Netherlands HAVO 5 (eindexamenjaar) Chemistry
Chapters: 5
1. Chemical processes and cycles (part 2)
Energy calculations · Reaction kinetics · Conservation laws and cycles
- Enthalpy, Calorimetry and Hess's Law – Enthalpy H = U + pV. At constant pressure the heat taken in or given out equals ΔH; at constant volume it equals ΔU. We measure ΔU in a sealed bomb calorimeter and ΔH in an open cup calorimeter, using q = C ΔT or q = m c ΔT. For gases, ΔH = ΔU + Δn_g RT. The reaction enthalpy ΔrH is negative for exothermic and positive for endothermic reactions, and ΔrH° = ΣΔfH°(products) − ΣΔfH°(reactants). Hess's law: the total enthalpy change is the same whether a reaction happens in one step or many, so thermochemical equations can be added like algebra.
- Rate of a Chemical Reaction – The rate of a reaction tells how fast a reactant is used up or a product is made, per unit time. Rate = −Δ[R]/Δt = +Δ[P]/Δt (unit mol L⁻¹ s⁻¹). The rate law, rate = k[A]^x[B]^y, is found by experiment; x + y is the order. Molecularity is the number of particles that collide in one elementary step.
- The Law of Conservation of Mass – In a chemical reaction, mass is not made and not destroyed. The total mass of the substances before the reaction equals the total mass after it. This is true because atoms are only rearranged: the same atoms, in the same numbers, are there before and after. If a gas leaves or joins from the air, the mass on a balance seems to change, but when we count every substance, the total stays the same. A related rule, the law of definite proportions, says a pure compound always has its elements in the same mass ratio (water is always 1 g hydrogen to 8 g oxygen).
2. Design and experiments (part 2)
Chemical process design · Molecular modelling
- Polymers – A polymer is a giant molecule made by joining many small molecules (monomers) into a long chain. In addition polymerisation, monomers with a C=C double bond open up and link with nothing lost (ethene → poly(ethene)). In condensation polymerisation, two kinds of monomer with reactive groups at both ends join and give off a small molecule such as water at every link (nylon, polyester). Nature makes polymers too: starch, cellulose, proteins, DNA, rubber. Separate chains give thermoplastics that melt and can be recycled; cross-linked chains give thermosets that never melt. Most plastics do not rot, so we must reduce, reuse and recycle them.
- Molecular Modelling: Seeing Molecules in 3D – A molecular model is a small stand-in for a molecule that you can see and turn around. Ball-and-stick models show bonds and angles, space-filling models show size, and computer models can also show how a reaction happens step by step. From the model you can predict the shape of a molecule and follow a reaction mechanism.
3. Innovation in chemistry
Features of innovative processes · Sustainability · Innovative processes
- How Structure Decides the Properties of Substances – The way particles are held together decides how a substance behaves. Ionic and giant covalent substances have strong bonds all through, so they melt very high. Small molecules have weak forces between molecules, so they melt and boil low. Metals have free electrons, so they conduct.
- Structure and Properties of Materials – What a material does (its property) depends on what is inside it (its structure). Metals conduct because they have free electrons. Solid salt does not conduct because its ions are locked, but melted or dissolved salt does because the ions can move. Sugar dissolves but stays neutral, so it does not conduct. Long plastic chains are strong; a chain with weak links can be cut by bacteria, so it is biodegradable. Chains with OH groups attract water, so they swell into a gel. To predict a property, ask: what are the particles, do they carry charge, can they move, and how strongly do they attract each other or water?
- Sustainability – Sustainability means meeting our needs today without taking away the ability of future people to meet theirs. It rests on three pillars — environment, society and economy. A resource is used sustainably when we use it no faster than it renews. Today humanity uses about 1.7 Earths' worth of resources a year, and this use is very unequal. Stewardship, careful planning and spatial tools like GIS help us move towards sustainability.
- Materials Innovation: From a Lab Idea to a New Product – Chemical innovation turns an idea into a product in stages: idea, lab test, pilot, factory, market. New materials (alloys, bio-based plastics, smart materials) and new food processes are designed from structure and tested for performance, cost and safety. Scale-up from grams to tonnes and the market decide which ideas succeed.
4. Chemical industry
Industrial processes and green chemistry · Energy conversions · Process technology and sustainability · Risk and safety · Quality and health
- Green Chemistry – Green chemistry means designing chemical products and processes that make less waste, use safer substances, save energy and use raw materials that can be renewed. Key tools are high atom economy, catalysts, safer solvents such as water, renewable feedstocks, and products that break down safely. A life cycle assessment checks the impact of a product from raw material to disposal.
- Conservation of Energy – Energy cannot be created or destroyed. It only changes from one form to another, or moves from one object to another. The total energy of a closed system stays the same. When there is no friction, mechanical energy (potential + kinetic) stays constant: mgh + ½mv² = constant. With friction, some mechanical energy turns into heat (thermal energy), but the total is still the same. Efficiency = useful energy out ÷ total energy in × 100%.
- Industrial Chemistry: How a Chemical Plant Works – A chemical plant turns cheap raw materials into useful products. It prepares the raw materials, reacts them in a reactor under chosen conditions, separates the product and sends unused material back (recycling). Engineers balance speed, yield, cost, safety and the environment.
- Industrial Safety: Risk and Safety in Chemical Production – A hazard is something that can cause harm. Risk is how likely the harm is and how bad it would be. Chemical plants name their risks (fire, poison, pressure, heat), mark them with hazard symbols, and use many layers of protection such as good design, alarms, relief valves and training. Risk is judged as chance times effect and is kept low by adding layers.
5. Society and chemical technology
Chemistry of life · Environmental standards · Sustainable chemical technology · Green chemistry at scale · Life-cycle analysis
- Biochemistry: The Chemistry of Life – Plants build glucose by photosynthesis: 6 CO2 + 6 H2O + light gives C6H12O6 + 6 O2. Four families of big molecules (carbohydrates, proteins, fats, nucleic acids) are built from small units. Cells break nutrients down to release energy, with enzymes speeding every step. Proteins are made by reading DNA, copying it to mRNA and joining amino acids on a ribosome.
- Environmental Chemistry – Environmental chemistry studies the chemicals in air, water and soil, where they come from and what they do. Dry air is about 78% nitrogen, 21% oxygen, 0.9% argon and 0.04% carbon dioxide. Burning fuels adds pollutants such as SO₂, NOₓ, CO and particulates. SO₂ and NO₂ form acids in rain (pH below 5.6). We measure pollution with quantitative tests such as titration, compare the results with standards, and use laws and cleaner technology to reduce harm.
- Sustainability – Sustainability means meeting our needs today without taking away the ability of future people to meet theirs. It rests on three pillars — environment, society and economy. A resource is used sustainably when we use it no faster than it renews. Today humanity uses about 1.7 Earths' worth of resources a year, and this use is very unequal. Stewardship, careful planning and spatial tools like GIS help us move towards sustainability.
- Green Chemistry – Green chemistry means designing chemical products and processes that make less waste, use safer substances, save energy and use raw materials that can be renewed. Key tools are high atom economy, catalysts, safer solvents such as water, renewable feedstocks, and products that break down safely. A life cycle assessment checks the impact of a product from raw material to disposal.
- Life Cycle Assessment and Recycling – A life cycle assessment (LCA) adds up the environmental impact of a product over its whole life: getting the raw materials, making it, using it and getting rid of it. LCAs let us compare products fairly. Reusing and recycling materials such as metals, glass and plastics cut the use of raw materials, energy and landfill.