Introduction to Chemistry of Water

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Questions and Answers

What does cohesion in water primarily facilitate?

Water's boiling point

Water's high specific heat

Capillary action in plants (correct)

Movement of groundwater

Which property of water is responsible for creating a 'skin' on its surface?

Viscosity

Adhesion

Surface tension (correct)

Density

What percentage of Earth's water is fresh and accessible for human use?

0.1%

10%

1% (correct)

Which of the following is a major cause of water pollution?

Chemical contaminants like pesticides Signup and view all the answers

At what pH range do most aquatic organisms thrive?

6 to 8 Signup and view all the answers

What is the purpose of the turbidity test in water analysis?

To assess the clarity of water Signup and view all the answers

During coagulation in water treatment, which substance is commonly added?

Aluminum sulfate (alum) Signup and view all the answers

Which of the following is NOT a biological pollutant?

Pesticides Signup and view all the answers

What is the molecular formula of water?

H₂O Signup and view all the answers

Which property of water is primarily responsible for its high boiling and melting points compared to similar molecules?

Hydrogen bonding Signup and view all the answers

What effect does the polarity of water have on its molecular structure?

Leads to an uneven distribution of electrons Signup and view all the answers

Which state of water has the highest density under normal conditions?

Liquid Signup and view all the answers

At what temperature does water freeze under standard atmospheric pressure?

0 °C Signup and view all the answers

What characteristic of water allows it to absorb significant heat without a great change in temperature?

High specific heat Signup and view all the answers

Which of the following correctly describes the density of ice compared to liquid water?

Ice is less dense than liquid water Signup and view all the answers

What is the pH level of pure water and what does it indicate?

7; neutral solution Signup and view all the answers

Study Notes

Introduction to Chemistry of Water

Water is crucial for life and regulates Earth's temperature.
Water is a universal solvent with multiple applications in various sectors (industrial, agricultural, domestic).
Water has renewable energy potential (hydropower and steam).

Properties of Water: Structure

A water molecule (H₂O) consists of two hydrogen atoms covalently bonded to an oxygen atom.
Covalent bonds hold the molecule together.
Other bond types exist including ionic, metal, and hydrogen bonds.

Properties of Water: Polarity

Water molecules are polar due to unequal electron sharing in polar covalent bonds.
This creates partial positive charges on hydrogen atoms and a partial negative charge on the oxygen atom.
Polarity is due to the uneven distribution of electrons.

Properties of Water: Physical Properties

Water exists in three states: solid (ice), liquid, and gas (water vapor).
Hydrogen bonds are responsible for water's high boiling and melting points, compared to similar molecules.
The density of ice is lower than liquid water, making ice float, a crucial property of aquatic life.

Properties of Water: Density

Solid ice (0.9167 g/mL) is less dense than liquid water (0.9998 g/mL).
Water vapor density (~0.0006 g/mL) varies with temperature and pressure.

Properties of Water: Additional Properties

Molecular formula: H₂O
Molecular weight: 18.0160 g/mol
Molecular geometry: Bent (V-shaped)
Boiling point: 100 °C
Freezing point: 0 °C
Density at 4°C: 1 g/mL or 1000 kg/m³
Polarity: Polar
pH: 7

Properties of Water: Key Properties

High specific heat: Water absorbs and retains heat effectively, maintaining stable temperatures in environments.
High heat of vaporization: A large amount of energy is needed to convert water to vapor, which assists in cooling.
Adhesion and cohesion: Water adheres to other surfaces and cohere, facilitating processes like capillary action in plants.
Surface tension: Water has a "skin" due to cohesive forces, facilitating movement for small organisms.

Water and Environment: Water Pollution

Only 1% of Earth's water is fresh and accessible.
Saline water (97%) is mostly in oceans, unsuitable for drinking.
Freshwater (2%) is mostly in ice caps and glaciers, largely inaccessible.
Accessible freshwater is a minute portion (less than 1%) for humans.

Water Pollution: Causes

Chemical contaminants (pesticides, heavy metals)
Biological pollutants (e.g., E. coli)
Radioactive pollutants (nuclear waste)

Water Pollution: Impacts

Health risks
Reduced water quality
Ecological damage

Water Analysis: Methods

Temperature Testing: Measures the rate of biochemical reactions and oxygen retention.
pH Testing: Measures the acidity of water. Most aquatic life thrives in a pH range of 6 to 8.
Dissolved Oxygen Test: Measures the amount of oxygen dissolved in water, essential for aquatic life respiration.
Chloride Test: Measures chloride levels in water, influenced by minerals and industrial pollution.
Turbidity Test: Measures suspended particles (water clarity), high turbidity impacts photosynthesis and water temperature.
Metal Test: Detects harmful heavy metals (Lead, Mercury, Arsenic, Cadmium).

Water Treatment: Processes

Coagulation: Adding aluminum sulfate or polymers to cause particles to clump (flocculate).
Sedimentation: Allowing flocs to settle to the bottom of basins.
Filtration: Removing particulate matter by passing water through filters (gravel, sand, activated carbon).
Disinfection: Adding disinfectants (e.g., chlorine) to kill microorganisms.
pH Correction: Adjusting pH with lime to stabilize soft water.

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Description

This quiz explores the essential properties of water, covering its molecular structure, polarity, and physical states. Understand the significance of water in various sectors and its role in sustaining life on Earth. Dive into the molecular interactions that make water unique.