Understanding Chemical Elements, Compounds, and Mixtures
Matter and Its Classification
What is Matter?
Matter is anything that occupies space. It exists in nature as pure substances and mixtures.
Classification of Matter
Matter can be classified into two main categories:
- Pure Substances: Each pure substance has a fixed composition and a unique set of properties.
- Mixtures: Mixtures are composed of two or more pure substances.
Pure substances can be further categorized into elements and compounds, while mixtures can be homogeneous or heterogeneous.
Pure Substances
Elements
A
Read MoreScience Experiments and Lab Materials
Science Education
Questions for Teachers about Teaching Models
Teachers should consider the following questions when planning science lessons:
- Who will lead the teaching?
- When will specific knowledge be transmitted?
- What knowledge will be transmitted?
- What content will be conveyed?
- What methodology will be used to transmit knowledge?
Historical Methods of Teaching Science
- Evolutionary Method
- Biographical Method
Evolutionary Method
This method involves explaining a scientific subject or phenomenon by starting
Read MoreAtomic Structure, Bonding, and Properties of Matter
1. The Nuclear Model of the Atom
Democritus proposed the concept of atoms. J. Dalton’s atomic theory stated that atoms were indivisible and unchanged by chemical processes.
1.1 The Gold Foil Experiment
E. Rutherford bombarded a thin gold foil with alpha rays. He expected all particles to pass through uniformly. However, some particles were deflected, demonstrating that:
- The atom has a central core (nucleus) containing most of its mass, including protons.
- Electrons revolve in concentric circular orbits
Matter Transformation and Atomic Structure
Matter Transformation
Physical Process: A transformation where matter retains its composition, structure, and properties. For example, changes in state (solid, liquid, gas).
Chemical Process: A transformation where matter changes its composition, structure, and properties. The resulting substances are different from the initial ones. For example, burning wood.
Mixtures
A mixture is the combination of several pure substances that retain their original properties.
Heterogeneous Mixture: Does not have
Read MoreNatural Resources, Manufacturing & Environmental Management
Item 11: Natural Resources and Manufacturing
Natural Resources
Water, air, minerals, rocks, oil, natural gas, timber, and agricultural products are examples of natural resources.
Manufacturing
Key processes involve acids and bases under specific conditions (durable, accessible, abundant).
Classification of Resources
Resources are classified based on their durability:
- Inexhaustible: Air (separation of components by distillation, nitrate combination, electrical discharges, ozone), Water (desalination, potable
Alkali, Alkaline Earth, Earthy & Carbonoide Elements
Alkali Metals
The alkali metals, Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium, are in Group 1 of the periodic table. They are named for the alkalinity of their compounds. Due to their chemical activity, they are not found in a free state and comprise almost 5% of the Earth’s crust (especially Sodium and Potassium).
Properties
- Electronic configuration: ns1
- Low first ionization energy
- Low electronegativity, decreasing down the group
- Common oxidation state: +1
- Form ionic compounds
- Low melting