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
With regards to redox reactions, which of the following statement is wrong?
A. Redox reaction are examples of chemical change
B. Reduction is the gain of electron
C. Substances that donates election during chemical reaction are termed reductants
D. Oxidizing agents are always reduced in chemical reactions
E. Oxidation occurs at the cathode in electrolysis
F. Hydrogen is a reducing agent
In chemistry, physical change is associated only with the rearrangement of molecules while the internal composition of the substance remains the same.
A. True
B. False
_____ 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
Boyle's law state that the volume of a given mass of a gas is inversely proportional to its pressure, provided the temperature remains constant. This law was formulated by an English scientist named Robert Boyle in 1662. However, it may also be referred to as Boyle-Mariotte law or Mariotte's law.
Please read a detailed explanation on Boyle's law here.
Instances of Boyle's law are often seen around us. In fact, the mechanism of breathing is a function of Boyle's law. Below are examples of Boyle's law in real life:
Boyle's law is typically observed when a bottle of soda is opened. Recall that when sealed, the bottle of soda contains a gas within it, and that's carbon (IV) oxide or CO2. This gas is pressurized, and it remains within the bottle due to its small volume. For this reason, the CO2 has little space to move about, and this is just within the sealed bottle of soda.
When the bottle is opened, and depending on how it is opened, the CO2 is released at varying speed. For instance, if the bottle of soda is vigorously shaken and opened suddenly, the CO2 rushes out with the liquid, hence a foamy substance fizzes up and spill over, and perhaps making a mess of our body or clothes. This happens because the pressurized CO2 mixes up with the liquid when shaken up vigorously. The sudden opening of the bottle rapidly increases the volume of CO2 exposure, thus making it fizz out immediately.
You can read on the physical and chemical properties of acid here.
Meanwhile, understand that one can gently allow the CO2 gas escape from the bottle if the cork is opened slowly. When this is done, the pressure of gas within the bottle gradually decreases while the volume increases simultaneously, which is in accordance with Boyle's law.
Boyle's law comes into play when a syringe is used. A syringe is a medical equipment utilized in the insertion of fluid into the body. It is also useful in obtaining fluid from the body system.
Parts of a syringe are the barrel, plunger, hub and needle. The barrel may contain fluid depending on its usage, while the plunger functions by increasing or decreasing the volume of the barrel whenever it is pulled up or down.
When the plunger is pulled up, the volume of the barrel increases and its pressure decreases. When this happens, fluid is sucked into the barrel through the needle and hub. This simple process explains how fluid is taken from the human body into a syringe.
When the plunger is pulled down, the volume within the barrel decreases while its pressure simultaneously increases. Through this process, fluid present inside the barrel is forced out. This is how fluid is passed into the body.
Please read on liquid state of matter here.
If a gas is present inside the barrel of a syringe (instead of a liquid), the same process will occur, and this is in accordance in Boyle's law. Meanwhile, understand that the bicycle pump works in a similar way as the syringe.
The filling of balloons is a popular activity carried out by kids; and interestingly, Boyle's law is seen during the process.
Before air is blown into a balloon, it typically has a low pressure and large volume within it. For this reason, the balloon remains deflated, and one can easily squeeze it since it contains insufficient air.
When air is blown into the balloon, the empty space (volume) within it is reduced as air fills it. The pressure within the balloon increases, and due to its soft and elastic nature, it begins to expand. If air is continually blown into it, the spaces or volume within the balloon may become filled up. If this continues, the balloon may eventually burst from the increased pressure.
Please read a summary of the kinetic theory of gases here.
The balloon ruptures due to the lightness of its material, its elastic nature, the increased pressure and decreased volume (since it has been replaced by air).
Breathing involves a process of inhalation and exhalation. During inhalation, the diaphragm contracts, and so does the internal intercostal muscles. Also, the rib cage expands. This process increases the volume of the thoracic cage and decreases its pressure, allowing in air through the nostrils into the lungs.
You can read on bones of the human skeleton here.
During the process of exhalation, the reverse happens, bringing about a decrease in the volume of the thoracic cage while its pressure increases. This is in accordance with Boyle's law as air rushes out from the lungs through the nostrils.
An inflated tyre contains air, and this leaves little space (or decreased volume) within the tubes of the tyre. At the same time, the air pressure is increased within the tyre, giving rise to its pumped and rigid shape. This process obeys Boyle's law.
When a tyre is deflated, air leaves the tyre tubes. The tyre lacks proper shape and strength, thus making vehicular movement difficult. Meanwhile, understand that the tyre was able to become deflated due to an increased air pressure already present within it. Therefore, this air pressure is released outwards if there is an external puncture to the tyre tubes.
Please read on the concept of force and motion here.
Meanwhile, understand that the deflation process (net movement of air out of the tyres) results from a reduced pressure within the tyre alongside its increased volume. This inverse relationship between pressure and volume is in conformity with Boyle's law
Aerosols comprises spray paints, deodorants, perfumes, insecticides and the likes. Within its container, there are usually two components. These are the primary liquid product, for instance, the perfume, paint or an insecticide chemical, and a highly pressurized sealed gas which had become a solution.
Please read the introduction to gas laws in chemistry here.
On pressing the nozzle of the aerosol, the seal on the pressurized gas is opened, reducing its pressure in the process. On leaving the seal, the volume occupied by the gas increases as the aerosol moves out to a region of lesser pressure. This is a function of Boyle's law, and the net diffusion is felt through the scent of the aerosol, especially if it's a perfume or an insecticide.
As the name implies, deep water diving requires the diver to dive deep inside a water body such as a river, sea or ocean. Such diver must take caution when going deep into the water, as well as their ascension upwards. If this is done wrongly, they could suffer a decompression sickness (also referred to as 'the bends'), and this happens to be a life-threatening condition.
In scuba diving, the deeper the diver goes, the more an increase in his/her body pressure, and a consequent decrease in the volume occupied by nitrogen gas. This implies that more nitrogen gas will enter into the diver's blood and body fluids. This is in accordance with Boyle's law, and the reverse happens whenever the driver ascend to the top of the water body.
You can read on red blood cells and hemoglobin here.
Now, the major challenge during deep water diving is the rate at which the diver ascend towards the top of the water. If this ascension is rapid, the nitrogen gas inside the diver's blood will also expand rapidly (that is, a sudden increase in volume), and this is dangerous. This is so because the pressure reduces suddenly also, and the nitrogen bubbles in the blood and body fluids begin to expand and return to their normal volume rapidly, which can result to a foamy blood. This process can also cause the blood capillaries to rupture, including the bladder cells and other cell membranes. This results into an expansion of the spaces between the divers joint, which is indeed a very painful experience. These joint pains are called 'the bends'. This explains a similar process why deep-water fish die when they are brought to the water surface.
Please read interesting facts for students.
If the diver ascends slowly in scuba diving, nitrogen gas molecules will expand slowly until they regain their normal volume without causing problems to the diver. This process of gradually reducing the pressure of nitrogen in the blood is termed depressurization, and it should be slow, not rapid.
This volume and pressure relationship of blood nitrogen encountered in scuba diving is a function of Boyle's law.
Similar to skuba diving, this law is supported by the air bubbles blown out by a diver. These bubbles are seen to expand in size as they rise upward, and this is due to their reducing pressure and increasing volume.
Please read calculation questions on Boyle's law here.
Other real life examples of Boyle's law are observed in the following:
Storage of gas
Space and space suits
Air bubbles
Fire extinguisher
Internal combustion engine
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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
Below are the physical properties of metals:
They exist in solid state.
The have high densities.
They are good conductors of heat and electricity.
The have the ability to be polished, to glow, sparkle and reflect light.
They can be bent, flattened and made into sheets called foils.
They can be drawn into wires.
Iron undergoes magnetism while most metals are poorly magnetized.
They typical have high melting point.
They generally have high boiling point.
With the exception of lithium, sodium and potassium, most metals are generally hard.
They have the ability to make sound when in contact with other objects or metals.
Please read details on the physical properties of metals here
John Dalton is an English chemist who brought clarity into the composition of matter and the basis for their chemical reactions.
Below are Dalton's Atomic Theory:
All matter consists of tiny indivisible particles called atoms.
Atoms of the same element are identical to each other in every aspect because they have the same shape and mass, while atoms of different elements are different in all respect.
Atoms are indestructible and can neither be created nor destroyed.
Atoms of different elements can combine with each other in simple whole number ratios to form compounds.
Atoms of the same element share similar physical and chemical properties. They can also combine in more than one ratio to form two or more compounds.
Meanwhile, understand that the above theories of John Dalton had been modified.
Please read on Dalton's atomic theory and its modifications here
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:
