I.6.1. Physical properties
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The characteristic attributes with a help of which a substance is recognized are called properties.
Properties can be physical and chemical.
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Physical properties are those attributes that refer to appearance or transformations that do not change the composition of the substance.
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Physical properties can be classified into:
1. Observable with the help of the sense organs:
- By sight: state of aggregation (solid, liquid, gas), color (colorless-without colour or colored), gloss (shine).
- By smell: odorless (has no smell), pleasant, irritating, specific smell (milk, chlorine, vinegar - we say they have a specific smell).
- By touch: plasticity, elasticity, soft (hardness), hard (hardness).
2. Measurable with the help of devices:
- Physical constants:
- Melting temperature (the temperature at which a solid substance begins to melt = Tt);
- Boiling temperature (the temperature at which a liquid begins to boil = Tv);
- Density
- Refractive index
- Solubility coefficient (shows how much substance dissolves in 100 g of water, at a certain temperature);
- Hardness (it is measured according to a scale of hardness from 1 to 10, called "Mohs Scale", where talc has 1 and diamond the highest hardness 10);
- Electrical and thermal conductivity (passage of electric current, respectively heat, without movement of substance).
