Y9 finals (science)

• Photosynthesis


  The process by which plants make food using water, carbon dioxide, and energy from sunlight
• Plants


  • Need water, carbon dioxide, and energy from sunlight to photosynthesize
• Chloroplast


  The green pigment found inside the cells of leaves which captures energy in sunlight
• Chlorophyll


  The green pigment found inside the chloroplast
• Waxy layer


  • Stops the leaf from drying out
• Vein


  • Carries water to the cells in the leaf
• Upper and lower epidermis

  • Protect the cells inside the leaf
• Palisade layer


  • Contains cells that do most of the photosynthesizing
• Spongy layer


  • Does small amounts of photosynthesizing
• Stoma


  • Tiny hole in the lower epidermis to allow carbon dioxide to be released from the leaf
• Fertiliser


  Helps plants receive enough minerals from the soil, grow to their full potential, and produce a higher yield
• Minerals for plants


  • Magnesium - makes chlorophyll
  • Nitrate - makes chlorophyll, converts carbohydrates into proteins
• Meteoroids, meteors, and meteorites

  Meteoroids - in space, meteors - in Earth's atmosphere, meteorites - collide with Earth's surface
• Collision of asteroids or asteroids with Earth

  Affects Earth through huge quantities of rock and dust into the air, high temperatures and shockwaves spreading from the crater, reduced light and heat from the sun - plants couldn't photosynthesize, animals had less food, Earth became colder
• Fossil fuels


  Formed by dead organisms that are not broken down quickly by decomposers millions of years ago
• Formation of fossil fuels

  Bodies fall into a place without oxygen where there are no decomposers, and they get buried by the sediment that builds up on top of them, high pressure and heat changes their remains into fossil fuels
• Carbon in fossil fuels


  Comes from carbohydrates, fats, and protein
• Coal


  Formed from the remains of plants millions of years ago in huge swamps, dug out of the ground and used to power stations and generate electricity
• Atomic number


  Number of protons
• Mass number


  Number of protons + number of neutrons
• Electrons


  Held together by electrostatic forces
• Groups in the periodic table

  • Group 1 - alkali metals, unstable, contain 1 electron on their outermost shell
  • Group 7 - halogens, unstable, contain 7 electrons on their outermost shell
  • Group 8 - noble gases, inert, have a full outermost electron shell
• Chemical bonds


  Bonds that hold together elements in a compound, formed by atoms gaining or losing electrons (ionic) or sharing electrons (covalent)
• Ionic bond


  A bond where an atom loses or gains an electron to have a full outermost electron shell and be stable, with one positive and one negative charge
• Potassium


  Loses an electron easily because the electrons in the outermost shell are further away from the protons, allowing them to be overcome by the electrostatic forces
• Fluorine


  Can attract an electron easily because the electrons in the outermost shell are closer to the protons, allowing them to be attracted more readily by the electrostatic forces
• Covalent bond


  A bond where electrons are shared between two non-metals
• Ionic compound


  • Creates a lattice structure, forms crystals with a regular shape because ions are arranged in a regular pattern
• Covalent structure


  • Formed of simple molecules, with weak intermolecular forces but strong covalent bonds between carbon and oxygen atoms inside the molecule
• Diamond


  Stronger than graphite because each carbon forms 4 strong covalent bonds with 4 other atoms, creating a strong 3D structure of a lattice, whereas in graphite, the carbon atoms only form 3 bonds, creating layers that easily slide
• Melting and boiling point

  Ionic - high, strong electrostatic forces holding ions together

  Covalent - low, strong covalent bonds but weak intermolecular forces
• Electricity conductivity


  Ionic - conduct if dissolved in water or melted

  Covalent - conduct if atoms are free to move
• Volume of regular and irregular objects

  Regular - multiply the length of sides

  Irregular - displacement method, placed into a measuring cylinder with water, the increase in volume of the water is the volume of the object
• Density


  Mass / volume
• Ships float


  They have large spaces containing air, making the average density of the whole ship less than the density of water
• Gas is less dense than liquid


  Particles in a gas are further apart
• Gas is compressed


  Same number of particles in a smaller volume, so the density increases
• Law of energy


  Energy cannot be created or destroyed, only changed or transferred
• Thermal energy transfer


  Moves from hotter places to colder places, the thermal energy dissipates
• Ways of transferring thermal energy


  • Conduction
  • Convection
  • Radiation