Cambridge IGCSE Combined Science (0653) Chemistry Syllabus Flashcards

Comprehensive revision flashcards covering key topics, definitions, chemical reactions, and qualitative tests from the Cambridge IGCSE Combined Science 0653 Chemistry syllabus.

How is the structure of an atom described?

A central nucleus containing neutrons and protons, surrounded by electrons in shells.

How is the proton number (atomic number) defined?

The number of protons in the nucleus of an atom.

How is the mass number (nucleon number) defined?

The total number of protons and neutrons in the nucleus of an atom.

How are outer-shell electrons and occupied electron shells related to an element's position in the Periodic Table?

The number of outer-shell electrons equals the group number in Groups I to VII (Group VIII noble gases have a full outer shell), and the number of occupied electron shells equals the period number.

What is an ionic bond?

A strong electrostatic attraction between oppositely charged ions.

What are the general properties of ionic compounds?

High melting points and boiling points, good electrical conductivity when aqueous or molten and poor when solid, and generally soluble in water.

How is the giant lattice structure of ionic compounds described?

A regular arrangement of alternating positive and negative ions, exemplified by sodium chloride.

How is a covalent bond formed?

When a pair of electrons is shared between two atoms leading to noble gas electronic configurations.

What are the characteristic properties of simple molecular compounds?

Low melting points and boiling points, and poor electrical conductivity.

How is the molecular formula of a compound defined?

The number and type of atoms in one molecule.

What is electrolysis?

The decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current.

In a simple electrolytic cell, what are the names and polarities of the electrodes and the definition of the electrolyte?

The anode is the positive electrode, the cathode is the negative electrode, and the electrolyte is the molten or aqueous substance that undergoes electrolysis.

What general types of substances form at the cathode and anode during electrolysis?

Metals or hydrogen are formed at the cathode, and non-metals (other than hydrogen) are formed at the anode.

What is the difference between an exothermic and an endothermic reaction?

An exothermic reaction transfers thermal energy to the surroundings leading to an increase in surrounding temperature, whereas an endothermic reaction takes in thermal energy from the surroundings leading to a decrease in surrounding temperature.

How is activation energy, $E_a$, defined?

The minimum energy that colliding particles must have to react.

In terms of energy changes, which process is bond breaking and which is bond making?

Bond breaking is an endothermic process and bond making is an exothermic process.

What is the definition and function of a catalyst?

A catalyst increases the rate of a reaction and is unchanged at the end of the reaction.

How are redox, oxidation, and reduction defined in terms of oxygen?

Redox reactions involve simultaneous oxidation and reduction; oxidation is the gain of oxygen, and reduction is the loss of oxygen.

What are bases and alkalis?

Bases are oxides or hydroxides of metals, and alkalis are soluble bases.

How are acidic and basic oxides classified based on metallic character?

Non-metallic oxides are generally acidic (including $SO_2$ and $CO_2$), and metallic oxides are generally basic (including $CuO$ and $CaO$).

What are the general trends observed down Group I (alkali metals)?

Decreasing melting point, increasing density, and increasing reactivity with water.

What are the physical appearances and states of chlorine, bromine, and iodine at room temperature and pressure (r.t.p.)?

Chlorine is a pale yellow-green gas, bromine is a red-brown liquid, and iodine is a grey-black solid.

What are the distinguishing properties of the transition elements?

They are metals that have high densities, high melting points, form coloured compounds, and often act as catalysts as elements and in compounds.

Why are Group VIII noble gases unreactive?

They are monatomic gases with a full outer shell of electrons (noble gas electronic configuration).

What physical properties explain the uses of aluminium in aircraft, overhead electrical cables, and food containers?

Aircraft: low density; overhead electrical cables: low density and good electrical conductivity; food containers: resistance to corrosion.

Why can alloys be harder and stronger than pure metals?

The different sized atoms in alloys disrupt the regular lattice so the layers can no longer slide over each other.

What is the order of metals and reference elements in the reactivity series from most to least reactive?

Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold.

What conditions are required for the rusting of iron?

The presence of both oxygen and water.

What are the three chemical equations representing the extraction of iron from hematite in the blast furnace?

1. $C + O_2 \rightarrow CO_2$
2. $C + CO_2 \rightarrow 2CO$
3. $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$

What chemical reagents are used to test for the presence of water?

Anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate.

What are the stages in the treatment of the domestic water supply and their purposes?

Sedimentation and filtration to remove solids, treatment with carbon to remove tastes and odours, and chlorination to kill microbes.

What is the composition of clean, dry air?

Approximately $78\%$ nitrogen ($N_2$), $21\%$ oxygen ($O_2$), and the remainder as a mixture of noble gases and carbon dioxide ($CO_2$).

What are the sources and adverse effects of carbon monoxide ($CO$) and sulfur dioxide ($SO_2$)?

Carbon monoxide comes from incomplete combustion of carbon-containing fuels and is a toxic gas; sulfur dioxide comes from combustion of fossil fuels containing sulfur compounds and causes acid rain.

What is the difference between a saturated and an unsaturated hydrocarbon?

A saturated compound has molecules in which all carbon–carbon bonds are single bonds, while an unsaturated compound has molecules in which one or more carbon–carbon bonds are not single bonds (e.g. double bonds).

What is a homologous series?

A family of similar compounds with similar chemical properties, having the same general formula and displaying a trend in physical properties.

What are the uses of the fractions obtained from petroleum: refinery gas, gasoline/petrol, naphtha, diesel oil, and bitumen?

Refinery gas: heating and cooking; gasoline/petrol: fuel in cars; naphtha: chemical feedstock; diesel oil/gas oil: fuel in diesel engines; bitumen: making roads.

How do the properties of fractions change from the bottom to the top of a fractionating column?

Decreasing chain length and lower boiling points.

How can saturated and unsaturated hydrocarbons be distinguished chemically?

By their reaction with aqueous bromine; unsaturated hydrocarbons (alkenes) decolourise aqueous bromine, whereas saturated hydrocarbons (alkanes) do not react.

What is the formula used to calculate the retention factor ($R_f$) in paper chromatography?

$$R_f = \frac{\text{distance travelled by substance}}{\text{distance travelled by solvent}}$$

How are chloride ($Cl^-$), bromide ($Br^-$), and iodide ($I^-$) ions tested and identified?

Acidify the test solution with dilute nitric acid, then add aqueous silver nitrate.

How is the sulfate ion ($SO_4^{2-}$) tested and identified?

Acidify with dilute nitric acid, then add aqueous barium nitrate.

What are the qualitative chemical tests and results for hydrogen ($H_2$), oxygen ($O_2$), and carbon dioxide ($CO_2$)?

Hydrogen 'pops' with a lighted splint; oxygen relights a glowing splint; carbon dioxide turns limewater milky.

What are the characteristic flame colours for lithium ($Li^+$), sodium ($Na^+$), potassium ($K^+$), and copper(II) ($Cu^{2+}$)?

Lithium: red; sodium: yellow; potassium: lilac; copper(II): blue-green.

What are the observed results when testing aqueous copper(II) ($Cu^{2+}$) with aqueous sodium hydroxide and aqueous ammonia?

With aqueous sodium hydroxide: light blue ppt., insoluble in excess. With aqueous ammonia: light blue ppt., soluble in excess, giving a dark blue solution.

What are the observed results when testing aqueous zinc ($Zn^{2+}$) with aqueous sodium hydroxide and aqueous ammonia?

With aqueous sodium hydroxide: white ppt., soluble in excess, giving a colourless solution. With aqueous ammonia: white ppt., soluble in excess, giving a colourless solution.

What is the volume of one mole of any gas at room temperature and pressure (r.t.p.)?

$$24\,dm^3$$