CHEM Chapter 2

States of Matter

• Solid

  • Fixed shape and volume.

  • Can be hard or soft, rigid or flexible.

• Liquid

  • Varying shape, conforming to the container shape.

  • Fixed volume with an upper surface.

• Gas

  • No fixed shape or volume.

  • No upper surface.

Physical States of Matter

• Solid: Particles are close together and organized.

• Liquid: Particles are close but disorganized.

• Gas: Particles are far apart and disorganized.

Definitions for Components of Matter

• Element:

  • Simplest substance (e.g., Cu, O2).

  • Cannot be broken down by chemical means.

• Molecule:

  • Structure consisting of two or more bound atoms (e.g., O2, NH3).

• Compound:

  • Substance made from two or more elements in a fixed ratio (e.g., NaCl).

  • Retains properties of original elements until separated by chemical means.

• Mixture:

  • Group of elements or compounds that are physically mixed.

  • Retains identities and can be separated by physical means.

Properties of Sodium, Chlorine, and Sodium Chloride

Mixtures: Heterogeneous and Homogeneous

• Heterogeneous Mixtures:

  • Visible boundaries, non-uniform composition.

• Homogeneous Mixtures (Solutions):

  • No visible boundaries, uniform composition.

Classification of Matter

• Matter:

  • Can be separated into mixtures and pure substances.

  • Mixtures can be homogeneous or heterogeneous. Pure substances are either elements or compounds.

Dalton’s Atomic Theory of Matter

• Postulates:

  1. Matter is made up of atoms.

  2. All atoms of an element are identical in mass and differentiate from other elements.

  3. Compounds form by chemical combinations of atoms in fixed ratios.

  4. During a reaction, atoms are not created or destroyed.

Laws of Composition

• Law of Definite Composition:

  • Compounds consist of the same elements in the same fraction by mass.

• Law of Mass Conservation:

  • Total mass remains constant during chemical reactions.

• Law of Multiple Proportions:

  • Elements combine in ratios of small whole numbers.

Cathode Rays and Atomic Structure

• Cathode rays indicate the presence of charged particles; electrons were discovered having a negative charge.

• Thomson's Model:

  • Atoms consist of negatively charged electrons in a positively charged matrix (Plum Pudding Model).

Millikan’s Oil-Drop Experiment

• Determined charge and mass of the electron.

  • Charge of electron: -1.602 x 10^-19 C.

  • Mass of electron: 9.109 x 10^-28 g.

Rutherford's Gold Foil Experiment

• Discovered atomic nucleus; identified that atoms consist mostly of empty space, with a dense center (nucleus) holding most mass.

Atomic Features

• An atom consists of:

  • Electrons (negatively charged) orbiting the nucleus.

  • A nucleus composed of protons (positively charged) and neutrons (neutral).

Subatomic Particles and Atomic Mass

• Table of Subatomic Particles:| Name | Symbol | Charge | Mass (amu) | Location | |-----------|--------|--------|------------|------------| | Proton | p | +1 | 1.007276 | Nucleus | | Neutron | n | 0 | 1.008665 | Nucleus | | Electron | e | -1 | <0.000549 | Outside nucleus |

Isotopes

• Isotopes: Atoms of the same element with different neutron counts, leading to different mass numbers.

• Isotopes can be stable or unstable (radioactive).

Chemical Bonds

• Ionic Bonds:

  • Formed by electron transfer (often between metals and nonmetals).

• Covalent Bonds:

  • Formed by sharing electrons between nonmetals.

Naming and Formulas for Compounds

• Principles:

  • Binary Compounds: Use prefixes to indicate the number of atoms.

  • Ternary Compounds: Involve polyatomic ions.

  • Acids: Recognize binary and ternary categories for naming.

Practice Questions

• Decide correct naming for compounds like PF5 and cobalt (III) oxide.

• Understand naming methods for hydrates and mixed salts, using prefixes and compound endings.