2024 F - SC102 - Ch1 - L1 - Org

Chapter 1: Units of Measurement for Physical & Chemical Change

1.1 Physical and Chemical Changes; Physical and Chemical Properties

• Physical Changes:

  • Do not alter the chemical composition of matter.

  • Example: Water boiling changes state from liquid to gas but consists of the same water molecules.

• Chemical Changes:

  • Alter the chemical composition of matter.

  • Atoms rearrange to transform original substances into different ones.

  • Example: Rusting of iron, represented as;Fe(s) + O2(g) → Fe2O3(s).

1.2 Energy: A Fundamental Part of Physical & Chemical Change

• Energy Forms:

  • Kinetic Energy: Energy associated with motion.

  • Potential Energy: Energy associated with position or composition.

  • Thermal Energy: Energy associated with temperature (related to positions of electrons and nuclei).

  • Chemical Energy: Potential energy related to the chemical bonds in a substance.

• Law of Conservation of Energy:

  • Energy is neither created nor destroyed; it only converts from one form to another.

• Examples of Energy Changes:

  • Chemical reactions may involve energy changes, such as exothermic reactions where chemical potential energy is converted to thermal energy.

  • Example reaction:C3H8(g) + 5 O2 → 3 CO2(g) + 4 H2O(l)ΔH = -2044 kJ mol-1 (indicates release of energy).

1.3 The Units of Measurement

• Importance of consistent units in scientific measurements.

1.4 The Reliability of a Measurement

• Discusses how to evaluate the accuracy and precision of measurements.

1.5 Solving Chemical Problems

• Introduces problem-solving methods and strategies in chemistry.

Properties Summary

• Physical Properties: Observed without changing the substance's composition.

  • Example: Mercury is liquid at room temperature.

• Chemical Properties: Show behavior during a chemical change.

  • Example: Hydrogen reacts explosively with oxygen.