T4 Assessment Notes PDF

9.4 Periodic table ================== Structure of the atom --------------------- **Matter:** Anything that takes up space and can be weighed and therefore has volume and mass. **Atom:** The smallest part of a substance that cannot be broken down chemically **Element:** A pure substance made of...

9.4 Periodic table ================== Structure of the atom --------------------- **Matter:** Anything that takes up space and can be weighed and therefore has volume and mass. **Atom:** The smallest part of a substance that cannot be broken down chemically **Element:** A pure substance made of only 1 type of atom that cannot be broken down further into other substances. **Structure:** The nucleus is at the centre and contains the protons (positively charged) and neutrons (no charge). Electrons (negatively charged) are on the outer shell. ### Atom models **Daltons Model (1803)** - **John Dalton** proposed that atoms were solid, indivisible spheres - He suggested that each element was made if identical atoms and that different elements had different types of atoms - Atoms combined in fixed ratios to from compounds - **Main idea:** All matter is composed of extremely small and indivisible particles called atoms. **Thomson's Plum Pudding Model (1897)** - **J.J. Thomson** discovered the electron through his experiments with cathode rays. - He proposed the Plum Pudding Model, where atoms were thought to be a positive (pudding) with negatively charged electrons scattered throughout, like plums in a pudding. - **Main idea:** Atoms are divisible and contain negatively charged electrons within a positive background. **Rutherford's Nuclear Model (1911)** - **Ernest Rutherford** conducted the famous gold foil experiment - He discovered that atoms have a small, dense, positively charged nucleus at the centre, with most of the atom being empty space. - Electrons were thought to orbit the nucleus like planets around the sun - **Main idea**: The atom has a small, dense nucleus containing protons, with electrons surrounding it in empty space. **Bohr's Model (1913)** - **Niels Bohr** refined Rutherford's model by suggesting that electrons move in specific energy levels in shells around the nucleus. - He proposed that electrons only exist in these fixed orbits and that they emit or absorb energy when they jump between these energy levels - **Main idea:** Electrons orbit the nucleus in specific, quantised energy levels. **Summary of changes:** - Dalton: Atoms are solid and indivisible - Thomson: Atoms contain electrons with positive mass (plum pudding model) - Rutherford: Atoms have a nucleus with electrons orbiting in mostly empty space - Bohr: Electrons orbit the nucleus in specific energy levels.   ### Benefits and limitations of models **Benefits:** Models helps us understand the structure of an atom as they are too small for us to observe. **Limitations:** They are not to scale which therefore doesn't properly show the proportions of the atom. Organisation of the periodic table ---------------------------------- ### Definitions **Atomic number:** Number of protons in an atom/element. **Mass number:** Number of protons and neutrons. **Atomic mass:** Relative mass of an atom compared with a certain amount of carbon. It appears as a decimal on the Periodic Table. **Electronic configuration:** The arrangement of the electrons in their shells e.g. 2,8,2 for magnesium **Metal:** An element on the left-hand side of the periodic table **Non-metal:** An element on the right-hand side of the periodic table **Number of neutrons** = Atomic mass -- atomic number **Atomic number** = protons and electrons ### diagrams  Magnesium Formation of compounds ---------------------- **Ionic compounds:** Formed when atom transfers electrons to another. This type of bond happens between metal and non-metal. **Covalent compounds:** Formed when one atom shares electrons with another **Valency for polyatomic ions to learn** = Hydroxide, nitrate, carbonate, sulfate **Salt:** A salt is a chemical compound formed from the reaction between an acid and a base, typically consisting of a metal ion and a non-metal ion or a polyatomic ion. ### examples **Naming Ionic Compounds from Chemical Formulas:** NaCl: Sodium Chloride MgO: Magnesium Oxide Al₂O₃: Aluminum Oxide **Writing Chemical Formulas from Names:** Calcium Chloride: CaCl₂ Iron(III) Oxide: Fe₂O₃ Barium Nitrate: Ba(NO₃)₂ Sodium Phosphate: Na₃PO₄ Copper(II) Sulfate: CuSO₄ REFER TO BOOK aCIDS AND BASES --------------- ### aCIDS IN EVERDAY LIFE - Vinegar - Lemon juice - Vitamin c - Car battery acid - Stomach acid ### Bases in everyday life - Detergent - Baking soda - Soap - Toothpaste - Pesticides ### Properties of acids - Sour taste - React with metals to form hydrogen gas - Can neutralise bases to form water and salt - Blue litmus turns red in acid - pH less than 7 - electrolytes ### properties of bases - Change the colour of litmus from red to blue - Bitter in taste - Can neutralise acids to form salt and water - pH greater than 7 Use a range of common indicators to determine if substances are acidic, basic or neutral (examples of indicators: red and blue litmus, and universal indicator examples of substances to test: dilute hydrochloric acid, vinegar, distilled water, ammonia, dilute sodium hydroxide) REFER TO BOOK ### Concentrated vs dilute, strong vs weak acids **Concentrated vs dilute:** Concentrated acids contain a high amount of acid relative to water, while dilute acids have a lower concentration of acid, meaning they are mixed with more water. Concentrated acids are typically stronger and more corrosive, while dilute acids are milder and safer to handle. A diagram of a reaction Description automatically generated with medium confidence **Strong vs weak:** Strong acids completely dissociate in water, releasing all their hydrogen ions (H⁺), while weak acids only partially dissociate, producing fewer hydrogen ions. Stronger acids have a lower pH.  Conduct investigations to identify the reactants and products of the following acid reactions: hydrochloric acid + metal → salt + hydrogen acid + metal carbonate → salt + water + carbon dioxide acid + base → salt + water **Test for hydrogen:** Pop test. Holding a burning splint near to the top of the test tube. The positive result is a squeaky pop sound as the hydrogen reacts with oxygen in the air in a small explosion. **Test for Carbon dioxide:** Limewater test. If carbon dioxide is bubbled through limewater, the limewater turns milky or cloudy white. New substances are formed during chemical reactions by **rearranging atoms rather than creating or destroying them.** Scientists Say: pH Identify some examples of important chemical reactions in living things including respiration. 9.5 tectonics ============= Plate tectonics --------------- ### Alfred Wegener theory of continental drift Alfred Wegener proposed that the continents were once united into a single supercontinent named Pangaea, meaning all earth in ancient Greek. He suggested that Pangaea broke up long ago and that the continents then moved to their current positions. **Evidence:** Continent shapes fit like a jigsaw and Types of rocks found on each continent was the same (age and type). ### Hess's theroy of sea floor spreading Hess realised that along the underwater mountain ranges that there were volcanic eruptions which were creating new igneous rock. The new crust formed by these eruptions is causing the seafloor to slowly spread apart. This process is called seafloor spreading. In 1962, Hess proposed the Theory of Seafloor Spreading which said **new crust forms at mid-ocean ridges.** This was a mechanism which supported Wegener's Theory of Continental Drift. **Evidence:** Magnetic striping - A pattern of magnetic fields in strips of rock as they radiate outward from an ocean ridge. Age of the ocean floor - The further away the rock is from the midocean ridge, the older it is. This shows that new rock is continuously being formed at the ridge and then spreading outwards. Sediment thickness - Over time, tiny particles called "sediments" fall to the ocean floor. The more time passes, the more sediment builds up on the ocean floor. The further away the rock is from the midocean ridge, the thicker the sediment is, showing that the rock is older. **Seafloor spreading:**  ### Plate tectonics **Theory of plate tectonics:** Earth's lithosphere is divided into large plates that float on the semi-fluid asthenosphere beneath. These plates move due to convection currents in the mantle, leading to interactions at their boundaries, which can cause earthquakes, volcanic activity, and the formation of mountains. **Evidence:** Earthquakes, mountain building and volcanic activity occur mostly at the boundaries of the moving plates. #### Mechanisms for tectonic plate movement **Mantle convection currents:** Heat from Earth's core causes convection currents in the mantle. Hot, less dense material rises, while cooler, denser material sinks, creating a continuous flow that drags tectonic plates along. **Gravitational forces:** [Ridge push] - A tectonic process involving the gravitational force that causes an oceanic plate to move away from a mid-ocean ridge, where it was originally formed. [Slab pull] - A force that results from denser oceanic plates sinking beneath less dense continental plates along convergent boundaries and subduction zones. **Convection currents:** heat-driven cycles that occur in the air, ocean, and mantle. **Importance:** Convection currents in the Earth\'s mantle are crucial for the movement of tectonic plates, acting as a primary driving force. Plate interactions ------------------ **Divergent:** Plates move apart from each other (volcanoes, earthquakes occur). Mid ocean ridges e.g. between USA and Europe **Convergent:** Plates move towards each other (volcanoes, earthquakes, deep ocean trenches). e.g. At a subduction zone. Nazca plate colliding with south America creating the Andes **Transform:** Plates slide past one another (volcanoes). E.g. San Andrea fault along west coast of USA **Subduction zones:** An area where oceanic crust collides with continental crust -- oceanic moves underneath continental as it denser. **Cause of earthquakes:** Earthquakes are usually caused when underground rock suddenly breaks and there is rapid motion along a fault. This sudden release of energy causes the seismic waves that make the ground shake. **Focus:** The focus is the place inside Earth\'s crust where an earthquake originates. **Epicentre:** the location on the surface of the Earth directly above where the earthquake starts (focus) ### type of earthquake waves **Name of wave** **Stands for** **Travels through** **Speed/arrival time** **Type of wave** **Instrument used to measure** ------------------ ----------------- -------------------------------- ------------------------ -------------------------- -------------------------------- P wave Primary waves Solid and liquid first Compression (longitudal) seismometer S wave Secondary waves Solid only second transverse seismometer Surface wave Along the surface of the earth last Seismometer (seismograph) **Earthquake magnitude:** Measured on the Richter scale **Role of earthquakes in causing tsunamis:** Earthquakes, especially at subduction zones, can trigger tsunamis by causing significant vertical displacement of the seafloor. 9.6 electricity =============== Electrical circuits ------------------- +-----------------------+-----------------------+-----------------------+ | **Term** | **Definition** | **Examples** | +=======================+=======================+=======================+ | Electric circuit | A closed loop that | No eg | | | provides path for | | | | transfer of | | | | electrical energy | | +-----------------------+-----------------------+-----------------------+ | Circuit diagram | Shows how different | No eg | | | components are | | | | arranged in a circuit | | +-----------------------+-----------------------+-----------------------+ | Conductor | A substance which | Metals (copper, | | | conducts energy | silver) | | | | | | | | Carbon (graphite) | +-----------------------+-----------------------+-----------------------+ | Insulator | A substance which | Plastic, rubber | | | blocks electric | | | | current | | +-----------------------+-----------------------+-----------------------+ **Term** **Symbol** **Definition** **Device used to measure it** **Unit** ------------ ------------ ---------------------------------------------------------------------------- ------------------------------- ---------- Current I The flow of charge in a circuit ammeter amp Voltage V Amount of energy supplied to charges by voltage source and used by charges voltmeter volt Resistance R The opposition to the flow of electrons multimeter Ohm Ω  Ohms law equation: V = IxR +-----------+-----------+-----------+-----------+-----------+-----------+ | **Type of | **Example | **Advanta | **Disadva | **The | **Voltage | | circuit** | where | ges** | ntages** | total | supplied | | | used** | | | current | by the | | | | | | in the | battery | | | | | | circuit.. | in the | | | | | |.** | circuit.. | | | | | | |.** | +===========+===========+===========+===========+===========+===========+ | Series | Older | Easy to | \- if one | Is the | Is | | circuit | Christmas | set up | globe | **same** | **divided | | | lights | | breaks | as it | ** | | | | | all the | flows | up | | | | | others | through | between | | | | | will not | each | the | | | | | work | component | number of | | | | | | | component | | | | | \- adding | | s | | | | | more | | in the | | | | | globes | | circuit. | | | | | reduces | | Brightnes | | | | | how | | s | | | | | brightly | | of the | | | | | they glow | | bulb | | | | | | | **decreas | | | | | | | es** | | | | | | | as more | | | | | | | bulbs are | | | | | | | added | +-----------+-----------+-----------+-----------+-----------+-----------+ | Parallel | Household | \- If one | \- harder | Is | Is the | | circuit | lights | globe | to | **equal** | **same** | | | and | blows | construct | to the | across | | | circuits | others | /need | sum of | each | | | | are | more | the | component | | | | unaffecte | equipment | currents | in each | | | | d | | through | separate | | | | | | the | loop so | | | | \- Adding | | separate | the | | | | extra | | component | brightnes | | | | globes | | s | s | | | | does not | | | of the | | | | effect | | | bulb | | | | other | | | stays the | | | | globes | | | same when | | | | | | | more are | | | | | | | added | +-----------+-----------+-----------+-----------+-----------+-----------+