Unit 1: Foundation and Fundamentals

Unit 1: Foundation and Fundamentals

Teaching Hours: 2 hours

1. General Introduction of Chemistry

• Chemistry: Chemistry is the branch of science that deals with the study of the composition, structure, properties, and changes of matter.
• It explains how substances interact, combine, and change to form new substances.
• Chemistry connects various branches of science like biology, physics, geology, and environmental science.

2. Importance and Scope of Chemistry

Chemistry has immense importance and scope in various fields:

• Medicine: Chemistry helps in the development of pharmaceuticals, vaccines, and diagnostic tools.
• Industry: Industrial applications include manufacturing chemicals, plastics, metals, and energy sources.
• Agriculture: Chemistry aids in the production of fertilizers, pesticides, and improving crop yields.
• Environmental Science: Chemistry is crucial for understanding pollution, its prevention, and devising methods for environmental conservation.
• Everyday Life: Chemistry governs the composition of the air we breathe, the food we eat, and the products we use in daily life.

3. Basic Concepts of Chemistry

• Atoms: The smallest unit of an element that retains its chemical properties. They are the building blocks of matter.

  • Atoms consist of protons, neutrons, and electrons.
  • Protons and neutrons form the nucleus, while electrons orbit the nucleus.

• Molecules: Two or more atoms chemically bonded together.

  • Example: H₂O (Water), CO₂ (Carbon Dioxide)

• Relative Masses of Atoms and Molecules:

  • The mass of an atom is measured relative to the mass of a standard atom, usually carbon-12.
  • The relative atomic mass (or atomic weight) of an element is the weighted average mass of all isotopes of that element.
  • Molecular Mass: The sum of the relative atomic masses of all the atoms in a molecule.

• Atomic Mass Unit (amu): A unit of mass used to express atomic and molecular masses.

  • 1 amu = 1/12th the mass of a carbon-12 atom.
  • Example: Hydrogen has a mass of approximately 1 amu, and carbon has a mass of 12 amu.

• Radicals: A radical (or free radical) is an atom, molecule, or ion that has an unpaired valence electron.

  • Radicals are highly reactive.
  • Example: Hydroxyl radical (OH•), Methyl radical (CH₃•).

• Molecular Formula: The molecular formula shows the exact number of atoms of each element in a molecule.

  • Example: Glucose's molecular formula is C₆H₁₂O₆, which means it contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

• Empirical Formula: The empirical formula represents the simplest whole-number ratio of the atoms in a compound.

  • Example: The empirical formula of glucose (C₆H₁₂O₆) is CH₂O.

4. Percentage Composition from Molecular Formula

The percentage composition of a compound refers to the percentage by mass of each element in the compound.

To calculate the percentage composition:

1. Find the molecular mass of the compound by summing the atomic masses of all the atoms present in the molecular formula.
2. For each element, divide the mass contributed by that element (atomic mass × number of atoms) by the total molecular mass.
3. Multiply by 100 to get the percentage.

Example: For water (H₂O):

• Atomic masses: H = 1 amu, O = 16 amu
• Molecular mass of H₂O = 2(1) + 16 = 18 amu
• Percentage of H = (2/18) × 100 = 11.11%
• Percentage of O = (16/18) × 100 = 88.89%

Thus, water is composed of approximately 11.11% hydrogen and 88.89% oxygen by mass.