Topics in Chemistry
Gas laws in chemistry Charles's law explained Calculation questions on Charles's law Examples of Charles's law in real life Boyle's law explained Calculation questions on Boyle's law Examples of Boyle's law in real life Summary on the kinetic molecular theory of gases Postulates of kinetic theory of gases Avogadro's number explained with worked examples Mole and Avogadro's Number explained Le Chatelier's Principle: Changes in concentration and pressure in dynamic equilibrium Chemical Equilibrium: Dynamic Equilibrium in Chemistry Static and Dynamic Equilibrium explained with their differences Chemistry Scheme of Work, SS1, First Term Chemistry Scheme of Work, SS1, Second Term Chemistry Scheme of Work, SS1, Third Term Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures What are mixtures? Characteristics of mixturesAcademic Questions in Chemistry
_____ electron(s) is a term that describes the number of electron(s) in the outermost shell of an atom.
A. Outer
B. Excess
C. Valence
D. Positive
E. Negative
F. Last
_____ is the negative electrode in electrolysis.
A. Anode
B. Anion
C. Cathode
D. Cation
E. Ion
F. Electrolyte
The above diagram shows the _____ type of bond.
A. Covalent
B. Polar covalent
C. Coordinate covalent
D. Metallic
E. Van dear walls
F. Ionic
Metals are referred to as _____ in their impure state.
A. Diluted
B. Consecrated
C. Coloured
D. Ores
E. Stained
F. Strained
Metals generally have the quality to shine, glow, sparkle, glitter, reflect light and be polished. This characteristic of metals is termed _____.
A. State
B. Ductility
C. Luster
D. Malleability
E. Hardness
F. Inflorescence
The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.
A. Mole
B. Volume
C. Weight
D. Number of moles
E. Mass
F. Amount of substance
John Dalton's first atomic theory was modified based on a discovery made by _____.
A. Sir Isaac Newton
B. Albert Einstein
C. Avogadro
D. Rutherford
E. Boyle and Charles
F. Gay Lussac
Which of the following isn't an element of the periodic table.
A. J
B. Y
C. W
D. B
E. U
F. K
Charles's law states that the volume of a given mass of a gas is directly proportional to its kelvin temperature, provided the pressure remains constant. This law was formulated by French Physicist, Jacques Charles in 1780.
Please read a detailed explanation on Charles's law here.
Various instances of Charles's law are seen around us. They include the following:
Children who had dented their table tennis (or ping-pong) balls will be familiar with Charles's law through an attempt of fixing it.
One way they go about this process is by placing the dented surface of the table tennis ball on warm water for some time. As the ball floats, the increased temperature within that surface on the table tennis ball causes an increase in the volume of gas present inside the ball. This is what Charles's law entails; and it causes the table tennis ball to expand in this instance, until its dented surface is restored to normalcy.
Please read on molar mass and its calculations here.
Charles's law is applicable whenever yeast is utilized for baking purposes. Recall that yeasts serve the purpose of making our bakery products swell and fluffy. It is able to do this because it releases carbon (IV) oxide (CO2) when heated at high temperature.
As the temperature increases, the volume occupied by the gas bubbles of carbon (IV) oxide also increases through its spreading around the baked product, making it swell in the process.
Please read interesting facts for students here.
The baking of bread is a typical example of this process, and it works in accordance with Charles's law.
The pop-up turkey timer is a type of thermometer whose mechanism of action is based on Charles's law. Within this timer is a gas that expands based on the available quantity of heat (temperature).
Recall that with Charles's law, when temperature increases, volume also increases.
Please read the concept of heat and temperature here.
Before the heating or roasting process, the thermometer (timer) is inserted inside the turkey. As it gets heated up, the turkey's temperature increases, bringing about an expansion (increase in volume) of the gas within the thermometer. A volume will eventually be reached, and it results into a pop sound by the thermometer. This pop-up by the thermometer indicates that the turkey had been cooked.
Have you ever wondered why a balloon could burst without been touched? Well, the simple answer is Charles's law which states that an increase in temperature results into an increased volume at constant pressure.
When a balloon is filled with air (or helium gas), then tied and exposed to a sunny condition (high temperature), the volume occupied by the gas within the balloon increases due to the high environmental temperature. This causes the balloon to expand and eventually burst due to the lightness of its material, its elastic nature, the increased volume of its gas and an increased temperature.
However, the volume of gas occupied within the balloon decreases on cold days (due to low temperature). As a result, helium balloons tend to shrink on cold days.
Please read examples of Boyle's law in real life here.
Jaques Charles himself utilized his law when he had a hydrogen balloon flight. In fact he was said to be a lover of hot air balloon.
At a basic level, hot air balloon comprises of a burner, an envelop that stores hot air and a gondola (or basket) that carry passengers. In order to fly, the hot air inside the envelop is first heated immediately after the fuel source had been ignited.
This increased temperature causes the air to expand, thus increasing its occupied volume, while also making it lighter (since it has less mass per unit volume), in contrast to the denser cooler air present outside the envelop (that is, the atmosphere). The hot air balloon goes higher up the sky through this process.
Please read the concept of gravity on the solar system here.
When filled with air, a pool float enables one to float on water. However, it is quite common for a pool float to become under-inflated when placed on a pool. This happens as a result of Charles's law.
The cause of an under-inflated pool foalt is a result of the pool's low temperature. As a result, the volume of air within it is reduced, resulting into its slightly shrinked size.
Please read on heat transfer by convection here.
If the pool float were to be placed on warm water, its occupied gas volume will increase, making it inflated again.
It is a common observation that an inflated basketball shrinks in size when left under a cold environment. This is true because a decrease in temperature results into a corresponding decrease in volume according to Charles's law. Therefore, the volume of air inside the basketball shrinks on cold day.
As you may have guessed, the volume of the basketball will be regained when placed in an environment with higher temperature since the volume occupied by the air within it increases.
Please read on the game of basketball here.
Aerosols refers to products like insecticides, perfumes, deodorants, spray paints and so on. They usually have two compartments within their container. These are the primary liquid product, for instance, the perfume, paint or an insecticide chemical, and a highly pressurized sealed gas which had become solution.
If an aerosol is exposed to a very high temperature, it may explode. This is true because when heated, the pressurized gas expands and increases in volume. Since the gas cannot escape from its locked nozzle, it eventually explodes. In fact, this is the reason behind the warning signs on its container, indicating that it should be stored in a cool environment, and kept away from the sunlight and high temperature.
Please read the summary of kinetic molecular theory of gases here.
With regards to the human body system, the air capacity of the human lungs decreases during cold conditions. Simply put, the volume of air received in the lungs is somewhat reduced due to its decreased environmental temperature. This implies less energy for daily activities, and may impact adversely on the performance of athletes, especially sprinters.
On the contrary, the air capacity of the lungs increases on a sunny day (higher temperature), allowing more air into it. This mechanism is explained through an internal bodily regulation called homeostasis.
Please read more on homeostasis here.
Other examples of Charles's law in real life are observed in the following instances:
Opening a soda drink from a can or bottle
Inflating and deflating tyres
Storage of gas
Car engines
Boiling of water in a covered pot
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Amazing facts in Chemistry
Plastic and Glass can decompose, but not in our lifetimes. It takes an average time of 450 years for plastics to decompose. As for the decomposition of glasses, it takes about 4,000 years
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals.
Copper is the only metal that is naturally antibacterial. For this reason, some children utilize 'copper water bottles' in schools
Water freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
NOTABLE POINTS IN Chemistry
The periodic table, also called periodic table of elements or Mendeleev's table, is a table that shows an organized arrangement of the 118 chemical elements according to their atomic number.
Out of the 118 elements; elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially.
The manner at which elements are arranged on this table reveals some similarities in their electronic configurations and chemical properties.
A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)
Step 1: Identify the given parameter from the question.
Fe = 69.94%, O = 30.06%.
Empirical formula = Fe?O?
Step 2: Convert the percentages to gram. (just attribute grams to the %).
Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in emperical formula.
Mole of Fe: 69.94/55.85 = 1.252mol
Mole of O: 30.06/16 = 1.879mol
Step 4: Divide both sides by the smallest mole ratio.
Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1, 1.879/1.252 = 1.5
We now have the formula = Fe1O1.5
Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.
For iron (Fe), we will have 1 x 2 = 2
For oxygen (O), we will have 1.5 x 2 = 3
Step 6: Write the empirical formula.
The empirical formula= Fe2O3
Iron(III)tetraoxosulphate(VI)
In chemistry, hydrocarbons can be classified as either aliphatic or aromatic. Recently, both classifications of hydrocarbon were based on their structure rather than their origin.
Aliphatic hydrocarbons are put into three main groups according to the types of bonds they possess. These are:
Alkanes
Alkenes
Alkynes
They are shown in the image below:
It's important to note the followings:
Alkanes have single bonds (only) in their structures.
Alkenes always have a carbon-carbon double bond present in their structure.
Alkynes always have a carbon-carbon triple bond present in their structure.
Aromatic hydrocarbons are classified into:
Organic chemistry is the study of carbon and it's compounds.
Carbon is the focus of organic chemistry because it has a wide chemical diversity in the sense that it can combine with other carbon atoms to form a long chain of carbon molecule. This ability and process whereby carbon can form a long chain of itself is called catenation.
A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.
Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.
The large molecules (above) have no specific chemical formula throughout their volume.
Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the modifications of Dalton's atomic theory.
Please read on Dalton's atomic theory and its modifications here.
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