Why is water polar?
Why is water polar and why is the water molecule a bent shape? Water is polar because it has one end that is slightly negatively charged, and another end that is positively charged. The water molecule is made of one Read More …
The Bohr Model
In 1913 Niels Bohr proposed a model to describe how energy levels are organized around an atom. While his model is now known to be incorrect, it is useful for understanding energy levels as Bohr’s model closely resembles planets orbiting Read More …
Ionization energy trend
Ionization Energy Trend Ionization energy is defined as the amount of energy needed to eject a valence electron from an atom in the gas phase. It is measured in kJ/mol. A valence electron is simply an electron located in the Read More …
Periodic Table Trends
Today, we are going to learn about how the periodic table is organized and the important information that it provides. Scientists discovered that if they arranged the elements according to their atomic number, properties of the elements would occur in Read More …
Electronegativity Bond Scale
Photograph of Linus Pauling: Nobel Foundation, Public domain, via Wikimedia Commons The above is an example of electronegativity bond scale. It shows the different types of chemical bonds formed between atoms based on the electronegativity difference. Bond scale varies slightly Read More …
The Mole Relationship to Carbon
Experiments have determined that in 12 g of carbon there are 6.022 x 10²³ atoms. 1 mole is defined as the number of atoms in 12 g of carbon. In other words, 1 mole of carbon contains 6.022 x 10²³ atoms!
Carbon to Carbon Bonds
Carbon-carbon bonds A carbon atom has 4 valence electrons A single bond Most bonds that carbon form are single bonds. Single bond simply means sharing one pair of bonding electrons between two atoms and is represented by a single line. Read More …
The Mole Concept
1 mole = 6.022 x 10^23 particles Avogadro’s Constant Molar mass = grams per 1 mole of a substance Molar mass Moles = Mass / Molar Mass Moles calculation 1 mole = number of atoms in 12 g of carbon Read More …
Covalent Bonding
What is a COVALENT BOND? The term covalent bond is used to describe the bonds in compounds that result from the sharing of one or more pairs of electrons. There are two types of covalent bonds – nonpolar and polar Read More …
What is Molecular Mass?
How to calculate molecular mass? Determine the formula of the compound Use the periodic table, determine the atomic mass of each element present in the formula Multiply the atomic mass of each element by the number of atoms Finally, add Read More …
3 Simple Steps – the Ring Structure of Glucose Molecule
For drawing purposes, the ring structure of the glucose molecule is broken down into three simple steps as shown below. Each molecule of glucose sugar is only 1 unit consisting of 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms in Read More …
Simple Sugars – Monosaccharides
What are Monosaccharides? Monosaccharides are known as simple sugars, they are the simplest form of carbohydrate. They are short chain molecules containing only one chemical ring. Since they are only one ring, they can undergo chemical reactions to provide quick Read More …
Carbohydrates and Sugar
Organic Chemistry Carbohydrate chemistry is a branch of organic chemistry that studies carbon compounds. Carbon can be found in food and non-food substance. As carbon plays a huge role in living things, organic chemistry is very important to medicine and life Read More …
4 Simple Steps – Chain Glucose Molecule
Glucose C6H12O6 Glucose is a carbohydrate and it is one of the smallest units of sugar Its chemical formula is C6H12O6 Glucose are hexoses – 6 carbon atoms sugars In total, there are 24 atoms that form the molecule Step 1: Draw Read More …
Open, Closed & Isolated Systems
Teach AP® chemistry with confidence and ease Open, Closed & Isolated Systems A system refers to any parts of the universe being studied. If you are conducting an experiment in a beaker, then the system you are studying is in Read More …
System and Surroundings
The Octet Rule of Electron Configuration
What is the Octet Rule of Electron Configuration? Electron configuration is the arrangement of electrons in each energy level or shell of an atom. If the outer shell of an atom is not filled to its maximum level, the atom Read More …
Enthalpy Change Calculation
Propane Combustion When 0.5 g of propane is burned, the heat produced is used to raise the temperature of 100 cm³ of water from 20ºC to 40ºC. Calculate the enthalpy change (ΔH) for the reaction. Given the density of water Read More …
Enthalpy, Entropy & Gibbs Free Energy
Enthalpy Entropy Gibbs Free Energy Enthalpy is the amount of heat energy transferred (heat absorbed or emitted) in a chemical process under constant pressure. Entropy measures the amount of heat dispersed or transferred during a chemical process. Gibbs Read More …
Enthalpy
The term enthalpy change is a term to describe the amount of heat that passes in or out of a system during a chemical reaction under constant pressure. Calorimeter In school, you can measure the heat exchange of a reaction Read More …
Reaction Spontaneity
(Picture above – dog escaping over the fence – winter 2015) A spontaneous process A spontaneous process is a physical or chemical change that occurs with no outside intervention. In life, many things happen spontaneously. For example, my dog escaped Read More …
Hess’s Law
Hess’s law states that energy change in the overall chemical reaction is the sum of energy change or enthalpy change in the individual reactions that comprises it. Hess’s Law states that the heat evolved or absorbed in a chemical process is Read More …
Hess Law – Calculation for Methane Formation
Methane gas – CH₄ What is the enthalpy change when methane is formed using carbon graphite and hydrogen? When a chemical reaction takes place, heat is either given off or absorbed. If heat is given off, it is called an Read More …
Understanding Gibbs Free Energy
What is Gibbs Free Energy? For a simple definition, Gibbs free energy can be described as the amount of energy available to do work. Gibbs Free Energy is invented by Josiah Willard Gibbs (February 11, 1839 – April 28, 1903) Read More …
Gibb’s Free Energy – Ammonia
The Haber process to manufacture ammonia using nitrogen and hydrogen is given by the equation below: Calculate Gibb’s free energy change (ΔG) at 298 K temperature. Given the entropy change (ΔS): -198 J K⁻¹ mol⁻¹ Enthalpy change (ΔH): -92 kJ Read More …
Entropy
What is entropy? Entropy refers to the amount of unusable energy in a system. When water flows over a dam, it loses some of its useful energy as heat Solid wood burns to become ash and releases gases. Solid ice Read More …
Carbon to Carbon – Single, Double & Triple Bonds
We know from the periodic table that a carbon atom has 4 valence electrons in the outermost shell. In order for the atom to be more stable, the outermost shell must be filled up. Carbon follows the octet rule Read More …
Condensation Polymerization
Condensation polymers are any kind of polymers formed through a condensation reaction where molecules join together–losing small molecules as by-products such as water or methanol.
Addition Polymerization
In addition polymerization, all the original atoms present in the monomers are retained in the polymer product.
Types of Plastics and their Classification
Plastic classifications is a system established to allow consumers to properly recycle and dispose of different types of plastics. Manufactures follow a coding system and place an SPI code on each plastic product, and are usually printed or modeled into the bottom.
Why is water polar?
Why is water polar and why is the water molecule a bent shape? Water is polar because it has one end that is slightly negatively charged, and another end that is positively charged. The water molecule is made of one Read More …
The Bohr Model
In 1913 Niels Bohr proposed a model to describe how energy levels are organized around an atom. While his model is now known to be incorrect, it is useful for understanding energy levels as Bohr’s model closely resembles planets orbiting Read More …
Ionization energy trend
Ionization Energy Trend Ionization energy is defined as the amount of energy needed to eject a valence electron from an atom in the gas phase. It is measured in kJ/mol. A valence electron is simply an electron located in the Read More …
Periodic Table Trends
Today, we are going to learn about how the periodic table is organized and the important information that it provides. Scientists discovered that if they arranged the elements according to their atomic number, properties of the elements would occur in Read More …
Electronegativity Bond Scale
Photograph of Linus Pauling: Nobel Foundation, Public domain, via Wikimedia Commons The above is an example of electronegativity bond scale. It shows the different types of chemical bonds formed between atoms based on the electronegativity difference. Bond scale varies slightly Read More …
The Mole Relationship to Carbon
Experiments have determined that in 12 g of carbon there are 6.022 x 10²³ atoms. 1 mole is defined as the number of atoms in 12 g of carbon. In other words, 1 mole of carbon contains 6.022 x 10²³ atoms!
Carbon to Carbon Bonds
Carbon-carbon bonds A carbon atom has 4 valence electrons A single bond Most bonds that carbon form are single bonds. Single bond simply means sharing one pair of bonding electrons between two atoms and is represented by a single line. Read More …
The Mole Concept
1 mole = 6.022 x 10^23 particles Avogadro’s Constant Molar mass = grams per 1 mole of a substance Molar mass Moles = Mass / Molar Mass Moles calculation 1 mole = number of atoms in 12 g of carbon Read More …
Covalent Bonding
What is a COVALENT BOND? The term covalent bond is used to describe the bonds in compounds that result from the sharing of one or more pairs of electrons. There are two types of covalent bonds – nonpolar and polar Read More …
What is Molecular Mass?
How to calculate molecular mass? Determine the formula of the compound Use the periodic table, determine the atomic mass of each element present in the formula Multiply the atomic mass of each element by the number of atoms Finally, add Read More …
3 Simple Steps – the Ring Structure of Glucose Molecule
For drawing purposes, the ring structure of the glucose molecule is broken down into three simple steps as shown below. Each molecule of glucose sugar is only 1 unit consisting of 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms in Read More …
Simple Sugars – Monosaccharides
What are Monosaccharides? Monosaccharides are known as simple sugars, they are the simplest form of carbohydrate. They are short chain molecules containing only one chemical ring. Since they are only one ring, they can undergo chemical reactions to provide quick Read More …
Carbohydrates and Sugar
Organic Chemistry Carbohydrate chemistry is a branch of organic chemistry that studies carbon compounds. Carbon can be found in food and non-food substance. As carbon plays a huge role in living things, organic chemistry is very important to medicine and life Read More …
4 Simple Steps – Chain Glucose Molecule
Glucose C6H12O6 Glucose is a carbohydrate and it is one of the smallest units of sugar Its chemical formula is C6H12O6 Glucose are hexoses – 6 carbon atoms sugars In total, there are 24 atoms that form the molecule Step 1: Draw Read More …
Open, Closed & Isolated Systems
Teach AP® chemistry with confidence and ease Open, Closed & Isolated Systems A system refers to any parts of the universe being studied. If you are conducting an experiment in a beaker, then the system you are studying is in Read More …
System and Surroundings
The Octet Rule of Electron Configuration
What is the Octet Rule of Electron Configuration? Electron configuration is the arrangement of electrons in each energy level or shell of an atom. If the outer shell of an atom is not filled to its maximum level, the atom Read More …
Enthalpy Change Calculation
Propane Combustion When 0.5 g of propane is burned, the heat produced is used to raise the temperature of 100 cm³ of water from 20ºC to 40ºC. Calculate the enthalpy change (ΔH) for the reaction. Given the density of water Read More …
Enthalpy, Entropy & Gibbs Free Energy
Enthalpy Entropy Gibbs Free Energy Enthalpy is the amount of heat energy transferred (heat absorbed or emitted) in a chemical process under constant pressure. Entropy measures the amount of heat dispersed or transferred during a chemical process. Gibbs Read More …
Enthalpy
The term enthalpy change is a term to describe the amount of heat that passes in or out of a system during a chemical reaction under constant pressure. Calorimeter In school, you can measure the heat exchange of a reaction Read More …
Reaction Spontaneity
(Picture above – dog escaping over the fence – winter 2015) A spontaneous process A spontaneous process is a physical or chemical change that occurs with no outside intervention. In life, many things happen spontaneously. For example, my dog escaped Read More …
Hess’s Law
Hess’s law states that energy change in the overall chemical reaction is the sum of energy change or enthalpy change in the individual reactions that comprises it. Hess’s Law states that the heat evolved or absorbed in a chemical process is Read More …
Hess Law – Calculation for Methane Formation
Methane gas – CH₄ What is the enthalpy change when methane is formed using carbon graphite and hydrogen? When a chemical reaction takes place, heat is either given off or absorbed. If heat is given off, it is called an Read More …
Understanding Gibbs Free Energy
What is Gibbs Free Energy? For a simple definition, Gibbs free energy can be described as the amount of energy available to do work. Gibbs Free Energy is invented by Josiah Willard Gibbs (February 11, 1839 – April 28, 1903) Read More …
Gibb’s Free Energy – Ammonia
The Haber process to manufacture ammonia using nitrogen and hydrogen is given by the equation below: Calculate Gibb’s free energy change (ΔG) at 298 K temperature. Given the entropy change (ΔS): -198 J K⁻¹ mol⁻¹ Enthalpy change (ΔH): -92 kJ Read More …
Entropy
What is entropy? Entropy refers to the amount of unusable energy in a system. When water flows over a dam, it loses some of its useful energy as heat Solid wood burns to become ash and releases gases. Solid ice Read More …
Carbon to Carbon – Single, Double & Triple Bonds
We know from the periodic table that a carbon atom has 4 valence electrons in the outermost shell. In order for the atom to be more stable, the outermost shell must be filled up. Carbon follows the octet rule Read More …
Condensation Polymerization
Condensation polymers are any kind of polymers formed through a condensation reaction where molecules join together–losing small molecules as by-products such as water or methanol.
Addition Polymerization
In addition polymerization, all the original atoms present in the monomers are retained in the polymer product.
Types of Plastics and their Classification
Plastic classifications is a system established to allow consumers to properly recycle and dispose of different types of plastics. Manufactures follow a coding system and place an SPI code on each plastic product, and are usually printed or modeled into the bottom.
