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Notes on 'Water'

Notes on 'Water'

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Water Slides Water Slides Presentation Transcript

  • PS 0266 SCIENCE I WEEK 3 WATER
  • Quotes of the Day
    • "We wait all these years to find someone who understands us, I thought, someone who accepts us as we are, someone with a wizard's power to melt stone to sunlight, who can bring us happiness in spite of trials, who can face our dragons in the night, who can transform us into the soul we choose to be. Just yesterday I found that magical Someone is the face we see in the mirror: It's us and our homemade masks." Richard Bach
  • Objectives
    • State the properties of water chemically and physically
    • Identify the states of water
    • Define the term ‘evaporation’, ‘boiling’, ‘condensation’, ‘freezing’ & melting
    • Draw a water cycle
    • Identify the factors that affect the amount of solid dissolves in water as a solvent
  • Overview of today’s lecture
    • Properties of water
    • Water’s Physical Properties
    • Water on and in the Earth
    • The states of water
    • Changes in states of water
    • The water cycle
    • Water as a solvent
    • Soft water & Hard water
  • Properties of Water
    • Pure water is virtually colourless, tasteless and it has no smell.
    • Water’s chemical description is H2O.
    • One atom of oxygen bound to two atoms of hydrogen.
  • Properties of Water
    • The hydrogen atoms are “attached” to one side of the oxygen atom.
    • Resulting in a water molecule having a positive charge on the side where the hydrogen atoms are negatively charged on the other side.
    • Water molecules tend to attract each other, making it kind of “sticky”.
  • Properties of Water
    • All these water molecules attracting each other mean they tend to clump together.
    • This is why water drops are,
    • in fact, drops!
    • Water’s original shape
    • is a perfect sphere but due
    • to gravity, it looks like a tear
    • when it drops.
    • Pure water has a neutral pH of 7.
  • Water’s Physical Properties
    • Water is unique, it is the only natural substance that is found in all 3 states: liquid, solid and gas.
    • Earth’s water is constantly interacting, changing and in movement.
    • Water freezes at 32° Fahrenheit (F) and boils at 212 ° F (at sea level, but 186.4° at 14,000 feet).
  • Water’s Physical Properties
    • Water is unusual in that the solid form, ice, is less dense than the liquid form, which is why ice floats.
    • Water has a high specific heat index.
    • The high specific heat index of water also helps regulate the rate at which air changes temperature.
    • Water has a very high surface tension.
  • Water on and in the Earth (http://ga.water.sgs.gov/edu/earthwherewater.html)
  • How much of Earth’s water is usable by humans?
  • The Three States of Water
    • The water that comes out of our taps is a liquid. We say it is water in the liquid state.
    • If we put water in a freezer, it changes to ice. Ice is a solid. Ice is water in the solid state.
    • If we boil water for a long time, it disappears. It changes to steam. Steam is a gas. Steam is water in the gaseous state.
  • Changes in States of Water
    • When heated, water gains heat. When cooled, water loses heat.
    • Heat energy can change water from one state to another. These changes are called:
    • Freezing.
    • Melting,
    • Boiling,
    • Evaporation, and
    • Condensation.
  • Freezing
    • When water becomes cold, it loses heat. It changes from the liquid state to the solid state. At 0°C , water changes to ice.
  • Melting
    • When water changes from solid to liquid, we say it is melting. Ice melts at 0°C
  • Boiling
    • When we heat water, it becomes hot. It will start to boil at 100°C. At this temperature, water bubbles and changes to steam. Steam is a gas.
  • Evaporation
    • Water does not have to boil to change into a gas.
    • This change can happen at any time and at any temperature.
  • Condensation
    • When water vapour in the air touches something cold, it changes into liquid water.
    • It also happens when water boils. When steam touches cold air, we can see a cloud, made up of tiny drops of water.
  • Changes in States of Water
  • The Water Cycle
  • Water as a Solvent
    • When sugar is put into the water, it dissolves.
    • When sugar dissolves in water, we get a solution.
    • Things dissolve in water are soluble.
    • Water is a universal solvent.
    • Things that are not dissolved in water are insoluble.
    • Gases also dissolved in water.
  • Water as a Solvent
    • More solid dissolves with:
    • More water and
    • At a higher temperature.
  • Soft Water & Hard Water
    • Soft water is the term used to describe types of water that contain few or no calcium or magnesium ions.
    • Usually comes from peat or igneous rock sources such as granite or sandstone.
  • Hard Water
    • Has a high mineral content.
    • Usually consists of high levels of metal ions such as Ca and Mg in the form of carbonates or bicarbonates or sulfates.
    • To determine if water is hard or soft, use the lather/froth test.
    • If the water is very soft, soap will tend to lather up easily when agitated.
    • Toothpaste will also not froth well in hard water.
  • Recap Changes in States of Water The States of Water Water on and in the Earth Water’s Physical Properties Properties of water
  • Recap Soft Water & Hard Water Water as a Solvent The Water Cycle
  • Next Week…
    • Week 7 Magnets
    • The End