Elements Compounds Symbols And Formula ICSE Class-6th Concise Selina Chemistry Solutions
Elements Compounds Symbols And Formula ICSE Class-6th Concise Selina Chemistry Solutions Chapter-4. We Provide Step by Step Answer of Objective, True False , Fill in the blanks , Match the following , Short/Long Answer Type of Exercise-4 Elements Compounds Symbols And Formula . Visit official Website CISCE for detail information about ICSE Board Class-6.
Elements, Compounds, Symbols And Formula ICSE Class-6th Concise Selina Chemistry Solutions Chapter-4
Classify the following substances into elements and compounds.
Mercury, sulphur, sugar, water, sand, gold, coal, oxygen, alcohol.
Ans. Element: Mercury, sulphur, gold, coal, oxygen.
Compound : Sugar, water, sand, alcohol.
Give the symbols of: Carbon, calcium, copper, chlorine, cobalt, argon.
Carbon is C Chlorine is Cl
Calcium is Ca Cobalt is Co
Copper is Cu Argon is Ar
Define a pure substance. How many types of pure substances do you know ?
Pure substances : “A substance of a definite composition which has consistent properties throughout, is called a pure substance”
Types of pure substances: Pure substances are of two types (i) Elements, (ii) Compounds.
Define : (a) Elements (b) Compounds.
Name the particles from which elements and compounds are made of.
(a) Elements : An element is defined as a pure substance made up of only one kind of atoms that cannot be converted into anything simpler than itself by any physical or chemical process.
(b) Compounds : Compounds are pure substances composed of two or more elements in definite proportion by mass and has a definite set of properties. Compound is made up of only one kind of molecules.
Give two examples for each of the following :
(d) Noble gases
(a) Metals : Iron, silver, gold.
(b) Non-metals : Carbon, sulphur, oxygen.
(c) Metalloids : Antimony, silicon, boron.
(d) Noble gases : Helium, argon, neon.
Name the elements which form water. How will you justify that water is a compound ?
The elements which form water are (i) Hydrogen and oxygen.
Justification : Water has entirely different properties (i.e. is a liquid, extinguishes fire) from the elements it is made up of i.e. Hydrogen a gas catches fire oxygen a gas supporter of combustion.
- Energy is needed to form water on combining O2 with H2.
- We can not seperate the constituents of water by simple physical means.
Give three differences between metals and non-metals.
- Metals are ductile i.e. can be drawn into wires.
- They are malleable i.e. can be beaten to form sheets.
- They are sonorous.
- Non-metals are mostly soft solids cannot be drawn into wires.
- They are mostly gases and are not malleable.
- They donot produce sound when struck.
How is sodium chloride different from its constituent elements, sodium and chlorine ?
Sodium is a metal that is stored in kerosene oil as it reacts very fast with air and water. Chlorine is a reactive greenish yellow gas which is poisonous. When these two elements combine chemically they form common salt sodium chloride which is non poisonous colourless solid substance that we use in our food to add taste and to obtain some nutrition.
State four important characteristics of compounds.
- When compound is formed energy like heat, light or electricity is either needed or produced.
- A compound has properties entirely different from the properties of its constituents.
- Change in weight takes place.
- It cannot be separated into its constituents by simple physical means.
Give two examples for each of the following :
(a) Non-metals which are solids
(b) Metals which are soft
(c) Non-metals which are lustrous
(d) Elements which are liquids.
(e) Inert gases
(a) Phosphorus, Sulphur
(b) Lead and Sodium
(c) Radium, Graphite
(d) Mercury, Bromine
(e) Helium, Neon
(f) Antimony, Arsenic
Name the elements present
(d) Washing soda
(d) Washing soda
(a) Carbon, hydrogen & oxygen
(b) Nitrogen and hydrogen
(c) Calcium, carbon & oxygen
(d) Sodium, carbon & oxygen
What is the proportion of elements present in the following compounds?
Name two compounds which dissolve in water.
Two compounds which dissolve in water are sugar, table salt.
EXERCISE-II Chapter -4 Elements Compounds Symbols And Formula ICSE
(ATOMS & MOLECULES)
(a) Atom : An atom is the smallest indivisible unit of an element which exhibits all the properties of that element and may or may not have independent existence.
(b) Molecule : A molecule can be defined as the smallest unit of an element or a compound which exhibits all the properties of that element or compound and has independent existence. They are divisible into atoms.
(c) Atomicity : The number of atoms in a molecule of an element is called its atomicity.
(d) Formula : Formula is a short way of representing the molecule of an element or a compound.
Why are symbols and formulae of substances important?
Importance of symbols and Formulae :
Symbols and formulae of substance gives a lot of information like.
- Types of elements present in the compound. E.g. (H20 is made of two elements hydrogen and oxygen).
- Number of each kind of atoms in one molecule. E.g. (water has 2 atoms of hydrogen combined with 1 atom of oxygen.)
- Mass of one molecule of the compound. E.g. [H2O has mass (1 × 2) + 16 = 18 g].
Mention three gaseous elements and write their molecular formula.
State the informations obtained from the formula of a compound.
A formula gives us the following information about a compound.
- Types of elements present in the compound.
- Number of each kind of atoms in one molecule of the compound.
- Mass of one molecule of the compound.
A molecule of carbon dioxide gas is represented by CO2 It indicates that a carbon dioxide molecule is formed by the combination of two elements i.e. carbon and oxygen. The number of carbon atom is one and that of oxygen atom is two. The mass of one molecule of carbon dioxide can be calculated by adding the mass of one atom of carbon and two atoms of oxygen.
What is meant by
(a) 2H and H2
(b) H20 and 3H2O ?
(a) 2H is two atoms of hydrogen. H2 is one molecule of hydrogen gas.
(b) H20 represents one molecule of water. 3H20 represents 3 molecules of water.
State the number of atoms of each kind, present in
(a) C6 H12O6
Also name these compounds.