Plant Growth, Reactions, and Materials

Xylem

  • Vessels in plants that transport water.

Starch

  • Polymer formed by linking glucose molecules.
  • Uses:
    • Photosynthesis
    • Storage in chloroplasts, broken down into sugars for transport, converted back to starch, stored in storage organs, or used to make cellulose.
  • Test: Iodine solution turns blue-black if starch is present.

Reactions in Plants

  • Reactants: Substances taking part in a chemical reaction.
  • Products: New substances made in a chemical reaction.

Photosynthesis

  • Process plants use to make their own food.
  • Word Equation: carbondioxide+water→glucose+oxygencarbon dioxide + water \rightarrow glucose + oxygen
  • Occurs in chloroplasts inside plant cells.
    • Chlorophyll: Substance inside chloroplasts that captures light energy.
  • Limiting Factor: Variable that slows down the rate of photosynthesis.

Aerobic Respiration

  • Process by which living organisms release energy stored in glucose.
  • Word Equation: glucose+oxygen→carbondioxide+waterglucose + oxygen \rightarrow carbon dioxide + water

Gas Exchange

  • Swapping of different gases from inside the leaf and the atmosphere.

Structure of a Leaf

  • Palisade Cells: Adapted for photosynthesis with lots of chloroplasts.
  • Cuticle: Waxy layer that stops leaves from losing too much water.
  • Stomata: Small holes that open/close to allow gas exchange.
  • Guard Cells: Cells that open and close the stomata.

Proteins

  • Polymer formed by joining long chains of amino acids.

Nitrates

  • Needed to make amino acids.

Germination

  • Water and oxygen enter seed, allowing molecules to move. Enzymes digest starch into glucose, which enters the embryo for respiration and growth.

Selective Breeding

  • Choosing organisms to breed based on desired offspring characteristics.

Cross-Breeding

  • Breeding different varieties together to produce offspring with characteristics of both.

Fertiliser

  • Problems: Can wash into rivers, causing algae growth that blocks light, leading to plant death and oxygen depletion.

Pesticide

  • Problems: Some are persistent, moving up the food web.

Varieties

  • Problems: Identical, so a disease affects them all; reduces biodiversity.

Phloem

  • Vessels in plants that transport glucose.

Plant Adaptations

  • Features that enable a plant to do a certain job.

Root Adaptations

  • Branched and spread out to get a large volume of water.

Root Hair Cells

  • Increase the surface area of roots for water absorption.

Lipids

  • Insoluble substances, including fats and oils.
  • Uses: Make cell membranes; energy store in seeds.
  • Cuticle: Waterproof due to lipids.

Pesticides

  • Kill pests.
    • Insecticides: Kill insect pests.
    • Fungicides: Kill fungi.
    • Herbicides: Kill weeds.

Polymer

  • Substance made up of a long chain of repeating groups of atoms (monomers).

Variety

  • Group of plants bred for a certain characteristic.

Yield

  • Amount of useful product from a crop.
    • Increasing: Forests cut down, hedgerows removed, machines used.

Fertilisers

  • Contain mineral salts that plants need to grow.

Decomposers

  • Microorganisms that break down manure and release mineral salts.

The Carbon Cycle

  • Photosynthesis: Removes CO2CO_2 from the air.
  • Respiration: Adds CO2CO_2 to the air.
  • Combustion: Adds CO2CO_2 to the air. Burning of forests, hedgerows removed.
  • Decomposers: Break down dead plants and animals, releasing carbon compounds.

Ceramics

  • Hard, durable, non-metallic materials.
  • Properties: Hard, strong, brittle, high melting point, heat resistant, good insulators.
    • Examples: Glass, china, porcelain.

Polymers

  • Substances with molecules made of long chains of repeated groups of atoms.
    • Examples: Rubber, DNA, proteins.
  • Natural Polymers: Found naturally.
  • Synthetic Polymers: Made in laboratories from crude oil.

Composite Materials

  • Combinations of 2 or more materials with properties of each.
    • Examples: Concrete, paper, GRP (Glass Reinforced Plastic).

Thermal Decomposition of Limestone

  • Calciumcarbonate→calciumoxide+carbondioxideCalcium carbonate \rightarrow calcium oxide + carbon dioxide

Cement

  • Mainly calcium oxide.

Monomer

  • Small molecule joined with identical molecules to form polymers.

Vulcanisation

  • Rubber heated with sulfur to form cross-links making it harder.

GRP (Glass Reinforced Plastic)

  • Glass fibres in a polyester resin. Strong, light, slightly flexible.

Concrete

  • Mixture of cement, sand, aggregate, and water. Strong, hardwearing, easy to mould.
  • Reinforced Concrete: Steel rods added for extra strength.

Problems With Materials

  • Finite Resources: Limited resources will run out.
  • Incomplete Combustion: Produces carbon monoxide and soot due to lack of oxygen.
  • Sulfur Dioxide: Causes acid rain.
  • Nitrogen Oxides: Form acid rain.
  • Carbon Dioxide: Traps the Sun's energy -> greenhouse effect, global warming.
  • Toxic Substances: Pass along the food chain.
  • Non-Biodegradable Materials: Do not break down naturally.

Recycling Materials

  • Using the same materials again.
  • Benefits: Reduce use of finite resources, save fuel/energy, reduce landfill use.
    • Metals: Can be melted down and used again.
    • Glass: Can be crushed, melted, and moulded into new glass.
    • Polymers: Difficult and expensive to separate so recycling levels are low.
    • Paper: Water added, filtered, heated, mixed to form pulp, squeezed and dried.
    • Concrete: Crushed using large machines and used as aggregate.

Types of Explosion

  • Sudden increase in volume of gas and huge transfer of energy to the surroundings.

Oxidation

  • Reaction in which a substance gains oxygen.

Thermite Reaction

  • Displacement reaction between aluminium and iron oxide.
  • Aluminium + iron oxide \rightarrow aluminium oxide + iron
  • Uses: Join railway tracks.

Reactivity Series

  • List of metals in order of reactivity.

Rust

  • Formed by the corrosion of iron and steel.
  • Preventing Rust: Use a barrier (paint/plastic/oil) or sacrificial protection (more reactive metals react instead).

Exothermic Reactions

  • Energy is transferred from the reactants to the surroundings.

Endothermic Reactions

  • Energy is transferred from the surroundings to the reactants.

Hydrocarbon

  • Compound containing only hydrogen and carbon.

Native State

  • When a metal is found in the Earth as an element.

Ore

  • Rock that contains enough of a metal.

Extracting Iron

  • Iron oxide + carbon iron + carbon dioxide. Oxygen is removed by heating with carbon.

Reduced

  • When a substance has lost oxygen.

Electrolysis

  • Used to extract reactive metals from their ores using electricity.
  • Aluminium oxide aluminium + oxygen

Displacement Reaction

  • Where a more reactive metal displaces a less reactive one.

Force Fields

  • Area around something where a non-contact force can affect things.

Static Electricity

  • A positive or negative charge on an insulating material caused when rubbing transfers electrons.

Magnetic Field

  • Space around a magnet where it can affect magnetic materials or other magnets.

Gravitational Field

  • Space around any object with mass where its gravity attracts other masses.

Electric Field

  • Space around an object with a charge where it can affect other objects.

Weight

  • The force with which a gravitational field pulls on each kilogram of mass. Measured in Newtons.

Electric Current

  • The flow of electrons in a circuit.

Resistance

  • How difficult it is for electricity to flow through something.

Voltage

  • How much energy is transferred by electricity by a cell/component.

Electromagnets

  • A coil of wire with electricity flowing in it that has a magnetic field.