無論你係Aim 3 定 5**嘅同學，definitions係Chem呢一科可以話係無可避免，一份Dse Chem卷起碼都有1-2分嘅definition題，看似好少，但已經足以成為你同其他人嘅差距，所以無論Aim咩嘅同學，一定要背熟曬啊！
係Chem要背嘅definitions其實唔算好多，好多背左其實可以令你更加容易理解Chem嘅內容，所以千其唔好死記爛背，理解左definitions所表達嘅野，然後將佢連貫起來，會學Chem學得更輕鬆！
以下係利用Definition就可以輕鬆答到嘅例子：
- Alkaline
Alkali is a water soluble substance reacts with an acid to give salts and water only.
呢個definitions可以得知acid可以同alkali react再form salt and water only。
係做題目上有好大幫助！點解咁講？平時大家做MC都應該遇到題目問
「Which of the reaction is an Acid-base reaction?」
A CuO(s) + H2SO4(aq)a`CuSO4(aq) + H2O(l)
B Mg(s) + 2HCl(aq)a`MgCl2(aq)+ H2(g)
C HCl(aq) + NaOH(aq) a` NaCl(s) + H2O(l)
D NH4Cl(s) + NaOH(aq)a`NaCl(aq) + NH3(g) + H2O(l)
唔知大家諗唔諗到答案呢，答案係C，等我解釋一下啦
A：首先CuO係solid，H2SO4係aqueous solution亦係一隻strong acid，同definitions嘅標準唔同所以就唔係答案。
B：Mg係solid，HCl係aqueous solution亦都係一隻strong acid，同definitions嘅標準唔同所以就唔係答案。
C：HCl係aqueous solution亦係一隻strong acid，NaOH都係aqueous solution係一隻strong base，除此之外，佢嘅product係NaCl，係salt嘅一種，然後H2O就係water。完全符合definiton，所以就係正確答案啦！
D：NH4Cl係solid，HCl係aqueous solution亦都係一隻strong acid，同definitions嘅標準唔同所以就唔係答案。
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isotopes |
Atoms with the same number of protons but different numbers of neutrons. |
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Octet structure |
Octet structure is fulfilled when there are 8 electrons in the outermost electron shell of an atom. |
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Metallic bond |
Metallic bond is a strong electrostatic force of attraction between the metallic ions and a ‘sea’ of delocalized electrons. |
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Ionic bond |
Ionic bond is a strong electrostatic force of attraction between the oppositely charged ions. |
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Ionization |
Ionization is a chemical process in which an atom gains or loses electrons to become an ion with negative or positive charge. |
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Covalent bond |
Covalent bond is a strong electrostatic force of attraction between the bond pair electrons and the positively charged nuclei of the bonded atoms. |
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Dative covalent bond |
Dative covalent bond is a covalent bond where the bond pair electrons are provided / contributed by the same atom. |
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Allotropes |
Allotropes are two or more forms of the same element in which the atoms or the molecules are arrange in different ways. |
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Aluminium anodization |
Aluminium anodization is an electrolytic process which increases the thickness of the oxide layer on aluminium, thus to increase corrosion resistance of aluminium. Note that in CANNOT increase the strength of aluminium. |
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Acid |
An acid ionizes in water to give hydrogen ion as the only cation. |
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Basicity |
Basicity is the maximum amount of ionization hydrogen atom in an acid molecule. |
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Alkali |
Alkali is a water soluble substance reacts with an acid to give salts and water only. |
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Strong acid |
A strong acid completely ionizes in water to give hydrogen ion as the only cations. |
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Weak acid |
A weak acid partially ionizes in water to give hydrogen ion as the only cations. |
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Strong alkali |
A strong alkali completely dissociates are already ionic compounds) in water to give hydroxide ion as the only anion. |
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Weak alkali |
A weak alkali partially dissociates are already ionic compounds) in water to give hydroxide ion as the only anion. |
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Standard solution |
Solution with accurately known concentrations. |
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Saturated solution |
A saturated solution is a solution that has dissolved all the solute it can at a given temperature |
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Petroleum |
Petroleum is formed when large quantities of dead marine organism that are buried underneath sedimentary rock and subjected to intense heat and pressure for a long time. |
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Functional group |
A functional group is an atom or a group of atoms which determines most of the properties of a compound. |
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Saturated hydrocarbons |
Saturated hydrocarbons do not contain any C=C or C≡C bond. |
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Addition polymerization |
Addition polymerization is a reaction in which monomers are joined together repeatedly to form a polymer molecule without elimination of small molecules. |
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Electronegativity |
Electronegativity is the ability of an atom of that element to attract bond pair electrons towards itself. |
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Hydrogen bond |
Hydrogen bond is a strong intermolecular force existing between a hydrogen atom bonded to highly electronegative atom in a molecule and the lone pair electrons from a highly electron negative atom in another molecule. |
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Electrolyte |
An electrolyte is a substance that contains mobile ions to conduct electricity only when it is in molten or aqueous state. |
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Salt bridge |
A salt bridge completes the circuit by allowing ions to pass across itself from one half cell to another. |
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Porous pot |
A porous pot is a device with very tiny holes on it. |
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Enthalpy change |
Enthalpy change is the heat change at constant pressure. |
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Standard enthalpy change |
Standard enthalpy change is the heat change at constant pressure with 1 atm and 298K. |
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Standard enthalpy change of neutralization |
It is the enthalpy change when an acid solution and a base / alkali solution react together / neutralize under standard conditions to produce 1 mole of water. |
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Standard enthalpy change of combustion |
It is the enthalpy change when 1 mole of substance is completely combusted in oxygen under standard conditions. |
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Standard enthalpy change of formation |
It is the enthalpy change when 1 mole of substance is formed from its constituent elements under standard conditions. |
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Standard enthalpy change of reaction |
It is the enthalpy change when the reactants react according to the molar quantity stated in a specific equation under standard conditions. |
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Hess’s Law |
The total enthalpy change of a chemical reaction is independent of the pathway between the initial and final states. |
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Initial rate |
Initial rate is the instantaneous rate at the start of the reaction |
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Activation energy |
the minimum energy possessed by the colliding reactant particles in order that a reaction can occur. |
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Effective collision |
An effective collision is a collision between reactant particles which leads to a chemical reaction. |
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Working principle of catalyst |
A catalyst provides an alternative reaction pathway with lower activation energy. |
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Avogadro’s Law |
It states that same number of moles of gas molecules at the same temperature and pressure contains the same volume of gas molecules. |
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Dynamic equilibrium |
At dynamic equilibrium, the rate of forward reaction is equal to the rate of backward reaction, and not equal to zero. |
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Condensation reaction |
Condensation reaction is a reaction in which two or more molecules are joined together to form a single product with the elimination of small molecules. |
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Amphoteric |
It can react as an acid or a base. |
