kalvi 8th Science Solutions Chapter 9: Overview
|
Board |
Samacheer Kalvi |
| Class |
8 |
|
Subject |
Science |
| Chapter |
9 |
|
Chapter Name |
Matter Around Us |
Samacheer Kalvi 8th Science Solutions Chapter 9 Pdf
(I) Choose the best answer.
(1 ) The liquid metal used in thermometers is
a) copper
b) mercury
c) silver
d) gold
(2) The pictorial symbol for water given by the alchemist was
a) ∆
b)\-/
c) \/
d) ∆
(3) Which one of the following element name is not derived from planet?
a) Plutonium
b) Neptunium
c) Uranium
d) Mercury
(4) Symbol of mercury is
a) Ag
b) Hg
c) Au
d) Pb
(5) A form of non – metal which has high ductility is
a) nitrogen
b) oxygen
c) chlorine
d) carbon
(6) The property which allows the metals to be hammered into their sheets is malleability
a) ductility
b) malleability
c) conductivity
d) shining strength
(7) The non – metal which conducts electric current is
a) carbon
b) oxygen
c) aluminium
d) sulphur
(8) Pencil lead contains
a) graphite
b) diamond
c) aluminium
d) sulphur
(9) Identify the state of matter based on the arrangement of the molecules
a) A – Gas , B- Solid, C- Liquid
b) A – Liquid, B- Solid, C- Gas
c) A- Gas , B- Solid, C- Liquid
d) A – Liquid, B – Gas, C- Solid
(II) Fill in the blanks .
1 ) The element which possesses the character of both metals and non metals are called metalloids.
2) The symbol of tungsten is W
3) Melting point of most metal is higher than non- metal.
4) Water contains Hydrogen and Oxygen element .
5) Silicon is used as semiconductor.
(III) Match the following.
a )
| Iron | For making wires |
| Copper | Sewing needle |
| Tungsten | As a fuel for ignition in rocket |
| Boron | Making the filament of a bulb |
Answer
| 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 kind |
| Compound | Atoms of the same kind |
| Molecule | Smallest unit of a substance |
Answer
| Atom | Building block of matter |
| Element | Atoms of the same kind |
| Compound | Atoms of different kind |
| Molecule | Smallest unit of a substance |
(IV)Answer very briefly .
1 ) What is ductility?
Ductility refers to such a property of metals, where metals possesses the ability to be drawn into thin wires. Copper wires is one such example.
2) Write the constituent elements and their symbols for the following compounds.
a) Carbon monoxide b) Washing soda
a) Carbon monoxide
- Carbon and oxygen are the constituent elements of Carbon monoxide.
- CO is the symbol of Carbon monoxide.
b ) Washing soda
- Sodium ,carbon and oxygen are the constituent elements of Washing soda.
- Na2CO3 is the symbol of Washing soda.
3) Write the symbols for the following elements .
a) Oxygen b) Gold c) Calcium
d) Cadmium e) Iron
a ) Oxygen
- The symbol of Oxygen is O
b ) Gold
- The symbol of Gold is Au
c ) Calcium
- Ca is the symbol of Calcium
d) Cadmium
- Cd is the symbol of Cadmium
e) Iron
- Fe is the symbol of Iron
4) Which non -metal is essential for our life and all living beings?
Answer –Oxygen is necessary for our life and all living things.
Explanation :
Oxygen is necessary for our survival and it is also essential for the existence of all living beings. Oxygen plays an important role in the process of development and reproduction of organisms and it also helps in converting our food into energy. Oxygen provides our cells the capability of breaking down food ,in order to acquire the energy that is essential for our survival.
5) Why are bells made of metals?
A typical sound is produced by the metals ,the moment they are hit. For this reason, they are known as sonorous. So, this property is utilized while making temple bells.
(6) What does a chemical symbol represent?
Chemical symbol refers to a shorthand method that is used for the purpose of representing an element.
7) Give two examples for metalloids.
Metalloids refers to those elements that manifests the properties of both metals as well as non- metals. Boron and silicon are some of the perfect examples of metalloids.
8) Mention any three compounds that exist in liquid state.
Water, Hydrochloric acid and Nitric acid are for instance, the three compounds that exist in liquid state.
9) Write three properties of metalloids .
The properties of metalloids are as follows :
- At room temperature ,metalloids are usually solids.
- With other metals ,they can form alloys.
- Silicon and germanium are called semiconductors because under certain conditions, they can act as electrical conductors.
- The appearance of silicon is lustrous , even though it is neither ductile nor malleable. It’s brittleness depicts the feature of some non- metals. It has low thermal and electrical conductivity when compared to metals.
(V) Answer briefly .
1) Can you store pickle in an aluminium utensil ? Give reason.
As aluminium is a metal and pickle is acidic, for this reason it is not possible for us to store the pickle in an utensil which is made up of aluminium. Acids depicts the tendency to react with metals in order to provide hydrogen ,which in turn would lead to the spoilage of the food, thus making it unsuitable for consumption. As we all know that, spoiled food brings about a detrimental effect on our health. So, it is always advisable to avoid eating such spoiled foods.
2) Tabulate the differences between metals and non -metals.
Metals
- Metals are usually solid at room temperature.
- Metals are said to be malleable, because they possess the ability to be formed into different So, most of the metals depicts sufficient hardness.
- As metals has the ability to be drawn into thin wires, for that reason they are said to have good ductility.
- Both melting and boiling point of metal is quite high.
- The density of metals is usually quite high.
- Metals possess good thermaland electrical conductivity.
Non –metals
- At room temperature, non- metals can occur in any state such as solids, liquids or gases.
- Non- metals does not possess sufficient hardness and they are often subjected to brittleness.
- Non- ductility is one of the prominent characteristics of non- metals.
- Melting and boiling point of non-metal is usually very low.
- The density of non- metal is quite low.
- Non- metals have very poor thermal and electrical conductivity.
3) Why are utensils made up of aluminium and brass?
As aluminium and brass possesses good thermal conductivity ,for that reason the cooking utensils are composed of aluminium and brass. These metal utensils are tinned from within, in order to avert any kind of reaction that occurs between the metal and the food products.
4) Define Alchemy .
Alchemist in their time period, used several distinct materials which were portrayed by different symbols and they were also involved in the process of transforming less valuable metal into gold which is known as alchemy and alchemist refers to those persons who executed this work.
5) Name the elements with the following symbols.
a) Na b) W c) Ba d) Al e) U
| Element | Symbol |
| a ) Sodium | Na |
| b) Tungsten | W |
| c) Barium | Ba |
| d) Aluminium | Al |
| e) Uranium | U |
6) Name six common non -metals and write their symbols.
| Name of some common non- metals | Symbols |
| Sulphur | S |
| Hydrogen | H |
| Oxygen | O |
| Carbon | C |
| Chlorine | Cl |
| Nitrogen | N |
7) Mention any four compounds and their uses.
1) Water
Uses
- In our daily life, water is used for several purposes such as drinking ,cleaning ,bathing, cooking and washing.
- As water possesses the ability to dissolve more substances in comparison to any other liquid, for this reason water is known as universal solvent.
2) Sugar
Uses
- Sugar is used for preparing a variety of sweets and toffees .
- Sugar is also used in the preparation of fruit juices.
3) Quick lime
Uses
- For manufacturing cement, quicklime is used to a considerable extent.
- In a glass making operation, quicklime is quite useful as a reactant.
4) Slaked lime
Uses
- The reaction of slaked lime with carbon dioxide leads to the formation of calcium carbonate on the wall, which in turn renders lustrous appearance to the wall. For this reason, slaked lime is used in white washing of walls.
8) Name the metals that are used in jewellery.
Silver and gold are used in making jewellery.
Explanation :
Silver and gold are always the preferred metals for making jewellery because they does not depict the tendency to react with air, water and acids, so they tend to be less reactive in nature. Both ductility and malleability of these metals are quite good and they are not easily susceptible to breakage, when moulded into different shapes.It’s high luster is one of the most notable properties of these metals.
9) Mention the uses of the following compounds.
a ) Baking soda b) Bleaching powder
c) Quick lime
a) Baking soda
Uses
- Baking soda is used in preparing cakes and bread. The moment sodium bicarbonate is heated, which is the chief component of baking soda, it undergoes the process of decomposition in order to produce carbon dioxide. This results in softening of the bread.
- Sodium bicarbonate which is the chief constituents of baking soda, turns into sodium carbonate the moment it is heated. In this procedure, there is formation of water and carbon dioxide. So, it terminates oxygen supply from the air and helps in extinguishing fire. For this reason, baking soda is used in fire extinguisher.
b) Bleaching powder
Uses
- Bleaching powder is used for sterilizing drinking water. As bleaching powder is an active agent, for this reason it is used to destroy germs and bacteria in drinking water, thus making it safe for the purpose of drinking.
- In the laundry, bleaching powder is mainly used for the purpose of bleaching dirty clothes. In the textile industry, it is used as a bleaching agent for linen and
c) Quick lime
Uses
- For manufacturing cement, quicklime is used to a great extent.
- In a glass making operation, quicklime is quite useful as a reactant.
(VI) Give reason .
1 ) Give reasons for the following.
a ) Aluminum foils are used to wrap food items.
Aluminum foils are used for wrapping food items because they are less reactive and does not manifest the tendency to react with food products. Furthermore, they are also very soft and possess the ability to be hammered into thin sheets, without the risk of breakage.
b) Immersion rods for heating liquids are made up of metallic substances.
As metals possess good thermal and electrical conductivity ,for this reason immersion rods that are used for heating liquids are composed of metallic substances.
c) Sodium and potassium are stored in kerosene.
Sodium and potassium depicts the tendency to react with air and water, so they are extremely reactive in nature. Due to this reason, sodium and potassium are stored in kerosene.
d) Mercury is used in thermometers.
Mercury generally have high density and it can also expand uniformly at varying temperature. For this reason, mercury is used in thermometers.
2) Why wires cannot be drawn from materials such as stone or wood?
Materials such as stone or wood is incapable of conducting electricity, for this reason these materials are said to be the non- conductors of electricity. Owing to this reason, it is not possible to draw wires form such materials that does not conduct electricity.
