Chemical reactions are not just for laboratories — they are happening in your kitchen right now, inside your body with every heartbeat, in the soap that cleans your hands, and in the concrete beneath your feet. Let's uncover the hidden chemistry of daily life.
Think about the last 24 hours. You have eaten food, washed your hands, breathed air and walked on solid ground.
Write down your answers before reading on:
Chemistry you can taste and smell
Cooking is applied chemistry. Every technique — baking, frying, fermenting — triggers specific chemical reactions that transform ingredients.
When baking powder is mixed with wet batter, a decomposition reaction produces carbon dioxide gas:
baking powder (heat) → carbon dioxide + other products
The CO₂ bubbles expand in the heat of the oven, making cakes and bread light and fluffy. Yeast uses fermentation to produce CO₂ and ethanol, which also makes bread rise:
glucose → ethanol + carbon dioxide + energy
When you toast bread, grill meat or roast coffee, the Maillard reaction occurs. Amino acids from proteins react with sugars at temperatures above about 140°C, producing hundreds of flavour and colour compounds. This is why grilled steak tastes different from boiled meat — new substances with new properties are formed.
Fermentation is used to make bread, yoghurt, cheese, beer and wine. In Australia, fermentation is central to winemaking in regions like the Barossa Valley and Margaret River. Yeast converts sugars from grapes into ethanol and carbon dioxide, transforming grape juice into wine.
The chemistry of staying alive
Your body is a continuous chemical reactor. Every second, billions of reactions convert food into energy, build new cells and remove wastes.
Digestion breaks large food molecules into smaller ones through chemical reactions. In your stomach, hydrochloric acid creates a strongly acidic environment (pH 1-2) that helps enzymes break down proteins. This is a form of decomposition — large protein molecules are broken into smaller amino acids.
Your cells release energy from glucose through cellular respiration, a type of combustion reaction:
glucose + oxygen → carbon dioxide + water + energy
This reaction is exothermic — it releases the energy your muscles, brain and organs need to function. Without it, life would not be possible.
Plants perform the reverse reaction — they capture light energy and store it in glucose:
carbon dioxide + water + light energy → glucose + oxygen
Photosynthesis is endothermic — it absorbs energy. It is also the foundation of nearly all food chains on Earth.
Reactions that keep us clean and build our world
Soap is made through saponification — a reaction between a fat or oil and a strong base (such as sodium hydroxide):
fat + base → soap + glycerol
Soap molecules have two ends: one attracted to water (hydrophilic) and one attracted to grease (hydrophobic). This allows soap to surround oil and dirt particles so water can wash them away. Detergents work similarly but are made from petroleum products and work better in hard water.
Bleaches such as sodium hypochlorite work by oxidation reactions that break apart coloured molecules, turning stains colourless. This is a chemical reaction — the stain molecules are changed into new substances.
Concrete is a mixture of cement, sand, gravel and water. When water is added to cement, a series of hydration reactions occur. Water molecules combine with compounds in the cement to form strong crystalline structures. This is why concrete gets harder over time — the chemical reactions continue for years, gradually increasing strength.
Rust is iron oxide, formed when iron reacts with oxygen and water:
iron + oxygen + water → hydrated iron(III) oxide (rust)
Rust is a problem for bridges, cars and ships. Prevention strategies include painting (barrier), galvanising (coating with zinc, which corrodes instead of iron), and using stainless steel (alloying iron with chromium).
"Cooking is just heating — no chemical reactions happen." No — cooking causes many chemical reactions (Maillard, caramelisation, denaturation) that create new substances with different properties from the raw ingredients.
"Soap and detergent are the same thing." No — soap is made from natural fats and bases. Detergents are synthetic and work better in hard water, but both use chemical reactions to remove grease.
Australia's industries rely on everyday chemical reactions. The Barossa Valley in South Australia is one of the world's great wine regions, where fermentation transforms grape sugars into ethanol, creating the complex flavours that make Australian wine famous.
The Sydney Harbour Bridge is protected from rust by regular maintenance including painting. The paint forms a physical barrier that prevents oxygen and water from reaching the steel. Without this rust prevention strategy, the bridge's iron would slowly convert to iron oxide through the same chemical reaction that turns an old nail orange.
In remote Indigenous communities, soap-making from local plant oils demonstrates practical application of saponification chemistry using available resources.
1. Which of the following is the main product of fermentation by yeast?
2. The Maillard reaction is responsible for which observation when cooking?
3. Which word equation best represents cellular respiration?
4. A builder notices that concrete hardens faster on a hot day than on a cold day. Which factor affecting reaction rate best explains this observation?
5. Which statement correctly compares soap and detergent?
1. Explain why bread rises when yeast is added to dough. Include the word equation for fermentation and describe how the products cause the bread to rise. 4 MARKS
2. Compare and contrast cellular respiration and photosynthesis using word equations. Explain how these two reactions are connected in the living world. 4 MARKS
3. Explain the chemistry of rust formation and describe TWO different strategies used to prevent rust on large steel structures such as the Sydney Harbour Bridge. For each strategy, explain how it interferes with the chemical reaction that produces rust. 4 MARKS
Go back to your Think First answer. Has your understanding changed?
C — Yeast fermentation produces ethanol and carbon dioxide. The CO₂ makes bread rise, while the ethanol evaporates during baking.
B — The Maillard reaction occurs between amino acids and sugars at high temperature, producing brown colour and complex flavours. This is why toasted bread tastes different from plain bread.
A — Cellular respiration: glucose + oxygen → carbon dioxide + water + energy. This is the reaction that releases energy in living cells.
D — Temperature affects the rate of the hydration reactions in concrete. Higher temperature means particles move faster and collide more frequently, so the reactions proceed faster.
C — Soap is made from natural fats and strong bases through saponification. Detergents are synthetic molecules designed to work well in hard water, where soap forms scum.
Model answer: Yeast causes fermentation, a chemical reaction that breaks down glucose without oxygen. The word equation is: glucose → ethanol + carbon dioxide + energy. The carbon dioxide gas forms bubbles in the dough. As the dough is heated in the oven, these bubbles expand (because gases expand when heated), causing the bread to rise and creating a light, airy texture. The ethanol evaporates during baking.
Model answer: Cellular respiration: glucose + oxygen → carbon dioxide + water + energy. Photosynthesis: carbon dioxide + water + light energy → glucose + oxygen. These reactions are essentially opposites. Photosynthesis captures energy from sunlight and stores it in glucose, while releasing oxygen. Respiration breaks down glucose using oxygen to release that stored energy, producing carbon dioxide and water. Together, they form a cycle: plants produce glucose and oxygen that animals use, and animals produce carbon dioxide and water that plants use.
Model answer: Rust forms when iron reacts with oxygen and water: iron + oxygen + water → hydrated iron(III) oxide. Strategy 1: Painting creates a physical barrier that prevents oxygen and water from contacting the iron surface, so the reactants cannot meet. Strategy 2: Galvanising involves coating steel with zinc. Zinc is more reactive than iron, so it reacts with oxygen and water first (sacrificial protection), preventing the iron from rusting. Both strategies work by removing one or more reactants from the reaction.
Jump into everyday chemistry! Match reactions to their real-world settings, from the kitchen to the construction site.
Tick when you have finished all activities and checked your answers.