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
Before we look into the physical properties of metals, it will be a good idea if we first understood what metals really are.
Majority of the naturally occurring elements on earth are metals. They normally do not exist in their pure form because rocks, sand and other earthen particles are mixed with them.
Metals are called 'ore' in their impure state. For instance, iron, tin and zinc are found on earth in their impure state as iron ore, tin ore and zinc ore respectively.
When metals are extracted from the earth, their purification is required before they can be used for the various beautiful things around us like airplanes, cars, engine and so on. A method of metal purification is via a process termed electrolysis.
Please read on the introduction to electrolysis here.
Note: Metals are generally solids at room temperature.
Metals will normally lose electrons(s) to form positive ions (called cations) in a chemical reaction. They are thus electropositive elements.
Please read on the periodic table of elements here
One of the ways to identify an object is through its physical properties or characteristics; and metals are no exception. Meanwhile, understand that metals have also got chemical properties too.
You can read on the chemical properties of matter here
Below are the physical properties or characteristics of metals:
They exist in the solid state at room temperature. However, understand that the metal 'mercury' is an exception since it exists in the liquid state at room temperature.
Please read on the solid state of matter and their characteristics here.
They generally have high densities. Among all metals, lithium has the lowest density while osmium has the highest density.
Please read more on density here.
Metals are generally good conductors of heat and electricity. This implies that they can transfer heat and electricity. For instance, the heat from a fire can be transferred to a cooking pot. We feel this heat whenever we touch the cooking pot with our bare hands.
It is worthy of note to state that metals conduct heat through a process termed conduction.
Please read more on heat transfer via conduction here.
Lead is the poorest conductor of heat while bismuth is the poorest conductor of electricity. The metal 'silver' is the greatest conductor of heat and electricity.
This is a feature that has to do with the state, quality or ability to be polished, to shine, glow, sparkle, glitter or reflect light. Metals generally have the luster quality.
Malleability is the ability of an object to withstand the process of hammering such that it can be bent or flattened and eventually made into thin sheets called foils.
Metals are able to take different shapes because of their malleability feature. Gold is the most malleable metal.
You can read interesting facts on gold here.
Being ductile is the ability of an object to be drawn into wires. For instance, copper wires and aluminium wires are drawn from copper and aluminium respectively.
Metals are generally ductile; and platinum is the most ductile of all.
Most metals are poorly magnetized. However, it is important to state that iron is a metal that is well magnetised.
The melting point (also called liquefaction point) of a substance is that point at which it changes from solid to liquid.
Metals generally have high melting points.
The metal tungsten (W) has the highest melting point at 3422°C while mercury (Hg) has the lowest melting point at -38.829°F.
Please read on the physical properties of matter here.
The boiling point of a liquid is the temperature at which the vapour pressure of the liquid equals the external atmospheric pressure.
When metals are heated, they melt into liquid before they start to boil. Metals generally have high boiling points.
Since mercury exists as liquid, it has the lowest boiling point of all metals. Conversely, the metal tungsten has the highest boiling point at 3422°C.
Please read on the concept of heat and temperature here.
With the exception of lithium (Li), sodium (Na) and potassium (K) which are soft metals, most metals are grenerally hard.
Most metals come in a variety of colors, although some are opaque. Below are some colors of metals:
Note: Most metals are coloured silver.
This is the ability of an object to make sound. Metals generally make different sounds when they come into contact with other objects or metals.
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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:
