Water properties Water Quality/chemistry Water-the universal solvent Dissolved Oxygen Turbidity Acid/base Nitrogen cycle (ammonia, nitrite, nitrate) Phosphates & Eutrophication Hard and Soft water Conductivity of water Alkalinity Water Physical properties Water pressure & Pascal's principle Scuba diving & dissolved gasses at pressure Surface Tension Heat capacity Buoyancy & Archimedes principle Density & the water density anomaly Bernoulli’s principle

Fluid = gases & liquids Fluid = A fluid is a substance that easily and continually deforms (flows) under an applied force Pressure of a fluid (gas and liquid) is the sum of all collisions of the particles on the substance

1) Pascal’s Principle Pressure applied to fluid in a closed container is equally transmitted to all parts of the fluid and the container. Think toothpaste…

1) Applications of Pascal’s Principle… We use pascal’s principle a lot in things that need power… car jacks, car brakes, tractors & construction machines Under water, the weight/pressure of the water is a “squeeze” not a downward weight

2) Effect of pressure on dissolved gas

Summary: There are several problems associated with scuba 1) Pressure is crushing even a small distance under the water (pascal’s principle) 2) Breathing air that is under pressure makes you a soda can! a) blood dissolves more air with pressure b) coming up fast can cause bubbles in your veins = painful… and deadly

4) Remember “convection” Heat makes things expand and rise Cold makes things contract and sink If one place is hotter,… what will happen to the air above it and thus the wind?

4) The “Sea breeze”… that all coastal people know about.

5) Buoyancy Tankers are made of steel and weigh as much as 585,000 tons!!! They are 1500 ft long, 225 ft wide… and extend >50 ft into the water! How do they float?

5) The Buoyant Force is why… --- some things float and sink & --- why even things that sink feel lighter in water

5) Archimedes principle

5)Archimedes’ Principle Buoyant force = weight of fluid displaced

5) Archimedes Example

5) Archimedes principle: example

5) Archimedes Example 2 lb fish, displacing 2.5lbs of water 2 lb fish,

6) Water’s density anomaly

6) MOST things are denser as solids – lamp oil “ice” vs water “ice” Most things continue to shrink as they “freeze” so the solid form is denser than the liquid form H2O is the only compound we know of that expands when it freezes. Solid water takes up more space than the same mass of liquid water… so due to Archimedes principle… it floats. CAREFUL!!! – some of you have heard something I didn’t say! Liquid water still, in general, shrinks as it gets colder!!!!!!!!!!!!!!!!!!!

Water is unique!!!!! Ice has a density of 920 kg/m3

6) Ever heard of a lake “turning over?” 8 8 8 8

7) Bernoulli’s Principle The pressure of a fluid (gas or liquid) decreases as the fluid’s velocity increases.

7) Bernoulli’s Principle The pressure of a fluid (gas or liquid) decreases as the fluid’s velocity increases.

7) Does Bernoulli's principle apply to water too? Of course, it applies to all fluids (gas & liquids) Sharks especially use it to stay up… they normally sink if they stop moving.

Reminder: know them by name We have talked about three principles that describe some physical properties of water Can you match them with their correct property: Bernoulli Archimedes Pascal Buoyancy force is weight of displaced water Fast flowing water has less pressure than slow water Pressure is evenly distributed in all directions