Water is the medium of life.
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Essential idea: What is the most important molecule in the world?
Challenge: Can you justify why?
Support: think what we need to live
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2.2 Vocabulary
The cohesive nature of water gives it surface tension.
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Water is so cool
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Brain Break – what do these 5 words mean?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
2.2 Water
Brain Break – what do these 5 words mean?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
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Understandings, Application and Skills
2.2.Syllabus Reference
| Statement | Guidance |
2.2.U1 | Water molecules are polar and hydrogen bonds form between them. | |
2.2.U2 | Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. | Students should know at least one example of a benefit to living organisms of each property of water. Transparency of water and maximum density at 4°C do not need to be included. |
2.2.U3 | Substances can be hydrophilic or hydrophobic. | |
2.2.A1 | Comparison of the thermal properties of water with those of methane. | Comparison of the thermal properties of water and methane assists in the understanding of the significance of hydrogen bonding in water. |
2.2.A2 | Use of water as a coolant in sweat. | |
2.2.A3 | Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water. | |
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Water is important because:
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What is water made up of?
2.2.U1 Water molecules are polar and hydrogen bonds form between them.
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Why is water dipolar?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
The hydrogen atoms have a slightly positive charge
The oxygen atom has a
slightly negative charge
2.2 Water
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
2.2 Water
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
2.2 Water
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
The bonds are made and broken quickly as the molecules move, however the large numbers of bonds contribute to the stability of water
Partly positive hydrogen atoms of one water molecule are attracted to the partially negative oxygen of another water molecule
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What is cohesion?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Hydrogen bonding between water molecules produces high cohesion
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2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Cohesion of water molecules along a surface produces surface tension
Fishing spiders and pond skaters rely on surface tension to move across the surface of ponds
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Brain Break – what do these 5 words mean?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
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Challenge:
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Can you make a paperclip float?
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What is adhesion?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Water molecules sticking to non water, polar or charged surfaces is called adhesion
Adhesion helps water climb up the thin tubes of plants to the leaves
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Adhesion and cohesion move water in plant stems
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Together they cause capillary action
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2.2.U3 Substances can be hydrophilic or hydrophobic..
Polar Molecules Like Water
Lic
HydrophiLic
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This term is used to describe substances that are chemically attracted to water.
2.2.U3 Substances can be hydrophilic or hydrophobic..
( water loving )
hydrophilic
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This term is used to describe substances that are insoluble in water
2.2.U3 Substances can be hydrophilic or hydrophobic..
hydrophobic
( water fearing )
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What is a solvent?
2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.
Water is an excellent solvent
A wide range of substances dissolve in water
Water is attracted to and can surround ions or polar molecules (such as sugars and amino acids, dissolving them
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Water as a solvent
2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.
Blood and cytoplasm are mostly water as water is an excellent transport medium
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Transport of molecules in the blood
2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.
Fats
They are carried in blood inside lipoprotein complexes (in the plasma
Cholesterol
They are carried in blood in lipoprotein complexes (in the plasma)
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2.2.A3 Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.
Sodium Chloride
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What is specific heat capacity?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
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Brain Break – what do these 5 words mean?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
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What is latent heat of vaporization?
2.2.A2 Use of water as a coolant in sweat.
Water can evaporate below its boiling point (100C). This can be seen when we sweat.
The (thermal) energy is transferred to the gaseous state and acts as a coolant.
Ice is unusual because it is less dense than liquid water (most substances become more dense when they solidify from a liquid).
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Why is ice special?
2.2.U2 Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
This is because the spacing between hydrogen and oxygen becomes fixed as it cools.
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Cool facts
Extra Information
Ponds and lakes freeze from the top down and never freeze completely to the bottom
Many plants and fish therefore are not frozen and can live underneath the ice
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Water is transparent
Extra Information
Water is transparent simply because it does not absorb light in the visible spectrum, and all frequencies of coloured light are transmitted through.
Because water is transparent, light penetrates tissue and aquatic environments, important for photosynthesis.
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Water Recap
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2.2.A1 Comparison of the thermal properties of water with those of methane.
Methane
Boiling point -164oC
Water
Boiling point 100oC
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2.2.A1 Comparison of the thermal properties of water with those of methane.
| Methane | Water |
| | |
Formula | CH4 | H2O |
Molecular mass | 16 | 18 |
Bonding | Single covalent | |
Polarity | nonpolar | polar |
Density (g cm-3) | 0.46 | 1 |
Specific Heat Capacity (J g-1 oc-1) | 2.2 | 4.2 |
Latent heat of vapourisation (J g-1) | 760 | 2257 |
Melting point (oC) | -182 | 0 |
Boiling point (oC) | -160 | 100 |
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2.2.A1 Comparison of the thermal properties of water with those of methane.
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2.2.
Saturn's moon Titan has lakes containing methane, it rains methane and it's water is as hard as rock. So what is the difference between water and methane?
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Kahoot
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Quiz
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