Chem Unit 2 exam flashcards

% of earths water thats fresh water and % that is accesable

Fresh water- 2.5% 

0.5% of that water is accessible

Portable water

clean water that is safe for human consumption

structure of water molecule

• Polar V shape molecule 

intramolecular and intermolecular forces of water.

• Covalent molecular compound 

• O has high electronegativity so electrons lie closer to O, so it's a polar covalent bond between O and H

• V shape of molecule results in polar molecule 

• H bonding occurs between water molecules

why waters melting point is high (soilid-liquid)

• Energy needs to be provided to increase kinetic energy of the water molecules so that they can break free of crystal lattice

why waters boiling point is high Liquid→ gas

• Molecules are separated from each other and all H bonds are broken, 

• requires a lot of energy to break these strong bonds

why does Solid ice has lower density than liquid water

• As water cools molecules slow down and form a crystal arrangement 

• Each molecule is bonded to 4 neighboring molecules making a very open arrangement

why is it important that Solid ice has lower density than liquid water

• Meaning that solid ice floats on liquid water (important to life on earth)

3 ways how water acts as a solvent (how it dissolves things)

• Dissociation of an ionic compound 

• Formation of H bonds with a suitable molecular compound e.g ethanol- H bond forms with H at the OH end and the O of water 

• Ionisation of highly polar molecular compounds e.g HCl

• Specific Heat capacity of water

• its high

• 4.18 J g^-1 °C^-1

• Specific heat capacity is…

• Amount of energy (in joules) needed to increase the temperature of 1g of that substance by 1 degrees celsius

• Higher the heat capacity of a substance….

• the more effectively it stores heat energy

equation for heat energy=

• Heat energy (J) = specific heat capacity x mass(g) x temp change (degrees celsius)

when would you use heat energy equation

• Calculate the quantity of heat required to raise the temperature of certain amount of water from x degrees to y degrees

specific heat capacity equation

• Latent heat value

• - energy required to change the state of a substance at its melting point

• Latent heat value equation and what each of the symbols are

• q= heat energy (units are kj)

• L= latent heat value

• n= mols, m/M