CHEM 1202 Lecture 2- Compounds, elements and mixtures and physical and chemical changes.

General Chemistry Overview

• Instructor: Dr. Sue Pyke

• Location: Room 3306, Physical Sciences Building

• Email: susan.pyke@flinders.edu.au

• Course Code: CHEM1201

Introduction to Chemistry

• Definition: Chemistry is the science that investigates matter and its changes.

• Chemicals: Make up matter.

Mixtures

• contain more than one compound or element.

• Can be separated into constituent parts by physical means.

Types of Matter

Pure Substances

• Elements: Cannot be broken down into simpler components; consist of one type of atom (e.g., silicon (Si), lead (Pb)).

• Compounds: composed of two or more different types of atoms in fixed proportions (e.g., carbon monoxide (CO), carbon dioxide (CO2), and sodium chloride (NaCl).

Mixtures

• Definition: Composed of more than one type of element and/or compound in variable proportions.

• Homogeneous Mixture: Composition consistent throughout (e.g. swimming pool water).

• Heterogeneous Mixture: Composition varies throughout (e.g. chicken noodle soup).

Physical States of Matter

Elements

• States: Solid, Liquid, Gas.

• Can mix elements in different states to create mixtures.

Separation of Mixtures

Techniques

• Liquid-Liquid Separation: Based on boiling point differences.

• Liquid-Solid Separation: Based on solubility differences.

• Physical Properties: Solubility is a key physical characteristic.

Physical Changes

• Definition: Change in physical state that does not alter chemical composition (e.g. boiling or freezing of water).

• Properties: Boiling point and melting point are examples of physical properties.

Chemical Changes

• Definition: Occurs when the composition of the material changes (e.g. rusting).

• Example Reaction: 4Fe + 3O2 → 2Fe2O3 (Formation of iron oxide).

Measurement and Units

• Significance: Measuring quantities is crucial in chemistry; consistency and inclusion of units are vital.

• S.I. Units:

  • Length: Metre (m)

  • Mass: Kilogram (kg)

  • Time: Second (s)

  • Temperature: Kelvin (K)

  • Amount of Substance: Mole (mol)

Conclusions from Demonstrations

• Phase Changes:

  • H2O(s) → H2O(l): Melting

  • N2(l) → N2(g): Vaporization/Evaporation/Boiling

  • CO2(s) → CO2(g): Sublimation

• Importance of Measurement: Units change the meaning (e.g. 5 kg vs. 5 g)

Understanding Density

• Definition: Density of a substance describes how much mass occupies a given volume.

• Comparative Density: Knowing density helps identify which substance is heavier in the same space.

• Density Formula: Density = mass/volume

Understanding Chemistry

• Concept: Connecting various pieces of information to form a clear understanding of the subject.