What do the Grade 9 Chemistry cards cover?

22 cards across 5 chapters of the national textbook: Chemistry and its importance, Measurements and scientific methods, Structure of the atom, Periodic classification of elements and Chemical bonding. You can take any chapter one card at a time on the page itself.

Is there a national exam in Grade 9?

No. Ethiopia sets national exams in Grade 6, Grade 8 and Grade 12 only. These cards are for your school's own exams, and for the national exam that comes a few years later.

Where do these cards come from?

They are drafted from Grade 9 Chemistry, the Ministry of Education textbook for this grade. A second pass that cannot see the chapter then re-derives every formula, constant and table row, and anything it cannot confirm is held back instead of published.

Yes. Every card here is free to read and the printable sheet is free to download. Neither needs an account.

When was this last checked?

6 September 2026. Cards arrive chapter by chapter, and the line under each one says when that card was last read through.

Free short notes and revision cards

Grade 9 Chemistry

Grade 9 Chemistry on Temari has 22 revision cards, arranged by the chapters of the Ethiopian national curriculum. Every card says when the rule applies, what each symbol in it stands for, and the mistake students most often make with it. They are free to read and need no account.

22
Cards: 5
Chapters: 5
Formulas: 11
Reference tables: Grade 9 Chemistry
Textbook: Free
Price: 6 September 2026
Last checked

Everything22Reference table11Formula5Common mistake3Rule3

Chemistry and its importance

Chemistry Overlap with Other Natural SciencesReference tableBiochemistry · Geochemistry · Physical chemistry · +1

Interdisciplinary Field	Overlapping Sciences
Biochemistry	Chemistry and Biology
Geochemistry	Chemistry and Geology
Physical chemistry	Chemistry and Physics
Medicinal chemistry	Chemistry and Medicine

When you use it

Use when explaining how chemistry connects and overlaps with other fields of science.

Watch out

Chemistry is regarded as the central science because all physical and biological systems depend on matter.

Drafted from Grade 9 Chemistry, pages 2-18, then checked twice before it went up

The five main branches of chemistryReference tableOrganic chemistry · Inorganic chemistry · Physical chemistry · +2

Branch	What it studies
Organic chemistry	Substances that contain carbon. Carbon forms a vast number of compounds, and most of the chemicals in living organisms are built on it.
Inorganic chemistry	Substances that are not primarily based on carbon, such as the compounds found in rocks and minerals.
Physical chemistry	Macroscopic properties, atomic properties and phenomena in chemical systems: reaction rates, the energy transferred in a reaction, and the structure of materials at the molecular level.
Analytical chemistry	The composition of matter. It separates, identifies and measures the chemicals in a sample.
Biochemistry	The chemical processes that take place in living things.

When you use it

Chemistry is the study of the properties, composition and structure of substances, the changes they go through and the energy released or absorbed during those changes, and modern chemistry splits into five main disciplines. Reach for this table to name them, and remember that industrial chemistry and environmental chemistry sit inside chemistry's scope rather than among the five.

Watch out

Every compound that contains carbon looks organic, so students file carbon dioxide, carbon monoxide, sodium carbonate, sodium hydrogen carbonate, calcium carbide and potassium cyanide under organic chemistry. All six are studied as inorganic. Organic chemistry begins at the hydrocarbons, and five carbon families stay on the inorganic side: the oxides of carbon, the carbonates, the hydrogen carbonates, the cyanides and the carbides. So the true or false item 'organic chemistry is the study of chemicals that are not based on carbon' is false. Organic chemistry takes the ones that are based on carbon, and inorganic chemistry takes the rest.

Measurements and scientific methods

Acid Dilution SafetyCommon mistake

When you use it

Use whenever mixing concentrated acid with water in the laboratory.

Watch out

Always add acid to water, never water to acid. Adding water to concentrated acid causes violent heat release and dangerous spattering.

Drafted from Grade 9 Chemistry, pages 19-52, then checked twice before it went up

Celsius to Kelvin ConversionFormula

T_{\text{K}} = T_{^\circ\text{C}} + 273.15

T_{\text{K}} = T_{^\circ\text{C}} + 273.15

$T_{\text{K}}$: temperature in Kelvin $\text{K}$
$T_{^\circ\text{C}}$: temperature in Celsius $^\circ\text{C}$

When you use it

Use to convert temperature values between Celsius and Kelvin scales.

Watch out

Never write a degree symbol on Kelvin temperatures. Write K, not degree K.

Drafted from Grade 9 Chemistry, pages 19-52, then checked twice before it went up

Density FormulaFormula

d = \frac{m}{V}

d = \frac{m}{V}

$d$: density $\text{kg}\,\text{m}^{-3}$
$m$: mass $\text{kg}$
$V$: volume $\text{m}^3$

When you use it

Use to calculate the density, mass, or volume of a substance.

Watch out

Check unit consistency. Mass in grams and volume in mL or cm^3 gives g/mL or g/cm^3, not kg/m^3.

Drafted from Grade 9 Chemistry, pages 19-52, then checked twice before it went up

SI Base UnitsReference tableLength · Mass · Time · +4

Base Quantity	Name of Unit	Symbol
Length	Meter	$\text{m}$
Mass	Kilogram	$\text{kg}$
Time	Second	$\text{s}$
Electrical current	Ampere	$\text{A}$
Temperature	Kelvin	$\text{K}$
Amount of substance	Mole	$\text{mol}$
Luminous intensity	Candela	$\text{cd}$

When you use it

Use when identifying or expressing the seven fundamental physical measurements.

Watch out

Mass is the only SI base unit that already includes a prefix (kilo- in kilogram).

Drafted from Grade 9 Chemistry, pages 19-52, then checked twice before it went up

Significant Figures in ArithmeticRule

When you use it

Use to round calculated answers to the correct precision after arithmetic operations.

Watch out

Addition and subtraction are limited by the fewest decimal places. Multiplication and division are limited by the fewest total significant figures.

Drafted from Grade 9 Chemistry, pages 19-52, then checked twice before it went up

Structure of the atom

Discovery of Fundamental Subatomic ParticlesReference tableCathode rays (electrons) · Anode rays (protons)

Ray / Particle	Discovered by	Key Properties
Cathode rays (electrons)	J. J. Thomson (1897)	Travel in straight lines, turn paddle wheels, deflect toward positive electric plates, independent of gas type.
Anode rays (protons)	Eugene Goldstein (1886)	Travel through perforated cathodes, deflect toward negative plates, properties and e/m ratio depend on gas.

When you use it

Use when reviewing the historical experiments and properties of cathode and anode rays.

Watch out

Cathode ray properties remain identical regardless of the gas used in the tube, whereas anode ray properties and their charge-to-mass ratio depend directly on the gas used.

Drafted from Grade 9 Chemistry, pages 53-110, then checked twice before it went up

Fundamental Laws of Chemical ReactionsReference tableLaw of Conservation of Mass · Law of Definite Proportions · Law of Multiple Proportions

Law	Scientist	Key Principle
Law of Conservation of Mass	Antoine Lavoisier (1789)	Mass is neither created nor destroyed during a chemical reaction.
Law of Definite Proportions	Joseph Louis Proust (1799)	A compound always contains the same elements in fixed proportions by mass.
Law of Multiple Proportions	John Dalton	Masses of one element combining with a fixed mass of another are in small whole-number ratios.

When you use it

Use when identifying or comparing the experimental laws that govern chemical combinations.

Watch out

The Law of Definite Proportions applies to one compound, while the Law of Multiple Proportions compares two or more different compounds formed from the same elements.

Drafted from Grade 9 Chemistry, pages 53-110, then checked twice before it went up

Number of Moles CalculationFormula

n = \frac{m}{M}

n = \frac{m}{M}

$n$: Number of moles $\text{mol}$
$m$: Given mass $\text{g}$
$M$: Molecular mass $\text{g}\,\text{mol}^{-1}$

When you use it

Use to calculate the amount of substance in moles from a known mass and molecular mass.

Watch out

Ensure the given mass is expressed in grams so that the unit cancels properly with molecular mass in grams per mole.

Drafted from Grade 9 Chemistry, pages 53-110, then checked twice before it went up

Periodic classification of elements

Average Atomic MassFormula

m_{\text{avg}} = \frac{p_1 m_1 + p_2 m_2}{100}

m_{\text{avg}} = \frac{p_1 m_1 + p_2 m_2}{100}

$m_{\text{avg}}$: Average Atomic Mass of an element $\text{amu}$
$p_1$: Percentage abundance of the first isotope $\%$
$m_1$: Atomic mass of the first isotope $\text{amu}$
$p_2$: Percentage abundance of the second isotope $\%$
$m_2$: Atomic mass of the second isotope $\text{amu}$

When you use it

Use to calculate the average atomic mass of an element from the isotopic masses and their natural abundances.

Watch out

Divide the total sum by 100 if using percentage values directly.

Drafted from Grade 9 Chemistry, pages 111-142, then checked twice before it went up

Electron Affinity Anomaly of Fluorine and ChlorineCommon mistake

When you use it

Use when comparing the electron affinity values of halogens in Group VIIA.

Watch out

Chlorine has a higher electron affinity than fluorine, despite fluorine being higher in the group. Fluorine has a very small 2p subshell, causing strong electron-electron repulsion that reduces the energy released.

Drafted from Grade 9 Chemistry, pages 111-142, then checked twice before it went up

Mass NumberFormula

A = Z + N

A = Z + N

$A$: Mass number, the total number of protons and neutrons $1$
$Z$: Atomic number, the number of protons in the nucleus $1$
$N$: Number of neutrons in the nucleus $1$

When you use it

Use when finding the mass number, atomic number, or number of neutrons in an atom.

Watch out

Do not count electrons in the mass number. Electrons contribute negligibly to total atomic mass.

Drafted from Grade 9 Chemistry, pages 111-142, then checked twice before it went up

Periodic Properties TrendsReference tableAtomic radius · Ionization energy · Electron affinity

Property	Across a Period (Left to Right)	Down a Group (Top to Bottom)
Atomic radius	Decreases	Increases
Ionization energy	Increases	Decreases
Electron affinity	Increases	Decreases

When you use it

Use when predicting or comparing periodic properties of elements based on their position in the periodic table.

Watch out

Across a period, nuclear charge increases while shielding remains constant, shrinking atomic radius and raising ionization energy.

Drafted from Grade 9 Chemistry, pages 111-142, then checked twice before it went up

Chemical bonding

Coordinate Covalent BondRule

When you use it

Use when a bonded electron pair is donated entirely by one atom rather than shared mutually.

Watch out

Do not assume both bonded atoms must each supply an electron. In a dative bond, a donor with a lone pair supplies both electrons to an acceptor atom with an empty valence shell.

Drafted from Grade 9 Chemistry, page 143 onwards, then checked twice before it went up

Electronegativity Difference and Bond TypeReference table< 0.5 · 0.5 - 2.0 · 2.0

Electronegativity Difference	Bond Type	Example
$< 0.5$	Nonpolar covalent	$H_2$ , $C_2H_6$
$0.5 - 2.0$	Polar covalent	$HCl$ , $H_2O$
\ge 2.0	Ionic	$NaCl$ , $KF$

When you use it

Use this guideline to classify a bond as nonpolar covalent, polar covalent, or ionic from the electronegativity values of bonded atoms.

Drafted from Grade 9 Chemistry, page 143 onwards, then checked twice before it went up

General Properties of Ionic CompoundsReference tablePhysical State · Melting/Boiling Points · Electrical Conductivity · +1

Property	Ionic Compounds	Explanation
Physical State	Hard, brittle crystalline solids	Strong electrostatic attraction; repulsive forces shatter lattice when struck.
Melting/Boiling Points	Very high (e.g. NaCl melts at $800^{\circ}C$ )	Requires large thermal energy to break strong electrostatic bonds.
Electrical Conductivity	Conducts in molten state and solution only	Ions are locked in solids but become free-moving mobile charges when melted or dissolved.
Solubility	Soluble in polar solvents	Polar solvent molecules interact with charged cations and anions.

When you use it

Use this summary to explain physical characteristics and conductivity behaviour of ionic salts.

Drafted from Grade 9 Chemistry, page 143 onwards, then checked twice before it went up

Polar Bonds in Nonpolar MoleculesCommon mistake

When you use it

Use when determining whether a molecule containing polar bonds is overall polar or nonpolar.

Watch out

Do not assume a molecule is polar just because it contains polar bonds. Symmetrical geometries such as linear in CO2 or tetrahedral in CCl4 cause opposing bond dipoles to cancel out, resulting in a nonpolar molecule.

Drafted from Grade 9 Chemistry, page 143 onwards, then checked twice before it went up

The properties of liquids: viscosity and surface tensionRuleShape and volume · Viscosity and fluidity · Viscosity and temperature · +5

Property	What it is	What to remember
Shape and volume	A liquid keeps its own volume but takes the shape of whatever container holds it.	Its particles are close together and are still free to slide past one another.
Viscosity and fluidity	Viscosity is a liquid's resistance to flowing and fluidity is how easily it flows. One is the reciprocal of the other, so no liquid is high in both.	Viscosity comes from the attraction between the particles and from long tangled molecules that cannot slide easily. Water is low, honey is high.
Viscosity and temperature	A liquid's viscosity falls as the liquid gets hotter, so it is not a fixed number for a substance.	Warmed honey pours like syrup and engine oil is thick on a cold morning. Gases do the opposite: their viscosity rises with temperature.
Surface tension	A molecule inside the liquid is pulled in every direction by its neighbours and the pulls cancel. One at the surface has no neighbours above it, so it feels a net inward pull and the surface shrinks to the smallest area it can.	Water is about 0.072 newtons per metre at 20 degrees Celsius, thanks to hydrogen bonding. Ethanol, whose molecules attract each other more weakly, is about 0.022.
The paper clip test	Steel is about eight times denser than water, so the clip has to sink once the surface gives way.	It stays up because the unbroken film bends under it and pushes back. One drop of detergent weakens the film and the clip goes straight down.
Diffusion	Liquid particles spread into one another, but far more slowly than gas particles do.	Each particle is hemmed in by its neighbours and can only take short crooked steps between collisions.
Density	A liquid is about a thousand times denser than a gas at ordinary pressure, because the particles are touching instead of far apart.	Compare a solid with a liquid only when the same substance is named. Ice at 0.92 against liquid water at 1.00 grams per cubic centimetre is the exception to know, and it is why ice floats.
Compressibility	Liquids are almost incompressible.	There is almost no empty space left between the particles. Water shrinks by well under one percent even at a hundred times atmospheric pressure.

When you use it

Reach for this when a question asks why honey pours slowly, why a paper clip rests on water without sinking, or why a liquid keeps its volume but takes the shape of its container. Every answer here comes back to how strongly the particles pull on each other.

Watch out

Students read the honey and water picture as a picture about density and write that honey flows slowly because it is heavier. Density and viscosity are separate properties, and one does not follow the other. Mercury is about 13.5 times denser than water and still pours almost as freely, roughly 1.5 times water's viscosity, while honey is only about 1.4 times denser than water and thousands of times more viscous. The question to ask is how strongly the particles grip each other as they slide. How heavy the liquid is does not answer it.

Common positive ions and their chargesReference tableHydrogen · Sodium · Potassium · +11

Ion	Formula	Where you meet it
Hydrogen	$\mathrm{H^{+}}$	every acid in water
Sodium	$\mathrm{Na^{+}}$	table salt, caustic soda
Potassium	$\mathrm{K^{+}}$	fertiliser, potash
Silver	$\mathrm{Ag^{+}}$	photographic salts
Ammonium	$\mathrm{NH_{4}^{+}}$	fertiliser, the one polyatomic cation
Magnesium	$\mathrm{Mg^{2+}}$	hard water, chlorophyll
Calcium	$\mathrm{Ca^{2+}}$	limestone, bone, cement
Barium	$\mathrm{Ba^{2+}}$	the sulfate used in X-ray meals
Zinc	$\mathrm{Zn^{2+}}$	galvanised sheet, dry cells
Iron(II)	$\mathrm{Fe^{2+}}$	the pale green solution
Copper(II)	$\mathrm{Cu^{2+}}$	the blue solution
Lead(II)	$\mathrm{Pb^{2+}}$	car batteries, old paint
Aluminium	$\mathrm{Al^{3+}}$	alum, water treatment
Iron(III)	$\mathrm{Fe^{3+}}$	rust, the yellow brown solution

When you use it

Use whenever you have to write a formula from a name. Take the charge of the metal from this table and the charge of the non-metal from its own, then swap the numbers so the total charge comes to zero.

Watch out

Iron and copper each form two ions, so the name must carry a Roman numeral: iron(II) is 2+ and iron(III) is 3+, and writing plain iron leaves the formula undecidable. Ammonium is the only positive ion here made of several atoms, and it behaves as one unit, so two of them are written as two brackets rather than eight hydrogens.

Common negative ions carrying one minusReference tableFluoride · Chloride · Bromide · +6

Ion	Formula	Where you meet it
Fluoride	$\mathrm{F^{-}}$	toothpaste, drinking water
Chloride	$\mathrm{Cl^{-}}$	table salt, hydrochloric acid
Bromide	$\mathrm{Br^{-}}$	sea water, photographic film
Iodide	$\mathrm{I^{-}}$	iodised salt, thyroid medicine
Hydroxide	$\mathrm{OH^{-}}$	every alkali in water
Nitrate	$\mathrm{NO_{3}^{-}}$	fertiliser, all of them soluble
Nitrite	$\mathrm{NO_{2}^{-}}$	meat curing salts
Hydrogencarbonate	$\mathrm{HCO_{3}^{-}}$	baking soda, blood buffering
Permanganate	$\mathrm{MnO_{4}^{-}}$	the deep purple oxidising agent

When you use it

Use for the right hand half of a formula. An ion of one minus needs one positive charge to balance it, so it pairs one to one with sodium and two to one with calcium.

Watch out

Nitrate and nitrite differ by a single oxygen and by one letter, and the ate ending is always the one with more oxygen. The same rule runs through sulfate and sulfite, and reading the wrong one changes the compound rather than just its name. Hydrogencarbonate is still written bicarbonate on shop packets, and both mean this ion.

Common negative ions carrying two or three minusReference tableOxide · Sulfide · Sulfate · +6

Ion	Formula	Where you meet it
Oxide	$\mathrm{O^{2-}}$	rust, quicklime, most minerals
Sulfide	$\mathrm{S^{2-}}$	ores, the rotten egg smell
Sulfate	$\mathrm{SO_{4}^{2-}}$	gypsum, copper sulfate
Sulfite	$\mathrm{SO_{3}^{2-}}$	food preservative
Carbonate	$\mathrm{CO_{3}^{2-}}$	limestone, washing soda
Chromate	$\mathrm{CrO_{4}^{2-}}$	the yellow solution
Dichromate	$\mathrm{Cr_{2}O_{7}^{2-}}$	the orange oxidising agent
Nitride	$\mathrm{N^{3-}}$	hard ceramic coatings
Phosphate	$\mathrm{PO_{4}^{3-}}$	fertiliser, bone, DNA

When you use it

Use when the formula needs brackets. An ion of this size takes two or three positive charges to balance, which is where subscripts outside a bracket start appearing.

Watch out

Brackets go round a polyatomic ion before the subscript, so calcium phosphate is written with the phosphate bracketed and a two outside it. Writing the subscript inside changes which atoms are multiplied and gives a different substance. Chromate and dichromate both carry two minus even though one holds twice the chromium, which is worth checking rather than guessing from the size.

The same subject in other years

An exam paper keeps asking for what the year below taught. Those cards are here too.

Your other Grade 9 subjects

Everything else in this year that has cards so far.

Questions students ask

What do the Grade 9 Chemistry cards cover?: 22 cards across 5 chapters of the national textbook: Chemistry and its importance, Measurements and scientific methods, Structure of the atom, Periodic classification of elements and Chemical bonding. You can take any chapter one card at a time on the page itself.
Is there a national exam in Grade 9?: No. Ethiopia sets national exams in Grade 6, Grade 8 and Grade 12 only. These cards are for your school's own exams, and for the national exam that comes a few years later.
Where do these cards come from?: They are drafted from Grade 9 Chemistry, the Ministry of Education textbook for this grade. A second pass that cannot see the chapter then re-derives every formula, constant and table row, and anything it cannot confirm is held back instead of published.
Is this free?: Yes. Every card here is free to read and the printable sheet is free to download. Neither needs an account.
When was this last checked?: 6 September 2026. Cards arrive chapter by chapter, and the line under each one says when that card was last read through.

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