Chemistry Notes
curriculum plan
o Trace the development of Chemistry
o Explain how chemistry is related to other sciences
o Describe the importance of chemistry in the society
The Scientific Process
Laboratory Orientation
o Demonstrate scientific methods and attitudes
o Manipulate carefully common laboratory apparatus following safety precautions
Measurement
Physical Quantities and Units
o Identifying the metric units of measurements
o Demonstrate accuracy and intellectual honesty in solving problems
o Explain what causes uncertainty in measurements
o Use measuring materials accurately with safety
o Express numbers in scientific notation with correct number of significant figures
o Convert a measurement from one unit to another
Classification of matter
o Point out different classifications of matter
o differentiate the states of matter and its properties
Changes in matter
o cite the importance of knowing the properties and changes in matter
o Identify the effects of physical and chemical changes to the environment
Mixtures and component substances
o Enumerate important mixtures naturally occurring
o Identify methods of separating mixtures into their component substances
o Describe the preparation of some mixtures
o Determine the importance of segregating wastes from households and industries
Investigatory Project
Scientific Demonstrations
o Construct a scientific research (involving chemical technology as much as possible)
o Defend constructed research paper
Matter at the Atomic Level
o Describe the states of matter at the atomic level
o Explain the characteristics of different types of matter using the atomic models
Atomic Theory
o Trace the development of the atomic theory
o Identify the features of the atomic theory
Periodic Table
o Trace the history of Periodic table
o Identify the scientists responsible for the development of periodic table and periodic trends
Modern Periodic Table
o Predict the properties and uses of elements
Electron Arrangement in Atoms
o Determine the features of the quantum mechanical model
o Write electronic configuration of elements
o Draw orbital diagrams to represent the electron configuration of atoms
Periodic Trends
o Explain the periodic properties of elements in the Periodic Table
o Describe and identify the periodic trends In the atomic properties
Chemical Bonds
o State the octet rule
o Differentiate the different types of bonds
o Describe how chemical bonding takes place
o Draw the Lewis structure of a certain compound
o Explain properties of compounds of different bond type
Naming and Writing Chemical Formulas
o Write and name formulas of common compounds in the environment
o Identify the ions involving in the formation of compounds
Molecular shapes
o Construct molecular models/shapes of compounds/elements
o Describe the shapes of simple molecules using the VSEPR and valence bond theories
Intermolecular forces
o Describe the three kinds of intermolecular forces of attraction
Writing and Balancing Equations
o Write chemical equations given a word equation
o Develop accuracy in balancing chemical equations
Chemical composition of Compounds
o Determine formula and molecular masses
o Describe a mole and its use in expressing chemical quantities
o Derive the empirical and the molecular formula of a compound from experimental data
(Stoichiometry) Chemical Reactions
o Define stoichiometry
o Calculate stoichiometric quantities from balanced chemical equations
o Amount of substances consumed and/or produced in a reaction
Properties of Gases
Kinetic Molecular Theory
o Understand the nature of gases
o Observe the properties of gases
o Relate problems of the environment specifically air pollution to some of the properties of gases
Gas Laws
o Expressing relationships in mathematical equations
o Demonstrate accuracy and creativity in solving problems involving gas laws
Air Pollution
o Discuss issues related to air pollution
o Recommend ways to minimize air pollution as a student
Solutions and its Types
Factors affecting Solubility
o Define operationally solute and solvent
o Distinguish between unsaturated, saturated and supersaturated solutions
o Recognize the importance of some properties of solutions
Ways of Expressing Concentrations of Solutions
Colligative Properties
o Express solution concentration in percent by weight, mole fraction, molarity and molality
o Determine the properties of solutions with different concentrations
Water Pollution
Colloids
o Explain the advantages and disadvantages of having dangerous pollutants in bodies of water
Ideal Gas law
The Ideal Gas law interrelates pressure, temperature, volume and number of moles of a gas sample. This law integrates the laws of Boyle, Charles and Avogadro.
Boyle's law : V ∞ 1/P
Charles' law: V ∞ T
Avogadro's law: V ∞ n
Combining these three laws will yield to a more general equation:
- How many moles of gas are contained in a 50.0L cylinder at a pressure of 100.0atm and a temperature of 35.0ºC?
- What would be the volume occupied by a 1mole gas at STP?
Gay-Lussac's Law
This law is mathematically expressed as:
P1 = P2
T1 T2
- A gas sample has a pressure of 950 torr at 120ºC. What is the final pressure of the gas after the temperature is dropped to 10ºC?
- Pressure of a gas in a 10.0L steel cylinder is 890torr at 56ºC. To what temperature should the gas be cooled in order to reduce the pressure to 760 torr?
Combined Gas Law
It states that "for a given mass of gas, the volume is inversely proportional to the pressure and directly proportional to its absolute temperature".
Derived from Boyle's law:
T1 T2
(2.4 atm)(4.0 L) = P2 (1.5 L)
313K 323K
P2 = (2.4 atm)(4.0L)(323K)
(313K)(1.5 L)
P2 = 6.60 atm
- A gas sample occupies a volume of 20m3at 40ºC and at a pressure of 1.60 atm. What volume will it occupy at STP?
- A certain amount of gas has a volume of 85cm3 at a temperature of 15ºC and a pressure of 800 torr. Calculate its temperature, in Kelvin, if the volume is increased to 120cm3 annd the pressure is changed to 700 torr.
- A gas has a volume of 38 Liters at 10ºC and a pressure of 1.24atm. At what pressure will its volume be 50 Liters if the temperature is increased to 25ºC?
Charles' Law
Charles' law is also known as Temperature-Volume Relationship. This law was studied by Jacques Charles in 1787 using a balloon.
This law states that if temperature is increased, the volume of the gas will increase. Volume is directly proportional to temperature if the pressure is kept constant.
Charles' law can be mathematically expressed as:
- V1 = initial volume
- T1 = initial temperature (in Kelvin)
- V2 = final volume
- T2 = final temperature (in Kelvin)
Problem Solving Reminders:
- Analyze the given problem.
- List down the given values and what is asked.
- Identify the formula to be used.
- Write your solutions clearly.
- Analyze if your answer is theoritically correct.
Sample Problem #1:
A balloon has a volume of 2500.0 mL on a day when the temperature is 30.0ºC. If the temperature at night falls to 10.0ºC, what will be the volume of the balloon if the pressure remains constant?
Sample Problem #2:
Find the final temperature of a 2.00-L gas sample at 20.0ºC compressed to a volume of 1.00-L.
Boyle's Law
This law states that if a pressure of a gas is increased, the volume of the gas is decreased. Study the following figures.
This law can be mathematically expressed as:
where:
- P1 = initial pressure
- V1 = initial volume
- P2 = final pressure
- V2 = final volume
Any units of pressure and volume may be used. However, uniformity must be observed.
Pressure Units
- 1 atmosphere (atm) = 760mm Hg = 760 torr = 150000 Pascal (Pa)
Volume Units
- 1 Liter = 1000 mL
- 1mL = 1 cm3
Problem Solving Reminders:
- Analyze the given problem.
- List down the given values and what is asked.
- Identify the formula to be used.
- Write solutions clearly.
- Analyze if you have the correct answer.
Sample Problem #1:
Two hundred milliliter of gas is contained in a vessel under a pressure of 850mm Hg. What would be the new volume of the gas if the pressure is changed to 1000mm Hg?
Given:
P1= 850 mm Hg
V1= 200 cm3
P2= 1000 mm Hg
V2= ?
Equation: P1V1 = P2V2- Solution:
P1V1 = P2V2
(850mm Hg)(200cm3)=(1000mm Hg) V2
(850mm Hg)(200cm3)= V2
(1000mm Hg)
170 cm3 = V2
Sample Problem #2:
A 2.5 liter sample of a gas is collected at a pressure of 1.25 atm. Calculate the pressure needed to reduce the volume of a gas to 2.0 liters. The temperature remains unchanged.
- Given:
P1= 1.25 atm
V1= 2.5 liter
P2= ?
V2= 2.0 liters
Equation: P1V1 = P2V2
Solution:
P1V1 = P2V2
(1.25 atm)(2.50 L) = P2 (2.0 L)
(1.25 atm)(2.50 L) = P2
(2.0L)
P2 = 1.56 atm
Gases
According to the philosopher Anaximenes, matter exists from air. Gases are classified as the third physical state of matter. Like everything, each one is different from the rest and it has its own characteristics. The Kinetic Molecular Theory of Gases, postulates based from basic behaviors of atoms, attempts to explain the properties of gases. The Kinetic Molecular Theory, also called as the Collision Theory has the following postulates:
- Gases are composed of atoms/molecules that are separated and far from one another. The space betweenn them is very wide, thus, occupying a wide space in the atmosphere.
- These tiny particles are moving constantly in a straight path but random direction, resulting to the collision between them and with the walls of the container, thus, creating pressure.
- The force of attraction between atoms is negligible.
Collision of the particles does not result in the energy change, although a transfer of energy may occur in the collision. - All gas molecules have the same average kinetic energy at the same temperature. Temperature is defined as avergae kinetic energy. (Brown et al 2000 1)
From these postulates, we can then draw the following properties:
- Gases are compressible. Since gas molecules are from from each other, they can be compressed closer to decrease the gap between molecules.
- Gases have low densities. Since gas molecules are from from each other, they would occupy a greater space compared with the other states of matter. Gases would have lighter mass to keep moving at a particular speed. With a small value of mass, and occupying a big volume, the ration (density) would be low.
- Gases exert pressure. Gas molecules are constantly moving, hitting everything in its path thus creating pressure.
- Gases diffuse easily. Since gas molecules move constantly, it then travels from one place to another.
Gases are affected by changes in temperature. (2)
Aside from the behavioral properties, gases also have the following measurable properties:
- Pressure (P). A measure of force applied on an object per unit area (P=F/A). Pressure in the atmosphere is caused by the weight of the air from the outer edge of the atmosphere down to the surface of the earth. Measurement of pressure was first introduced by Evangelista Toricelli.
- Temperature (T). The average kinetic energy. If a gas is to reach absolute zero (O Kelvin), its particles would have no energy or motion.
- Volume (V). Volume of a gas is equal to the volume of the container since a gas completely fills its container.
- Amount of gas (n). The amount of gas is measured in moles or number of particles.
Other properties:
- Diffusion. the process of spreading out of molecules to fill a space uniformly.
- Effusion. the process by which gas molecules spread out in an empty space through a small opening.