Key Concepts in Chemistry | Edexcel GCSE Combined Science Chemistry, Foundation tier (1SC0)
Key Concepts in Chemistry
- 359 questions
- 27 subtopics
- Paper 3
- Paper 3 and Paper 4
Key Concepts in Chemistry is examined in both chemistry papers, Paper 3 and Paper 4, as the key concepts that run through the whole course.
It covers formulae, word equations and balanced equations, hazard symbols and assessing risk, the changing model of the atom, protons, neutrons and electrons, the nucleus, mass number and atomic mass, elements and isotopes, calculating particle numbers and relative atomic mass, Mendeleev's periodic table, how the modern periodic table is arranged, electronic configuration and the periodic table, how ionic bonds form, ions in ionic compounds, formulae of ionic compounds, naming compounds and the ionic lattice, covalent bonds and molecules, dot and cross diagrams for simple molecules, classifying substances and the properties of ionic compounds, properties of simple molecular substances, and forms of carbon, graphite and diamond, fullerenes and graphene, polymers and models of bonding, the properties of metals, relative formula mass and percentage composition, empirical and molecular formulae, conservation of mass in closed and open systems, reacting masses from balanced equations and concentration in grams per cubic decimetre.
Sample questions from Key Concepts in Chemistry
Answer each one closed book first, then open the answer.
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Formulae, word equations and balanced equations
Give the formulae of calcium carbonate and sodium hydroxide.
Show the answer
They are CaCO₃ and NaOH. -
Protons, neutrons and electrons
Which subatomic particle has a mass so small it is treated as negligible?
Show the answer
The electron has a negligible mass compared with a proton or a neutron. -
Calculating particle numbers and relative atomic mass
An atom of fluorine has atomic number 9 and mass number 19. How many neutrons does it have, and how is this worked out?
Show the answer
It has 10 neutrons, found by subtracting the atomic number from the mass number: 19 − 9 = 10. -
Electronic configuration and the periodic table
Write the electronic configuration of a calcium atom.
Show the answer
Calcium is 2.8.8.2. -
Formulae of ionic compounds
Deduce the formula of aluminium oxide from the ions Al³⁺ and O²⁻.
Show the answer
The formula is Al₂O₃. -
Dot and cross diagrams for simple molecules
Describe the bonding in a molecule of water.
Show the answer
The oxygen atom shares one pair of electrons with each of the two hydrogen atoms. -
Graphite and diamond
What happens to the fourth outer electron of each carbon atom in graphite?
Show the answer
It becomes delocalised and can move through the layer. -
The properties of metals
Explain why metals are malleable.
Show the answer
Layers of ions can slide over one another without the metallic bonding being broken.
The 27 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Formulae, word equations and balanced equations | Formulae of oxygen, the diatomic elements, ammonia, methane, common acids and ions such as sulfate, carbonate, hydroxide and ammonium, writing word equations, and balancing equations with state symbols without changing any formula. | 20 |
| Hazard symbols and assessing risk | The purposes of hazard symbols and what the corrosive, flammable, oxidising, toxic, harmful and environmental symbols warn of, hazard and risk in practical work, suitable precautions, and how the likelihood, severity and perception of a risk are judged. | 19 |
| The changing model of the atom | Dalton's solid spheres, the discovery of the electron and the plum pudding model, alpha scattering and the nucleus, the neutron and electron shells, why models change, the structure of the atom, and peer review and how scientific results are communicated. | 18 |
| Protons, neutrons and electrons | The relative mass and charge of the proton, neutron and electron, why an atom has equal numbers of protons and electrons and no overall charge, and what happens to its charge when it loses an electron. | 11 |
| The nucleus, mass number and atomic mass | The sizes of the atom and the nucleus, why most of an atom is empty space yet nearly all its mass is in the nucleus, what mass number means and how neutrons are found from it, and the symbols <, ≪ and ~ for comparing sizes and masses. | 18 |
| Elements and isotopes | What every atom of one element shares, why the proton number identifies an element, what isotopes are, how their mass numbers differ and why they react identically. | 11 |
| Calculating particle numbers and relative atomic mass | Working out protons, neutrons and electrons from atomic and mass numbers, what relative atomic mass means, why chlorine's is 35.5 while fluorine's is almost exactly 19, and the isotope masses and abundances that decide it. | 12 |
| Mendeleev's periodic table | How Mendeleev ordered the elements by relative atomic mass and grouped them by properties, why he left gaps and how his predictions were confirmed, what periodic means, why some pairs fell out of order and were swapped, and ordering by atomic number today. | 15 |
| How the modern periodic table is arranged | How atomic number fixes an element's place in the table, periods and groups and why elements in a group behave alike, where the metals, non-metals and transition metals sit, and the metal and non-metal divide explained in terms of electrons. | 18 |
| Electronic configuration and the periodic table | How many electrons each shell holds, the configurations of sodium, chlorine, calcium and oxygen, the order shells fill, and how group and period follow from the configuration. | 13 |
| How ionic bonds form | Electron transfer between a metal and a non-metal, cations and anions, what dot and cross diagrams show, what an ion is and why a chloride ion is negative. | 11 |
| Ions in ionic compounds | Protons, neutrons and electrons in magnesium, chloride, oxide and aluminium ions, the ions formed by groups 1, 2, 6 and 7, and why atoms gain or lose electrons. | 14 |
| Formulae of ionic compounds | Deducing the formulae of ionic compounds such as calcium chloride, sodium sulfate, aluminium oxide and magnesium hydroxide from their ions, the rule that the charges must cancel, and why brackets are placed around a whole ion. | 8 |
| Naming compounds and the ionic lattice | What the –ide and –ate endings show about the elements in a compound, naming compounds such as calcium chloride and calcium carbonate, and the giant ionic lattice held together by strong electrostatic forces acting in all directions. | 12 |
| Covalent bonds and molecules | How covalent bonds form when non-metal atoms share electron pairs and why they are strong, single, double and triple bonds, what a molecule is, and the size of a small molecule in powers of ten and nanometres. | 15 |
| Dot and cross diagrams for simple molecules | The bonding in molecules of hydrogen, hydrogen chloride, water, methane, oxygen and carbon dioxide, the single and double bonds each contains, and the bonding and non-bonding electron pairs shown in dot and cross diagrams. | 8 |
| Classifying substances and the properties of ionic compounds | The four structure types, telling them apart by melting point, conductivity and solubility, and why ionic compounds melt high and conduct only when molten or dissolved. | 14 |
| Properties of simple molecular substances, and forms of carbon | Why simple molecular substances melt low and do not conduct, how molecule size affects boiling point, intermolecular forces, and why diamond and graphite are giant covalent forms of carbon. | 11 |
| Graphite and diamond | The bonding and arrangement of carbon atoms in diamond and graphite, the delocalised electrons in graphite, and how structure explains graphite's use for electrodes and as a lubricant, diamond's use in cutting tools, and graphite's softness yet high melting point. | 13 |
| Fullerenes and graphene | The size, shape and bonding of the C₆₀ fullerene, why it melts low and feels slippery, and what graphene is and why it conducts and is so strong. | 8 |
| Polymers and models of bonding | Poly(ethene) as a polymer of ethene with a covalently bonded carbon backbone and chains of varying length, why it is solid, and the limitations of dot and cross diagrams, ball and stick models, two-dimensional drawings and ionic lattice diagrams. | 13 |
| The properties of metals | The metallic lattice of positive ions and delocalised electrons, why metals conduct electricity and heat, are malleable and melt at high temperatures, the typical properties of metals and non-metals, and exceptions such as mercury and graphite. | 13 |
| Relative formula mass and percentage composition | Adding up relative formula masses for CO₂, CaCO₃, Ca(OH)₂ and H₂SO₄, finding the percentage by mass of an element, and working out empirical formulae from reacting masses. | 17 |
| Empirical and molecular formulae | Empirical formulae of glucose, hydrogen peroxide and butane, going from empirical formula and relative molecular mass to molecular formula, and the crucible experiment that finds the formula of magnesium oxide. | 16 |
| Conservation of mass in closed and open systems | The law of conservation of mass and why it holds, how mass changes in closed and open systems when a precipitate forms, a carbonate decomposes, magnesium burns or a candle burns, and calculating the mass of gas released. | 8 |
| Reacting masses from balanced equations | What a reacting mass calculation needs, why the equation must be balanced, and worked masses for calcium carbonate decomposing, magnesium burning, iron(III) oxide reduced and hydrogen burning. | 9 |
| Concentration in grams per cubic decimetre | What g dm⁻³ means, converting cm³ to dm³, calculating the concentration, mass or volume of a solution, what adding water does to concentration, and giving answers to an appropriate number of significant figures. | 14 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel GCSE Combined Science Chemistry, Foundation tier Active Recall Guide
Every topic, not just this one. 1,206 questions with their answers.