Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
function of the boiling chips |
to ensure smooth boiling of the mixture |
|
isotopes definition |
isotopes are atoms of the same element with the same number of protons and electrons, but different numbers of neutrons. add on: same chemical properties, but slightly different physical properties |
|
difference between a mixture and a compound in terms of its composition and separation methods |
mixture has no fixed composition, can be separated into its different components by physical separation methods. compound have a fixed composition, cannot be separated into its different components by physical separation methods, only chemical. |
|
one example of a compound and mixture each. |
compound -> water mixture -> air |
|
describe in terms of electrons, how a chlorine atom becomes a chloride ion. |
a chlorine atom will gain one valence electron to become a chloride ion |
|
explain why ionic bonds have high melting points |
it has strong electrostatic forces of attractions between the opposite charged ions |
|
why sodium chloride has to be dissolved in water or molten before it will conduct electricity |
to form molten that can carry charges to conduct electricity. solid = cannot conduct electricity |
|
this change always occurs when a metal atom turns into an ion. |
it becomes positively charged |
|
explain why the reaction stops. |
the reaction stopped as all the calcium present completely reached with water, hence no more hydrogen gas is produced. |
|
element |
a pure substance that cannot be broken down into two or more simpler substances by chemical processes |
|
compound |
a pure substance containing two or more elements that are chemically combined in a fixed ratio. |
|
mixture |
made up of two or more substances that are not chemically combined |
|
ion |
in an atom, the number of protons is the same as the number of electrons. an imbalance in the number of protons or electrons returns in ions. |
|
carbonate , ammonia and nitrate |
CO32- , NH3 , SO42- |
|
ionic bonds |
the strong electrostatic forces of attraction between positive and negative ions |
|
covalent bonds |
are a bond formed by the sharing of electrons between the two non-metallic atoms |
|
relative atomic mass Ar, defined by comparing the mass of one atom with the mass of another atom. what is that atom ? |
Carbon -12 or 12C |
|
relative formula mass Mr of MgSO4 = ? |
Mr of MgSO4 = 24 + 32 + 4(16) = 120 |
|
the mole and avogadro’s no. |
one mole of any substance contains 6X10 power 23 particles |
|
mole calculations |
no. of moles (mol) = mass of substance over molar mass of substance ( mol = mass over Mr ) |
|
maximum mass produced |
moles X Mr |
|
acids and bases |
an acid is a substance that produces hydrogen ions, H+ , in aqueous solution. |
|
properties of acids |
-> sour taste -> dissolve in water to form solution which conduct electricity -> turns blue litmus paper red (blue -> red) |
|
test for hydrogen gas |
test : place a lighted splint at the mouth of the test tube. reaction : if there is hydrogen gas present, hydrogen gas will extinguish the lighten splint with a ‘pop’ sound. |
|
metal + acid -> salt + hydrogen carbonate + acid -> salt + water + carbon dioxide hydrogen carbonates + acid -> salt + water + carbon dioxide |
metal oxide + acid -> salt + water metal hydroxide + acid -> salt + water base + acid -> salt + water alkali + acid -> salt + water |
|
test for carbon dioxide |
test : bubble the gas through limewater reaction : carbon dioxide forms a white precipitate with limewater. |
|
bases |
a base is any metal oxide or hydroxide that reacts with an acid to produce a salt and water only. |
|
alkali (a base that is soluble in water) |
an alkali is a substance that produces hydroxide ions, OH- , in aqueous solution |
|
when ammonia gas dissolves in water, ammonia ions and hydroxide ions are formed. |
ammonia + water ≈ ammonia ion + hydroxide ion |
|
properties of alkalis |
-> bitter taste and feel soapy -> turns red litmus paper blue (red -> blue) |
|
neutralisation reaction |
H+ (aq) + OH- (aq) -> H20 (l) |
|
alkalis, when heated with ammonia salts, causes ammonia gas to be given off. |
alkali + ammonium salt -> salt + water + ammonia ammonia gas can be recognised by its characteristic pungent smell |
|
test for ammonia gas , NH3 |
test : place damp red litmus paper into the gas observation : it turns blue in the presence of ammonia |
|
universal indicator |
ROYGBIV red, orange, yellow = acidic (pH0-6) green = neutral blue, indigo, violet = alkaline (pH 8-14)
|
|
colour change |
litmus paper : strong acidic solution -> red strong alkaline solution -> blue universal indicator : strong acidic solution -> red strong alkaline solution -> violet |
|
controlling pH of soil |
it is important to control the pH of soil because it will affect the growth and development of plants. most plants grow best in neutral or slightly acidic/alkaline soils. |
|
pH of soil may become unsuitable for plants to grow due to: |
-> too much fertilisers added to the soil. -> environmental pollution such as acid rain. |
|
way to treat acidity in soil |
add calcium hydroxide (slaked lime) or calcium oxide (quick lime). this process known as ‘slaking’. these bases neutralise the acid in the soil. |
|
classification of oxides |
|
|
acidic oxides |
- non-metallic oxides - often gases at room temperature (low bp) - most dissolve in water to form acids (H+ ions) -react with bases to form a salt and water only |
|
neutral oxides |
- insoluble in water - show neither acidic nor basic properties. do not react with neither acids nor bases. - e.g h20, NO (nitric oxide), CO (carbon monoxide) |
|
basic oxides |
- metallic oxides - often solids at room temp (high mp and bp) -some dissolves in water to form alkalis - react with acids to form a salt and water only. - can be soluble or insoluble. |
|
amphoteric oxides |
- react with acids to form a salt and water, behaving like a base. - react with bases to form a salt and water, behaving like an acid only 3 amphoteric oxides - lead(II) oxide (Pb0), aluminium oxide (AL2O3) , zinc oxide (ZnO) |
|
test that can be carried out on each sample, to show that the solution had changed from alkaline to acidic. |
test : add a few drops of universal indicator to a sample of the solution. observation before : universal indicator turns blue or purple in an alkaline solution. observation after : universal indicator turns red, orange or yellow in an acidic solution. |
|
explain in terms of the chemistry involved, the effect this chemical has on the soil |
calcium hydroxide or calcium oxide is a base that will neutralise the acids in the soil and raise its pH so that the soil becomes less acidic. |
|
composition by volume of clean, dry air |
78% nitrogen 21% oxygen 10% other gases (noble gases (argon) and carbon dioxide) |