Chapter 2 - Water Flashcards
(19 cards)
Cells are mostly what percent water?
~70% Water
4 Important Facts About Water
SmallStrongly PolarStrong Covalent BondsTetrahedral Charge Distribution.
What is a hydrogen bond?
Electrostatic connection between a covalently bonded hydrogen atom (with its partial positive charge) and a covalently bonded oxygen or nitrogen atom (with its partial negative charge). H-Bonds are continuously breaking and forming again.
What is cohesion?
Water molecules sticking together.Water crawls up because of capillarity caused by cohesion to itself and adhesion to the surface. This helps plants pull water up.
What is adhesion?
Water molecules sticking to wet surfaces.Water crawls up because of capillarity caused by cohesion to itself and adhesion to the surface. This helps plants pull water up.
Surface tension?
Strong cohesion between water molecules. At the surface of water the H bonds form a skin.
Why is water a tetrahedral?
Two corners are positively charged and two are negatively charged.
Moderation of Temperature
Heat is molecular motion. Water resists motion because they tend to stick together. Takes more heat to raise the temperature of water than to raise the temperature of most other things.
Ice
Each molecule of water has four ways to bond to other water molecules. Usually it doesn’t. Unless its ice. Each molecule bonds to another and this makes it expand.
The expansion of ice makes it less dense than water so ice floats.
Solutions. Solvent. Solute
One kind of molecule (solute) disperses in a liquid made of another molecule (solvent; usually water). Solute molecules never settle out of the solvent.
What bonds can be dissolved in water?
Ionic and Weak bonds. Covalent bonds can’t be.
How does water dissolve?
It doesn’t break up the molecules in a substance when it dissolves them - it separates them from each other. Only the weak bonds between the molecules are broken.
They stick to the water molecules instead of each other.
What is concentration?
Concentration of a solution means the number of atoms per unit of water. Moles/Liter (molarity)
What is a hydration shell?
Molecules that are dissolved in water are surrounded by a hydration shell.
It’s a skin of water molecules with their positive or negative ends contacting the solute.
What is hydrophilic?
Hydrophilic substances like water. They go into a solution rapidly. e.g. Polar Molecules
What is hydrophobic?
Hydrophobic hates water. Nonpolar molecules. Oils.
What is an acid?
Any solute molecule that increases H+ ions in water. Therefore low OH-. Lower end of the pH scale.
What is a base?
Any solute molecules that increases OH- ions in water is a base. Therefore higher H+. Higher end of the pH scale.
What is the pH scale
Measure of H+ or OH- ions in a solution.
