Samacheer Kalvi Class 7 Science Term 1 Unit 3 Matter Around Us Solutions
Welcome to NCTB Solutions. Here with this post we are going to help 7th class students by providing Solutions for Samacheer Kalvi Class 7 Science Term 1 Unit 3 Matter Around Us. Here students can easily find all the solutions for Matter Around Us Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 3 exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.
Unit 3 Matter Around Us Exercise Questions Solutions :
(I) Choose the appropriate answer.
(1) Which one of the following is an example for a metal?
(a) Iron
(b) Oxygen
(c) Helium
(d) Water
Answer :
The answer is option – (a)
Iron is an example for a metal.
(2) Oxygen, hydrogen, and sulphur are examples for
(a) metals
(b) non-metals
(c) metalloids
(d) inert gases
Answer :
Correct Option → (b)
Oxygen, hydrogen, and sulphur are examples of Non-metals.
(3) Which of the following is a short and scientific way of representing one molecule of an element or compound?
(a) Mathematical formula
(b) Chemical formula
(c) Mathematical symbol
(d) Chemical symbol
Answer :
Chemical symbol is a short and scientific way of representing one molecule of an element or compound.
(4) The metal which is liquid at room temperature is
(a) chlorine
(b) sulphur
(c) mercury
(d) silver
Answer :
Correct option → (c)
The metals Mercury is a liquid at room temperature.
(5) An element which is always lustrous, malleable and ductile is
(a) non-metal
(b) metal
(c) metalloid
(d) gas
Answer :
Correct Option → (b)
Metal is always lustrous, malleable and ductile.
(II) Fill in the blanks :
(1) The smallest particle of matter that can exist by itself is ___
(2) A compound containing one atom of carbon and two atoms of oxygen is ___
(3) ____ is the only non-metal conducts electricity
(4) Elements are made up of __ kinds of atoms
(5) ___ of some elements are derived from Latin or Greek names of the elements
(6) There are ___ number of known elements
(7) Elements are the form of ___ pure substances.
(8) The first letter of an element always written in ___ letter.
(9) Molecule containing more than three atoms are known as __
(10) ___ is the most abundant gas in the atmosphere.
Answer :
(1) → Atom.
(2) → CO2
(3) → Graphite
(4) → Same
(5) → Symbol
(6) → 118
(7) → Simplest
(8) → Capital
(9) → Polyatomic molecule
(10) → Nitrogen
(III) Analogy :
(2) Non metal conducting electricity : __ Metal conducting electricity : Copper
Answer :
Non metal conducting electricity : Graphite : Metal conducting electricity : Copper.
(3) Elements : Combine to form compounds : : Compounds : __
Answer :
Elements : combine to form compounds : : Compounds : split into elements.
(4) Atoms : fundamental particle of an element : ___ fundamental particles of a compound.
Answer :
Atoms : fundamental particle of an element : : Elements fundamental particles of a compound.
(IV) State true of false. If false, give the correct statement
(1) Two different elements may have similar atoms.
(2) Compounds and elements are pure substances.
(3) Atoms cannot exist alone. They can only exist as groups called molecules.
(4) NaCl represents one molecule of sodium chloride.
(5) Argon is mono atomic gas.
Answer :
(1) → True
(2) → True
(3) → True
(4) → True
(5) → True
(V) Answer in brief :
(3) What do you understand by chemical formula of a compound? What is its significance?
Answer :
It is symbolic representation of one molecule of an element or a compound.
Significance :
(a) It tell us the number of atoms of each element in a compound.
(b) It provides information about the elements present in the molecule and the number of atoms of each element.
(4) Define the following terms with an example for each.
(a) Element :
Answer :
An element is a pure substance consisting only of atoms that all have the same numbers of protons in their atomic nuclei. Example : Iron, Copper.
(b) Compound :
Answer :
Something that consists of two or more things or substances combined together. Example : Water, Salt
(c) Metal :
Answer :
Metal : An element that readily forms positive ions (cations) and has metallic bond. Example : Copper, Silver.
(d) Non-metal
Answer :
Non-metal : It is an element whose characteristics are different from metal. Example : Sulphur.
(e) Metalloid
Answer :
Metalloid : It’s a chemical element whose properties are either metal and some non metals. Example : Boron and silicon.
(6) Classify the following as metals, non-metals and metalloids.
Sodium, Bismuth, Silver, Nitrogen, Silicon, Carbon, Chlorine, Iron, Copper
Answer :
Metals : Sodium, Bismuth, Silver, Iron, Copper.
Non-Metals : Nitrogen, Carbon, Chlorine.
Metalloids : Silicon.
(7) Classify the following as elements and compounds.
Water, Common salt, Sugar, Carbon dioxide, Iodine and Lithium
Answer :
Elements : Iodine, Lithium
Compounds : Water, Common salt, Sugar, Carbon dioxide.
(8) Write the chemical formula for the following elements.
(a) Hydrogen
(b) Nitrogen
(c) Ozone
(d) Sulphur
Answer :
Hydrogen → H
Nitrogen → N
Ozone → O3
Sulphur → S
(9) What are elements? What are they made of? Give two examples.
Answer :
Elements are simpler chemical substance which cannot be broken down when using chemical reactions.
Example : Hydrogen and oxygen.
(10) Define molecule.
Answer :
A molecule is made up of two or more atoms chemically combined.
(11) What are compounds? Give two examples.
Answer :
As we know that it is a pure substance that is formed when the atoms of two or more elements combine chemically in definite proportions.
Example : CO2, NaCl
(12) Give an example for the elements derived from their Latin names.
Answer :
Example for the elements derived from their Latin names are
(i) Copper – Cuprum – Cu
(ii) Potassium – Plumbum – Pb
(iii) Iron – Ferrum – Fe
(13) What is atomicity of elements?
Answer :
It is defined as the total number of atoms present in a molecule.
(14) Calculate the atomicity of H2SO4.
Answer :
As we know that,
Molecule of Sulphuric acid consist H = 2 atoms, S = 1 atom and O = 4 atoms
Atomicity,
= 2 + 1 + 4
= 7
(VI) Answer in detail :
(1) Differentiate metals and non-metals.
Answer :
Metals :
(i) It is a good conductor of heat and electricity.
(ii) Metals have high density.
(iii) Metals have high melting and boiling point.
(iv) Metals are ductile.
(v) Example : Tin, Nickel.
Non-Metals :
(i) It is a bad good conductor of heat and electricity.
(ii) Non- Metals have low melting point.
(iii) Non- Metals have low melting and boiling points.
(iv) Non- Metals are non- ductile.
(v) Example : Carbon, Sulphur.
(2) Explain the characteristics of compounds
Answer :
Characteristics of compounds :
(a) The properties of a compound are different from those of its constituent elements.
(b) A compound can be separated into its constituent elements by chemical methods only.
(c) It has a homogeneous composition.
(3) Describe the different ways in which we can write the symbols of elements. Give appropriate examples.
Answer :
The different ways in which we can write the symbols of elements are –
(a) The first letter is capitalized while the second letter has a lower case.
(b) Chemicals symbols usually consist of one or two letters.
(c) When there are is more than one element that begins with the same letter, their symbols take two letters.
Example :
Elements –
Hydrogen – H
Aluminium – Al
Argon – Ar
Cobalt – Co
(4) Differentiate between elements and compounds.
Answer :
Elements :
(i) It consist only one kind of atoms.
(ii) It is a pure substance.
(iii) Smallest particle is atom.
Compound :
(i) Compounds always have more than one kind of atoms.
(ii) It is an impure substance.
(iii) Smallest particle is molecule.
(7) Write down the properties of metalloids.
Answer :
Properties of metalloids are –
(a) Metalloids have a solid state of matter.
(b) All are solids at room temperature.
(c) They can from alloys with metals.
(d) Example : Boron, Silicon
(VII) Rewrite the given sentence in correct form.
(1) Elements contain two or more kind of atoms and compounds contain only one kind of atom.
Answer :
Elements contains two or more kinds of atoms and compounds contains two or more kinds of elements.
(VIII) Higher Order Thinking Skills.
(2) What changes take place in the movement and arrangement of particles during heating process?
Answer :
As we know that the during heating process the internal energy and movement of particles increases and when the substance melts and evaporates breaking bond between particles then the volume of matter increases.
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