CLASS 6 CHEMISTRY CHAPTER 2
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Questions and Answers

Which of the following best defines an element?

  • A pure substance made up of identical atoms. (correct)
  • A mixture of two or more substances.
  • A particle that cannot exist independently.
  • A compound formed by chemical reactions.

    • What is the basis for the arrangement of elements in the Periodic Table?

  • Decreasing atomic size.
  • Increasing atomic number. (correct)
  • Chemical reactivity.
  • Increasing atomic mass.

    • Which type of element is characterized by being good conductors of heat and electricity?

  • Metals. (correct)
  • Non-metals.
  • Noble gases.
  • Metalloids.

    • Which of the following is an example of a diatomic molecule?

    <p>Oxygen (O₂).</p> Signup and view all the answers

    What distinguishes a compound from a mixture?

    <p>A compound is formed by a fixed proportion of atoms.</p> Signup and view all the answers

    Which particles are found in the nucleus of an atom?

    <p>Protons and neutrons.</p> Signup and view all the answers

    Which of the following describes noble gases?

    <p>Inert and unreactive elements.</p> Signup and view all the answers

    What is an atom's atomic number determined by?

    <p>The number of protons in the nucleus.</p> Signup and view all the answers

    What distinguishes a compound from a mixture?

    <p>Compounds contain elements in a definite proportion.</p> Signup and view all the answers

    Which method would be appropriate for separating iron from a mixture of iron and plastic?

    <p>Magnetic separation</p> Signup and view all the answers

    What is the chemical formula for sodium hydroxide?

    <p>NaOH</p> Signup and view all the answers

    What is the product of a reaction between hydrochloric acid and sodium hydroxide?

    <p>Sodium chloride and water</p> Signup and view all the answers

    Which of these statements about acids is correct?

    <p>Acids react with metals to produce a salt and hydrogen.</p> Signup and view all the answers

    What is an example of a sublimable substance?

    <p>Ammonium chloride</p> Signup and view all the answers

    What type of mixture is formed when sand settles to the bottom of water?

    <p>Suspension</p> Signup and view all the answers

    Which of these represents the chemical reaction between zinc and dilute sulfuric acid?

    <p>Zn + H2SO4 → ZnSO4 + H2</p> Signup and view all the answers

    Which chemical formula represents a base?

    <p>NaOH</p> Signup and view all the answers

    What is the term for the process in which a solid turns directly into vapor when heated?

    <p>Sublimation</p> Signup and view all the answers

    What is the significance of atomicity in the context of elements?

    <p>It denotes the number of atoms in a molecule of the element.</p> Signup and view all the answers

    Which of the following statements about metalloids is accurate?

    <p>Metalloids can exhibit characteristics of both metals and non-metals.</p> Signup and view all the answers

    How are the properties of molecules represented in the context of substances?

    <p>Molecules represent the smallest particle that retains the properties of a substance.</p> Signup and view all the answers

    What distinguishes a compound from a simple mixture?

    <p>Compounds are made up of two or more different types of atoms in a fixed ratio.</p> Signup and view all the answers

    Which statement accurately describes the role of symbols in chemistry?

    <p>Symbols serve as the unique identifiers for elements in the periodic table.</p> Signup and view all the answers

    Why are noble gases considered inert elements?

    <p>They have complete electron shells, making them less reactive.</p> Signup and view all the answers

    What is the relationship between atomic number and the position of an element on the periodic table?

    <p>Increasing atomic number determines the order of elements in the periodic table.</p> Signup and view all the answers

    In what form do metallic elements primarily exhibit their characteristics?

    <p>They retain lustre and can conduct heat and electricity effectively.</p> Signup and view all the answers

    Which method would NOT effectively separate the elements in a compound?

    <p>Magnetic separation</p> Signup and view all the answers

    In which case does the chemical formula represent a mixture rather than a compound?

    <p>Sand and salt</p> Signup and view all the answers

    What distinguishes a compound from a mixture in terms of composition?

    <p>Compounds have elements in a definite proportion.</p> Signup and view all the answers

    What is a characteristic feature of acids compared to bases?

    <p>Acids are often derived from minerals or plants.</p> Signup and view all the answers

    Which of the following is a characteristic of sublimable substances?

    <p>They turn directly into vapour when heated.</p> Signup and view all the answers

    Which chemical equation correctly represents the reaction of sodium hydroxide with hydrochloric acid?

    <p>NaOH + HCl → NaCl + H2O</p> Signup and view all the answers

    Which of the following substances would be separated by the process of sedimentation?

    <p>Sand mixed with water</p> Signup and view all the answers

    What does a chemical equation represent in a reaction?

    <p>The reactants are consumed while the products are formed.</p> Signup and view all the answers

    Which of the following acids is derived from mineral sources?

    <p>Hydrochloric acid</p> Signup and view all the answers

    An element is a pure substance made up of identical ______.

    <p>atoms</p> Signup and view all the answers

    The arrangement of elements in the form of a table is called the ______ Table.

    <p>Periodic</p> Signup and view all the answers

    The atomic number of an element is determined by the number of ______ in its nucleus.

    <p>protons</p> Signup and view all the answers

    Metallic elements are known for their ______, malleability, and ductility.

    <p>lustre</p> Signup and view all the answers

    A ______ is formed when atoms of the same element or different elements combine.

    <p>molecule</p> Signup and view all the answers

    A compound is made up of two or more different ______ combined in a fixed proportion.

    <p>elements</p> Signup and view all the answers

    Noble gases are characterized as ______ elements.

    <p>inert</p> Signup and view all the answers

    The symbol for sulphur is ______.

    <p>S</p> Signup and view all the answers

    Elements in a compound are present in a definite ______.

    <p>proportion</p> Signup and view all the answers

    The chemical formula for water is ______.

    <p>H2O</p> Signup and view all the answers

    Sublimation is the process where substances turn directly into ______ on heating.

    <p>vapour</p> Signup and view all the answers

    A mixture is formed by combining two or more pure substances in any ______.

    <p>ratio</p> Signup and view all the answers

    Iron cannot be separated from its compound using a ______.

    <p>magnet</p> Signup and view all the answers

    Sodium chloride has the chemical formula ______.

    <p>NaCl</p> Signup and view all the answers

    The process of separating insoluble solid particles using a filter paper is called ______.

    <p>filtration</p> Signup and view all the answers

    ______ are formed from the reaction of a base with an acid.

    <p>Salts</p> Signup and view all the answers

    A simple reaction between zinc and sulphur produces ______.

    <p>zinc sulphide</p> Signup and view all the answers

    The chemical formula for hydrochloric acid is ______.

    <p>HCl</p> Signup and view all the answers

    The basic unit of matter is called an ______.

    <p>atom</p> Signup and view all the answers

    Elements in the Periodic Table are arranged in increasing order of their ______ number.

    <p>atomic</p> Signup and view all the answers

    A ______ is a molecule formed from two or more different elements combined in a fixed proportion.

    <p>compound</p> Signup and view all the answers

    Noble gases, such as helium and argon, are known for being ______.

    <p>inert</p> Signup and view all the answers

    A ______ is the short form or abbreviated name of an element that distinguishes it from others.

    <p>symbol</p> Signup and view all the answers

    Diatomic molecules consist of two atoms of the same or different ______.

    <p>elements</p> Signup and view all the answers

    Metallic elements can be described as ______, meaning they can be beaten into sheets.

    <p>malleable</p> Signup and view all the answers

    The process of separating a solid from a liquid by using a filter paper is called ______.

    <p>filtration</p> Signup and view all the answers

    Elements in a compound cannot be separated by ______ methods.

    <p>physical</p> Signup and view all the answers

    The chemical formula for sodium chloride is ______.

    <p>NaCl</p> Signup and view all the answers

    Sublimable substances turn directly into ______ when heated.

    <p>vapour</p> Signup and view all the answers

    The process of ______ separates large sized particles from smaller particles.

    <p>sieving</p> Signup and view all the answers

    The product of a reaction between hydrochloric acid and sodium hydroxide is ______.

    <p>sodium chloride</p> Signup and view all the answers

    Evaporation leaves behind the ______ component in a mixture.

    <p>solid</p> Signup and view all the answers

    A chemical equation is a shorthand form representing the result of a ______ change.

    <p>chemical</p> Signup and view all the answers

    Zinc and sulphur react to form ______ sulphide.

    <p>zinc</p> Signup and view all the answers

    In sedimentation, insoluble solid particles settle down by ______.

    <p>gravity</p> Signup and view all the answers

    The chemical formula for hydrochloric acid is ______.

    <p>HCl</p> Signup and view all the answers

    The chemical formula for water is $H_2O$.

    <p>True</p> Signup and view all the answers

    A mixture is a pure substance formed by combining two or more elements in a fixed ratio.

    <p>False</p> Signup and view all the answers

    Iron can be separated from iron sulfide using a magnet.

    <p>False</p> Signup and view all the answers

    Sublimation is the process where substances turn directly into vapor on heating.

    <p>True</p> Signup and view all the answers

    The chemical formula for sodium hydroxide is $KOH$.

    <p>False</p> Signup and view all the answers

    Sedimentation is the process of dissolving a solid in a liquid.

    <p>False</p> Signup and view all the answers

    Salts are formed from the reaction between a base and an acid.

    <p>True</p> Signup and view all the answers

    The symbol for sulfur is $S$.

    <p>True</p> Signup and view all the answers

    A chemical equation is a visual representation of a physical change.

    <p>False</p> Signup and view all the answers

    All bases are acidic in nature.

    <p>False</p> Signup and view all the answers

    An element is a pure substance made up of identical atoms.

    <p>True</p> Signup and view all the answers

    The Periodic Table arranges elements in decreasing order of their atomic number.

    <p>False</p> Signup and view all the answers

    Noble gases are known for being highly reactive elements.

    <p>False</p> Signup and view all the answers

    A molecule is the smallest particle of a pure substance that can exist independently.

    <p>True</p> Signup and view all the answers

    Compounds are made up of two or more identical elements combined.

    <p>False</p> Signup and view all the answers

    Metallic elements are generally poor conductors of heat and electricity.

    <p>False</p> Signup and view all the answers

    Atoms in a molecule may belong to the same or different elements.

    <p>True</p> Signup and view all the answers

    The symbol for potassium is 'K'.

    <p>True</p> Signup and view all the answers

    A molecule is the smallest particle of a pure substance that can exist independently and retains its chemical properties.

    <p>True</p> Signup and view all the answers

    Noble gases are highly reactive elements that are found abundantly in nature.

    <p>False</p> Signup and view all the answers

    The atomic number of an element indicates the total number of neutrons in its nucleus.

    <p>False</p> Signup and view all the answers

    Elements like potassium and copper are classified as non-metals.

    <p>False</p> Signup and view all the answers

    A compound is a pure substance that consists of only one type of atom.

    <p>False</p> Signup and view all the answers

    The symbol for hydrogen is represented as 'H'.

    <p>True</p> Signup and view all the answers

    Metalloids possess characteristics of both metals and non-metals.

    <p>True</p> Signup and view all the answers

    Elements in a mixture are always combined in a fixed proportion.

    <p>False</p> Signup and view all the answers

    Elements in a compound can be separated by physical methods.

    <p>False</p> Signup and view all the answers

    The chemical formula for potassium nitrate is KNO₃.

    <p>True</p> Signup and view all the answers

    Sublimation is the process where substances turn directly into a solid on cooling.

    <p>False</p> Signup and view all the answers

    The substances that take part in a chemical reaction are called products.

    <p>False</p> Signup and view all the answers

    Hydrochloric acid is represented by the formula HCl.

    <p>True</p> Signup and view all the answers

    Iron sulfide is a compound that can be separated into iron and sulfur using a magnet.

    <p>False</p> Signup and view all the answers

    The chemical equation for the reaction between zinc and sulfuric acid includes zinc sulfate as a product.

    <p>True</p> Signup and view all the answers

    Salts are formed from the reaction of an acid with a base, producing salt and water.

    <p>True</p> Signup and view all the answers

    Dinitrogen oxide is represented chemically as N₂O.

    <p>True</p> Signup and view all the answers

    Filtration is a method used to separate sublimable substances from non-sublimable substances.

    <p>False</p> Signup and view all the answers

    What basic units make up an element and what particles are found in the nucleus?

    <p>Elements are made up of atoms, which contain protons and neutrons in the nucleus.</p> Signup and view all the answers

    How do metalloids differ from metals and non-metals?

    <p>Metalloids exhibit properties of both metals and non-metals, making them unique.</p> Signup and view all the answers

    What process occurs when atoms of different elements combine to form a molecule?

    <p>Atoms combine through chemical bonding to create a molecule, the smallest particle of a pure substance.</p> Signup and view all the answers

    What do you call elements that do not readily react with other elements, and can you name two?

    <p>Noble gases are unreactive elements; examples include helium and argon.</p> Signup and view all the answers

    In what way does the Periodic Table organize elements?

    <p>The Periodic Table arranges elements in increasing order of their atomic number.</p> Signup and view all the answers

    What defines a compound and give an example?

    <p>A compound is a pure substance made of two or more different elements combined in a fixed ratio; an example is water (H₂O).</p> Signup and view all the answers

    What is the significance of atomicity in describing elements?

    <p>Atomicity refers to the number of atoms in a molecule of an element, indicating its molecular structure.</p> Signup and view all the answers

    What role do symbols play in chemistry regarding elements?

    <p>Symbols provide a shorthand reference for elements, distinguishing one from another.</p> Signup and view all the answers

    What is a compound, and how does it differ from a mixture?

    <p>A compound is a pure substance formed from two or more different elements combined in a fixed ratio, whereas a mixture consists of two or more pure substances combined without a fixed ratio.</p> Signup and view all the answers

    Describe the process of sublimation and provide an example of a sublimable substance.

    <p>Sublimation is the process where a solid turns directly into vapor upon heating and returns to a solid upon cooling. An example of a sublimable substance is ammonium chloride.</p> Signup and view all the answers

    What are the physical methods that cannot be used to separate elements in a compound?

    <p>Elements in a compound cannot be separated by physical methods such as filtration or magnetic separation.</p> Signup and view all the answers

    Explain what a chemical formula represents and provide an example.

    <p>A chemical formula represents a substance using symbols of the elements and indicates the ratio of atoms in the compound. For example, the chemical formula for water is H₂O.</p> Signup and view all the answers

    What is the significance of a chemical equation in representing a chemical reaction?

    <p>A chemical equation provides a shorthand representation of the reactants and products involved in a chemical reaction, indicating the direction of the reaction.</p> Signup and view all the answers

    How does filtration work to separate substances in a mixture?

    <p>Filtration involves passing a mixture through a filter to separate insoluble solid particles from a liquid. For example, it can be used to separate chalk from water.</p> Signup and view all the answers

    What are salts, and how are they formed?

    <p>Salts are chemicals formed from the reaction of an acid and a base, resulting in salt and water. An example is the formation of sodium chloride from hydrochloric acid and sodium hydroxide.</p> Signup and view all the answers

    Can you identify a method for separating iron from a mixture that includes plastic?

    <p>Iron can be separated from a mixture with plastic using magnetic separation, as iron is magnetic while plastic is not.</p> Signup and view all the answers

    Describe the characteristics of acids and provide examples.

    <p>Acids are sour in taste and can be derived from plants or minerals, such as citric acid from oranges and hydrochloric acid (HCl) from minerals.</p> Signup and view all the answers

    What is sedimentation, and how does it occur in a solid-liquid mixture?

    <p>Sedimentation is the process where insoluble solid particles settle down by gravity in a solid-liquid mixture, as seen when sand settles in water.</p> Signup and view all the answers

    Why can't the elements in a compound be separated by physical methods?

    <p>Elements in a compound are chemically bonded together, which cannot be undone by physical methods.</p> Signup and view all the answers

    Describe the process of filtration and provide an example.

    <p>Filtration is the separation of insoluble solid particles from a liquid using filter paper; for example, separating chalk from water.</p> Signup and view all the answers

    What is the significance of chemical formulas in representing compounds?

    <p>Chemical formulas provide a clear representation of the composition and structure of compounds using elemental symbols.</p> Signup and view all the answers

    Explain sublimation and mention a sublimable substance.

    <p>Sublimation is the process where a solid turns directly into vapor when heated; ammonium chloride is an example.</p> Signup and view all the answers

    What does the arrow in a chemical equation signify?

    <p>The arrow in a chemical equation indicates the direction of the reaction, showing reactants converting into products.</p> Signup and view all the answers

    Define mixtures and highlight their characteristics.

    <p>Mixtures are impure substances formed by the physical combination of two or more pure substances in any ratio.</p> Signup and view all the answers

    What distinguishes acids from bases in terms of taste?

    <p>Acids generally taste sour, while bases are characterized by a bitter taste.</p> Signup and view all the answers

    How can we separate iron from a mixture of iron and plastic?

    <p>Iron can be separated from plastic using magnetic separation, as iron is magnetic while plastic is not.</p> Signup and view all the answers

    What is the reaction outcome when a base reacts with an acid?

    <p>A base reacts with an acid to produce a salt and water.</p> Signup and view all the answers

    Name a process to separate sand from a mixture in water.

    <p>Sedimentation is the process used to separate sand from a mixture in water, where sand settles by gravity.</p> Signup and view all the answers

    What defines the basic structure of an atom?

    <p>An atom consists of a nucleus containing protons and neutrons, surrounded by electrons in orbits.</p> Signup and view all the answers

    How do noble gases differ from metallic and non-metallic elements in terms of reactivity?

    <p>Noble gases are characterized by their lack of reactivity, unlike metallic and non-metallic elements which can easily form compounds.</p> Signup and view all the answers

    Explain the term 'atomicity' and its significance.

    <p>Atomicity refers to the number of atoms in a molecule of an element, indicating whether the element exists as single atoms or in clusters.</p> Signup and view all the answers

    What is the significance of the periodic table in chemistry?

    <p>The periodic table systematically organizes elements by increasing atomic number, reflecting their properties and relationships.</p> Signup and view all the answers

    Describe how compounds differ from elements and provide an example.

    <p>Compounds are made up of two or more different elements bonded in fixed proportions, while elements consist of identical atoms. For example, water (H₂O) is a compound of hydrogen and oxygen.</p> Signup and view all the answers

    What role do symbols play in the identification of elements?

    <p>Symbols provide a standardized abbreviation for each element, differentiating them based on their chemical identity.</p> Signup and view all the answers

    How do metalloids demonstrate characteristics of both metals and non-metals?

    <p>Metalloids, like boron, exhibit properties such as partial conductivity and varying malleability, bridging the traits of metals and non-metals.</p> Signup and view all the answers

    What does it mean for a compound to have a fixed proportion of elements?

    <p>It means that in a compound, the elements combine in specific ratios that do not change, regardless of the sample size.</p> Signup and view all the answers

    Study Notes

    Elements

    • Pure substance made up of identical atoms.
    • Cannot be broken down into simpler substances.
    • Basic unit of matter.
    • About 118 elements have been discovered.

    Atomicity

    • Number of atoms present in one molecule of the element.

    The Periodic Table

    • Elements are arranged in increasing order of their atomic number.

    Atomic Number

    • Number of protons or electrons in an atom of an element.

    Atom

    • Basic unit of an element.
    • Contains a nucleus with protons and neutrons, surrounded by electrons.

    Metallic Elements

    • Have lustre, malleable, ductile, and good conductors of heat and electricity.
    • Examples include potassium, sodium, zinc, and copper.

    Non-Metallic Elements

    • Lack lustre, not malleable or ductile, and poor conductors of heat and electricity.
    • Examples include carbon, sulfur, and phosphorus.

    Metalloids

    • Elements with properties of both metals and non-metals.
    • Example is boron.

    Noble Gases

    • Unreactive, inert elements present in trace amounts in air.
    • Examples include helium, neon, and argon.

    Symbol

    • Short form or abbreviated name of an element.
    • Used to distinguish one element from another.
    • Example: symbol of sulfur is ‘S’.

    Molecule

    • Formed by the combination of atoms of the same or different elements.
    • Smallest particle of a pure substance that can exist independently and retain its properties.
    • Example: diatomic molecule of nitrogen ‘N₂’.

    Compounds

    • Pure substance made up of two or more different elements combined in a fixed proportion.
    • Example: hydrogen and oxygen form the compound water (H₂O).

    Characteristics of Compounds

    • Elements are present in a definite proportion.
    • Compounds have a definite set of properties, different from the elements within them.
    • Elements within a compound cannot be separated by physical methods.

    Chemical Formula

    • Representation of a substance using symbols.
    • Example: chemical formula of sodium chloride is ‘NaCl’.

    Mixture

    • Impure substance formed by combining two or more pure substances in any ratio.

    Separation Techniques:

    • Sieving: Separates large particles from smaller ones. (e.g. bran from wheat flour)
    • Magnetic Separation: Separates magnetic particles from non-magnetic ones using a magnet. (e.g. iron from plastic)
    • Sublimation: Used to separate sublimable (turn directly into vapor on heating) substances from non-sublimable ones. (e.g. ammonium chloride from a mixture of ammonium chloride & sodium chloride)
    • Filtration: Separates insoluble solid particles from a liquid using a filter paper. (e.g. chalk from water)
    • Sedimentation: Insoluble solid particles settle down by gravity in a liquid. (e.g. sand settles down in water)
    • Evaporation: Liquid component evaporates from a mixture leaving behind the solid component. (e.g. salt from seawater)

    Important Chemical Formulas

    • Gases:

      • Hydrogen (H₂)
      • Nitrogen (N₂)
      • Oxygen (O₂)
      • Chlorine (Cl₂)
      • Hydrogen chloride (HCl)
      • Ammonia (NH₃)
      • Carbon monoxide (CO)
      • Carbon dioxide (CO₂)
      • Nitrous oxide (N₂O)
      • Dinitrogen oxide (N₂O)
      • Nitrogen dioxide (NO₂)
      • Sulfur dioxide (SO₂)
      • Nitrogen monoxide (NO)

    • Acids:

      • Hydrochloric acid (HCl)
      • Nitric acid (HNO₃)
      • Sulphuric acid (H₂SO₄)
      • Carbonic acid (H₂CO₃)

    • Bases:

      • Potassium hydroxide (KOH)
      • Sodium hydroxide (NaOH)
      • Calcium hydroxide (Ca(OH)₂)
      • Zinc hydroxide (Zn(OH)₂)

    • Salts:

      • Potassium nitrate (KNO₃)
      • Zinc sulphate (ZnSO₄)
      • Calcium carbonate (CaCO₃)
      • Ammonium chloride (NH₄Cl)

    • Metallic Oxides & Sulphides:

      • Zinc oxide (ZnO)
      • Calcium oxide (CaO)
      • Magnesium sulphide (MgS)
      • Calcium sulphide (CaS)

    Chemical Equations:

    • Shorthand representation of a chemical reaction.
    • Reactants: Substances that participate in the reaction.
    • Products: Substances formed as a result of the reaction.
    • The arrow (→) indicates the direction of the reaction.
    • [A] Indicates heat applied.

    Examples of Chemical Equations:

    • Zinc and Sulphur:
      • Word Equation: Zinc + Sulphur → Zinc sulfide
    • Sodium Hydroxide and Hydrochloric Acid:
      • Word Equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
    • Zinc and Sulphuric Acid:
      • Word Equation: Zinc + Sulphuric acid → Zinc sulphate + Hydrogen
      • Molecular Equation: Zn + H₂SO₄ (dil.) → ZnSO₄ + H₂ (g)

    Elements

    • An element is a pure substance made up of identical atoms
    • It cannot be broken down into simpler substances
    • There are about 118 elements discovered
    • Scientists needed to arrange elements systematically, leading to the creation of the Periodic Table
    • Atomicity refers to the number of atoms in a molecule of an element

    The Periodic Table

    • Elements are arranged in increasing order of their atomic number
    • The atomic number represents the number of protons or electrons in an atom

    Atom

    • The basic unit of an element
    • Contains a nucleus with protons (positively charged) and neutrons (neutral)
    • Orbits surrounding the nucleus contain electrons (negatively charged)

    Metallic Elements

    • Examples: potassium, sodium, zinc, copper
    • Characterized by luster, malleability (can be beaten into sheets), ductility (can be drawn into wires), and good conductivity of heat and electricity

    Non-Metallic Elements

    • Examples: carbon, sulfur, phosphorus
    • Lack luster, are non-malleable and non-ductile, and are poor or non-conductors of heat and electricity

    Metalloids

    • Elements exhibiting properties of both metals and non-metals
    • Example: boron

    Noble Gases

    • Unreactive, inert elements
    • Present in traces in the air
    • Examples: helium, neon, argon

    Symbol

    • A short form or abbreviated name of an element
    • Distinguishes one element from another
    • Example: the symbol for sulfur is "S"

    Molecule

    • Formed by combining atoms of the same element or different elements
    • The smallest particle of a pure substance that can exist independently and retain its physical and chemical properties
    • Example: diatomic molecule of nitrogen "N₂"

    Compounds

    • Pure substances made up of two or more different elements combined in a fixed proportion
    • Example: hydrogen and oxygen combine to form water (H₂O)
    • The elements in a compound are present in a definite proportion (e.g., 2 atoms of hydrogen combine with 1 atom of oxygen to form 1 molecule of water).
    • Compounds possess a unique set of properties distinct from the properties of the individual elements they contain.
    • Elements in a compound cannot be separated by physical methods (e.g., iron cannot be separated from iron sulfide (FeS) using a magnet).

    Chemical Formula

    • A representation of a substance (element or compound) using symbols
    • Example: the chemical formula for sodium chloride is "NaCl"

    Mixture

    • An impure substance formed by combining two or more pure substances in any ratio
    • Components of the mixture can be separated using various physical methods

    Separation Techniques

    • Sieving: Separating large particles from smaller ones (e.g., bran from wheat flour)
    • Magnetic Separation: Separating magnetic particles from non-magnetic particles using a magnet (e.g., iron from plastic)
    • Sublimation: Separation of sublimable substances from non-sublimable substances by heating the mixture (e.g., ammonium chloride from a mixture of ammonium chloride and sodium chloride).
    • Filtration: Separating insoluble solid particles from a solid-liquid mixture using filter paper (e.g., chalk from water)
    • Sedimentation: Settling down of insoluble solid particles in a solid-liquid mixture due to gravity (e.g., sand settles down in water)
    • Evaporation: Removing a liquid from a mixture by vaporizing it, leaving behind the solid component (e.g., evaporating sea water to obtain salt)

    Chemical Formulas of Important Compounds

    • Gases:
      • H₂ (Hydrogen)
      • N₂ (Nitrogen)
      • O₂ (Oxygen)
      • Cl₂ (Chlorine)
      • HCl (Hydrogen chloride)
      • NH₃ (Ammonia)
      • CO (Carbon monoxide)
      • CO₂ (Carbon dioxide)
      • NO (Nitrous oxide)
      • N₂O (Dinitrogen oxide)
      • NO₂ (Nitrogen dioxide)
      • SO₂ (Sulfur dioxide)
      • CO (Carbon monoxide)
      • NO (Nitrogen monoxide [nitric oxide])
    • Acids:
      • HCl (Hydrochloric acid)
      • HNO₃ (Nitric acid)
      • H₂SO₄ (Sulfuric acid)
      • H₂CO₃ (Carbonic acid)
    • Bases:
      • KOH (Potassium hydroxide)
      • NaOH (Sodium hydroxide)
      • Ca(OH)₂ (Calcium hydroxide)
      • Zn(OH)₂ (Zinc hydroxide)
    • Salts:
      • KNO₃ (Potassium nitrate)
      • ZnSO₄ (Zinc sulfate)
      • CaCO₃ (Calcium carbonate)
      • NH₄Cl (Ammonium chloride)
    • Metallic Oxides & Sulfides:
      • ZnO (Zinc oxide)
      • CaO (Calcium oxide)
      • MgS (Magnesium sulfide)
      • CaS (Calcium sulfide)

    Chemical Reactions and Equations

    • Chemical Equation: A concise representation of a chemical change.
    • Reactants: Substances that participate in the chemical reaction.
    • Products: Substances that are formed as a result of the chemical reaction.
    • Arrow (→): Indicates the direction of the reaction.
    • Heat (Δ or A): Represents heat being applied to initiate the reaction.
    • Example:
      • Word Equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
      • Molecular Equation: NaOH + HCl → NaCl + H₂O
    • Simple Reaction: Zinc (Zn) + Dilute Sulfuric acid (H₂SO₄) → Zinc Sulfate (ZnSO₄) + Hydrogen (H₂)

    Elements

    • Pure substances made up of identical atoms.
    • Cannot be broken down into simpler substances.
    • Basic unit of matter.
    • Approximately 118 elements have been discovered.
    • Arranged in the periodic table in increasing order of atomic number.

    Periodic Table

    • A table where elements are arranged in increasing order of atomic number.
    • Atomic number of an element represents the number of protons or electrons in its atom.

    Atom

    • The basic unit of an element.
    • Contains a nucleus with protons (positively charged) and neutrons (neutral).
    • Orbits around the nucleus contain negatively charged particles called electrons.

    Metallic Elements

    • Examples: potassium, sodium, zinc, copper.
    • Possess luster, malleability (can be beaten into sheets), ductility (can be drawn into wires), and are good conductors of heat and electricity.

    Non-metallic Elements

    • Examples: carbon, sulfur, phosphorus.
    • Lack luster, are non-malleable, non-ductile, and are poor or non-conductors of heat and electricity.

    Metalloids

    • Elements exhibiting properties of both metals and non-metals.
    • Example: boron.

    Noble Gases

    • Unreactive, inert elements found in trace amounts in the air.
    • Examples: helium, neon, argon.

    Symbol

    • A short form representation of an element, distinguishing one element from another.
    • Example: the symbol for sulfur is ‘S’.

    Molecule

    • Formed when atoms of the same or different elements combine.
    • The smallest particle of a pure substance that can exist independently, retaining the substance's physical and chemical properties.
    • Example: diatomic molecule of nitrogen, ‘N₂’.

    Compounds

    • Pure substances made up of two or more different elements combined in a fixed proportion.
    • Example: water (H₂O) formed from hydrogen and oxygen.

    Characteristics of Compounds

    • Elements in a compound are present in a definite proportion.
    • Compounds have a distinct set of properties different from their constituent elements.
    • Elements in a compound cannot be separated by physical methods.

    Chemical Formula

    • Represents a substance (element or compound) using symbols.
    • Example: the chemical formula of sodium chloride is ‘NaCl’.

    Mixture

    • An impure substance formed by combining two or more pure substances in any ratio.
    • Components can be separated by physical methods.

    Separation Techniques

    • Sieving: Separates large-sized particles from smaller ones. (Example: bran from wheat flour)
    • Magnetic Separation: Separates magnetic particles from non-magnetic particles using a magnet. (Example: iron from plastic)
    • Sublimation: Separates sublimable substances from non-sublimable ones by heating the mixture. (Example: ammonium chloride from a mixture of ammonium chloride and sodium chloride)
    • Filtration: Separates insoluble solid particles from a solid-liquid mixture using a filter paper or filtration apparatus. (Example: chalk from water)
    • Sedimentation: Allows insoluble solid particles to settle down in a solid-liquid mixture by gravity. (Example: sand settles down in water)
    • Evaporation: Evaporates the liquid in a mixture leaving behind the solid component. (Example: evaporation of seawater leaves behind salt)

    Chemical Formulas of Important Compounds

    • Gases: H₂ (Hydrogen), N₂ (Nitrogen), O₂ (Oxygen), Cl₂ (Chlorine), HCl (Hydrogen chloride), NH₃ (Ammonia), CO (Carbon monoxide), CO₂ (Carbon dioxide), NO (Nitrous oxide), N₂O (Dinitrogen oxide), NO₂ (Nitrogen dioxide), SO₂ (Sulfur dioxide)
    • Acids: HCl (Hydrochloric acid), HNO₃ (Nitric acid), H₂SO₄ (Sulfuric acid), H₂CO₃ (Carbonic acid)
    • Bases: KOH (Potassium hydroxide), NaOH (Sodium hydroxide), Ca (OH)₂ (Calcium hydroxide), Zn (OH)₂ (Zinc hydroxide)
    • Salts: KNO₃ (Potassium nitrate), ZnSO₄ (Zinc sulphate), CaCO₃ (Calcium carbonate), NH₄Cl (Ammonium chloride)
    • Metallic Oxides & Sulfides: ZnO (Zinc oxide), CaO (Calcium oxide), MgS (Magnesium sulphide), CaS (Calcium sulphide)

    Chemical Equations

    • Representing a chemical reaction: A chemical equation is a shorthand form representing the result of a chemical change.
    • Components of a chemical equation:
      • Reactants: Substances that participate in the chemical reaction.
      • Products: Substances formed as a result of the chemical reaction.
      • Arrow (→): Indicates the direction of the reaction.
      • [A]: Indicates heat is applied.

    Examples of Chemical Equations

    • Simple reaction between zinc and sulfur:
      • Word equation: Zinc + Sulfur → Zinc sulfide
      • Molecular equation: Zn + S [A] → ZnS
    • Simple reaction between sodium hydroxide and dilute hydrochloric acid:
      • Word equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
      • Molecular equation: NaOH + HCl [dil.] → NaCl + H₂O
    • Simple reaction between zinc and dilute sulfuric acid:
      • Word equation: Zinc + Sulfuric acid → Zinc sulfate + Hydrogen
      • Molecular equation: Zn + H₂SO₄ [dil.] → ZnSO₄ + H₂ [g]

    Elements

    • A pure substance made up of identical atoms.
    • Cannot be broken down into simpler substances.
    • The basic unit of matter.
    • Around 118 elements discovered to date.
    • Arranged in a table known as the Periodic Table.
    • Atomicity refers to the number of atoms in a molecule of an element.
    • Elements are arranged in the Periodic Table by increasing atomic number.

    Atomic Number

    • Represents the number of protons or electrons in an atom of an element.
    • Protons and electrons are equal in number.
    • For example, Hydrogen has one electron and an atomic number of 1, placing it first in the table.

    Atom

    • The basic unit of an element.
    • May not exist independently.
    • Contains a nucleus with positively charged protons and neutral neutrons.
    • Orbits surrounding the nucleus are home to negatively charged electrons.

    Metallic Elements

    • Possess luster, meaning they are shiny.
    • Malleable, capable of being beaten into sheets.
    • Ductile, capable of being drawn into wires.
    • Good conductors of heat and electricity.
    • Examples include Potassium, Sodium, Zinc, and Copper.

    Non-metallic Elements

    • Lack luster.
    • Non-malleable and non-ductile.
    • Poor conductors or non-conductors of heat and electricity.
    • Examples include Carbon, Sulfur, and Phosphorus.

    Metalloids

    • Exhibit properties of both metals and non-metals.
    • Example: Boron

    Noble Gases

    • Unreactive and inert elements found in traces in the air.
    • Examples include Helium, Neon, and Argon.

    Symbol

    • A short form or abbreviation representing an element, distinguishing it from others.
    • For example, the symbol for sulfur is 'S.'

    Molecule

    • Formed when atoms of the same or different elements combine.
    • Smallest particle of a pure substance that can exist independently while retaining its properties.
    • For example, a diatomic molecule of nitrogen 'N₂.'

    Compounds

    • A pure substance made up of two or more different elements combined in a fixed proportion.
    • For example, hydrogen and oxygen combine to form water (H₂O).

    Characteristics of Compounds

    • Elements in a compound are present in a definite proportion.
    • For example, two hydrogen atoms combine with one oxygen atom to form one molecule of water.
    • Compounds have a specific set of properties different from the elements they contain.
    • Elements in a compound cannot be separated by physical means.
    • For example, iron cannot be separated from iron sulfide using a magnet.

    Chemical Formula

    • Represents a substance, whether an element or compound, using symbols.
    • For example, the chemical formula for sodium chloride is 'NaCl'.

    Mixture

    • An impure substance formed by combining two or more pure substances in any ratio.

    Separation Techniques

    • Sieving: Separates large particles from smaller ones. (e.g., bran from wheat flour).
    • Magnetic Separation: Separates magnetic particles from non-magnetic ones using a magnet. (e.g., iron from plastic).
    • Sublimation: Separates sublimable substances from non-sublimable ones by heating the mixture. (e.g., ammonium chloride from a mixture of ammonium chloride and sodium chloride).
    • Filtration: Separates insoluble solid particles from a solid-liquid mixture using a filter paper or other apparatus. (e.g., chalk from water).
    • Sedimentation: Insoluble solid particles settle down by gravity in a solid-liquid mixture. (e.g., sand settles down in water).
    • Evaporation: The process of evaporating a liquid from a mixture, leaving behind the solid component. (e.g., evaporation of seawater leaves behind salt).

    Important Chemical Formulae (Examples)

    Gases

    • H₂ (Hydrogen)
    • N₂ (Nitrogen)
    • O₂ (Oxygen)
    • Cl₂ (Chlorine)
    • HCl (Hydrogen chloride)
    • NH₃ (Ammonia)
    • CO (Carbon monoxide)
    • CO₂ (Carbon dioxide)
    • NO (Nitrous oxide)
    • N₂O (Dinitrogen oxide)
    • NO₂ (Nitrogen dioxide)
    • SO₂ (Sulfur dioxide)

    Acids

    • Derived from plants (e.g., citric acid from oranges) or minerals (e.g., hydrochloric acid [HCl] from sodium chloride).
    • Typically sour in taste.

    Examples of Acids

    • HCl (Hydrochloric acid)
    • HNO₃ (Nitric acid)
    • H₂SO₄ (Sulfuric acid)
    • H₂CO₃ (Carbonic acid)

    Bases

    • Typically hydroxides (or oxides) of metals.
    • Bitter in taste.
    • Example: Sodium hydroxide (NaOH), which is the hydroxide of the metal Sodium (Na).

    Examples of Bases

    • KOH (Potassium hydroxide)
    • NaOH (Sodium hydroxide)
    • Ca(OH)₂ (Calcium hydroxide)
    • Zn(OH)₂ (Zinc hydroxide)

    Salts

    • Chemicals formed by the reaction of a base with an acid, producing salt and water.
    • Example: Potassium nitrate (KNO₃)

    Examples of Salts

    • KNO₃ (Potassium nitrate)
    • ZnSO₄ (Zinc sulphate)
    • CaCO₃ (Calcium carbonate)
    • NH₄Cl (Ammonium chloride)

    Metallic Oxides and Sulfides

    • ZnO (Zinc oxide)
    • CaO (Calcium oxide)
    • MgS (Magnesium sulfide)
    • CaS (Calcium sulfide)

    Chemical Equations

    • A shorthand representation of the results of a chemical change.

    Representing a Chemical Equation

    • Reactants: Substances that participate in the chemical reaction.
    • Products: Substances formed as a result of the chemical reaction.
    • → (arrow): Indicates the direction of the reaction.
    • Δ: Indicates heat - meaning reactants are heated to produce the product.

    Examples of Chemical Equations

    • Reaction: Zinc (metal) and sulfur (non-metal) react on heating.

    • Reactants: Zinc and sulfur

    • Product: Zinc sulfide

    • Chemical Equation: Zn + S → ZnS + Δ

    • Reaction: Sodium hydroxide (NaOH) and dilute hydrochloric acid (HCl) react.

    • Word Equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water

    • Chemical Equation: NaOH + HCl → NaCl + H₂O

    • Reaction: Zinc (Zn) and dilute sulfuric acid (H₂SO₄) react.

    • Word Equation: Zinc + Sulfuric acid → Zinc sulfate + Hydrogen

    • Chemical Equation: Zn + H₂SO₄ (dil.) → ZnSO₄ + H₂ (g)

    Elements

    • Pure substances made up of identical atoms
    • Cannot be broken down into simpler substances
    • Basic unit of matter
    • About 118 elements discovered
    • Arranged in a periodic table in increasing order of atomic number
    • Atomic number is the number of protons or electrons in an atom
    • Atomicity refers to the number of atoms in a molecule of an element

    Periodic Table

    • Elements are arranged in increasing order of their atomic number

    Atom

    • The basic unit of an element
    • Consists of a nucleus containing protons and neutrons, surrounded by orbiting electrons

    Metallic Elements

    • Examples: potassium, sodium, zinc, copper
    • Have luster, malleable, ductile, and are good conductors of heat and electricity

    Non-metallic Elements

    • Examples: carbon, sulfur, phosphorus
    • Lack luster, not malleable or ductile, and are poor conductors of heat and electricity

    Metalloids

    • Elements that exhibit properties of both metals and nonmetals
    • Example: boron

    Noble Gases

    • Unreactive, inert elements found in trace amounts in air
    • Examples: helium, neon, argon

    Symbol

    • A short form or abbreviated name of an element
    • Distinguishes one element from another
    • Example: the symbol for sulfur is S

    Molecule

    • Formed by the combination of atoms of the same or different elements
    • Smallest particle of a pure substance that can normally exist independently and retain its properties
    • Example: diatomic molecule of nitrogen - N₂

    Compounds

    • Pure substances made up of two or more different elements combined in a fixed proportion
    • Example: water (H₂O) formed from hydrogen and oxygen

    Characteristics of Compounds

    • Elements present in a definite proportion
    • Compound has unique properties different from its constituent elements
    • Elements cannot be separated by physical methods

    Chemical Formula

    • Represents a substance (element or compound) using symbols
    • Example: chemical formula of sodium chloride is NaCl

    Mixture

    • An impure substance formed by combination of two or more pure substances in any ratio

    Methods of Separation

    • Sieving: separating large particles from smaller ones (e.g., bran from wheat flour)
    • Magnetic separation: separating magnetic particles from non-magnetic particles using a magnet (e.g., iron from plastic)
    • Sublimation: separating sublimable substances from non-sublimable substances by heating (e.g., ammonium chloride from a mixture of ammonium chloride and sodium chloride)
    • Filtration: separating insoluble solid particles from a liquid using a filter paper (e.g., chalk from water)
    • Sedimentation: allowing insoluble solid particles to settle down in a liquid by gravity (e.g., sand settling in water)
    • Evaporation: removing a liquid from a mixture by evaporation, leaving behind the solid component (e.g., evaporating seawater to obtain salt)

    Important Chemical Formulas

    • Gases: H₂, N₂, O₂, Cl₂, HCl, NH₃, CO, CO₂, NO, N₂O, NO₂, SO₂
    • Acids: HCl (hydrochloric acid), HNO₃ (nitric acid), H₂SO₄ (sulfuric acid), H₂CO₃ (carbonic acid)
    • Bases: KOH (potassium hydroxide), NaOH (sodium hydroxide), Ca(OH)₂ (calcium hydroxide), Zn(OH)₂ (zinc hydroxide)
    • Salts: KNO₃ (potassium nitrate), ZnSO₄ (zinc sulphate), CaCO₃ (calcium carbonate), NH₄Cl (ammonium chloride)
    • Metallic Oxides & Sulphides: ZnO (zinc oxide), CaO (calcium oxide), MgS (magnesium sulphide), CaS (calcium sulphide)

    Chemical Equations

    • Shorthand representation of a chemical change
    • Reactants are substances that undergo change
    • Products are substances formed as a result of the change
    • Arrow indicates the direction of the reaction
    • [A] indicates heat
    • Example: Zn + S [A] → ZnS (zinc reacts with sulfur when heated to form zinc sulfide)

    Elements

    • Elements are pure substances made up of identical atoms.
    • Elements cannot be broken down into simpler substances.
    • About 118 elements have been discovered.
    • The need to arrange elements systematically led to the creation of the periodic table.
    • Atomic number represents the number of protons or electrons in an element.
    • Elements with the same atomic number are considered the same element.
    • The atomic number determines the element's position on the periodic table.

    The Periodic Table

    • Elements are arranged in increasing order of their atomic number.
    • The periodic table helps organize and understand the properties of elements.

    Atom

    • Atoms are the basic unit of an element.
    • Atoms are divisible into a nucleus and surrounding orbits.
    • The nucleus contains protons (positively charged) and neutrons (neutral).
    • Electrons (negatively charged) orbit the nucleus.

    Types of Elements

    • Metallic elements like potassium, sodium, zinc, and copper have lustre, are malleable, ductile, and good conductors.
    • Non-metallic elements like carbon, sulfur, and phosphorus lack lustre, are non-malleable and non-ductile, and are poor conductors.
    • Metalloids like Boron exhibit properties of both metals and non-metals.
    • Noble gases are inert, unreactive elements found in air. Examples include helium, neon, and argon.

    Symbols

    • Symbols are abbreviated names that distinguish one element from another.
    • For example, the symbol for sulfur is 'S'.

    Molecule

    • A molecule is formed by the combination of atoms of the same or different elements.
    • It's the smallest independently existing particle of a substance.
    • A diatomic molecule of nitrogen is represented by 'N₂'.

    Compounds

    • Compounds are pure substances made of two or more different elements combined in fixed proportions.
    • For example, hydrogen and oxygen combine to form water (H₂O).

    Characteristics of Compounds

    • Elements in a compound are present in a definite proportion.
    • Compounds have a specific set of properties distinct from their constituent elements.
    • Elements within a compound cannot be separated by physical methods.

    Chemical Formula

    • A chemical formula represents a substance using symbols.
    • For example, the chemical formula for sodium chloride is 'NaCl'.

    Mixtures

    • Mixtures are impure substances formed by combining two or more pure substances in any ratio.

    Separation Techniques

    • Sieving: Separating large particles from smaller ones.
    • Magnetic separation: Separating magnetic particles from non-magnetic particles.
    • Sublimation: Separating sublimable substances from non-sublimable substances by heating the mixture.
    • Filtration: Separating insoluble solid particles from a solid-liquid mixture.
    • Sedimentation: Settling down of insoluble solid particles in a solid-liquid mixture.
    • Evaporation: Evaporating the liquid in a mixture to leave behind the solid component.

    Important Chemical Formulas

    • Gases: H₂ (hydrogen), N₂ (nitrogen), O₂ (oxygen), Cl₂ (chlorine), HCl (hydrogen chloride), NH₃ (ammonia), CO (carbon monoxide), CO₂ (carbon dioxide), NO (nitrous oxide), N₂O (dinitrogen oxide), NO₂ (nitrogen dioxide), SO₂ (sulfur dioxide).
    • Acids: HCl (hydrochloric acid), HNO₃ (nitric acid), H₂SO₄ (sulfuric acid), H₂CO₃ (carbonic acid).
    • Bases: KOH (potassium hydroxide), NaOH (sodium hydroxide), Ca(OH)₂ (calcium hydroxide), Zn(OH)₂ (zinc hydroxide).
    • Salts: KNO₃ (potassium nitrate), ZnSO₄ (zinc sulphate), CaCO₃ (calcium carbonate), NH₄Cl (ammonium chloride).
    • Metallic Oxides & Sulphides: ZnO (zinc oxide), CaO (calcium oxide), MgS (magnesium sulphide), and CaS (calcium sulfide).

    Chemical Equations

    • Chemical Equations are a shorthand representation of chemical changes.
    • Reactants: Substances that participate in the chemical reaction.
    • Products: Substances formed as a result of the reaction.
    • Arrow (→): Indicates the direction of the reaction.
    • [A]: Indicates heat.

    Example of a Chemical Equation

    • Reaction: Zinc (Zn) reacts with dilute sulfuric acid (H₂SO₄)
    • Word Equation: Zinc + Sulphuric acid → Zinc sulphate + Hydrogen
    • Molecular Equation: Zn + H₂SO₄ [dil.] → ZnSO₄ + H₂ [g]

    Elements

    • An element is a pure substance made up of identical atoms.
    • Elements cannot be broken down into simpler substances.
    • There are about 118 known elements.
    • The elements are arranged in a periodic table in order of increasing atomic number.
    • The atomic number of an element is the number of protons or electrons in an atom of that element.
    • Atomicity indicates the number of atoms present in a molecule of an element.
    • Metallic elements have luster, are malleable, ductile, and good conductors of heat and electricity.
    • Non-metallic elements lack luster, are not malleable or ductile, and are poor conductors of heat and electricity.
    • Metalloids possess properties of both metals and non-metals.
    • Noble gases are unreactive inert elements found in trace amounts in air.

    Compounds

    • Compounds are pure substances formed by the combination of two or more different elements in a fixed proportion.
    • Elements in a compound are present in a definite proportion, meaning they always combine in the same ratio.
    • Compounds have a definite set of properties that differ from the properties of the individual elements they are composed of.
    • Elements in a compound cannot be separated by physical means.
    • Chemical formulas represent substances using symbols.

    Mixtures

    • Mixtures are impure substances formed by combining two or more pure substances in any ratio.
    • Mixtures can be separated by physical means.
    • Common separation techniques include sieving, magnetic separation, sublimation, filtration, sedimentation, and evaporation.

    Important Chemical Formulas

    • Gases:
      • H₂: Hydrogen
      • N₂: Nitrogen
      • O₂: Oxygen
      • Cl₂: Chlorine
      • HCl: Hydrogen chloride
      • NH₃: Ammonia
      • CO: Carbon monoxide
      • CO₂: Carbon dioxide
      • NO: Nitrous oxide
      • N₂O: Dinitrogen oxide
      • NO₂: Nitrogen dioxide
      • SO₂: Sulphur dioxide
    • Acids: (Derived from plants or minerals)
      • HCl: Hydrochloric acid
      • HNO₃: Nitric acid
      • H₂SO₄: Sulphuric acid
      • H₂CO₃: Carbonic acid
    • Bases: (Hydroxides or oxides of metals)
      • KOH: Potassium hydroxide
      • NaOH: Sodium hydroxide
      • Ca(OH)₂: Calcium hydroxide
      • Zn(OH)₂: Zinc hydroxide
    • Salts: (Formed by the reaction of a base with an acid)
      • KNO₃: Potassium nitrate
      • ZnSO₄: Zinc sulphate
      • CaCO₃: Calcium carbonate
      • NH₄Cl: Ammonium chloride
    • Metallic Oxides and Sulphides:
      • ZnO: Zinc oxide
      • CaO: Calcium oxide
      • MgS: Magnesium sulphide
      • CaS: Calcium sulphide

    Representing Chemical Reactions

    • Chemical equations are a shorthand way to represent the results of a chemical change.
    • A chemical equation includes reactants (substances that take part in the reaction) and products (substances formed as a result of the reaction).
    • The arrow in a chemical equation indicates the direction of the reaction.
    • The symbol "[→]" represents heat, indicating that the reactants are heated to produce the products.

    Examples of Chemical Reactions

    • Example 1: Zinc and Sulfur
      • Word equation: Zinc + Sulfur → Zinc sulphide
    • Example 2: Sodium Hydroxide and Hydrochloric Acid
      • Word equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
    • Example 3: Zinc and Dilute Sulphuric Acid
      • Word equation: Zinc + Sulphuric acid → Zinc sulphate + Hydrogen
      • Molecular equation: Zn + H₂SO₄ [dil.] → ZnSO₄ + H₂ [g]

    Elements

    • Pure substance made of identical atoms
    • Cannot be broken down into simpler substances
    • Basic unit of matter
    • 118 elements discovered to date
    • Arranged in the periodic table

    Periodic Table

    • Elements arranged in increasing order of their atomic number
    • Atomic number is the number of protons or electrons in an atom
    • Examples:
      • Hydrogen: one electron, atomic number 1
      • Helium: two electrons, atomic number 2

    Atom

    • Basic unit of an element
    • Composed of:
      • Nucleus: contains protons (positively charged) and neutrons (neutral)
      • Orbits: contain electrons (negatively charged)

    Metallic Elements

    • Examples: Potassium, Sodium, Zinc, Copper
    • Characteristics:
      • Lustrous
      • Malleable (can be beaten into sheets)
      • Ductile (can be drawn into wires)
      • Good conductors of heat and electricity

    Non-metallic Elements

    • Examples: Carbon, Sulfur, Phosphorus
    • Characteristics:
      • Lack luster
      • Non-malleable
      • Non-ductile
      • Poor or non-conductors of heat and electricity

    Metalloids

    • Exhibit properties of both metals and non-metals
    • Example: Boron

    Noble Gases

    • Unreactive, inert elements found in trace amounts in air
    • Examples: Helium, Neon, Argon

    Symbol

    • Short form or abbreviated name of an element
    • Distinguishes one element from another
    • Example: Symbol for sulfur is 'S'

    Molecule

    • Formed by the combination of atoms of the same element or different elements
    • Smallest particle of a pure substance that can normally exist independently and retain the substance's physical and chemical properties
    • Example: Diatomic molecule of nitrogen 'N2'

    Compounds

    • Pure substance composed of two or more different elements (atoms) combined in a fixed proportion
    • Example: Hydrogen and oxygen form the compound water (H2O)

    Characteristics:

    • Elements in a compound are present in a definite proportion.
    • Compounds have a definite set of properties.
    • Elements in a compound cannot be separated by physical methods.

    Chemical Formula

    • Represents a substance (element or compound) using symbols
    • Example: Chemical formula of sodium chloride is 'NaCl'

    Mixture

    • Impure substance formed by combining two or more pure substances in any ratio

    Separation Techniques

    • Sieving: Separates large particles from smaller particles (e.g., bran from wheat flour)
    • Magnetic Separation: Separates magnetic particles from non-magnetic particles (e.g., iron from plastic)
    • Sublimation: Separates sublimable substance from a mixture by heating (e.g., ammonium chloride from a mixture of ammonium chloride and sodium chloride)
    • Filtration: Separates insoluble solid particles from a solid-liquid mixture using filter paper (e.g., chalk from water)
    • Sedimentation: Insoluble solid particles settle down in a solid-liquid mixture by gravity (e.g., sand settles in water)
    • Evaporation: Liquid is evaporated from a mixture leaving behind the solid component (e.g., evaporation of seawater leaves behind salt)

    Important Chemical Formulas

    Gases

    • H2: Hydrogen
    • N2: Nitrogen
    • O2: Oxygen
    • Cl2: Chlorine
    • HCl: Hydrogen chloride
    • NH3: Ammonia
    • CO: Carbon monoxide
    • CO2: Carbon dioxide
    • NO: Nitrous oxide
    • N2O: Dinitrogen oxide
    • NO2: Nitrogen dioxide
    • SO2: Sulfur dioxide

    Acids

    • HCl: Hydrochloric acid
    • HNO3: Nitric acid
    • H2SO4: Sulphuric acid
    • H2CO3: Carbonic acid

    Bases

    • KOH: Potassium hydroxide
    • NaOH: Sodium hydroxide
    • Ca(OH)2: Calcium hydroxide
    • Zn(OH)2: Zinc hydroxide

    Salts

    • KNO3: Potassium nitrate
    • ZnSO4: Zinc sulphate
    • CaCO3: Calcium carbonate
    • NH4Cl: Ammonium chloride

    Metallic Oxides and Sulphides

    • ZnO: Zinc oxide
    • CaO: Calcium oxide
    • MgS: Magnesium sulphide
    • CaS: Calcium sulphide

    Chemical Equations

    • Shorthand form representing the result of a chemical change

    Components of a Chemical Equation

    • Reactants: Substances that participate in the chemical reaction.
    • Products: Substances formed as a result of the chemical reaction.
    • Arrow (→): Indicates the direction of the reaction.
    • [A]: Indicates heat (e.g., Zinc and sulfur are heated to give zinc sulfide)

    Examples of Chemical Equations

    • Zinc and Sulfur reaction:
      • Word Equation: Zinc + Sulfur → Zinc sulphide
    • Sodium hydroxide and hydrochloric acid reaction:
      • Word Equation: Sodium hydroxide + Dilute hydrochloric acid → Sodium chloride + Water
      • Molecular Equation: NaOH + HCl (dil.) → NaCl + H2O
    • Zinc and dilute sulphuric acid reaction:
      • Word Equation: Zinc + Dilute sulphuric acid → Zinc sulphate + Hydrogen
      • Molecular Equation: Zn + H2SO4 (dil.) → ZnSO4 + H2 (g)

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    Description

    Test your knowledge on the basic concepts of elements, atomic structure, and the organization of the periodic table. This quiz covers definitions, properties of metallic and non-metallic elements, and explores the unique characteristics of noble gases and metalloids. Ideal for anyone studying introductory chemistry.

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