Science 10 Chapter 6 & 7

State the Law of Conservation of Mass.

Matter is neither created nor destroyed in a chemical reaction. The total mass of the reactants equals the total mass of the products.

How do balanced chemical equations relate to the Law of Conservation of Mass?

A balanced equation has equal numbers of each type of atom on both sides, showing that atoms are rearranged — not created or destroyed. This reflects that mass is conserved.

In the equation 2H₂ + O₂ → 2H₂O, how is conservation of mass demonstrated?

Left side: 4 H atoms, 2 O atoms. Right side: 4 H atoms, 2 O atoms. Atom count is equal on both sides, so mass is conserved.

What is a word equation? Give an example.

A word equation uses the full names of reactants and products. Example: hydrogen + oxygen → water

hydrogen + oxygen → water

Unbalanced: H₂ + O₂ → H₂O | Balanced: 2H₂ + O₂ → 2H₂O

What do the symbols (s), (l), (g), and (aq) mean in a chemical equation?

(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water).

What is the role of coefficients when balancing equations?

Coefficients are numbers placed in front of chemical formulas to balance the number of atoms on each side without changing the formula of any substance.

Name the 6 types of chemical reactions.

1. Synthesis (combination) 2. Decomposition 3. Single displacement 4. Double displacement 5. Combustion 6. Neutralization

What is a synthesis reaction? Give an example.

Two or more substances combine to form one new substance. Example: 2Na + Cl₂ → 2NaCl

What is a decomposition reaction?

One substance breaks down into two or more simpler substances. Example: 2H₂O → 2H₂ + O₂

What is a single displacement reaction?

One element replaces another element in a compound. General form: A + BC → AC + B. Example: Zn + 2HCl → ZnCl₂ + H₂

What is a double displacement reaction?

The positive ions of two ionic compounds switch partners. General form: AB + CD → AD + CB. Example: NaCl + AgNO₃ → NaNO₃ + AgCl

What is a combustion reaction? Write the general form.

A substance reacts rapidly with oxygen, releasing energy (heat and light). Complete combustion: fuel + O₂ → CO₂ + H₂O

What is a neutralization reaction?

An acid reacts with a base to produce a salt and water. General form: acid + base → salt + water. Example: HCl + NaOH → NaCl + H₂O

What is incomplete combustion and why does it occur?

Incomplete combustion occurs when there is not enough oxygen for complete burning. Instead of producing only CO₂ and H₂O, it produces carbon monoxide (CO), soot (carbon particles), and other toxic compounds.

What are the problems/issues associated with incomplete combustion?

Produces toxic carbon monoxide (CO) gas; releases soot and fine particles causing air pollution; contributes to smog; harmful to human respiratory health; less energy released than complete combustion; CO is colourless and odourless — a silent danger.

What is the difference between complete and incomplete combustion products?

Complete: CO₂ + H₂O (clean burning). Incomplete: CO + soot (carbon) + H₂O + other pollutants. Incomplete combustion is less efficient and more harmful.

What is corrosion?

Corrosion is the gradual deterioration (wearing away) of a metal due to a chemical reaction with substances in its environment, such as oxygen, water, or acids.

What is rusting, and how does it differ from corrosion?

Rusting is a specific type of corrosion that affects only iron and iron alloys (e.g. steel). It produces iron oxide (Fe₂O₃). Corrosion is the broader term — all rusting is corrosion, but not all corrosion is rusting.

Write the chemical equation for rusting.

4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃. The iron hydroxide further dehydrates to form rust (Fe₂O₃·xH₂O), reddish-brown iron oxide.

What conditions speed up rusting?

Presence of water (moisture), oxygen, salt (electrolytes), and acids all accelerate rusting. Saltwater environments are especially corrosive.

What is beneficial corrosion? Give two examples.

Corrosion that is actually useful or protective: 1. Patina on copper (green coating) protects the underlying metal. 2. Aluminium oxide layer on aluminium acts as a barrier against further corrosion.

List 4 ways to prevent corrosion.

1. Painting or coating the metal surface 2. Galvanizing (coating with zinc) 3. Using stainless steel or alloys 4. Cathodic protection (sacrificial anode — attaching a more reactive metal like magnesium)

What problems are associated with corrosion and rusting in everyday life?

Structural damage to bridges, buildings, and infrastructure; vehicle rust leading to unsafe cars; pipeline failures; costly repairs and replacements; environmental contamination from corroded industrial equipment; safety hazards from weakened metal structures.

Define an acid using the Arrhenius definition.

An Arrhenius acid is a substance that produces hydrogen ions (H⁺) when dissolved in water. Example: HCl → H⁺ + Cl⁻

Define a base using the Arrhenius definition.

An Arrhenius base is a substance that produces hydroxide ions (OH⁻) when dissolved in water. Example: NaOH → Na⁺ + OH⁻

Give 4 examples of common acids and where they are found.

1. Hydrochloric acid (HCl) — stomach acid 2. Acetic acid (CH₃COOH) — vinegar 3. Sulfuric acid (H₂SO₄) — car batteries 4. Citric acid — lemons and citrus fruits

Give 4 examples of common bases and where they are found.

1. Sodium hydroxide (NaOH) — drain cleaner 2. Ammonia (NH₃) — household cleaners 3. Sodium bicarbonate (NaHCO₃) — baking soda 4. Magnesium hydroxide — antacids (Milk of Magnesia)

List 4 properties of acids.

1. Taste sour (e.g. lemon) 2. Turn blue litmus paper red 3. React with metals to produce hydrogen gas 4. Have a pH below 7

List 4 properties of bases.

1. Taste bitter 2. Feel slippery or soapy 3. Turn red litmus paper blue 4. Have a pH above 7

What is the pH scale and what does it measure?

The pH scale runs from 0-14 and measures the concentration of H⁺ ions in a solution. pH < 7 = acidic; pH = 7 = neutral; pH > 7 = basic (alkaline). Each unit represents a 10× change in concentration.

What is a neutralization reaction and what does it produce?

When an acid and a base react together, they neutralize each other to produce a salt and water. Example: HCl + NaOH → NaCl + H₂O

How do acids affect the environment? Give examples.

Acid rain (from SO₂ and NOₓ emissions) lowers pH of lakes, killing aquatic life; damages forests and soils; corrodes stone buildings and statues; makes drinking water unsafe.

How are acids and bases used in agriculture?

Farmers test soil pH and adjust it — adding lime (calcium carbonate, a base) to neutralize acidic soil, or adding sulfur compounds to lower pH for acid-loving plants. Proper pH maximizes nutrient uptake.

How does your stomach use acid, and what happens when there is too much?

The stomach produces hydrochloric acid (HCl) to digest food and kill bacteria. Excess acid causes acid reflux and heartburn. Antacids (bases like Mg(OH)₂) neutralize the excess acid.

Household uses of bases?

1. Baking soda (NaHCO₃) used in baking — reacts with acids to release CO₂, making baked goods rise. 2. Drain cleaners (NaOH) break down fats and proteins to unclog pipes.

What is acid deposition and what causes it?

Acid deposition (including acid rain, acid snow, and dry acid particles) is caused by sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) released from burning fossil fuels. These react with water in the atmosphere to form sulfuric and nitric acids.