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What is the best method to classify a chemical substance? - Coggle Diagram
What is the best method to classify a chemical substance?
Background Information
Groups
Group 8 - Noble Gases
Noble gases have stable electron configurations, therefore they rarely form few or no chemical bonds.
Functional groups
Functional groups such as Carboxyl, Hydroxyl, Carbonyl, Sulfhydryl etc. have covalent single or double bonds between different atoms.
Groups 1 and 2
Groups 1 and 2 have less than 1 or 2 valence electrons respectively and exist as cations (positively charged ions), and will form ionic bonds with metals.
Group 7 - Halogens
Group 7 elements have 7 valence electrons, and are anions (negatively charged ions). They will accept 1 electron from metals to complete their octet and to form ionic bonds.
Chemical substances
Structure
Molecular structures have covalent bonds, lattice structures have ionic bonds, metallic structures have metallic bonds.
Compounds
Elements that are combined using ionic, covalent or metallic bonds are compounds, and have distinct properties to the original element.
Mixtures
Heterogenous
Mixture made of multiple different substances which do not mix uniformly, and does not have any bonds. It can be separated easily.
Homogenous
Multiple different substances which do mix uniformly, and has no bonds. It is not able to be easily separated.
State of Matter
State of matter can impact the classification of substances in unique ways depending on the properties of the original substance. For example: water becomes more dense in the solid state, and becomes more brittle and less mobile.
Acids and Base
Acids have a sour taste, and the capacity to conduct electricity when dissolved in water. Bases have a bitter taste, and conduct electricity in aqueous solutions. Both can be ionic or covalent bonds
Substance groups
Metalloids
Transition metals have various numbers of valence electrons, and are known to form covalent bonds. They are semi-conductive, reactive, and have properties from both metals and non metals.
Metals
Key features of metals include luster, conductivity, malleability, ductility, density, reactivity and high melting/boiling points. They usually form metallic bonds.
Non-Metals
Non-metals are characterised as poor conductors, brittle, and can be found in solid, liquid and gas form. They always form ionic bonds.
Bonds
Covalent
Covalent bonds form when an atom shares electrons to form pairs between 2 atoms. This allows the atoms to have a more stable electron configuration because of their full outer shell. They also have low melting/boiling points
Metallic
Metallic bonds are a type of bond that are specific to metals. The electrons in metallic bonding become shared by all the atoms in the solid metal. This allows the substance to have properties such as ductility, malleability, electrical conductivity, and luster.
Ionic
Ionic bonds are created when one atom accepts or gives electrons to another atom, between an anion and a cation due to their attraction. Generally ionic Bonds are created between metals and nonmetals, which allows for high electrical conductivity, and high melting/boiling point. They also have High solubility, and their crystalline structure makes them very strong.
Limitations
Possible random errors
Random errors in experiments, like temperature fluctuations in heating, inconsistent electrode placement, magnetic field variations, sample discrepancies, incomplete reactions, and calibration issues, can affect the accuracy of results.
Equipment
Limited supplies - As there are limited supplies in the school, it is likely that a lot of equipment will be in use, therefore limiting the experiment.
Cost - Expensive equipment like X-ray diffraction, Infrared and UV spectroscopy machines are likely to be unavailable. Computational methods such as molecular modeling might also be unavailable, which limits identification of covalent bonds.
Sophisticated equipment - High precision instruments and sophisticated analysis tools may not be available in a school as they are usually not needed.
Safety - Some equipment involving toxic, corrosive, or hazardous materials could be restricted to students.
Factors effecting classification
Chemical composition
Composition of elements
Structural arangement
What a substance is made of and how it is structured is chemical composition. Example: H2O contains two hydrogen atoms bonded to an oxygen atom.
Physical Properties
State of Matter
Color
Density
Melting and boiling points
Solubility
Conductivity
Different substances have different physical properties. Example: Gold is solid at room temperature, has a high density and boiling point, a good conductor of electricity.
Functionality
Specific atomic arangement
Chemical reacitvity
Substances can be used for different functions and have different specific atomic arrangement. Example: Ethanol contains a hydroxyl functional group and is reactive as a primary alcohol.
Toxicity
Level of hazard
Toxicity levels
Substances with a different level of toxicity can be dangerous if consumed. Eg. Mercury is classified as a highly toxic substance and can be harmful.
Classification by use
Pharmaceutical
Agriculture
Industrial
Electronics
Energy
Different substances are used for different purposes. Example: Asprin is a pharmaceutical which reduces pain and inflammation.
Reactivity
Reaction with other substances
Readiness to react
Rate of reaction
Some substances react to other substances differently. Eg. Sodium chloride is a result of the combination of Sodium and chlorine which forms an ionic .
Isomeric forms
Structure difference
Isomers are molecules with the same number of atoms for each element but in a different arangement. Example: There are 2 possible isomers for C4H10 which are 2-methylpropane and n-butane.
Classification by source
Organic
Inorganic
Substances can be naturally or synthetically obtained. Eg. Asprin can be made in a lab and can be naturally found in Willow bark.
Bond
Ionic
Chemical
Metallic
Different substances have Ionic, covalent or metallic bonds which hold atoms together in place. Eg. NaCl contains an ionic bond while H2 contains a covalent bond.
Risk assessment
Precautions
Using Personal Protective Equipment (PPE), Handle chemicals properly, And use insulated materials when handling electrical materials.
Operating in a controlled environment and minimizing contamination by washing hands etc.
List of potential risks
Chemical hazards, Electrical Hazards, Burn Risks, Safety with Glassware, Fire Hazards are some potential risks.
Disposal
Dispose of Chemical waste, glassware, metallic objects, and electrical equipment in a safe and environmentally friendly way
Emergency procedures
Evacuating the area if there is a chemical spill, Fire alarm if a fire erupts, First aid kit for minor burns and cuts. Medical attention needed if there is electrical shock, or a major injury.
Research questions
What is a chemical substance?
What are some chemical substances that we have learned?
What are the methods to test the substances?
How do you test that you have an ionic compound?
What are the limitations to these methods?
What are the risk assessments to these methods?
Research design type
Experiment Design
Experimental design type aims to collect data regarding variation in different controlled environments. One of two scientific variables is used as the constant, and the other is used to measure the difference based on the constant.
Classification tests
For metallic bonds
Sturdiness test
Sturdiness is an object's ability to withstand stress. It can be tested with an Impact test, in which a weight is dropped on the substance to test the impact. Ionic compounds are hard and brittle. Metallic compounds are ductile and malleable, and covalent bonds are more soft.
UV Spectroscopy
This method detects metallic bonds in substances. Through using UV rays to test absorption of specific wavelengths, it signifies the presence of metallic bonds.
Magnetism test
If a compound attracts to a magnet, it likely contains a metallic bond.
For ionic bonds
Solubility Test
Solubility test can be carried out by dissolving a compound in water. Ionic compounds usually dissolve in water as they form ions. If the substance dissolves it is likely to have ionic bonds or polar covalent bonds.
Oxidisation test
As ionic compounds react differently with oxidising agents, if a substance reacts by forming ions, it is likely to contain ionic bonds.
Conductivity test
Ionic compounds are the best conductors of electricity in aqueous solutions because of their ions. This method tests conductivity by electrodes submerged into the solution of water and substance to record conductivity.
Melting/Boiling point test
Ionic compounds usually have higher melting and boiling points than other bonds to the strong electrostatic forces in ionic bonds. This test is carried out by monitoring the temperature at which a substance melts/boils.
For covalent bonds
Infrared Spectroscopy
Through this test the stretching and bending of covalent bonds can be observed. Each type of bond has a unique Infrared absorbtion frequency, therefore covalent bonds can be identified
X-ray diffraction
This method provides information about the crystal lattice structure of a substance, which allows for identification of covalent or ionic bonds.
General tests
Observational test
Through touch, it can be observed if a substance is in gaseous, solid, or liquid state, which can indicate the arrangement of molecules. The texture of a substance can also indicate type of bond. Through sight, color and appearance can indicate the type of bond. These tests alone are not enough to classify a substance definitively.