The Hydrosphere Water’s Unique Properties & The Water Cycle

What’s So Special About Water? Water affects all of the spheres on the Earth: *Hydrosphere Lithosphere Atmosphere Biosphere * For the purposes of your test, we will be focusing on just the hydrosphere. Water is one of the most common substances on Earth’s surface. The hydrosphere is the total amount of water on a planet. This means on the surface, underground, or in the atmosphere

The Basics: Earth’s Hydrosphere The hydrosphere accounts for approximately 70% of Earth’s surface. ~97% is undrinkable saltwater. …the remaining 3% is drinkable freshwater. ~77% of the drinkable freshwater is frozen in icecaps, glaciers, and icebergs. …the remaining 23% is not frozen. However, only ~1% of this unfrozen water is accessible by living organisms.

Water’s Unique Properties

Water’s “Unique” Properties Water is the only substance on Earth that exists as a solid, liquid, and a gas. Considered the “universal solvent” because so many other elements react with it. If a substance is hydrophilic, then it is attracted to water and tends to mix or dissolve in water. Ex. Water and milk are hydrophilic If a substance is hydrophobic, then it is repelled by water and cannot combine, mix, or dissolve in water. Ex. Oils and fats are hydrophobic

Water’s “Unique” Properties Water has properties that no other element on Earth has. These properties allow water to exist in all of the spheres and interact with all areas of life. Can you name the 4 spheres that water exists in? Water’s Unique Properties* Polarity Cohesion Adhesion High surface tension Density High specific heat High heat of vaporization * These are not all of water’s unique properties, but these are the ones you are responsible for understanding for the test.

Water’s Polarity Water is a bipolar substance because it possesses both a negative (O - ) charge and positive (H + ) charges. Due to water’s molecular structure of H + (2 hydrogens) and O - (oxygen), polarity allows it to continuously connect, or “bond,” to each other—as well as other substances that have negative charges that want to bond with positive charges. Remember, opposites attract!

Water’s Property of Cohesion Water’s polarity also contributes to its cohesion, which is when particles of the same substance stick, or unite, together. This bonding is called a hydrogen bond and requires a large amount of energy. This is why water is considered “sticky,” because the particles ‘stick’ to one another. Essentially, water attracts water

Water’s Property of Adhesion Much like cohesion, water also has the property of adhesion. Adhesion is when the particles of a substance unite, or bond, with the particles of a different substance. Glue is a good example of an adhesive substance. This is why water sticks to many other substances, such as your skin.

Water’s High Surface Tension Due to water’s property of cohesion and adhesion, water has high surface tension. Surface tension is when the surface of a liquid allows it to resist an external force. When the weight of an external force is GREATER than the surface tension of water, the bond will break.

Water’s Density If something is made up of molecules, then it has density. Density is the weight/mass for a chosen volume. Water density depends on temperature. Ice is about 90% that of water, which is why ~10% of ice is above water (iceberg). If ice was more dense than water, what would happen?

Water’s High Specific Heat Specific heat is the amount of heat, or energy, it takes for 1 gram of a substance to absorb or lose in order to change its temperature by 1 degree Celsius. Water has a very high specific heat rating of Joules, which is x4 the amount it takes for air! Oceans cool slower than land does because of water’s high specific heat. This explains why the ocean is one of the world’s best habitats for living organisms that cannot survive in sudden temperature changes.

Water’s High Heat of Vaporization Heat of Vaporization is the energy required to transform the quantity of a given substance from a liquid to a gas. Water’s “boiling point” is based on its Heat of Vaporization Water’s boiling point is 100 degrees Celsius, or 212 degrees Fahrenheit. What are some examples of heat of vaporization? Evaporation, boiling water, and sweating

The Water Cycle The Water Cycle is made possible by the temperature of the atmosphere—or most importantly, the Sun! Directly relates to evaporation and condensation

Evaporation Evaporation is the process by which a liquid state changes into a gaseous/vapor state due to temperature or pressure. LIQUID  GAS Water begins to evaporate at its freezing point of 0 degrees Celsius, or 32 degrees Fahrenheit. As evaporation occurs, H 2 O vapor is released into the air, thus cooling down the area it came from. Transpiration is the evaporation of water in plants leaves, stems, etc. when they have enough hydration.

Condensation Condensation is the process by which gas, or vapor, in the air changes into a liquid, or water. The accumulation of vapor is called a cloud. In a cloud, vapor changes back to water. Once the droplets become too heavy, precipitation occurs. Fog is a low-lying cloud and forms when condensed water vapor is “stuck” in the air due to the difference in air temperature and the dewpoint. Mist is a term for “fog you can see through.” This means that mist is not as dense as fog. Haze is when large quantities of vapor adhere to dry particles in the air (smoke, dust, sulfur, etc.)

Precipitation Precipitation is the process by which water is released from the clouds in the form of rain, freezing rain, sleet, snow, or hail. Precipitation is the primary system for the delivery of atmospheric water to Earth. Precipitation is when droplets become too heavy for the cloud to keep bonded. The droplets become too heavy due to… Particles in the air (rain is NOT pure “clean water”!) Gravity Air updrafts Atmospheric winds

Runoff Runoff occurs both on the surface and underground. The process of underground runoff is through infiltration. The underground runoff creates large quantities of water beneath the surface called aquifers, which is where a majority of the water we use come from. About 1/3 of precipitation is surface runoff that returns to the ocean. The remaining 2/3 is evaporated, transpired, or infiltrated as groundwater.

The Phases of Water We know that water is the only substance on Earth that can turn into a solid, liquid, and gas. But do you know what it is called when water changes form?

The Phases of Water Melting: When H 2 O turns from a solid to a liquid. Occurs from a change in pressure/temperature. Sublimation: When H 2 O turns from a solid to a gas while skipping the liquid form. Requires energy. (chemical reaction, heat, etc.) Freezing: When H 2 O turns from a liquid to a solid. Occurs from a change in pressure/temperature. Evaporation / Boiling: When H 2 O turns from a liquid to a gas. Requires energy. Deposition, or Desublimation: When H 2 O turns from a gas to a solid while skipping the liquid form. Occurs from a change in pressure/temperature. Condensation: When H 2 O turns from a gas to a liquid. Requires energy.

Examples of Water’s Phase Changes Melting (S  L): A solid ice cube melting into a puddle of water Sublimation (S  G): When snow turns to vapor on the top of Mt. Everest Freezing (L  S): Freezing the water in an ice cube tray to make solid ice cubes Evaporation (L  G): Water from the ocean evaporating into the clouds as vapor Deposition (G  S): Frost that accumulates on the grass early in the morning Condensation (G  L): Water forming around the bottom of a glass of iced tea