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Understanding the Properties of Water
Introduction to Water
- Water covers nearly three-quarters of our planet and exists in solid, liquid, and gaseous states. Life on Earth began in water and evolved for over three billion years before moving onto land. Even terrestrial species remain closely linked to water.
Chemical Properties of Water
- The session will explore the properties of water.
- Chemical properties relate to changes in composition when substances react. Water reacts with many compounds, including acidic oxides, basic oxides, metals, non-metals, and salts. Its pH is neutral at 7, indicating it is neither acidic nor basic.
Molecular Structure of Water
- A water molecule consists of two hydrogen atoms and one oxygen atom connected by covalent bonds. In a 2D representation, the molecules form a "V" shape with a 104.5-degree angle between the hydrogens; in 3D, they create a tetrahedral structure.
- Water is a polar molecule: oxygen acts as the negative pole while hydrogen atoms represent the positive pole. When multiple water molecules interact, they bond through weak electrostatic attraction known as hydrogen bonding.
Physical Properties of Water
- Physical properties allow identification without altering composition: water is colorless (incolora), odorless (inodora), and tasteless (insípida). At one atmosphere pressure, it freezes at 0 degrees Celsius and boils at 100 degrees Celsius.
- Density measures mass per unit volume; at 4 degrees Celsius under one atmosphere pressure, water's density is 1 kg/L. At 0 degrees Celsius (ice), its density drops to 0.9 kg/L—explaining why ice floats on liquid water.
Surface Tension and Capillary Action
- Water has high surface tension due to intermolecular forces that minimize surface area; this allows lightweight objects like needles or leaves to float on its surface.
- This property also enables capillary action—allowing water to rise through plant roots due to molecular attraction.
Specific Heat Capacity