Chapter 3 The Chemistry of Water
Specific of water is?
1 cal/g/°C
What is mole, molecular wight, and molarity?
1. Mole: Amount of a substance that has a mass in grams numerically equivalent to its molecular weight in daltons 2. Molecular weight: Sum of weight of all atoms in a molecules (expressed in daltons) 3. Molarity: Number of moles of solute per liter of solution
List 2 major properties of water, and explain how the structure of water causes this property, and how this property benefits the biological world.
1. One major property of property is that it is cohesive and adhesive, cohesive meaning clinging water molecules to each other through hydrogen bonds, and adhesive means water molecules clinging to other molecules through hydrogen bonds. This helps in transporting water in plants. 2. When water freezes and becomes ice, ice floats because hydrogen bonds stabilize and keep the molecules further apart than molecules of liquid water. This benefits the biological world because ice can act as a heat insulator in a lake for life in water, and ice will not sink and freeze the entire lake, or sea.
What is a solution, solvent, solute, and aqueous solution?
1. Solution: a liquid that is a homogeneous mixture of 2 or more substances. 2. Solvent: dissolving agent of a solution 3. Substance dissolved in a solution Aqueous solution: solution in which water is the solvent.
The nutritional information on a cereal box shows that 1 serving of dry cereal has 200 kilo calories. If one were to burn 1 serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water of how many degrees Celsius?
10.0 °C
At what temperature is water at its densest?
4 °C
How many molecules of glycerol (C3H8O3) would be present in 1 L of a 1M glycerol solution?
6.02 x 10^23
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?
A hydrogen bond
Water's specific heat is mainly a consequence of the?
Absorption and release of heat when hydrogen bonds break and form
What happens as the crystal lattice of water form?
Each water molecule forms a maximum of 4 hydrogen bonds, which keeps water molecules further apart than they would be in the liquid state.
What do hydrogen bonds need to break and from?
Hydrogen bonds must absorb heat to break, and release energy to form.
Why does ice float in liquid water?
Hydrogen bonds stabilize and keep the molecules of ice further apart than the water molecules of liquid water
What is hydrophilic and hydrophobic?
Hydrophilic means the property of having an affinity for water, and hydrophobic is the property of not having an affinity for water.
Explain in detail why water is classified as a polar molecule.
In water, oxygen is more electronegative than hydrogen, so the electrons spend more time on oxygen. This leaves the oxygen with a partially negative charge, and hydrogen with a partially positive charge.
What is surface tension?
It is a measure of how difficult it is to stretch or break the surface of a liquid.
What is an acid?
It is a substance that increases the relative [H+] of a solution. It also removes OH- because it tends to combine with H+ to form water.
What is a buffer?
It is a substance that prevents large sudden changes in pH. They are combinations of H= donors and H=-acceptor forms of weak acids or bases.
What is a base?
It is a substance that reduces the relative [H+] of a solution. It may also alternately increase OH-.
What is specific heat?
It is the amount of heat that must be absorbed or lost for 1 gram of a substance to change its temperature by 1°C.
What is evaporative cooling?
It is the cooling of a liquid's surface when a liquid energy. The surface molecules with the highest kinetic energy are most likely to escape in gaseous form, the average kinetic energy of the remaining surface molecules is thus lower.
What is temperature?
It is the measure of heat intensity due to the average kinetic energy of molecules in that body of mater
What does it mean if water has a high specific heat?
It means that it resists temperature changes when it absorbs or releases heat.
What takes place as an ice cube cools a drink?
Kinetic energy in the drink decreases
What is kinetic energy and heat?
Kinetic energy is the energy of a motion and heat is the total kinetic energy due to molecular motion in a body of matter.
When is a solution basic, acidic, or neutral?
Neutral: When it is pH 7, meaning H+=OH- Acidic: when pH<7, meaning more H+than OH- Basic: when pH>7, meaning more OH- than H+
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by what bond?
Polar covalent bonds
What is a kilo calorie?
The amount of heat required to raise the temperature 1 kg of water by 1°C
Water is able to form hydrogen bonds because?
The bonds that hold together the atoms in a water molecule are polar covalent bonds
A lake that originally has a pH of 6 has pollution which drains into the lake from nearby strip mining and the pH of the lake is lowered to 4. How many more times acidic is the lake now than originally?
The lake is 100 times more acidic than original, because if the pH is lowered by 1, the acidity increase by tenfold, so if lowered by 2, it becomes 100 times more acidic.
How do buffers work?
They work by accepting H= ions from solution when they are in excess, and donating H= ions to the solution when they have been depleted.
An example of a hydrogen bond is the bond between?
the H of one water molecule and the O of another water molecule
