Science Year 7 Biology Cells Definition- the smallest functional unit of an organism. All living things are made up of one or more cells. ● Multicellular organisms = Made up of many cells. ● Unicellular organisms = Made up of a single cell. Eg. Humans and animals are examples of Multicellular organisms. Eg. Bacteria and yeast are examples of Unicellular organisms. E Cell diagrams Nucleus = Contains Cell DNA and controls all cell activities. Cell Membrane = Controls what enters and leaves the cell. Cytoplasm = Site of chemical reactions. Mitochondria = Powerhouse of the cell, releasing energy from food and storing energy, Cell wall = supports the Cell. Chloroplast = Traps light energy to make food. Vacuole = Contains Cell sap. Animal Cells VS Plant Cells Animal Cells (Dependant) = circular and squishy because animals have bones for support. Plant Cells (Independent) = Cells are compact and next to each other like bricks because plants don’t have bones so they need that extra support. Animal Cell Plant Cell Specialised Cells Cell Structure How does this help its function? Red Blood Cells No Nucleus It can fit more Oxygen in the Cell. Ciliated Cells It has special hairs on the surface called Cilia. The Cilia hairs wafter away mucus containing dirt and bacteria up our airways so we can swallow and destroy it. Root Hair Cells It has a large surface area. The large surface area provides more absorption of water and nutrients. Nerve Cells (Neurons) It has branched-out structures. Allows the cell to communicate with different parts of the body. Palisade Cells It has lots of Chloroplasts that are closely packed together. Allows maximum light absorption for photosynthesis. Organism Organisation Food Chains Definition= A food chain shows the movement of energy from one organism to another. ● We can use food chains to tell if an organism is a producer, consumer, prey, predator, herbivore or carnivore. ● Only 10% of the energy available at any level of the food chain is transferred to the next level (when the plant or animal is eaten). Example of a situation: If the grass in the food chain above contained 1000kj of energy how much energy would the snake get? When we move across the food chain we get less and less energy as it becomes more and more inefficient. The Grasshopper would get 10% of the grass so 100kj of energy, then the bluebird would get 10kj of energy and the snake would get 1kj of energy. Food webs Definition= food webs can show us more about the feeding relationships in a population. ● Most animals eat more than one type of organism ● Any animal that eats something is called a consumer. Important thesis statement Only 10% of the energy is transferred between organisms in a food chain. If we eat producers directly less energy is waste. Decomposers Definition= Decomposers consume all the energy and give it back to the producers. In real time: when an animal dies all of its energy remains in the body. ● Decomposers help to break down the remains of any dead organism, this includes plants and animals. ● They use some of the remains for energy for themselves. ● But the rest is waste for the decomposers, and they get excreted out. ● This ‘waste’ is actually made up of important nutrients such as nitrates, which can be taken up by plants and used to make important molecules or energy. Examples of decomposers are toadstools, worms, mushrooms and fungi. ● Decomposers help to recycle energy through the food chain. Bioaccumulation Bioaccumulation is the accumulation of toxic substances as we move along a food chain or food web. For example: as one animal eats lots of another animal with toxic substances inside, more toxic substances are accumulated in that animal. Examples of toxic substances: insecticides, pesticides etc. Keys Biological keys are sets of statements that act as clues leading to the identification of an organism. • By following the keys we can be able to place an organism in its group. • The most common key is the dichotomous key. Species Definition= a group of organisms that share similar characteristics/features and can reproduce fertile offspring. Two different species can be bred out but the baby will be infertile. Only the same species can reproduce. ● Species-a group of organisms with similar features, that can breed successfully to produce fertile offspring. ● Population- a group of the same species. ● Community- a group of different species living together. ● Ecosystem- a combination of all the living and nonliving things in a region. MRS GREN- the 7 characteristics of life. ● Viruses are not living things because they don’t show all the characteristics of living things. Movement The process of being able to change place or position. Respiration The process of creating energy from food. (Not breathing) Sensitivity The ability to detect and respond to changes in the environment. Growth A permanent increase in mass. Reproduction The ability to produce offspring. Excretion The removal of metabolic waste. (Metabolic=the reaction that takes place inside cells, the cytoplasm) Nutrition Taking in materials for growth. Chemistry Atoms Definition= An atom is a substance that cannot be broken down into anything simpler. ● All things are made up of atoms. ● An atom is the smallest part of an element that can exist. Elements Definition= Elements are pure substances that are made of the same type of atom. ● An element is a substance that cannot be broken down into a smaller substance. ● There are 92 naturally occurring elements in the periodic table. The periodic table Definition= the periodic table presents the known elements in increasing atomic number. (The number of protons in one atom of an element.) ● It can be split into 3 main groups based on the properties of the elements. Metals, Metalloids and Non-metals. Metals Non-Metals Good conductors of heat Poor conductors of heat Good conductors of Electricity Poor conductors of electricity Shiny Dull High-density Low-density Malleable Brittle Ductile Brittle Sonorous (makes a ding sound when hit) Not sonorous Metalloids Definition= Metalloids are neither metals nor non-metals their properties fall in between both categories. They’re known as semiconductors. Mixtures VS Compounds Compound = one or more different elements are chemically combined. Mixtures = a combination of substances that are not chemically combined. ● Molecules vs Compounds. ● Molecules can have only one type of element but compounds can’t. Compounds have to have different elements chemically combined to be a compound. States of Matter Changing from one state of matter to another: when you put energy (heat) into the atom it will start vibrating a lot. Slowly the bonds will weaken causing them to break, turning the solid into a liquid. If you keep putting energy into the particles, the bonds will break and it will turn into a gas. If you do the opposite, take out energy (cool) from the atom, the particles will slowly stick to one another making weak bonds. Thus forming a liquid, if you continue the bonds will get stronger, eventually forming a solid. Gas Pressure Pressure definition = the action of a force against an opposing force. Gas Pressure definition= gas particles colliding with each other and with container walls. How can you increase gas pressure? ● You can add more gas particles. ● You can make the space/container smaller. ● You can increase the temperature (giving the gas particles more energy to move around). How can you decrease gas pressure? ● You can release gas particles. ● You can increase the size of the container. ● You can decrease the temperature. Vacuums Definition= A vacuum is a space where there is no matter, not even gas particles. ● Sound cannot travel in vacuums because sound is transmitted by vibrating particles. Partial Vacuums Definition= In a partial vacuum, there are almost no particles in the container. This means that there are fewer particles inside the container than outside. Less pressure inside the container than outside. ● If there are fewer gas particles inside a container than outside, the gas particles outside will want to get into the container to equalise the pressure. This means there will be a great deal of pressure on the outside of the container. (A lot of particles collide with the container from the outside to equalise.) ● This pressure will cause the container to collapse very quickly. Alloys Definition= Alloys are mixtures composed of two or more elements where at least one element is a metal. ● They are useful as they can change the physical properties of metals, such as their strength or appearance. Particle Arrangements in METALS VS NON-METALS VS ALLOYS ● A metal. The difference between metals and non-metals is that in metal the layers of atoms are able to slide along each other which is metals can be bent and shaped. ● In an alloy, however, we’re adding other elements to this structure and because of that the layers will not fit as neatly anymore making it harder for it to be bent and shaped. ● This makes alloys stronger but less malleable but much stronger. ● Steel is an example of an alloy made from iron with less than 1% carbon. Acids and Alkali Definition of an Acid= Acids are solutions that contain hydrogen (H+)ions. Definition of an Alkali= Alkalis are solutions which contain hydroxide(OH-)ions. Acids and Alkalis are compounds. (Explained below) Acids and alkalis are compounds because they are made up of molecules that contain two or more different types of atoms that are chemically bonded together. Acids are compounds that release hydrogen ions (H+) when dissolved in water, while alkalis are compounds that release hydroxide ions (OH-) when dissolved in water. For example, hydrochloric acid (HCl) is an acid because it is composed of hydrogen and chlorine atoms that are bonded together, and it releases hydrogen ions when it dissolves in water. On the other hand, sodium hydroxide (NaOH) is an alkali because it is composed of sodium and hydroxide ions that are bonded together, and it releases hydroxide ions when it dissolves in water. In summary, acids and alkalis are compounds because they are made up of molecules that contain two or more different types of atoms that are chemically bonded together. (Notice how Acids contain H+ ions while Alkalis contain OH-ions). ● They look the same as they are colourless and odourless. ● The only way to tell the difference between the two is with litmus paper, Phenotholine acid or a universal indicator. Litmus paper Use= Litmus paper changed colour depending on which substance we expose it to. ● Blue litmus paper= changes to red when exposed to an acid however it will remain the same colour when exposed to Alkaline or Neutral solutions. ● Red litmus paper= changes to blue when exposed to an alkaline solution however it will remain the same colour when exposed to Acids or Neutral solutions. The flaw of Litmus paper While it is great at detecting if a substance is acidic or alkaline it cannot indicate the strength of the solution. *Universal indicator comes in dramatically* Universal Indicators Use= the Universal Indicator will change colour according to a colour-coded chart numbered from 0-14 called the PH scale. Neutral liquids such as water will show up as green or (7) on the PH scale. Neutrality is when there is an equal amount of hydrogen ions and hydroxide ions when acids and alkalis are balanced. Distilled water is exactly 7 on the PH scale. A concentrated solution is one that has a relatively large amount of dissolved solute. Eg, a concentrated solution of acid. Neutralisation Definition= when an acid and an alkali react and there are no excess hydrogen or hydroxide ions present in the solution. ● When an acid reacts with an alkali the compound will have more hydroxide ions making the acid weaker. The same thing happens when an alkali reacts with an acid the compound would have fewer hydrogen ions making the alkali weaker. ● If we add enough we can neutralise the solution when we reach the PH level of 7. This process is called Neutralisation. ● When you react to an Acid with an Alkali/base you will always get salt+water (Neutral). This reaction is called Neutralisation. *Forget colour theory, red+blue=green* Titration Definition=the process scientists use to find out how much acid is needed to neutralise an alkali (and vice versa) by performing a titration. Behold the steps: 1) A known volume of acid is placed in a flask. The universal Indicator is added. 2) A long glass tube called a burette is then filled with alkali and placed over the flask. 3) The tap is turned on and the alkali is added to the flask. 4) When the solution in the flask turns green it has been neutralised. 5) Scientists can measure how much alkali was needed to neutralise the known volume of an acid. For future reference: the concentration of solution being titrated = (Volume of titrant used x Concentration of titrant) / Volume of solution being titrated. Safety Measures: ● Wear protective equipment: Always wear appropriate personal protective equipment, including gloves, safety glasses, and a lab coat. ● Work in a well-ventilated area: Titration involves the use of chemicals that can emit harmful fumes, so it is important to work in a well-ventilated area or use a fume hood. ● Handle chemicals with care: Handle all chemicals with care and follow the instructions on their labels. Be aware of the hazards associated with the chemicals being used and take appropriate precautions. ● Keep the work area clean: Keep the work area clean and tidy to avoid spills or accidents. Clean up any spills immediately. ● Use proper equipment: Use properly calibrated equipment, including burettes and pipettes, to ensure accurate measurements. ● Dispose of chemicals properly: Dispose of all chemicals properly, according to the instructions on their labels or your institution's safety procedures. ● Be familiar with emergency procedures: Be familiar with emergency procedures and know how to respond in case of an accident or spill. Making Salts Definition= A salt is a compound formed when an acid reacts with a metal or a base (alkali). acid + base → salt + water acid + metal→salt + hydrogen Hydrochloric acid → Chloride salt Sulfuric acid → Sulfate salt Nitric acid → Nitrate salt For example Magnesium + sulphuric acid → magnesium sulphate + hydrogen (This is because magnesium is a metal and sulphuric acid is an acid.) Sodium hydroxide + nitric acid → sodium nitrate + water (This is because Sodium hydroxide is a base and nitric acid is an acid.) Testing for different gases Squeaky Pop Test (testing for Hydrogen Gas) : ● The squeaky pop test is a simple way to identify the presence of hydrogen gas. It involves taking a small flame, like from a matchstick or a lighter, and holding it near the opening of a container that may have hydrogen gas inside. ● If the container contains hydrogen gas, the gas will react with the flame and make a distinctive squeaky sound or a popping noise. This happens because hydrogen gas is highly flammable and combustible, and when it reacts with the flame, it creates a small explosion. ● So, in summary, if you hold a flame near the opening of a container and you hear a squeaky sound or a popping noise, it could mean that Hydrogen gas is being released. (Hydrogen is highly reactive so it explodes in the air boom boom boom squeaky pop sound.) Testing for Oxygen gas: ● Testing for oxygen typically involves observing whether a substance can support combustion or not. Oxygen is a gas that is necessary for combustion to occur, so if a substance contains oxygen, it should be able to burn. ● To perform the test, you can take a small sample of the substance you want to test and hold it over a flame. If the substance ignites and burns, it indicates that it contains oxygen. If it doesn't burn, then it likely doesn't contain enough oxygen to support combustion. ● It's important to be careful when performing this test, as some substances may produce toxic or flammable gases when they burn. It's also important to note that not all substances that contain oxygen will necessarily ignite when exposed to a flame, as other factors such as the concentration of oxygen and the presence of other chemicals can also affect combustion. (The triangle of life for fire includes oxygen, when the splint lights up the triangle is complete. Illuminati.) Testing for Carbon Dioxide Gas ● The limewater test is a simple chemical test used to detect the presence of carbon dioxide gas. ● To perform the test, a small amount of limewater (a solution of calcium hydroxide) is added to a sample of gas being tested. If carbon dioxide is present in the gas, it will react with the limewater to form a white, cloudy precipitate of calcium carbonate. ● If the limewater remains clear, then there is no carbon dioxide present in the gas. If it turns cloudy, then it indicates the presence of carbon dioxide. ● This test is commonly used in various settings such as in the laboratory, in the medical field, in the food industry, and in environmental monitoring. (Carbon Dioxide farts in the limewater making everyone’s smell vision to go blurry.) Chemical Reactions Physical VS Chemical reactions/changes Physical change (Reversible)= something that changes the physical properties of a substance. Like size, shape or form. Changing the states of matter where the substance remains the same. List of things present: ● Size ● State of matter ● Does not change substance Chemical change (Irreversible)= a reaction that rearranges the particles of two or more substances to create at least one new substance. List of things present: ● Always forms a new substance ● May change colour, produce odour, create sound, release gas or produce light ● May absorb or release heat ● Usually cannot be undone Examples of chemical and physical changes: ● Ice melting, it changed a state of matter, is reversible= physical change. ● Baking a cake, it cannot be undone as it rearranges the the ingredients to form a new substance ‘cake’. Chemical Reactions ● ● In some reactions, a gas is released without noticeable fizzing occurring. In this case you can test for the gas being released by using the Gas tests mentioned above. Thermal Decomposition= when a compound breaks down if heated to a certain temperature. (Unnoticeable chemical reaction.) How can we tell if a reaction has occurred in these cases? We can measure the mass of our substances before and after heating it. ● If mass has been lost, a reaction has occurred. ● If mass has increased, a reaction has occurred. Sometimes in a chemical reaction, the products gain mass. So a change in mass between reactants and products is also an indicator of a chemical reaction. Relating to the topic above. Rules and Laws In a chemical reaction, the total mass of reactants is equal to the total mass of products. Whatever mass we start with, we also have to end with. This is known as the law of conservation of mass. For example: If we had 5g of magnesium and we burned it in the air to produce 8.3g of magnesium, how much oxygen has reacted with the 5g of magnesium. 5g = reactant1 8.3g = product 8.3g-5g= product-reactant1=3.3g=reactant2 3.3g = reactant2 Precipitation Another observation is a sign of a reaction is the formation of a precipitate. A precipitate is an insoluble substance which is formed when two solutions are mixed together. Reactions that produce these observations are known as precipitation reactions. Precipitation specifically refers to the formation of a solid from a solution during a chemical reaction or a physical process. Physics Forces Definition= force is the push or pull on an object with mass causes it to change its velocity. Definition= Velocity is the speed of something in a given direction. A force is something which acts on an object causing energy to be transferred from that object to somewhere else. ● This is usually on another object. ● Forces are not the same as energy. ● We can’t see forces but we can see what they do and show them using force arrows. Force arrows Rules ● Arrows show the size/strength of the force. If an object is moving in one direction, the arrow in that direction must be the largest one in order for the object to be moving. ● Arrows show the direction of the force. ● Arrows must touch the object where the force is acting. Most objects have at least two forces acting against each other. If these forces are balanced, then the object will not be moving (or moving at a constant speed where no force is overtaking the other). If these forces are unbalanced, the object will be speeding up or slowing down. (When one force overtakes the other.) Measuring Forces Forces are measured in Newtons, N. We can measure forces using a Newton meter (also called a forcemeter or a spring balance). Gravity Gravity is the force that pulls objects towards the centre of the earth, or other large objects in space such as moons, planets, stars and black holes. Everything has gravity but gravity is very weak so the object needs to be very big to show a noticeable force. Weight= the weight of an object is different from its mass, which tells us how much matter is in an object. Weight is the force generated on an object by gravity and is measured in Newtons. Mass = the amount of matter in an object. (Masser, matter?) Weight = a force of gravity. Weight formula = mg (Mass x acceleration of gravity) For example My mass: 45 kg Gravity on Earth: 10N Weight: 450N (mg=45x10) Mass never changes (unless of course if you gain mass by eating and stuff). The force of gravity depends on the mass of the object that is exerting the force. ● Heavier= more gravitational pull ● Lighter= less gravitational pull Reason to why Mass affects gravity (I found this on Google for you Rebekah): According to theory, the reason mass is proportional to gravity is that everything with mass emits tiny particles called gravitons. These gravitons are responsible for gravitational attraction. The more mass, the more gravitons. More mass = more gravitons = more gravitational attraction Distance also affects Gravity- the further you are away from the object the weaker the force of gravity. Think of it like two magnets, the farther away the two magnets are the less powerful the attraction would be. Think of long-distance relationships even, the further you are away from someone you’ll get less attracted to them, even in friendships. The further you are away from them mentally, the weaker the gravitational pull. Name of Force Their definition Gravity An attractive force that pulls objects together. The size of this force depends on where you are in the universe, mass and distance. Normal Force A force that prevents solid objects from passing through each other. Weight The force on an object is caused by gravity. Water resistance The force is caused by particles when an object is moving in water. It slows the object down. (The force acting against the upthrust in water.) Thrust A force that propels an object in a particular direction. Air resistance The force is caused by particles when an object is moving in the air. It slows the object down. (The force acting against the thrust in the air.) Upthrust An upwards force that acts in the water. Upthrust is what makes objects float in a fluid. It’s also known as the buoyancy force. Friction A force that acts on objects that are moving against another surface. It slows the object down. Energy Changes Definition= Energy changes are the result of an event or a process and energy tends to dissipate and in doing so it becomes less useful. The law of conservation of Energy states that energy cannot be created or destroyed, only transferred from one for to another. The 8 main forms of energy are 1) Kinetic Energy 2) Electrical Energy 3) Sound Energy 4) Light Energy 5) Thermal Energy 6) Chemical Energy 7) Gravitational Potential 8) Elastic Energy Dissipation Definition= energy waste that has spread. The loss of energy through its conversion into heat. Not all energy that is put into an object is transferred into energy that is usable. Some of this energy is transferred into thermal energy. This energy then spreads out or dissipates into the surrounding environment. An Ai explanation: When we talk about dissipation in physics, we are referring to the process by which energy is lost or transferred away from a system. Imagine you're playing with a bouncy ball. When you throw the ball against the ground, some of the energy you put into the ball is transferred into the ground, causing it to bounce back up. However, some of the energy is also lost as heat and sound, which means the ball won't bounce back up to the same height as it was thrown from. This loss of energy is called dissipation. Another example of dissipation is when you rub your hands together quickly. As you do this, you might notice that your hands start to feel warm. That's because the friction between your hands is causing the energy you're putting into the system to be lost as heat. In this case, the energy is dissipated as thermal energy. Overall, dissipation is a natural process that happens all around us. Any time energy is transferred from one place to another, some of it will be lost as it moves through the system. It's an important concept to understand because it can help us predict how much energy will be lost in different situations, which can be useful in a variety of fields, including engineering, chemistry, and physics. Energy Waste The dissipation of thermal energy from electrical energy is a problem as this energy is not useful to us. The electrical energy we use is generated mainly from the burning of fossil fuels which we know is contributing to global warming. However, the loss of thermal energy from electrical energy is a problem because it would waste energy, thus increasing fossil fuel consumption. This leads to a higher energy bill and a higher demand for fossil fuels which is bad for the environment. Incandescent light bulbs, your average lightbulb, will dissipate 90% of the energy into heat making it very inefficient. In contrast, LEDs will dissipate only 5% of the energy into heat making it very efficient. Sound Energy Defintion= Sound Energy is a form of energy produced by the vibrations of matter. Sound Energy is a type of mechanical energy because it requires the movement of particles to be generated. Sound Waves Definition= the vibrations that make air molecules move backwards and forwards cause a soundwave. ● Sound needs particles to travel through because it is the energy that is produced by the vibrations of matter, therefore an absence in matter would mean no energy. ● Sound can travel through solids, liquids and gases. ● When you shout you make your vocal cords vibrate. This movement energy is converted to sound energy in air molecules which vibrate and move backwards and forwards due to the fluctuations in air pressure. ● Loud noises over a period of time damage hair in the cochlea. The hair can recover at first but after a while the damage becomes permanent. Sound travels fastest through a solid because the particles in a solid are packed closely together, and they are tightly bound to each other by strong intermolecular forces. This makes it easier for sound waves to propagate through the solid. Because the particles in a solid are closely packed together, sound waves are able to vibrate through the particles without losing much energy. The speed of sound is calculated using the formula Speed = Distance/Time The Speed of sound through different mediums: Gases: 340m/s Liquids: 1500m/s Solids: 5000m/s Loudness and Pitch The more vibrations the higher the frequency, the higher the pitch. Amplitude= height of sound waves. (Measured in Decibels, db.) Frequency= sound waves per second. (Measured in Hertz, hz.) Pitch= hearing range, the rate of vibrations producing it, highness or lowness of tone. (Relies on Frequency however pitch is like high and low.) ● The hearing range of a healthy young person is 20Hz to 20,000Hz. (When drawing soundwaves they must be equal and finish and start on the line.) Echo Definition= An echo is the bouncing back of a soundwave. When calculating the speed of sound using an echo you have to bear in mind that the distance between the sound of the echo and you would be twice the distance between you and the object because the echo bounces back. Eg. A girl stands 102 metres away from a wall, it takes her 0.6 seconds to hear the echo. What was the speed of sound? Here we know the time which is 0.6 seconds but for the distance between the girl and the wall, we cannot just say 102 metres because echoes bounce back so it would be 204 metres. 204 divided by 0.6 is 340, so the speed of sound would be 340m/s. (340 m/s is really accurate in this situation as 340 is the speed of sound in gases.) You can use soft materials to help absorb sound and reduce echoes. Soft materials are often more effective at absorbing sound than hard materials because they have a greater ability to deform and vibrate in response to the sound waves. This means that when sound waves encounter a soft material, they are more likely to be absorbed rather than reflected or transmitted through the material. Ultrasound Definition= Ultrasound is sound waves with frequencies above 20,000 Hz. https://youtu.be/4JLNb8-LOB0 TedEd video explaining Ultrasound. ● While Humans cannot produce or hear ultrasonic waves, Bats can. Bats use ultrasound to see. They will produce this sound that will rapidly bounce off surfaces, every nook and cranny which bounce back to the Bats. The echoes carry information that allows bats to map out their environment. ● Sonars use this to travel underwater because sound waves travel faster underwater. ● Scientists also use this as a noninvasive way to examine our bodies, the echoes that come back are rendered into dots forming an ultrasonic picture. ● These tiny echoes can notice even the smallest changes in our hearts and brains. Electric Currents Definition= Electric current is the flow of electric charge in a circuit or a material. Measured in amperes (amps). Charges When the cell or battery pushes (electrons) charges around the circuit. There are two types of charges, positive and negative. The charges (electrons) are already inside the cables. Current= the amount of charge flowing per second. ● When you complete a circuit charged particles (electrons) move in the metal wire. If you add more components (lamps, motors) to a circuit, the current decreases. A current is a steady flow. The current is the same at any point in the circuit. Electrons= negative Protons= positive Neutrons=Neutral (Remember it is as caviar on a master chef plate.) Insulators vs Conductors The electrons in an insulators/conductors are stuck in their orbit to the Nucleus. The electrons in metals/conductors can jump between atoms and move wherever they want, when energy is put into these electrons they travel through the metal. Note that the electrons will not permanently be separated from the atoms when this happens, they will simply be free to move. Opposites attract Definition= when two particles of an opposite polarity charge are attracted to each other by an electrical force. For example, if a negatively charged particle (such as an electron) is brought near a positively charged particle (such as a proton), the negative charge of the electron will attract the positive charge of the proton, and they will be drawn towards each other. Electrical Symbols ● Remember to draw the buzzer like a barbeque, not a toadstool. ● Note the difference between cells and batteries. Resistance Definition= Resistance is anything that is put in a circuit that is resisting the flow. Measured in Ohms Ω (Greek Omega letter). ● Every component in a circuit has resistance. ● Resistance is about how easy or difficult it is for the changes to pass through the component. Conductors VS Insulators (revisited) Conductors have low resistance, they have lots of electrons that can move freely. Insulators have high resistance, there are fewer charges that can move freely. ● The lower the number of ohms the lower the resistance. More conductive. https://youtu.be/FFHUoWFtab0 (Explains resistance visually.) Potential Difference Definition= Potential difference is the push provided by a cell/battery that makes charges move. Measured using a voltmeter in voltages (V). The external work needed to bring a charge from one place to another. Basically, the amount of force needed to push the charges. Think of the voltage needed to light up a lightbulb. How is Potential Difference calculated? For current you can use (A) since we currently use amperes in Year 7. Remember it as a V.AR from football. Eg. The circuit has a resistance of 0.87 Ohms, the current is 0.3 Amps. What is the potential difference? 0.87x0.3=AxR=V= 0.261 The potential difference across the circuit is 0.261 Volts. Earth and Space The Structure of the Earth ● Crust= A thin layer of solid rock that sits on top of the mantle. ● Mantle= A layer of hot liquid rock (magma). ● Core=The inner core is mostly made of solid iron while the outer core is made of liquid iron and nickel. Tectonic Plates In 1912, a German scientist called Alfred Wegener suggested that millions of years ago, all the land was one large continent. This idea is called continental drift. His evidence was: ● The shapes of the continents fit together like a jigsaw puzzle. ● The types of rock on the different continents match up where they fit together. ● The fossils on the different continents match up where they fit together. When Wegener came out with this theory he could not explain why or how the continental drift happened so not everyone believed his ideas. We now know that the Earth’s crust is made up of large tectonic plates. Continental drift= When tectonic plates move slowly on the liquid rock called magma between them. ● These plates move about 4cm each year, the same speed as your fingernails. Plate Boundaries Definition= Plate boundaries are where tectonic plates meet. Many Geological changes and events such as earthquakes and volcanoes will occur here. Volcanoes= weak points in the Earth’s crust. Movements of Plates The movement of tectonic plates creates three types of plate boundaries. ● Subductions= when plates slide under another plate, it creates subduction. This is how mountains are formed. ● Plates moving apart= As tectonic plates drift away from each other they break and crack when they become too thin. Lava (liquid rock when on land) erupts from the mantle and hardens to form a new crust with new rocks. This causes a volcano. ● Plates sliding past= Pressure builds up and eventually, the pressure will cause violent movement, this is an earthquake. Mountains=Subduction, Volcano= Plates moving apart and Earthquake=Plates sliding past. Volcanoes Magma= is the name of liquid rock when it is underground. Lava= the name of liquid rock when it is on the surface. ● Sometimes if the magma is really thick and contains dissolved gases, pressure builds u and the eruption is violent. Volcano stages: ● Active volcanoes are those that have erupted recently or are showing signs of eruption, such as increased seismic activity, deformation, or gas emissions. These volcanoes have an active magma chamber and are capable of erupting at any time. The eruptions can be explosive or effusive and can cause significant damage and hazards to nearby communities. ● Dormant volcanoes are those that have not erupted recently but have the potential to do so in the future. These volcanoes are currently inactive but have a magma chamber that is still considered to be active. Although they may not show any signs of activity, they can become active again in the future and pose a potential threat. ● Extinct volcanoes are those that are not currently active and have not erupted in historical times. These volcanoes have no active magma chamber, and there is no evidence of recent volcanic activity. Although they are no longer active, they may still be considered geologically significant and can provide important clues about the Earth's history and past volcanic activity. The composition of clean air Impacts of pollution of Natural Emissions: ● ● ● What is the impact of putting more sulfur dioxide into the atmosphere? When sulfur dioxide mixes with water and air it forms sulphuric acid and turns into acid rain which causes deforestation and creates hostile environment for living beings. What is the impact of putting more carbon dioxide into the atmosphere? Increasing CO2 in the atmosphere traps more heat increasing global temperatures and resulting in more extreme weather events and rising sea levels due to the melting of polar ice caps. How does the composition of the atmosphere change with natural emissions? As the population of humans increases, so does our demand for food, which means more farming is needed-including livestock. The combination of increasing numbers of people and animals results in more CO2 (from respiration) being released into the atmosphere. Overall, natural emissions can play an important role in shaping the composition of the atmosphere, and understanding their impacts is crucial for predicting and mitigating their effects on the environment and human health. Planetary Formation Before the world was nothing. There was energy but in another form because remember the law of conservation of energy means energy cannot be created or destroyed so energy was always present. Just in another form. 1. The particles of dust and gas pull on each other with very weak forces (like mentioned in physics with the gravitons, everything has gravitational force) due to their own gravity. 2. As they stick together their mass increases and so does their strength of gravity. Helping them attract more dust particles and gases with a stronger force. 3. This starts to form a ball that gradually gets bigger. 4. Eventually the ball will get beyond a size it will get hot enough to become a star, otherwise it will remain a planet. 5. This process takes millions of years to complete. *Jupiter had the potential to become a star however it did not get big enough to become one. However, it is still a gas giant* Tides, Moons and eclipses Tides ● ● The Earth’s gravity keeps the moon orbiting around our planet however the moon also exerts a pull of gravity on the Earth. This gravitational pull causes the water on our planet to bulge on whatever side of Earth the Moon is facing. https://youtu.be/KlWpFLfLFBI (Useful video to watch.) Centrifugal Force The high tide on the side farthest from the moon is caused by the centrifugal force of the Earth spinning on its axis. Imagine you are on a merry-go-round or a spinning top. When the merry-go-round or top starts to spin, you feel like you're being pushed outwards. This is because of something called "centrifugal force." In the same way, the Earth is like a giant spinning top. As it rotates on its axis, it creates a force that pushes everything away from the centre of the Earth. This force is called "centrifugal force." However, because the Earth is so big and heavy, the centrifugal force is not strong enough to make things fly off into space. Instead, it just makes things feel a little bit lighter, or like they are being pushed away from the centre of the Earth. So, when you jump up and down or spin around, you feel a little bit lighter because of the centrifugal force created by the spinning of the Earth on its axis. Spring Tides If the moon and sun are facing the same side of the earth, the pull of gravity of both these objects causes higher gravity on that side of the Earth. The tides are the highest during a specific point in the lunar cycle known as the "spring tide." Spring tides occur twice a month, around the time of the new moon and the full moon. During a spring tide, the gravitational forces of the Moon and the Sun both act together to create a stronger gravitational pull on the Earth's oceans. This results in higher high tides and lower low tides than usual. When the Moon is closer to the Earth though, it will exert a stronger pull on the water than the Sun if it is in a different position because the Moon is closer to the Earth than the Sun. When the moon is facing one side of the earth high tides will occur on that side and the other side as well. Low tides will occur in the centre point of this. Solar Eclipse Definition= A solar eclipse is when the moon blocks the sun’s light from hitting the Earth. Lunar Eclipse Definition= A lunar eclipse is when the earth blocks the sun’s light from the moon. However, some light still escapes from the Earth’s atmosphere which is what makes the moon red.
