Learn Unit I: Chemical Substances - Nature and Behaviour with Free Lessons & Tips

To observe what happens when quicklime (calcium oxide) is added to water in a beaker, follow these steps:

1. Take a small amount of quicklime (calcium oxide) and place it in a clean, dry beaker.
2. Add a small amount of water to the quicklime in the beaker, using a dropper or a stirring rod to mix them together.
3. Observe the reaction carefully and note down any changes that occur.

Saturated hydrocarbons contain only single carbon-carbon bonds and are fully saturated with hydrogen atoms. An example is methane (CH4). Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond and may not be fully saturated with hydrogen atoms. An example is ethene (C2H4), which contains a carbon-carbon double bond.

• Catenation Property of Carbon: Carbon exhibits the property of catenation, which is the ability of an element to form covalent bonds with other atoms of the same element to form long chains or rings. This property is unique to carbon due to its small atomic size, intermediate electronegativity, and ability to form stable covalent bonds with itself through sp3 hybridization. Carbon atoms can form single, double, or triple bonds with each other, allowing for the formation of a wide variety of organic compounds with diverse structures and properties.

• Element A Burning with Golden Flame in Air and Reacting with Element B:

  • Element A is sodium (Na).
  • Element B with atomic number 17 is chlorine (Cl).
  • Product C is sodium chloride (NaCl).
  • Aqueous solution of C on electrolysis gives compound D, which is sodium hydroxide (NaOH), and liberates hydrogen gas (H2).
  • Reactions:
    • 2Na(s) + Cl2(g) → 2NaCl(s)
    • 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g)

• Element A Burning with Golden Flame in Air and Reacting with Element B:

  • Element A is sodium (Na).
  • Element B with atomic number 17 is chlorine (Cl).
  • Product C is sodium chloride (NaCl).
  • Aqueous solution of C on electrolysis gives compound D, which is sodium hydroxide (NaOH), and liberates hydrogen gas (H2).
  • Reactions:
    • 2Na(s) + Cl2(g) → 2NaCl(s)
    • 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g)

• Characteristics of a period include:

  • Elements in the same period have the same number of electron shells.
  • The number of valence electrons increases across a period from left to right.
  • Chemical properties of elements within a period gradually change as one moves across the periodic table.

• Three points of difference between Mendeleev's Periodic Table and the Modern Periodic Table are:

  • Mendeleev's table was based on increasing atomic mass, while the modern periodic table is based on increasing atomic number.
  • Mendeleev left gaps in his table for undiscovered elements, while the modern table does not have gaps and accommodates all known elements.
  • Mendeleev's table did not accurately predict the properties of all elements, while the modern table provides a more accurate representation of element properties based on atomic structure and periodic trends.

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