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 a uniform appearance throughout. Example: water and sand.
Homogeneous Mixture: Has a uniform appearance throughout. Example: seawater.
Characteristics of Mixtures
- Components can be in any proportion.
- Components retain their properties.
- Components can be separated by physical methods.
Pure Substances
Pure substances have constant composition and properties. They can be elements or compounds.
Elements: Pure substances that cannot be decomposed into simpler substances by ordinary chemical processes.
Compounds: Pure substances formed by the chemical combination of two or more elements in definite proportions. Compounds can be decomposed into elements by chemical means.
Methods of Mixture Separation
- Magnetic Separation: Used to separate magnetic solids from non-magnetic ones.
- Filtration: Used to separate a solid from a liquid in which it is insoluble. Example: water and sand.
- Decantation: Used to separate two immiscible liquids. Example: oil and water.
- Crystallization: Used to separate a dissolved solid from a liquid by crystallizing the solute. Example: separating salt from saltwater.
- Distillation: Used to separate a liquid mixture based on the different boiling points of its components.
- Chromatography: Used to separate individual components of a mixture using a fluid.
- Extraction: Used to separate a solid dissolved in a liquid by using another liquid in which the solid is more soluble.
Atomic Theory
Early Atomic Theory
Early atomic theories were philosophical and lacked experimental basis. They proposed that everything is made of indivisible, eternal, and constantly moving particles called atoms, differing only in size, shape, and weight.
Dalton’s Atomic Theory
- Matter is made of indivisible atoms.
- Atoms are unchanged.
- Elements are formed by identical atoms with the same mass and properties.
- Atoms of different elements have different masses and properties.
- Compounds are formed by the combination of atoms from different elements.
- Atoms combine in simple whole number ratios to form compounds.
- Atoms are neither created nor destroyed in chemical reactions, only rearranged.
Plum Pudding Model (Thomson)
This model proposed that the atom is a positively charged sphere with embedded electrons to maintain neutrality. It explained electrification and ion formation but failed to explain atomic spectra and Rutherford’s experiment.