The Amazing World of Solutes, Solvents, and Solutions
1. Mixtures
1. Uniform Mixtures: Components evenly distributed (e.g., sugar/salt in water, ORS).
2. Non-Uniform Mixtures: Components not evenly distributed (e.g., chalk, sand, or sawdust in water).
2. Solutions
1. Solution: Uniform mixture of solute (dissolved substance) and solvent (dissolving medium).
Example: Sugar (solute) + Water (solvent) = Solution.
2. Air: Gaseous solution with nitrogen (solvent) and oxygen, argon, etc. (solutes).
3. Saturated Solution: Cannot dissolve more solute at a given temperature.
4. Unsaturated Solution: Can dissolve more solute.
5. Dilute Solution: Less solute;
6. Concentrated Solution: More solute.
3. Solubility
Solubility: Maximum solute dissolved in 100 ml solvent at a specific temperature.
Solids: Solubility increases with temperature (e.g., baking soda in water).
Gases: Solubility decreases with temperature (e.g., oxygen in water).
Water as Solvent: Dissolves many substances (e.g., sugar, salt) but not oil due to molecular attraction.
4. Density
1. Density: Mass per unit volume (Density = Mass/Volume).
SI Unit: kg/m³; others: g/cm³, g/mL.
Example: Aluminum (27 g, 10 cm³) has density 2.7 g/cm³.
2. Relative Density: Density of substance ÷ Density of water (1 g/cm³).
3. Relative Density: Objects with density < liquid float; > liquid sink.
- Example: Oil (0.91 g/cm³) floats on water; ice (0.92 g/cm³) floats due to lower density.
5. Measuring Mass and Volume
Mass: Measured in g/kg using a weighing balance.
- Activity: Use digital balance, tare to zero, measure object (e.g., stone = 16.4 g).
Volume:
Liquids: Use measuring cylinder, read at meniscus bottom (water) or top (colored liquids).
Regular Solids: Volume = length × width × height.
Irregular Solids: Displacement method (e.g., 50 mL water rises to 55 mL, volume = 5 cm³).
6. Effect of Temperature and Pressure
1. Temperature:
- Heating increases volume, decreases density (e.g., hot air balloons rise).
- Cooling decreases volume, increases density.
2. Pressure:
- Gases: Higher pressure decreases volume, increases density.
- Liquids/Solids: Minimal effect due to incompressible nature.
7. Applications
Floating: Bamboo/wood rafts float due to low density.
Medicinal Solutions: Ayurveda uses water, oils, milk as solvents.
Traditional Salt Making: Ningel village, Manipur, makes salt cakes from boiled salty water.
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