water notes only
TRANSCRIPT
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Water as a molecule
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Water as a molecule
• Water has a polar covalent bond
• The electrons are shared unevenly
• Oxygen is stronger, so it pulls the electrons to itself
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Water as a molecule
• Water is a polar molecule• One part is more negative,
and one part is more positive
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Water as a molecule
• The polar parts of water will connect, giving water special properties
**You will see these properties in lab**
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Vocabulary
• POLAR – a molecule that has an uneven distribution of electrons
• POLAR - una molécula que tiene una distribución desigual de los electrones
• POLAR - 的分子,具有電子的不均勻分佈
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Vocabulary
• Cohesion – when similar things stick to each other (ex: water molecule to other water molecules to form drops)
• Adhesion – When different things stick to each other (ex: water sticks to grass)
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Lab part 1
• Talk in lab group – record in notebook– What did you observe? – Explain why you saw what you did
• Share out – whole group– Many drops could fit on the penny than we
predicted– This happened because of cohesion. The water
molecules stuck to each other to allow more water to fit.
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Lab part 2
• Talk in lab group – record in notebook– What did you observe? – Explain why you saw what you did
• Share out – whole group– The paper clip could float on water. – This happened because of cohesion. The water
molecules stuck to each other to allow more water to fit.
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Lab part 3
• Question: How do different chemicals affect the surface tension of water?
• Safety!! – Wear goggles when handling chemicals
• Make sure to get your procedure approved BEFORE conducting your experiment
• Use a new pipette for each solution to avoid contamination (mixing the chemicals by accident)
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Vocabulary
• Nonpolar - a compound where electrons are shared equally. Areas of the compound are neutral.
• Hydrophobic – “scared of water” a substance that does not dissolve in water. Nonpolar substances are hydrophobic.
• Hydrophilic – “Water loving” a substance that will dissolve in water. All polar substances are hydrophilic
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Detergents (Soap)
• Micelle– Forms when hydrophobic ends clump together
• Detergent molecules have a polar end and a non polar end
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Detergents• Amphiphilic – has a polar and a nonpolar end.
Detergents have a hydrophobic end and a hydrophilic end.
The polar end will dissolve in water The nonpolar end will dissolve in oil
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Properties of water
• Cohesion – water sticks together• Resistance to temperature change – needs a
lot of energy to raise temperature• Density – solid ice floats in liquid water• Universal Solvent – can dissolve almost
anything
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How soap dissolves oil
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How soap dissolves oil
• Green head=hydrophillic, polar, dissolves in water
• Yellow tail – hydrophobic, nonpolar, dissolves oil
• LIKE DISSOLVES LIKE
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Quiz next week: Properties of water
• 4 properties from reading # 3.5• Solubility• Polar• Non-polar• Amphipathic• Experimental design– Controlling an experiment
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As you read…
Create definitions for the following terms• Solubility• Solute• Solvent• Homogeneous• Solution• Mixture
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Vocab
• Mixture - a system where 2 or more things are combined, but not chemically
• Solution – when 2 or more things are combined evenly
• Solubility – The amount of solute that can be dissolved by a solvent
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Vocab
• Homogeneous mixture – a mixture that is evenly mixed. (ex. CO2 bubbles in soda) AKA a solution
• Heterogeneous mixture – a mixture that is unevenly mixed. (ex. Sand in water)
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Vocab
• Solvent – the substance that dissolves the solute (often, it is water)
• Solute - the substance that is dissolved