Science

• Photosynthesis


  The process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
• Photosynthesis


  1. Carbon dioxide + water + sunlight= oxygen + glucose

  2. Chlorophyll absorbs light usually sunlight
• Starch


  The storage form of glucose stored in seed, roots and tubers
• Testing a leaf for starch

  1. Dip the leaf in water – this softens it. Spread the leaf onto a white tile and add iodine

  2. A chemical reagent, which changes from yellow-brown to blue-black in the presence of starch
• Plant parts


  • Roots (root hair cells)
  • Stem (xylem & phloem)
  • Leaves (stomata & chloroplasts)
  • Flowers - structure and function
• Leaves


  • Broad and flat to absorb as much sunlight as it possibly can
  • Veins that bring the water to the leaf that helps support it
  • The water also carries the food and the nutrients that the plant needs
• Roots


  • Main job is to absorb the water and the nutrients from the ground and transport it to where it is needed
  • They do this with root hair cells that cover a large surface area to absorb the most that they can
• Stem


  • Used for transportation to the leaves and other parts of the plant
  • Contains the tubits that transport the water and the nutrients, Xylem and Phloem
• Xylem


  Transports water and mineral salts from the roots up to other parts of the plant
• Phloem


  Transports sucrose and amino acids from the leaves and other parts of the plant
• Mineral salts


  • The minerals plants need are present in the soil or fertiliser, but for the roots to absorb them the minerals must be available as a salt solution in water
  • Minerals are required for the production of chlorophyll and the process of photosynthesis
• Plants need water for

  • Support
  • Transport
  • Cooling
  • Photosynthesis
• Flower structure and function

  • Sepal
  • Stem
  • Petals
  • Pistil = stigma, style, ovary, ovule (egg)
  • Stamen= anther, filament, pollen
• Pollination


  1. POLLINATION is the transfer of pollen from an anther to a stigma

  2. Flower adaptations for wind pollination and insect pollination
• Fertilisation


  1. Illustrate the process of fertilisation using the terms gametes and zygotes

  2. Describe how zygotes grow into seeds
• Fruit


  • The fleshy part around a seed(seed is formed when fertilisation happens in plants)
  • The main function of a fruit is to disperse and protect the seeds
• Fruit dispersal methods


  • Explosive
  • Gravity
  • Water
  • Wind
  • Animals
• Species


  • A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
  • Examples are humans, dogs and cats etc
• Variation


  Inherited genes come from your parents vs. environmental genes you get from the environment
• Inheritance


  1. The sperm cell goes into the egg cell which is called fertilisation

  2. The DNA is stored in the chromosomes each parent contributes 23

  3. Sexual reproduction: genes, DNA, chromosomes, egg cell (ovum), sperm cell, fertilisation, zygote, embryo
• Selective breeding


  Choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics
• Natural selection and evolution

  Explain the theory and give examples the process whereby organisms better adapted to their environment tend to survive and produce more offspring
• Atomic Number


  Indicates the number of protons in the nucleus of an atom, defining the element
• Atomic Mass


  Approximate mass of an atom, composed mostly of protons and neutrons
• Periodic table groups


  • Group 1 the reactivity increases as it goes down
  • Group 7 it gets less reactive as it goes down
  • Group 8 the reactivity stays the same (alkali metals, halogens, noble gases)
• Alkali Metals


  Very reactive metals. Include elements like sodium and potassium. They're shiny and soft. React strongly with water. Used in things like batteries and soaps
• Halogens


  Very reactive nonmetals. Include elements like chlorine and iodine. Often found as diatomic molecules. Used in disinfectants and water purification
• Noble Gases


  Very stable and nonreactive. Include elements like helium and neon. They're gases at room temperature. Used in things like neon signs and as coolants
• Material properties


  • Shiny
  • Malleable
  • Solid
  • Dense
  • Strong
  • High melting point
  • Ductile
  • High boiling point
  • Sonorous
  • Good conductor of heat
  • Good conductor of electricity
• Reactivity of metals with

  1. Water: Metal + water = metal oxide + hydrogen

  2. Acid: Metal + acid → salt + hydrogen

  3. Oxygen: metal + oxygen → metal oxide
• Salts


  • Substance produced by the reaction of an acid with a base
  • Naming salts made from; hydrochloric acid: chloride salts, nitric acid: nitrate salts and sulphuric acid: sulfate acid
• Making salts


  1. Metal+Acid=Salt+Hydrogen

  2. Metal oxide & acid=salt+water

  3. Carbonate & acid=salt+water+carbon dioxide

  4. Acid & metal hydroxide=salt+water (neutralisation, define acid and alkali, explain titration)
• Exothermic reactions


  A reaction that gives out heat because the end product needs less energy, examples: making ice cubes, burning of candles, rusting of iron
• Combustion


  A chemical process in which a substance reacts rapidly with oxygen and gives off heat
• Oxidation


  The result of something reacting with oxygen
• Endothermic reactions


  A reaction that makes it surroundings cold, the end product has more energy than the initial substances, examples: photosynthesis, melting ice, dissolving salt in water
• Chemical reactions


  The processes by which chemicals interact to form new chemicals with different compositions
• Collision Theory


  For a chemical reaction to occur, the reacting particles must collide with one another at the correct angle with enough energy so that the reaction can start
• Measuring the Rate of Reaction

  The rate of reaction can be observed by watching the disappearance of a reactant or the appearance of a product over time
• Factors influencing rate of reaction

  • Temperature
  • Concentration
  • Pressure
  • Surface area
  • Catalysts