Water Flashcards
Why is water polar?
H20 has a covalent bond - electrons shared between hydrogen and oxygen atoms
Oxygen is more electronegative than hydrogen, so hydrogen electrons are drawn more closely to the oxygen region
More electrons surrounding the oxygen region results in a slightly negative charge
Less electrons surrounding the hydrogen region results in a slightly positive charge
How does water’s polarity affect its ability as a solvent?
Ionic or polar compounds (which are hydrophilic) enters water
Many smaller water molecules surround one molecule of the solute
Negatively charged poles of the water are attracted to positive poles of the solvent and vice versa.
Define: hydrophilic and hydrophobic
Hydrophilic: dissolves in water (eg. Ionic and polar compounds)
Hydrophobic: does not dissolve in water (eg. non polar substances)
Describe how NaCl (table salt) dissolves in water
When NaCl (an ionic solute) enters waters it separates into positive sodium ions, which are attracted to the negative pole of water; and negative chloride ions, which are attracted to the positive pole of water
Define: cohesion
Water molecules sticking to other water molecules, like in a water droplet
Explain how cohesion and polarity are related
Cohesion is due to polarity
The positive pole (hydrogen) of one molecule is attracted to the negative pole (oxygen) of another electron, forming a hydrogen bond
This causes water molecules to stick together
Why does water expand as a solid, in terms of hydrogen bonds?
In water, there is enough energy to break hydrogen bonds so the can move closer more freely
In ice, there is not enough energy to break hydrogen bonds (because it’s cold) so atoms will be arranged in a lattice and will take up more space than a liquid
Explain surface tension
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Water is polar: what does this mean?
One side of the molecule has a slightly positive charge and the other side has a slightly negative charge
