Formulae, equations and hazards

Welcome to the foundation of your GCSE Chemistry course! Every reaction, calculation, and practical experiment you do will rely on the concepts in this section. If you can confidently write chemical formulae, balance equations, and assess laboratory hazards, you will be set up for success across all other topics.

What you'll learn:

How to write and interpret the chemical formulae of elements, simple compounds, and ionic salts.
The step-by-step process of writing balanced word and symbol equations with state symbols.
How to construct balanced ionic equations by identifying and removing spectator ions (Higher Tier only).
How to identify laboratory hazard symbols and evaluate the safety risks of practical investigations.

1. Chemical Formulae

Before we can write equations, we need to speak the language of chemistry. This starts with chemical formulae.

Definition

Chemical formula

A chemical formula represents the type and number of atoms of each element present in a substance.

Formulae of Elements

Most elements exist as single atoms (monatomic), such as Helium ( $He\text{He}$ ) or Iron ( $Fe\text{Fe}$ ). However, there are seven common elements that exist as diatomic molecules (pairs of atoms bonded together). You must memorize these seven:

Hydrogen ( $H2\text{H}_2$ )
Nitrogen ( $N2\text{N}_2$ )
Oxygen ( $O2\text{O}_2$ )
Fluorine ( $F2\text{F}_2$ )
Chlorine ( $Cl2\text{Cl}_2$ )
Bromine ( $Br2\text{Br}_2$ )
Iodine ( $I2\text{I}_2$ )

Tip

Diatomic mnemonic

To easily remember these seven diatomic elements, use the mnemonic: Have No Fear Of Ice Cold Beer (Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine).

Formulae of Simple Compounds

You are expected to recognize and recall the chemical formulae of several common simple compounds:

Water: $H2O\text{H}_2\text{O}$
Carbon dioxide: $CO2\text{CO}_2$
Ammonia: $NH3\text{NH}_3$
Methane: $CH4\text{CH}_4$
Hydrochloric acid: $HCl\text{HCl}$
Sulfuric acid: $H2SO4\text{H}_2\text{SO}_4$
Nitric acid: $HNO3\text{HNO}_3$

Formulae of Ions

Ionic compounds are made up of charged particles called ions. These consist of positively charged metal ions (cations) and negatively charged non-metal ions (anions).

While some ions consist of single charged atoms (like $Na+\text{Na}^+$ or $Cl−\text{Cl}^-$ ), others are polyatomic ions (groups of atoms with an overall charge). You must memorize the charges of these common polyatomic ions:

Hydroxide: $OH−\text{OH}^-$
Nitrate: $NO3−\text{NO}_3^-$
Sulfate: $SO42−\text{SO}_4^{2-}$
Carbonate: $CO32−\text{CO}_3^{2-}$
Ammonium: $NH4+\text{NH}_4^+$

To work out the chemical formula of an ionic compound, the total positive charge must exactly balance the total negative charge so that the overall compound has a neutral charge of zero.

Example

Deducing the formula of an ionic compound

Determine the chemical formula of aluminium sulfate.

Identify the individual ions and their charges. Aluminium is in Group 3 of the periodic table, so it forms a cation with a charge of $+ 3$ , written as $Al3+\text{Al}^{3+}$ . The sulfate ion is a polyatomic anion with a charge of $- 2$ , written as $SO42−\text{SO}_4^{2-}$ .
Find the lowest common multiple of the charges. The charges are $+ 3$ and $- 2$ . The lowest common multiple of $3$ and $2$ is $6$ .
Calculate the ratio of ions needed to balance the charges. To achieve a total charge of $+ 6$ from the aluminium, we need two aluminium ions:

\times (+3) = +6

To achieve a total charge of $- 6$ from the sulfate, we need three sulfate ions:

\times (-2) = -6

Write the final formula using subscripts and brackets. Because we need three of the polyatomic sulfate ion, we must place it in brackets before adding the subscript:

\text{Al}_2(\text{SO}_4)_3

Common Mistake

Incorrect bracket placement

Only use brackets around polyatomic ions when there is more than one of them in the formula. For example, sodium hydroxide is written as $NaOH\text{NaOH}$ , not $Na(OH)\text{Na(OH)}$ . However, calcium hydroxide is written as $Ca(OH)2\text{Ca(OH)}_2$ because two hydroxide ions are needed.

2. Chemical Equations

Chemical equations show what happens to atoms during a chemical reaction. Because of the law of conservation of mass, atoms cannot be created or destroyed. This means that every single atom present in the reactants must also be present in the products.

Word Equations

A word equation is a simple way of showing a chemical reaction using the names of the substances involved. Reactants are always on the left, and products are on the right.

\text{Reactant 1} + \text{Reactant 2} \rightarrow \text{Product 1} + \text{Product 2}

Common Mistake

The reaction arrow

Always use a single arrow pointing from left to right ( $→\rightarrow$ ) to represent the reaction. Never use an equals sign ( $=$ ), as this is not chemically correct.

Symbol Equations and State Symbols

A balanced symbol equation uses the chemical formulae of the reactants and products. It must also include state symbols to show the physical state of each substance at the reaction temperature:

(s) = solid
(l) = liquid (only used for pure liquids like water, $H2O(l)\text{H}_2\text{O}\text{(l)}$ , or molten metals)
(g) = gas
(aq) = aqueous (a substance dissolved in water, forming a solution)

Balancing Equations

To balance an equation, you add numbers (coefficients) in front of the chemical formulae. You must never change the small subscript numbers inside a chemical formula, as doing so changes what the substance actually is.

Example

Balancing a chemical equation

Write a balanced symbol equation, including state symbols, for the combustion of propane gas ( $C3H8\text{C}_3\text{H}_8$ ) in oxygen gas to produce carbon dioxide gas and water vapour.

Write the unbalanced equation with formulas and state symbols.

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(g)}

Balance the carbon atoms first. There are $3$ carbon atoms on the left, but only $1$ on the right. Place a $3$ in front of $CO2\text{CO}_2$ :

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(g)}

Balance the hydrogen atoms next. There are $8$ hydrogen atoms on the left, but only $2$ on the right. Place a $4$ in front of $H2O\text{H}_2\text{O}$ to make $8$ hydrogen atoms on the right ( $\times 2 = 8$ ):

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + 4\text{H}_2\text{O}\text{(g)}

Count and balance the oxygen atoms. There are now $10$ oxygen atoms on the right-hand side: $\times 2 = 6$ (from $CO2\text{CO}_2$ ) plus $\times 1 = 4$ (from $H2O\text{H}_2\text{O}$ ). To get $10$ oxygen atoms on the left, place a $5$ in front of $O2\text{O}_2$ ( $\times 2 = 10$ ):

\text{C}_3\text{H}_8\text{(g)} + 5\text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + 4\text{H}_2\text{O}\text{(g)}

Double-check the count for every element.
- Left side: $C=3\text{C} = 3$ , $H=8\text{H} = 8$ , $O=10\text{O} = 10$
- Right side: $C=3\text{C} = 3$ , $H=8\text{H} = 8$ , $O=10\text{O} = 10$ The equation is balanced!

3. Ionic Equations (Higher Tier Only)

In many reactions involving solutions, not all the ions present actually take part in the chemical reaction. Some ions simply remain in solution unchanged. We call these spectator ions.

Definition

Spectator ion

A spectator ion is an ion that exists in the same state on both the reactant and product sides of a chemical equation without undergoing any chemical change.

An ionic equation shows only the reacting particles (atoms, molecules, or ions) that undergo a chemical change.

Example

Writing a balanced ionic equation

Write a balanced ionic equation for the precipitation reaction between aqueous barium chloride and aqueous sodium sulfate, which forms solid barium sulfate and aqueous sodium chloride.

Write the full, balanced molecular equation including state symbols.

\text{BaCl}_2\text{(aq)} + \text{Na}_2\text{SO}_4\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + 2\text{NaCl}\text{(aq)}

Split all soluble ionic compounds (marked as 'aq') into their individual ions. Leave solids, liquids, and gases exactly as they are:

\text{Ba}^{2+}\text{(aq)} + 2\text{Cl}^-\text{(aq)} + 2\text{Na}^+\text{(aq)} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + 2\text{Na}^+\text{(aq)} + 2\text{Cl}^-\text{(aq)}

Identify and cross out the spectator ions. Look for ions that appear identical on both sides of the equation. Here, $2Na+(aq)2\text{Na}^+\text{(aq)}$ and $2Cl−(aq)2\text{Cl}^-\text{(aq)}$ are spectator ions:

\text{Ba}^{2+}\text{(aq)} + \cancel{2\text{Cl}^-\text{(aq)}} + \cancel{2\text{Na}^+\text{(aq)}} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + \cancel{2\text{Na}^+\text{(aq)}} + \cancel{2\text{Cl}^-\text{(aq)}}

Write down the remaining reacting species. This is your final, balanced net ionic equation:

\text{Ba}^{2+}\text{(aq)} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)}

4. Hazards, Risks, and Safety Precautions

Working in a chemistry laboratory is highly rewarding, but many chemicals can be dangerous if handled incorrectly. You must understand the difference between a hazard and a risk.

Definition

Hazard

A hazard is an intrinsic property of a substance or procedure that has the potential to cause harm.

Definition

Risk

A risk is the likelihood or probability that a hazard will cause harm under the specific conditions of its use.

For example, concentrated hydrochloric acid is a hazard because it is corrosive. However, the risk of it burning your skin is very low if you are wearing protective gloves and goggles, using a small volume, and working under supervision.

Hazard Symbols

To help identify dangers instantly, containers of chemicals are marked with standardized hazard symbols. These symbols are designed to be understood globally, regardless of language.

Common Laboratory Hazard Symbols

Here are the key hazard symbols you must recognize and understand:

Hazard Symbol	Meaning & Danger	Laboratory Precaution
Corrosive	May chemically destroy living tissue (skin, eyes) and attack metals.	Wear safety goggles, protective gloves, and a lab coat.
Flammable	Catches fire easily when exposed to air, sparks, or naked flames.	Keep away from naked flames (e.g., Bunsen burners); use a water bath or electric heater instead.
Toxic	Can cause serious health damage, systemic poisoning, or death if inhaled, swallowed, or absorbed through the skin.	Wear gloves, wash hands thoroughly after use, and work in a fume cupboard to avoid inhaling vapours.
Oxidising	Releases oxygen easily, which can cause other materials to burn much more intensely or violently.	Keep far away from flammable substances and organic materials.
Harmful / Irritant	Can cause irritation, reddening of the skin, or respiratory irritation, though less severe than toxic substances.	Avoid direct skin contact by wearing gloves and safety goggles.

Exam technique

In the exam

Always double-check your diatomic elements: When a question mentions "chlorine gas" or "oxygen gas" reacting, always write them as $Cl2(g)\text{Cl}_2\text{(g)}$ or $O2(g)\text{O}_2\text{(g)}$ , never as single atoms like $Cl\text{Cl}$ or $O\text{O}$ .
Never change subscripts when balancing: If you need to balance the oxygen in $H2O\text{H}_2\text{O}$ , write $2H2O2\text{H}_2\text{O}$ . Never change it to $H2O2\text{H}_2\text{O}_2$ (which is hydrogen peroxide, a completely different chemical!).
Watch for state symbols: Many exam questions will explicitly ask you to include state symbols. Re-read the question carefully; if it says "include state symbols", you will lose an easy mark if you omit them.
Be specific with safety precautions: Avoid writing generic answers like "be careful" or "wear safety equipment". Instead, state exact precautions relevant to the hazard, such as: "use a fume cupboard because the gas is toxic" or "wear gloves because the chemical is corrosive".

Self review

Check yourself

Can you write down the formulas of the polyatomic nitrate, sulfate, and carbonate ions including their charges?
Why is it incorrect to change the subscripts in a chemical formula when balancing an equation?
[Higher Tier] Can you explain what a spectator ion is and why they are left out of ionic equations?
What is the difference between a hazard and a risk?

What you'll learn:

How to write and interpret the chemical formulae of elements, simple compounds, and ionic salts.
The step-by-step process of writing balanced word and symbol equations with state symbols.
How to construct balanced ionic equations by identifying and removing spectator ions (Higher Tier only).
How to identify laboratory hazard symbols and evaluate the safety risks of practical investigations.

1. Chemical Formulae

Before we can write equations, we need to speak the language of chemistry. This starts with chemical formulae.

Definition

Chemical formula

A chemical formula represents the type and number of atoms of each element present in a substance.

Formulae of Elements

Hydrogen ( $H2\text{H}_2$ )
Nitrogen ( $N2\text{N}_2$ )
Oxygen ( $O2\text{O}_2$ )
Fluorine ( $F2\text{F}_2$ )
Chlorine ( $Cl2\text{Cl}_2$ )
Bromine ( $Br2\text{Br}_2$ )
Iodine ( $I2\text{I}_2$ )

Tip

Diatomic mnemonic

To easily remember these seven diatomic elements, use the mnemonic: Have No Fear Of Ice Cold Beer (Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine).

Formulae of Simple Compounds

You are expected to recognize and recall the chemical formulae of several common simple compounds:

Water: $H2O\text{H}_2\text{O}$
Carbon dioxide: $CO2\text{CO}_2$
Ammonia: $NH3\text{NH}_3$
Methane: $CH4\text{CH}_4$
Hydrochloric acid: $HCl\text{HCl}$
Sulfuric acid: $H2SO4\text{H}_2\text{SO}_4$
Nitric acid: $HNO3\text{HNO}_3$

Formulae of Ions

Ionic compounds are made up of charged particles called ions. These consist of positively charged metal ions (cations) and negatively charged non-metal ions (anions).

Hydroxide: $OH−\text{OH}^-$
Nitrate: $NO3−\text{NO}_3^-$
Sulfate: $SO42−\text{SO}_4^{2-}$
Carbonate: $CO32−\text{CO}_3^{2-}$
Ammonium: $NH4+\text{NH}_4^+$

To work out the chemical formula of an ionic compound, the total positive charge must exactly balance the total negative charge so that the overall compound has a neutral charge of zero.

Example

Deducing the formula of an ionic compound

Determine the chemical formula of aluminium sulfate.

Identify the individual ions and their charges. Aluminium is in Group 3 of the periodic table, so it forms a cation with a charge of $+ 3$ , written as $Al3+\text{Al}^{3+}$ . The sulfate ion is a polyatomic anion with a charge of $- 2$ , written as $SO42−\text{SO}_4^{2-}$ .
Find the lowest common multiple of the charges. The charges are $+ 3$ and $- 2$ . The lowest common multiple of $3$ and $2$ is $6$ .
Calculate the ratio of ions needed to balance the charges. To achieve a total charge of $+ 6$ from the aluminium, we need two aluminium ions:

\times (+3) = +6

To achieve a total charge of $- 6$ from the sulfate, we need three sulfate ions:

\times (-2) = -6

Write the final formula using subscripts and brackets. Because we need three of the polyatomic sulfate ion, we must place it in brackets before adding the subscript:

\text{Al}_2(\text{SO}_4)_3

Common Mistake

Incorrect bracket placement

2. Chemical Equations

Word Equations

A word equation is a simple way of showing a chemical reaction using the names of the substances involved. Reactants are always on the left, and products are on the right.

\text{Reactant 1} + \text{Reactant 2} \rightarrow \text{Product 1} + \text{Product 2}

Common Mistake

The reaction arrow

Always use a single arrow pointing from left to right ( $→\rightarrow$ ) to represent the reaction. Never use an equals sign ( $=$ ), as this is not chemically correct.

Symbol Equations and State Symbols

A balanced symbol equation uses the chemical formulae of the reactants and products. It must also include state symbols to show the physical state of each substance at the reaction temperature:

(s) = solid
(l) = liquid (only used for pure liquids like water, $H2O(l)\text{H}_2\text{O}\text{(l)}$ , or molten metals)
(g) = gas
(aq) = aqueous (a substance dissolved in water, forming a solution)

Balancing Equations

Example

Balancing a chemical equation

Write a balanced symbol equation, including state symbols, for the combustion of propane gas ( $C3H8\text{C}_3\text{H}_8$ ) in oxygen gas to produce carbon dioxide gas and water vapour.

Write the unbalanced equation with formulas and state symbols.

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(g)}

Balance the carbon atoms first. There are $3$ carbon atoms on the left, but only $1$ on the right. Place a $3$ in front of $CO2\text{CO}_2$ :

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(g)}

Balance the hydrogen atoms next. There are $8$ hydrogen atoms on the left, but only $2$ on the right. Place a $4$ in front of $H2O\text{H}_2\text{O}$ to make $8$ hydrogen atoms on the right ( $\times 2 = 8$ ):

\text{C}_3\text{H}_8\text{(g)} + \text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + 4\text{H}_2\text{O}\text{(g)}

Count and balance the oxygen atoms. There are now $10$ oxygen atoms on the right-hand side: $\times 2 = 6$ (from $CO2\text{CO}_2$ ) plus $\times 1 = 4$ (from $H2O\text{H}_2\text{O}$ ). To get $10$ oxygen atoms on the left, place a $5$ in front of $O2\text{O}_2$ ( $\times 2 = 10$ ):

\text{C}_3\text{H}_8\text{(g)} + 5\text{O}_2\text{(g)} \rightarrow 3\text{CO}_2\text{(g)} + 4\text{H}_2\text{O}\text{(g)}

Double-check the count for every element.
- Left side: $C=3\text{C} = 3$ , $H=8\text{H} = 8$ , $O=10\text{O} = 10$
- Right side: $C=3\text{C} = 3$ , $H=8\text{H} = 8$ , $O=10\text{O} = 10$ The equation is balanced!

3. Ionic Equations (Higher Tier Only)

In many reactions involving solutions, not all the ions present actually take part in the chemical reaction. Some ions simply remain in solution unchanged. We call these spectator ions.

Definition

Spectator ion

A spectator ion is an ion that exists in the same state on both the reactant and product sides of a chemical equation without undergoing any chemical change.

An ionic equation shows only the reacting particles (atoms, molecules, or ions) that undergo a chemical change.

Example

Writing a balanced ionic equation

Write a balanced ionic equation for the precipitation reaction between aqueous barium chloride and aqueous sodium sulfate, which forms solid barium sulfate and aqueous sodium chloride.

Write the full, balanced molecular equation including state symbols.

\text{BaCl}_2\text{(aq)} + \text{Na}_2\text{SO}_4\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + 2\text{NaCl}\text{(aq)}

Split all soluble ionic compounds (marked as 'aq') into their individual ions. Leave solids, liquids, and gases exactly as they are:

\text{Ba}^{2+}\text{(aq)} + 2\text{Cl}^-\text{(aq)} + 2\text{Na}^+\text{(aq)} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + 2\text{Na}^+\text{(aq)} + 2\text{Cl}^-\text{(aq)}

Identify and cross out the spectator ions. Look for ions that appear identical on both sides of the equation. Here, $2Na+(aq)2\text{Na}^+\text{(aq)}$ and $2Cl−(aq)2\text{Cl}^-\text{(aq)}$ are spectator ions:

\text{Ba}^{2+}\text{(aq)} + \cancel{2\text{Cl}^-\text{(aq)}} + \cancel{2\text{Na}^+\text{(aq)}} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} + \cancel{2\text{Na}^+\text{(aq)}} + \cancel{2\text{Cl}^-\text{(aq)}}

Write down the remaining reacting species. This is your final, balanced net ionic equation:

\text{Ba}^{2+}\text{(aq)} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)}

4. Hazards, Risks, and Safety Precautions

Working in a chemistry laboratory is highly rewarding, but many chemicals can be dangerous if handled incorrectly. You must understand the difference between a hazard and a risk.

Definition

Hazard

A hazard is an intrinsic property of a substance or procedure that has the potential to cause harm.

Definition

Risk

A risk is the likelihood or probability that a hazard will cause harm under the specific conditions of its use.

Hazard Symbols

To help identify dangers instantly, containers of chemicals are marked with standardized hazard symbols. These symbols are designed to be understood globally, regardless of language.

Common Laboratory Hazard Symbols

Here are the key hazard symbols you must recognize and understand:

Hazard Symbol	Meaning & Danger	Laboratory Precaution
Corrosive	May chemically destroy living tissue (skin, eyes) and attack metals.	Wear safety goggles, protective gloves, and a lab coat.
Flammable	Catches fire easily when exposed to air, sparks, or naked flames.	Keep away from naked flames (e.g., Bunsen burners); use a water bath or electric heater instead.
Toxic	Can cause serious health damage, systemic poisoning, or death if inhaled, swallowed, or absorbed through the skin.	Wear gloves, wash hands thoroughly after use, and work in a fume cupboard to avoid inhaling vapours.
Oxidising	Releases oxygen easily, which can cause other materials to burn much more intensely or violently.	Keep far away from flammable substances and organic materials.
Harmful / Irritant	Can cause irritation, reddening of the skin, or respiratory irritation, though less severe than toxic substances.	Avoid direct skin contact by wearing gloves and safety goggles.

Exam technique

In the exam

Always double-check your diatomic elements: When a question mentions "chlorine gas" or "oxygen gas" reacting, always write them as $Cl2(g)\text{Cl}_2\text{(g)}$ or $O2(g)\text{O}_2\text{(g)}$ , never as single atoms like $Cl\text{Cl}$ or $O\text{O}$ .
Never change subscripts when balancing: If you need to balance the oxygen in $H2O\text{H}_2\text{O}$ , write $2H2O2\text{H}_2\text{O}$ . Never change it to $H2O2\text{H}_2\text{O}_2$ (which is hydrogen peroxide, a completely different chemical!).
Watch for state symbols: Many exam questions will explicitly ask you to include state symbols. Re-read the question carefully; if it says "include state symbols", you will lose an easy mark if you omit them.
Be specific with safety precautions: Avoid writing generic answers like "be careful" or "wear safety equipment". Instead, state exact precautions relevant to the hazard, such as: "use a fume cupboard because the gas is toxic" or "wear gloves because the chemical is corrosive".

Self review

Check yourself

Can you write down the formulas of the polyatomic nitrate, sulfate, and carbonate ions including their charges?
Why is it incorrect to change the subscripts in a chemical formula when balancing an equation?
[Higher Tier] Can you explain what a spectator ion is and why they are left out of ionic equations?
What is the difference between a hazard and a risk?

What you'll learn:

1. Chemical Formulae

Formulae of Elements

Formulae of Simple Compounds

Formulae of Ions

2. Chemical Equations

Word Equations

Symbol Equations and State Symbols

Balancing Equations

3. Ionic Equations (Higher Tier Only)

4. Hazards, Risks, and Safety Precautions

Hazard Symbols

Recap questions

Review Formulae, equations and hazards by teaching Genie

Remember key concepts with flashcards

Formulae, equations and hazards

What you'll learn:

1. Chemical Formulae

Formulae of Elements

Formulae of Simple Compounds

Formulae of Ions

2. Chemical Equations

Word Equations

Symbol Equations and State Symbols

Balancing Equations

3. Ionic Equations (Higher Tier Only)

4. Hazards, Risks, and Safety Precautions

Hazard Symbols

Recap questions

Review Formulae, equations and hazards by teaching Genie

Remember key concepts with flashcards

Formulae, equations and hazards

What you'll learn:

1. Chemical Formulae

Formulae of Elements

Formulae of Simple Compounds

Formulae of Ions

2. Chemical Equations

Word Equations

Symbol Equations and State Symbols

Balancing Equations

3. Ionic Equations (Higher Tier Only)

4. Hazards, Risks, and Safety Precautions

Hazard Symbols

Recap questions

Review Formulae, equations and hazards by teaching Genie

Remember key concepts with flashcards

Formulae, equations and hazards Revision Guide

Formulae, equations and hazards

What you'll learn:

1. Chemical Formulae

Formulae of Elements

Formulae of Simple Compounds

Formulae of Ions

2. Chemical Equations

Word Equations

Symbol Equations and State Symbols

Balancing Equations

3. Ionic Equations (Higher Tier Only)

4. Hazards, Risks, and Safety Precautions

Hazard Symbols

Recap questions

Review Formulae, equations and hazards by teaching Genie

Remember key concepts with flashcards

Formulae, equations and hazards Revision Guide