Polymerization is simply the process of putting together monomers (single molecules), to become a long chain of molecules (called polymers) with the use of a catalyst.
Polymerization is an important process for making plastics.
A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.… Read the rest
Question: How many moles are in 1000 g of sucrose?
1. Obtain the atomic mass
First, write down the formula for sucrose: C12H22O11
2. Calculate the molar mass of sucrose C12H22O11
The formula tells us there are 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms.… Read the rest
Molar mass is the weight in grams of one mole of a chemical substance.
How to calculate the molar mass of a single element (eg.hydrogen)?
The molar mass for an element is the sum of atomic masses, expressed as g/mol.
Molar mass of hydrogen = 1.008 g/mol
How to calculate molar mass of a compound (eg.
… Read the rest
The mole is used in measurements in a way similar to the use of “dozens”.
- The reason why we use moles in chemistry is because of the vast number of molecules and atoms involved in the calculations
- Just like it’s easier to manage the thought of 2 dozen eggs instead of 24, scientists prefer to think of a reaction requiring 2 moles of carbon rather than 1,204,428,200,000,000,000,000,000 particles
- The number is huge and unimaginable, a bit like the number of stars in the galaxy
- Using the mole unit helps simplify calculations
Note: the symbol for mole is “mol”
The mole concept
The mole is equal to 602 thousand billion billion!
… Read the rest
Sublimation is the process of turning from solid to vapor without going through the intermediate liquid phase.
Sublimation of Ice
We are all familiar with ice melting before it evaporates. However, in sublimation, the liquid phase is omitted. In order for a solid to sublime, it must exhibit a higher than usual vapor pressure and weak intermolecular attractions.… Read the rest
Dissociation is the breaking down of a compound into elements
The word dissociate and disassociate have similar meaning – to remove from being connected.
When a compound dissociates, the bonds are broken.
Ionic compound dissociation
All ionic compounds dissociate to some extent when they dissolve in water.… Read the rest
In 1784, a French physicist and clergyman named Jean Antoine Nollet made an interesting discovery. He filled a pig’s bladder with a concentrated solution of alcohol. He then put the bladder in water and the bladder expanded!
This interesting process is caused by a phenomenon called osmosis.… Read the rest
Do you know that the cloudy water syndrome in a fish tank is caused by colloids? Over a period of time, organic waste produced by the fish and algae in the tank are turned into nitrates. These particles are interspersed in the water and do not settle.… Read the rest
Irregular motion of suspended particles is called “Brownian motion”.
Watch an interesting Youtube video on the discovery of Brownian Motion by British botanist Robert Brown
Robert Brown was a Scottish botanist who first discovered the Brownian motion.
He noticed random motion of pollen grains dispersed in water under a microscope as though they are constantly dancing.… Read the rest
Water always evaporates no matter what the temperature or atmospheric pressure is.
Even in the coldest of winter, snow and ice can evaporate by a process called sublimation. They can turn straight into vapor (the gaseous stage) without melting.
The vapor that escaped into the air whether by evaporation or sublimation had sufficient energy to break away from the intermolecular forces of the water.… Read the rest
Molality is defined as the number of moles of solute per 1 (kg) of solvent.
- Solute = particles you dissolve
- Solvent = the liquid you use for dissolving the particles
Calculate molality (m) of 29.8 g of glucose (C6H12O6) dissolved in 622.8 g of water
Step 1.… Read the rest
Freezing point depression is simply the process of LOWERING THE FREEZING POINT OF A LIQUID by adding a solute to it.
Ordinarily, water freezes at 32°F (0°C), but can you add salt to lower its freezing point to 20°F (-6°C). That’s why we use salt to melt ice on the road in the winter!… Read the rest
Boiling point elevation is the elevation of a solid’s normal boiling point by adding a substance to it.
When you add a solute (such as salt or sugar) to a pure solvent (such as water), the boiling point of the liquid solvent is now increased.… Read the rest
Adding a solute to a pure solvent lowers the solvent’s vapor pressure. For example, water normally boils at 100ºC (212ºF) but if you add a substance like salt to the solution, it decreases the vapor pressure of the solution.
First, recall what the vapor pressure of a liquid is.… Read the rest
The characteristics of a solution such as the boiling point, freezing point and vapor pressure are known as colligative properties. Colligative properties apply only to solutions and not gases or solids.
COLLIGATIVE PROPERTIES ARE DEPENDENT ON THE NUMBER OF ATOMS AND MOLECULES
The word colligative comes from the same Latin root that the word collection comes from.… Read the rest
Nonpolar molecules do not dissolve readily in water
- Nonpolar molecules do not become hydrated – they are repelled by water
- The molecules are insoluble or almost insoluble in water
Oils and fats are examples of hydrophobic substances. For example, if you mix oil with water, the mixture will separate.… Read the rest
A nonpolar covalent bond is a chemical bond where electrons are shared equally between two atoms
The electrons are shared equally between the two atoms
Nonpolar covalent bond electronegativity scale
If the difference in electronegativity between two atoms is 0.4 or less, the bond formed between the two atoms is a nonpolar covalent bond.… Read the rest
The electrons are unequally shared between two atoms
When a chemical bond involves “the sharing of a pair of electrons by two atoms in a molecule”, it is generally called a covalent bond.
In a polar covalent bond, the electrons are not equally shared between the atoms
The unequal sharing of electrons causes a separation of partial charges within the bond.… Read the rest
An ionic bond
An ionic bond is formed between elements of large differences in electronegativities, which are typically found between metals and non-metals.
The atom that loses the electron(s) becomes a positively charged ion called a cation, and the one that gains the electron(s) is called the anion.… Read the rest
A QUICK LOOK AT THE THREE DIFFERENT TYPES OF MOLECULAR BONDS
HOW DO YOU FIND OUT THE TYPE OF BOND
If you’re given two elements, such as carbon and oxygen, how do you tell what type of bond they will form?… Read the rest
The solubility of a substance is the amount of that substance that will dissolve in a given amount of solvent.
The difference between solute and solvent
- SOLUTE – the substance to be dissolved
- SOLVENT – the liquid for dissolving the substance
Fizzy drinks are made by dissolving carbon dioxide gas in water.… Read the rest
The valence electrons are the electrons in the outermost shell or last energy level of an atom.
valence electrons are electrons in the last shell of an atom
Valence electrons are electrons in the highest principal energy level.
They are electrons that sit in the outermost shell of an atom.… Read the rest
Electronegativity is a measure of how strongly an atom – in a molecule – is able to attract electrons in a bond to itself.
Factors affecting electronegativity:
1) The atomic number
The atomic number is the number of protons in the nucleus of an atom.… Read the rest
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Surfguppy provides free online chemistry notes for high school and college students. If you’re a teacher or student, please feel free to use our materials for non-commercial purposes. A small portion of materials on this website belongs to Creative Commons, please check the Creative Commons Licensing Terms to use them.… Read the rest