Organic and inorganic chemicals in the home
Organic compounds are built on carbon chains. Examples at home: acetic acid in vinegar, ethanol in hand sanitiser, sugar, soap and detergent, cooking oil, plastics.
Inorganic compounds are mostly not built on carbon chains. Examples: sodium chloride (table salt), sodium hydrogen carbonate (baking soda, NaHCO₃), sodium hypochlorite (bleach, NaOCl), sodium hydroxide (drain cleaner, NaOH), hydrochloric acid (some toilet cleaners).
Useful words: solute (what dissolves), solvent (what it dissolves in), concentration (how much solute in a volume), corrosive (eats away skin or metal), toxic (poisonous).
The pH of household products
The pH scale runs from 0 to 14. Below 7 is acidic, 7 is neutral, above 7 is basic. Each step of 1 means 10 times stronger.
- Toilet cleaner (HCl): about 1–2
- Vinegar: about 2.5–3
- Dish soap: about 7–8
- Baking soda solution: about 8.3
- Ammonia cleaner: about 11–12
- Bleach: about 12–13
- Drain cleaner (NaOH): about 13–14
Products at both ends are corrosive. Acids remove limescale and rust; bases break down grease and hair. You can test pH at home with red cabbage juice or pH paper.
Why some substances mix and others do not
Water molecules are polar: one end is slightly positive, the other slightly negative. They pull on ions (like Na⁺ and Cl⁻ in salt) and on other polar molecules (like sugar), so these dissolve.
Oil molecules are non-polar. Water molecules stick to each other more strongly than to oil, so oil is pushed out and floats as a layer. Rule: like dissolves like.
Soap and detergent have two ends: a water-loving head and an oil-loving tail. They hold oil and water together, which is why soap removes grease.
Dilution: making a strong product weaker
When you add water, the amount of chemical stays the same, but the volume grows, so the concentration falls.
C₁V₁ = C₂V₂ (C = concentration, V = volume; 1 = before, 2 = after).
Example: 50 mL of 6% bleach made up to 600 mL gives C₂ = 6 × 50 ÷ 600 = 0.5%.
Safety: always add the concentrated chemical to water (especially acid), never water to concentrated acid, because heat can make it spit.
Chemical reactions at home and how conditions change them
Common reaction types at home:
- Neutralisation (acid + base → salt + water): vinegar + baking soda, antacid in the stomach.
- Combustion: gas stove, candle (fuel + oxygen → CO₂ + H₂O).
- Decomposition: hydrogen peroxide slowly breaks into water and oxygen.
- Single displacement / corrosion: rusting of iron.
- Double displacement: hard water forms soap scum.
Conditions change the speed: higher temperature, higher concentration, smaller pieces (more surface area) and a catalyst all make a reaction faster. You can test this with a fizzing tablet in hot and cold water.
Never mix: bleach + ammonia gives toxic chloramine gas; bleach + acid cleaner gives chlorine gas. Wear gloves, open windows, read the label hazard symbols.
Products at work, comparing products and safe disposal
Many jobs use chemical products: hairdressers use peroxide and ammonia dyes, cleaners use disinfectants, mechanics use solvents and battery acid, farmers use fertilisers and pesticides. Workers learn the safety data sheet (SDS) for each one.
To compare products in one group (for example three dish soaps), look at the active ingredient, its concentration, price per use, hazard symbols and how green the packaging is.
Improper disposal (drain, soil, normal bin) can poison fish, add excess nutrients to lakes (algae blooms), harm sewage bacteria, and leak into ground water. Better: buy only what you need, use it up, keep it in its original labelled bottle, and take leftovers, batteries and paint to a hazardous waste drop-off.
Key formulas and definitions
- pH < 7 acidic, 7 neutral, > 7 basic; 1 pH step = 10 times
- C₁V₁ = C₂V₂ (dilution)
- Acid + base → salt + water (neutralisation)
- NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂
- Like dissolves like: polar with polar, non-polar with non-polar
- Never mix bleach with ammonia or acids
Worked examples
1. Sort these as acidic, neutral or basic: vinegar (pH 3), dish soap (pH 7), bleach (pH 12.5).
Vinegar: pH 3 is below 7, so acidic. Dish soap: pH 7, neutral. Bleach: pH 12.5 is above 7, so basic.
2. You have 100 mL of 10% cleaner. You add 400 mL of water. What is the new concentration?
V₂ = 100 + 400 = 500 mL. C₂ = C₁V₁ ÷ V₂ = 10 × 100 ÷ 500 = 2%.
3. A label says: mix 1 part cleaner with 9 parts water. The cleaner is 20%. What is the final concentration?
Total parts = 10. C₂ = 20 × 1 ÷ 10 = 2%.
4. How much 12% hydrogen peroxide do you need to make 300 mL of 3% solution?
V₁ = C₂V₂ ÷ C₁ = 3 × 300 ÷ 12 = 75 mL. Put 225 mL water in a container and add the 75 mL peroxide.
5. Why does a fizzing tablet react faster in warm water than in cold water?
In warm water the particles move faster and hit each other more often and with more energy, so more collisions lead to reaction each second.
Common mistakes
- Thinking a higher pH means more acidic. Higher pH means more basic.
- Thinking diluting removes the chemical. The amount stays the same; only the concentration falls.
- Mixing two cleaners to make a 'stronger' cleaner. Bleach with ammonia or acid makes toxic gas.
- Pouring leftover paint, oil or solvent down the sink because it 'goes away'. It reaches rivers and ground water.