Grade 7 Science Study Guide Unit 1 Interactions and Ecosystems Topic 1- Interactions Within Ecosystems There is a growing need to understand more about our environment and what impacts that we have on it. Ecology: the study of the relationship between living organisms and their environment. People who study these relationships are called ecologists. What all living things need: -food -water -habitat -air (gas exchange) Adaptation: Is an inherited characteristic or behavior that helps an organism survive and reproduce in its environment. Ex. Birds bones are hollow which makes them able to fly. Ecosystem: the complex set of interactions between living and non-living things in a particular environment. Ex. A rotting log Interactions Between Living Things in an Ecosystem Symbiosis: occurs when two species live closely together in a relationship that lasts over time. Three Types: Mutualism: each partner benefits form the relationship. Ex remora and shark Parasitism: one partner benefits and the other is harmed. The benefactor is known as the parasite and the victim is known as the host. Ex tapeworm, mosquito, leech (or you and your parents. Ha) Commensalism: one partner benefits and the other appears to be unaffected. Ex. Orchid plant and tree trunk. Impacts on Ecosystems As mentioned, relationships exist between the living and non-living. These can have a major impact on an environment. Ex. Beaver – water. Beavers (living) build dams to stop water (non-living) dramatically changing the environment around them. Topic 2 – Human Impacts on Ecosystems Human beings also belong to the animal kingdom and happen to have a more dramatic effect on the Earth’s ecosystems than any other animal. Natural Resources: The materials or products that are found in nature and are used to meet our basic needs. *Know Flow Chart on Gathering Food in Alberta (buffalo – small farm – feedlot) Needs and Wants Want: things that make our lives more enjoyable Needs: The lack of something necessary. Ex. Food is a need but having food from distant locations year round is a luxury (want). It is primarily the wants of humans that causes the biggest ecological footprint. Topic 3 – Environmental Choices Ecological Footprint: is a calculation of the total area of land and water needed to supply all of the materials and energy that you use as well as absorb all of the waste you produce. Sustainability: a term describing a system in which the resources of nature are being renewed at least as quickly as they are used, and that all wastes are able to be completely absorbed. Ways to Help the Environment The three R’s Reduce: the amount of garbage you produce Reuse: reuse products rather than throwing them away Recycle: find other ways to make use of products if they cannot be reused. Topic 4 – How Organism Interact Biotic: living parts of the ecosystem. (plants, animals) Abiotic: non-living parts of the ecosystem. (Rocks, wind, sun, water) Niche: the role of an organism in its ecosystem Producers: make food for themselves using photosynthesis. E.g. plants Consumers: eat and consume things made by producers, or other consumers. E.g. humans Herbivores: are animals that eat consumers and fill the plant-eating niche. E.g.. Cows, horses. Carnivores: are animals that eat other consumers and fill the meat-eating niche. E.g.. Wolves, coyotes, sharks Predators: kill and eat other animals ( cougar, etc) Prey: get killed and eaten by predators (mouse, feeder guppies) Omnivores: Eat both producers and consumers (e.g. Raccoon, Skunk, and humans) Food Chain is a model that shows how energy is stored in food passes from organism to organism. (See figure 1.30 in text) Food Webs are even more complex than food chains, they show all of the relationships between predator and prey in an ecosystem (they are a combination of several food chains) Food Chains and Webs show how food energy moves throughout the system but not how many organisms it involves. To solve this, scientists invented the pyramid of numbers, which states how many organisms are involved at each level. Biomass: the total mass of all the organisms in an ecosystem Clean-Up Squads Scavengers: are organisms that feed on dead or decaying plant and animal matter. Decomposers: don’t actually eat dead material, instead they grow on or in dead material, absorbing some nutrients into their own cells. Topic 5 – Cycles in the Environment Evaporation: is the process in which a liquid changes into water vapour. Liquid water evaporates to form invisible water vapour. Transpiration: is the process in which water that is taken in through a plants roots evaporates from the plant’s leaves, stem, and flowers. Condensation: is the process in which water vapour changes into a liquid. Precipitation: is the process in which liquid water forms from condensation occurring inside clouds and then falls as rain, sleet, snow, and hail. Ground Water: is water in the soil. Plant roots can grow down to reach ground water. People can reach ground water by digging wells. Run-off: is water that runs off the ground into lakes, rivers, or streams. Pollution: occurs when a substance is added to the environment at such a fast rate that it cannot be broken down, stored, or recycled in the air, land, or water in a non-damaging form. Acid rain: occurs when pollutants containing sulfur and nitrogen are found in high levels in the air. The Movement of pollution: *Chemicals like DDT and PCB (polychlorinated biphenyl) take a very long time to breakdown in the environment, this causes a great deal of damage plants and animals. Bioaccumulation: When pollutants move from level to level in the food chain. (see figure 1.46) Topic 6 – Succession and Change in Ecosystem Succession: the gradual process by which some species replace others in a ecosystem. Primary Succession: is the gradual growth of organisms in an area that was bare, such as rock. E.g.. Lichens produce acids that breakdown the rocks, then ferns and mosses begin to grow. Secondary Succession: The gradual growth of organisms in an area that previously had a number of organisms. E.g.. A burnt forest area is an example of secondary succession. Biological Control: controlling pests using their natural enemies. Problems with Introduced Species When exotic species (occur naturally in a different part of the world) are introduced to an environment where they have no natural enemies they can often survive and reproduce better than the native species and therefore take over. E.g.. Zebra mussel Extinction: when a species no longer exists anywhere in the world. Topic 7 – Environmental Monitoring Ecosystem Monitoring: is a way to check the condition of an ecosystem by comparing the results of investigations done at different times Four Main Ways -Physical Monitoring: uses satellites to track changes in landscape over time -Environmental Monitoring: tracks changes in climate, temperature, and weather patterns. -Chemical Monitoring: assesses air, soil and water quality -Biological Monitoring: tracks changes in organisms and populations of organisms over time. Indicator Species: a species that is sensitive to environmental change and is the first to be affected; they help to monitor the overall health of our environment. Baseline Data: a starting point of data that allows scientist to go back and see if changes have occurred. Permanent Plots: study areas that scientists always return to. A report that outlines how an activity will affect the environment is called an Environmental Impact assessment. Unit 2 Plants for Food and Fibre – Study Guide Topic 1 – People and Plants Plants are used by humans for food and fibre Fibre: is the tissue of plants from the stem, leaves, seeds, and roots Plants have numerous uses, some examples include - using carbon dioxide and giving off oxygen - the base of most food webs - shelter - cleaning and filtering water - prevention of soil erosion Plants for food 75% of the world’s food supply is based on seven crops - Wheat - rice -maize (corn) - potatoes -Barley -cassava -sorghum Plants and final products Cocoa tree – chocolate Canola – vegetable oil Seaweed – ice-cream, yogurt Sugar beets – sugar Plants for Fibre Cotton – used for clothing, plastics, and papers Hemp – the oldest cultivated plant in the world, the first bible was printed on hemp. Early sails and ropes were made of hemp. Advantages of Hemp - Can be harvested in one year - hemp paper can be recycled 7 times longer than wood paper - not eaten by most insect pests Flax – 2-3 times as strong as cotton Used in varnishes and some types of linoleum Plants for Medicine More than 7000 medicines today are made from plants White willow bark – aspirin – pain relief Opium poppies – morphine – strong pain killer Cinchona trees – quinine – used to prevent malaria Plants for transportation and Construction Rubber Trees – brought about tires, which has enabled cars, planes and spacecraft Wood is used in construction around the world Plants are also used for fuel – ethanol-blended gasoline, coal for furnaces and electricity. Topic 2 – Structure and Adaptations Plant roots – often the plant is the tip of the iceberg Roots perform several important functions - they absorb water and minerals - they support and anchor the plant - they store food for the plant Taproot: main root, which can reach deep into the ground with numerous small roots, coming out of it. Root hairs: increase the surface area in which the plant can absorb water and nutrients. Fibrous Roots: shallow system of similar sized roots that quickly soak up moisture. Carrots, beets, turnips, radishes and parsnips are all edible roots Diffusion and Osmosis Two key functions that allow roots to absorb water and dissolved substances Diffusion: a tendency of particles to move from an area of high concentration to an area of low concentration. E.g.: air particles of perfume spread throughout the room. Differentially Permeable Membrane: allows some materials to pass through, yet keep other materials out. E.g. Marbles and sand in a mesh bag. Osmosis: a type of diffusion in which water moves form a high concentration to a low concentration. Functions of the Stem - transport water and nutrients between the leaves and the roots - provide support for the plant - food storage Leaves – the energy producers of the plants Leaves contain chlorophyll the pigment that makes them green. Photosynthesis takes place in the leaves. CO2 + H2O + Sunlight + nutrients ----- sugar + O2 Gases like carbon dioxide and oxygen enter and leave the plant through little openings in the leaves called stomata. Guard cells around the stoma (singular of stomata) regulate how much comes and goes. Respiration: process by which plants release CO2 and take in O2, this takes place at night and is slower than photosynthesis (good thing) Transpiration: the loss of water from a plant through evaporation, acts as a pump using osmosis to move water up the stem of the plant. Topic 3 – Plant reproduction and Breeding Selective Breeding: people choose specific plants with specific characteristics and encourage these plants to reproduce. Canola- made by using selective breeding of rapeseed. Genes: the part of the cell that controls plants characteristics. Types of Reproduction Sexual: involves the specialized seeds and fruits of two plants Asexual/vegetative reproduction: occurs when a parent plant grows plants from its roots, stems, or leaves. E.g. Grafting, taking the branch of one tree and attaching it to another. Seed Plant Reproduction Cones: the part of the tree that has a series of woody scales. Female cones contain ovules (eggs); Pollen grains containing sperm develop on the smaller male cone. When these two meet the sperm swims down the pollen tube and fertilizes the egg Pollination: The process of pollen travelling to the female cone. Flowers A flowers main job is to attract insects that will spread the plant pollen to other plants. Parts of a Flower Stamen: male part of the flower Pistil: female part of the flower Petals: usually brightly coloured Sepals: green parts found underneath the flower The pistil has three main parts: Stigma: sticky tip of the pistil that catches pollen Style: the tube connecting the stigma and the ovary Ovary: a tiny chamber that holds the ovule (eggs). Each Stamen has two parts: Filament: the stalk Anther: tip, produces pollen Pollination 3 steps 1) Pollen grain lands on the stigma 2) A pollen tube grows down the style into the ovary and enters an ovule 3) A sperms travels down the tube to fertilize the egg. Seed to Fruit Once a plant is pollinated a seed is formed, inside the seed is a tiny living plant called an embryo which is surrounded by food to keep it alive. Fruit: a growing ovary of a plant, which swells and protects the seeds until they are ripe. How seeds are dispersed: - carried by animals and insects - carried by winds or water - Humans use machines to efficiently plant crops This can take place in many creative ways *see page 127 for more Germination: is the development of a seed into a new plant. Topic 4 – Meeting the Need for Food and Fibre Canada is one of the leading exporters Food and Fibre in the World. Sustainability: being able to grow food and fibre while keeping our natural systems healthy for long term. Crops in Alberta Wheat: ground up for flour Barley: Fed to livestock, Used for making Malt. Oats: mostly fed to livestock some for breakfast cereals Legumes: Such as Peas, Faba Beans and Lentils, all high in protein Canola: used to make margarine, salad dressing etc. Potatoes: french fries, potato chips Alfalfa: feeds livestock, strong root system Specialty Crops: ginseng, beans, safflower, and spices Farming Practices Irrigation: watering crops using a system of large pipes and sprinklers Monoculture: growing only one type of plant in the field for greater efficiency *Copy Chart pg. 141 Forestry is a major industry in Canada Diversity: variety of plants and animals in an ecosystem Common Alberta Trees Lodgepole Pine: largely used in construction White Spruce: used in plywood, pulp and paper Black Spruce: lumber and strong paper Aspen: good for furniture, pulp and paper White Birch: Furniture and Firewood Tamarack (Larch): has a fungus that resist decay, so it is used on fence posts and railway ties. *Check out pie charts and tree pictures on Pg. 145 Steps in Harvesting Trees -Planning the cut (based on careful review of the site) -Building a road into the area -Felling and delimbing trees -Dragging the logs to a central loading point -Hauling the logs to sawmill -Preparing the site for reforestation -Reforestation Global Problems Erosion: Soil that is blown away by wind and water Desertification: as a result of drought desert takes over agricultural land Topic 5 - Sustaining the Soil Developing Soils – five main factors affect how soil develops: 1) parent material 2) vegetation 3) landscape 4) climate 5) time Humus: a dark soil rich in nutrients holds water well Healthy soil needs decomposers to break down dead organisms so plants can use the nutrients. There are four key types, which work differently: 1) Bacteria – actively break down dead material 2) Fungi – make nutrients available to plants 3) Microscopic actinomycetes – special kind of bacteria that help to create humus 4) Earthworms –grind, digest and mix soil. Healthy Plants require six nutrients -Nitrogen phosphorous potassium Sulfur calcium magnesium Challenges and Solutions Salty Soil – caused by too little vegetation and two much water Solution: replant areas so the water can’t dissolve the salt and leave it behind Soil Erosion – caused by too much cultivating mixed with water and wind Solution – leaving a root system in place to hold the dirt, zero tillage, shelter belts, crop rotation Hydroponic Technology - Growing plants without dirt, high energy cost Topic 6 – Pests and Pest Control Pest: any organism that humans find annoying or harmful Dandelions – the most successful plant pest, here’s why 1) Powerful roots 2) Broad leaves 3) Super seeds 4) Adaptable 5) Chemical weapons Check Wanted Poster on Pg. 166 Introduced Species: species not common to an area (often with no natural enemies) Pests were controlled by herbicides, insecticides, fungicides, and a bunch of other “cides”. Problems are associated with all of these chemicals E.g. bioaccumulation, and poisoning “innocent” species On top of this, Some pests are becoming resistant to chemicals Organic Food: food grown without the use of pesticides or chemical fertilizers. The need for chemicals is reduced by: -Sowing good quality seeds -Removing weeds early -Cutting weeds along property edges -Cleaning equipment so that it doesn’t transfer weeds. -Using biological controls Unit 3 – Heat and Temperature Topic 1 – Using Energy for Heat Thermal energy: (heat) is the total energy of all of the particles in a material or object. Throughout the ages people have invented a variety of devices to help create and capture heat for use. Topic 2 – Measuring Temperature Thermometer: Mechanical or electrical devices for measuring temperature. Early Thermometers were invented by Galileo. Scale: A series of equally measured sections that are marked and numbered for use in measurement. Celcius Scale: temperature system most commonly used in Canada and many other parts of the world. Unit of temperature is called a degree. Freezing Point: 0 degrees at sea level on the Celcius scale, the temperature at which water freezes. Boiling Point: 100 degrees at sea level on the celcius scale, the temperature at which water boils. Kelvin Scale: a scale used for measuring temperatures in scientific experiments. On the Kelvin scale, water freezes at 273 K and boils at 373K, the coldest possible temperature (also known as absolute zero) is 0 K. Most thermometers contain these components; Sensor: a material which is affected by changes in some features of the environment, such as temperature. Signal: information about temperature, such as an electrical current Responder: a pointer, light, or other mechanism that uses the signal in some way. Thermocouple: wires made of two different metals are twisted together so that a small electrical current is generated, the strength of the current depends on temperature. Used to measure high temperatures. Bimetallic Strip: two different metals joined together firmly. When heated, one metal expands more than another does and the strip curls up. (commonly used in thermostats in homes). Recording Thermometer: bimetallic strip connected to a writing device and paper which records temperature fluctuations over time. Infrared Thermogram: records infrared radiation, (heat sensor) as different colors according to their temperature. Topic 3 – The Particle Model, Temperature, and Thermal Energy The Particle Model: - All substances are made of tiny particles too small to be seen - Particles are always in motion - Particles have spaces between them The motion of particles increases as temperature increases and decreases as temperature decreases. *Temperature indicates the average speed of particle motion in a substance. Energy: is a measure of something’s ability to do work. Two Principals apply whenever change occurs: - changes happen when there is a difference in energy - Energy is always transferred from a high-energy source to something with a low energy source. Law of Conservation of Energy (important) Energy cannot be created or destroyed, only transformed from one type to another or passed form one object to another. Topic 4 – Expansion and Contraction Contract: decrease in volume Expand: Increase in volume Temperature changes cause things to expand and contract Heated – usually causes expansion Cooled – usually causes contraction Usually more drastic changes in gases, then liquids, then solids. Topic 5 – The Particle Model and Changes of State Heat Capacity: amount of thermal energy that warms or cools the object by one degree Celcius Specific Heat Capacity: amount of thermal energy that warms or cools one gram of a material by one degree Celcius. *See Table 2 pg. 218 Changes of State Gas vaporization Sublimation condensation Melting (also called fusion) Solid Liquid Freezing (also called solidification) Melt: turn from a solid to a liquid Freeze: turn from a liquid to a solid Evaporate: turn from a liquid to a gas Condense: Turn from a gas to a liquid Sublimation: turn from a solid to a gas or a gas to a solid. Evaporative cooling: a process in which the faster-moving particles on the surface of a liquid evaporate and escape into the air, the slower ones are left behind creating a lower average kinetic energy (cooling it). Particles are less organized as the energy increases. This means the warmer the substance, the more disorganized the particles. Phase Changing During a change from solid to liquid or liquid to gas the average temperature does not change even though heat is being added, the name for the heat that is added is Latent heat Topic 6 – Transferring Energy There are three Main ways to transfer energy -Radiation -Conduction -Convection Energy Source: an object or material that can transfer its energy to other objects. Radiation: the transfer of energy without any movement of matter. Radiant energy: (also known as electromagnetic radiation or EMR for short) Energy that is transferred by radiation. All of the forms of Radiant energy share several characteristics: - They behave like waves - They can be absorbed and reflected by objects - They travel across empty space at the same very high speed 300000 km/s Conducting Energy Through Solids Thermal Conduction: the process of transferring thermal energy through direct collisions between particles. Heat Insulators: are very poor conductors Fluid: Materials that can be poured or that flow from place to place. Convection: A warm fluid, moves from place to place, carrying thermal energy with it. Convection Current: a moving fluid. * Know Energy Transfer Diagram (Figure 3.26 on pg. 232) Topic 7 – Sources of Thermal Energy Energy appears in many forms. Potential energy: Stored energy Two examples of this type are:- gravity (a rock sitting on a counter) - elastic (pulled back and ready to be shot). Kinetic energy: Energy of motion. (the energy present in a moving object) Chemical energy: is the kind used by our body (complex sugars are broken down to provide your muscles with energy). It can also be found in batteries (which also have potential energy). Different forms of energy can be converted into another form. e.g. a candle can convert chemical energy into heat and light (candles are energy converters) Energy Converters: Devices that convert or change energy from one form to another. Mechanical Forces- is a source of thermal energy caused by friction (car engine) Geothermal Energy: energy that can we harness from the Earth’s interior. Electrical Converters- Generate electrical Energy Dams: Gravitational potential energy of water held in reservoirs converted into electrical Coal: Chemical energy is turned into thermal, which converts into electrical Solar Energy – 2 types: Passive Solar: using materials and in the structure to absorb, store and release solar energy. Active Solar: Convert light energy absorbed by solar collectors into electrical (much like plants do) Wind Energy: the energy of moving air which can be harnessed through the use of windmills. Fossil Fuels: chemicals made from plants and animals that died and decomposed millions of years ago and have preserved deep underground. Problems with Fossil Fuels -Pollution -Non-renewable Global Warming: when fossil fuels are burned and released into the air, the CO2 concentrations increase, which trap heat. Thermal Pollution: accidentally warming up the environment. Cogeneration: using waste heat to heat needed areas, generate electricity and do other useful tasks. Topic 8 – Conserving Our Fossil Fuel Resources There are many things that we can do to conserve energy -Insulate homes and water lines -Reduce the amount of energy we use (take shorter showers etc.) -Install a programmable thermostat -Carpool -Many other things *See Figure 3.43 on page 252 to learn how a refrigerator works. Unit 4 – Structures and Forces Topic #1 – Types of Structures Structures – things with a definite size and shape, which serve a definite function. Natural Structures – are not made by people - e.g. feathers, sand dunes. Manufactured Structures – things that are built by people – e.g. Calgary Tower, spoon. Structures can be classified according to how they are built. Three kinds of designs for structures exist. These are: 1. Mass Structures – are made by piling up or forming similar materials into a particular shape – e.g. dams, brick walls, cakes, breads. 2. Frame Structures – the body of most buildings have a skeleton of very strong materials, which support the weight of the roof and covering materials – e.g. house frame. 3. Shell Structures – these objects are strong and hollow. They keep their shape and support loads without a frame or a solid mass inside – e.g. eggs, igloos, bottle, pipe. (These objects have a thin outer layer that is carefully shaped to provide strength.) Some manufactured structures are combinations of Frame and Shell structures – e.g. football helmets, airplanes, the Calgary Golf Dome. Topic 2 – Describing Structures When designers or engineers plan new projects they must consider the structures: 1) Function – this is the job that the structure is designed to do e.g. a train bridge is designed to support the weight of the train. 2) Aesthetics – making a structure look good. The best designs not only serve their purpose but they are also “aesthetically pleasing” meaning they look good. (Aesthetics – the study of beauty in art and nature) 3) Safety – almost all structures are built with a large “margin of safety”. This means that structures are designed to withstand much more pressure than they would normally need to deal with e.g. a bridge can hold much more weight than it ever would have to. 4) Balancing Cost with Safety – it is difficult to design safe, well built projects that are not too expensive. 5) Materials – the properties of the material must match the purpose of the structure e.g. you would not build a bridge for cars out of rubber. Composite materials – are made from more than one material e.g. concrete can be reinforced using steel rods. Layered materials – layers of different materials pressed or glued together often produce useful products. These layers are called “laminations” e.g. layers of a juice box container involve paper, plastic and aluminum foil, making it lightweight, waterproof, and airtight. Woven and Knit materials – weaving and knitting are effective ways to make flexible materials. E.g. yarn in dishcloths is woven together to be flexible & strong When engineers choose what materials to use when building structures they must consider: 1) Cost of the material 3) Environmental Impact 2) Appearance 4) Energy Efficiency Joints – this is where a structures parts are joined together. Mobile Joints – joints that allow movement. These hold parts together while still allowing movement e.g. elbows, door hinges Rigid Joints – attach parts of a structure without allowing movement. These types of joints fall into 5 categories: - Fasteners – nails, bolts, screws - Interlocking Shapes – Lego bricks, some pavement stones - Ties – thread, string, rope - Adhesives – glues (thermosetting – harden when cooled, solvent based – harden when dried - Melting – welding or soldering materials together Topic 3 – Mass and Forces The mass of an object is the measure of the amount in it. A balance is the most common type of measuring instrument for mass. Forces are stresses such as pushes or pulls. Standard unit of force is called Newton (N). Eg: 1N is a small force. Just enough to stretch a thin rubber band. Force Meter (spring scale) – a common laboratory instrument for measuring forces. However, this scale is not very accurate. To describe force, you need to determine both its direction and its size. Gravitational Force – the force exerted by gravity on an object; measured in Newtons (N). This is the scientific term for the everyday term “weight”. Force Diagram – a simple picture that uses arrow to show the strength and direction of one or more forces. Topic 4 – Forces, Loads and Stresses External Forces – are stresses that act on a structure from outside it Eg. Your kick when striking a soccer ball. These forces produce: Internal forces - which are stresses, put on the materials that make up a structure. Internal forces are the result of external forces. Internal stresses can change the shape of a structure. This change of shape to a structure is called Deformation. External Forces Dead load – a permanent force acting on a structure. Over time can cause the structure to sag, tilt or pull apart. Live load – a changing or non-permanent force acting on a structure Eg. snow, weight of vehicles or people (Impact forces are a type of live load). Internal Forces Tension forces – stretch the material by pulling its ends apart. - Tensile strength – measures the largest tension force the material can stand before breaking Shear forces – bend or tear the material by pressing different parts in opposite directions at the same time - Shear strength – measures the largest shear force the material can stand before breaking Compression forces – crush the material by squeezing it together. - Compressive strength - measures the largest compression forces the material can stand before losing its shape or breaking. Torsion forces – twist the material by turning the ends in opposite directions - Torsion strength – measures the largest torsion force the material can stand and still regain its original shape. Bending forces – are a combination of tension and compression forces. The strength of a material is dependent on the forces between its particles. Eg. Steel has high tensile strength while rubber has high torsion strength. Topic 5 – How Structures Fail If a great enough force is applied to a structure, it will begin to fail. Levers create large forces – a lever is a device that can change the amount of force needed to move an object (e.g. with a crowbar, you can lift very heavy objects. Some levers consist of a long arm that rests on a pivot or fulcrum) Materials Fail: external forces can cause internal forces in the structure. These internal forces can cause the following types of damage: - Shear ( wieght of building causes soil to shear and the building to collapse) - Bend or Buckle ( a tin can will bend or fold up when it is compressed) - Torsion (twisting can lead structures to break apart or become tangled) Materials that snap, break, bend, and shear can be put to good use in the following ways: Buckle – car bumpers and sheet metal used in cars are designed to buckle in a collision. Therefore the car becomes badly damaged but the people in the car may not be badly injured because the metal crumpled and absorbed the energy of the collision. Shear- in a boats outboard motor, the propeller is held to the engine with a shear pin. This pin breaks if the propeller gets tangled in weeds. This is done to save the engine. Twist – spinning cotton or wool fibres very tightly together can make very strong fabric. Controlled twisting can turn string into ropes Metal Fatigue – this is when metal weakens due stress. Is process often results in the metal cracking and breaking. Topic 6 – Designing with Forces Designers often rely on one of three key methods to help structures withstand forces: 1) Distribute the load throughout the structure so that no single part is carrying most of the load. 2) Direct the forces along angled components so that the forces hold pieces together instead of pulling them apart. 3) Shape the parts to withstand the specific type of force they are likely to experience. (Examine 3 structural problems and their solutions on pgs. 321/322) Structures can be strengthened by using materials that are appropriate for their function ex. in a swing set – use a rope or chain that has high tensile strength to attach the seat to the frame. Friction – a force that resists, or works against the movement of two surfaces rubbing together ex. brick wall – each layer of bricks rests on the layer below. This “friction” holds the bricks in place. - frictional forces are greater between rough surfaces. Topic 7 – Stable Structures A stable structure is one that is not likely to tip or fall over. Center of Gravity – the point at which all of the gravitational force of an object may be considered to act. It is important that home builders understand the properties of the ground they are building on. If they do not, then the houses that they are building can be damaged by the shifting soil. Constructing stable structures on shifty ground 1. Find something solid – below the soil lies solid bedrock. Builders can build solid foundations on the bedrock, or they can sink large metal, concrete or wood cylinders into the soil to rest directly on the bedrock. 2. Make a solid layer – Road builders always pack loose surface soil before paving to create a solid base for the asphalt or concrete (packed gravel foundations are also useful for road construction). 3. Spread the load – If the weight of the structure is spread over a large area, any particular part of the ground supports only a small part of the weight ex. This is why footings (concrete foundations beneath houses) are wider than the walls themselves. Spin Stabilization – the tendency of an object that is spinning on its axis to move in a predictable manner ex. the faster a bicycle wheel spins the more stable it is. (pg. 340) Unit 5 – Planet Earth Topic #1 – Minerals Rock – is made up of one or more pure, naturally occurring, non-living, crystal like materials called minerals. Earths Crust – the thin outermost layer of the earth - A mineral can be called an element (a pure substance) or a compound (two or more elements combined) The Mohs Hardness Scale – a scale developed to identify minerals according to how hard they are. A mineral that is rated as a 1 is very soft and a mineral that is rated a 10 is very hard (Gold is a 10 – the hardest mineral). Crystals – are the building blocks of minerals. A mineral’s crystals are used to help people identify it (Figure 5.2 on pg. 355 illustrates the six major crystal systems). Other clues to mineral identification - Lustre – the “shininess” of the mineral - Color – the color of the mineral can be used to identify it. However, a mineral will be a different color if it is pure versus if it is not. - Streak – is the color of the powdered form of the mineral (this is a good way to identify fake gold) - Cleavage and Fracture – the way a mineral breaks apart can be a clue to its identity. If it breaks along smooth, flat surfaces, it is said to have cleavage. If it breaks with rough or jagged edges it is said to fracture. Unit #2 – Rocks and the Rock Cycle Igneous Rock - forms when hot magma or lava cools and solidifies. Magma is melted rock found below the earth’s crust where temperatures are high. When magma cools and hardens below the earths surface it is called intrusive rock (ex. Granite). When magma breaks through the earth’s surface in a volcanic eruption, it is called lava. Rock that forms when lava cools is called extrusive rock. Sedimentary Rock – makes up about 75% of all rocks that we can see on earth. This kind of rock is made from sediments, which are loose materials, such as bits of rock, minerals, and plant and animal remains that get packed in layers and cemented together. The arrangement of these layers is called stratification. The process of squeezing these layers together is called compaction. In some rocks, minerals dissolve as water soaks into the rock, forming a natural cement that sticks pieces of sediment together (this is called cementation). Metamorphic Rock – meaning “changed form”. This type rock may be formed below the earths surface when extremely high pressures and heat cause the original rock or parent rock to change form. The Rock Cycle – rocks continue to change in an ongoing process (see figure 5.19, pg. 368). Rocks change as a result of the rock cycle. In order to identify rocks after they have been weathered, you need to identify the minerals found within the rock. - Soil is formed from the combination of compost (which is decaying plant matter), rock, sediments, living material like twigs and leaves and dead worms or insects. The dark- colored portion of soil is called humus and is very fertile. - Layers of soil make up a soil profile. The top layer is called topsoil (it consists of humus and small grains of rock). The second layer is lighter in color, and contains less humus and larger rock chunks. The third layer contains even larger rocks that are only beginning the process of being broken down into soil. Topic #3 – Erosion Erosion – is the movement of rock and mineral grains from one place to another. Sediment – comes from larger rocks that have been broken down or worn away through weathering. Sedimentation – the process were eroded material is deposited and built up. Mechanical Weathering – is the physical break-up of rocks (Ex. Gravity causes rocks to fall down a cliff and break apart. These rocks rub against each other and become smoother and rounder). Frost wedging – during the daytime in the spring water runs into cracks in rocks. Then at night the water freezes in the cracks and pushes the rocks apart. Each day more water runs into these cracks until eventually the rock breaks apart. Chemical Weathering – breaks down minerals through chemical reactions (Ex. Acidic rain works to break down some rocks like limestone & dolomite). Biological Weathering – is the physical or chemical breakdown of rock caused by living organisms, such as plants, animals, bacteria and fungi (Ex. Plant roots wedge into rocks by forcing themselves into cracks. As the root expands the rock is pushed apart). Mechanical, Chemical and Biological weathering work together constantly to change our landscape. Glaciers, gravity, wind and water all cause erosion. Changes in our earth’s surface that happen slowly (those caused by glaciers) are called “gradual changes”. Those that happen quickly like floods, landslides and rockslides are called “sudden changes”. Water in motion is a very powerful cause of erosion (Ex. Rivers erode their banks and carry with them large amounts of soil). Topic #4 - The Moving Crust The earth’s crust is the layer of the earth that we walk on and build our homes on. It also includes deeper areas where minerals and oil and gas are mined. The mantle is found under the crust. It is made of rock material. The upper mantle is solid and the lower mantle has the consistency of taffy. The earth’s crust and the upper mantle form the lithosphere. The outer core is under the mantle and consists of iron and nickel. The temperature here is 5500 degrees Celsius and is so hot that iron and nickel are in a liquid state. The intense pressure of all the layers forces the inner core to have a temperature of over 6000 degrees Celsius. Continental drift – the belief that the continents at one time where completely joined together and over the years have drifted apart. - A German scientist named Alfred Wegener found evidence that supported his theory. This evidence came in the form of rock similarities, fossil similarities, and climatic similarities between continents. Wegener believed that all of the earth’s continents had been joined together in a giant supercontinent called “Pangea". He had difficulty proving this theory and died in 1930 still trying to prove it. Sonar (sound wave technology) – revealed to scientists that the ocean’s floor is not flat. It revealed that mountain ranges exist on the ocean floor. Sea floor spreading – the process in which an ocean floor slowly increases in size over time because of the formation of new igneous rock along a fault (pg. 388). The ocean floor is spreading and getting wider by about 2cm per year (about the same speed at which your fingernails grow). Theory of plate tectonics – states that the earth’s crust is broken up into pieces called plates. These plates are always moving on the earth’s mantle. Plates that are moving together are called converging plates and plates that are pulling apart are called diverging plates. - One explanation for why plates move is based on the theory that a convection current is causing the earth’s plates to move. (see diagram on pg. 392/393) Topic #5 - Earthquakes Scientists use a machine called a seismograph to measure earthquakes. This machine is attached to bedrock in order to feel vibrations that result from an earthquake (see diagram of seismograph on page 397). Seismologists (scientists who study earthquakes) use a method of measurement called the Richter Scale to describe the strength of the earthquake. The smaller the number the less devastating the quake. Most earthquakes that cause damage and loss of life register between 6 and 8 on the Richter Scale. The energy waves that travel outward from the source of the earthquake are called seismic waves. Aftershocks are smaller quakes that happen after the initial quake. Types of Earthquake Waves Primary (P waves) – travel the fastest of all three types of waves and can pass through solids, liquids and gases. These cause slight vibrations that rattle dishes and warn people that an earthquake is taking place and that larger earth movement may be on it’s way. Secondary (S waves) – travel more slowly than p waves and can only pass through solids. Surface waves – are the slowest of the three waves, but their rolling motion causes the most damage. They break up roads and buildings, because they cause one part of a structure to move up while the other part moves down. These waves travel outward like the ripples in a pond when you throw a pebble. Focus – is the place deep in the earth’s crust where the earthquake begins. Epicentre - the place on the earth’s surface directly above the focus of the earthquake. Rock in the earth’s surface is under intense pressure. When bedrock breaks suddenly a fault is created. Faults occur where tectonic plates meet. Three kinds of faults can occur: - Normal fault – occurs because of tension forces (rock being pulled apart). In this type of fault, rock generally moves down. - Reverse fault – occurs because of compression forces (rock being pushed together). In this fault, rock generally is forced upward. - Strike-slip or Transform fault – occurs because of shear forces. Rock along the edges of these faults generally have many bumps and bulges. People who live in earthquake zones have to prepare for quakes by doing things like bolting pictures to walls and by using steel and wood in the construction of their homes (wood and steel can bend slightly without breaking where as concrete can not). Tsunamis – huge title waves that are caused by earthquakes that take place under the ocean. Topic 6 – Volcanoes A volcano is an opening in the Earth’s crust that releases lava, steam, and ash when it erupts (becomes active). The openings in the earth’s crust when a volcano erupts are called vents. When volcanoes are not active, they are described as dormant. Volcanoes are formed when rock surfaces beneath the earth’s surface push against each other. The rock pushing downwards begins to melt and turn into magma. Eventually there is so much magma that it is forced up through cracks in the earth’s crust and an eruption occurs. Volcanoes erupt in stages over a period of weeks, months, or even years. Famous Volcanoes - Mount St. Helens (U.S.A.) erupted in 1980. - Mount Vesuvius in Italy has been dormant since 1944 and scientists believe that it is set to erupt any time. Topic #7 – Mountains Sedimentary rocks that are places under slow, gradual pressure can either fold or break. Rock that has been heated and is soft begins to fold. The top part of this folded rock is called the anticline, and the bottom of the fold is called the syncline (see figure 5.67, pg.413) If the rock is too brittle to fold, it can break, forming a fault. Faults can be the result of squeezing the earth’s crust or of stretching the earth’s crust. When the earth’s crust is squeezed together, sedimentary rock forms into slabs that move up over each other like shingles on a roof. This process is called thrust faulting. When the earth’s crust is stretched blocks of rock can tilt and slide down. Here, older rocks may end up on top of younger rock, and these huge amounts of rocks can form mountains called fault block mountains. The Canadian Rockies have been formed by sedimentary rock sliding on the basement rock and pushing the crust upwards (Sedimentary rock is seen at the surface). The American Rockies have been formed by igneous and metamorphic (basement rock) rock being shoved on top of each other and pushed upwards (Basement rock is seen at the surface). Ages of Mountains - Young mountains are jagged at the top. - Older mountains are more rounded because their surfaces have been eroded and weathered due to mechanical, biological and chemical weathering (The Canadian Rockies are fairly young, the Laurentian Mountains in Quebec are older and are in the process of being worn down). Topic #8 – Fossils Fossils provide clues about when life began, and when plants and animals first lived on the land. A fossil is formed when soft parts of a dead animal (skin, muscles and organs) decay quickly, but the hard parts of the animal (teeth, bones and shells) are altered and then fossilized. Bones of the animal become petrified or turned into a rock like substance. This happens when water penetrates the bones of the dead animal and dissolves the calcium carbonate in the bone. Then a very hard mineral (silica) is deposited and left behind. This mineral turns the bones into a rock like substance. Sometimes the actual organism or parts of it may be preserved as a fossil. These are called original remains (ex. fly’s preserved in resin, dinosaurs preserved in tar pits and woolly mammoths preserved in ice.) Trace fossils are evidence of animal activity (ex. Footprints, or worm holes that have become fossilized). A mould is a type of fossil, in which the hard parts of the organism have dissolved, leaving a cavity in the rock. A cast is a type of fossil in which sediments or minerals have filled a mould and hardened into rock. Topic #9 – Geological Time Principle of superposition states that in undisturbed layers of sedimentary rock, the oldest layers are always on the bottom and the youngest layers are always on the top. Strata is layers of sedimentary rock. Relative dating is a strategy that scientists use to figure out the age of the rocks according to their position in the strata. Index fossil – a type of fossil that can be used to determine the age of the material n which it is found. The half-life of a substance is the amount of time that a given amount of a radioactive substance takes to be reduced by one-half. Radiometric dating is the process of determining the age of a rock specimen by measuring the amounts of radioactive particles that are present in the rock and by knowing the half life of the parent rock. The geological time scale is a division of Earth’s history into smaller units based on the appearances of different life forms (Examine the illustrated geological time scale in figure 5.87 on page 426). Divisions within the Geological Time scale - Precambrian period – was the first 4 billion years that the earth existed until 590 million years ago (during this time the first super continent called Rodinia was formed) - Paleozoic Era means ancient life (approximately from 590 million years ago to 248 million years ago) - Mesozoic Era means middle life (approximately from 248 million years ago to 65 million years ago) - Cenozoic Era means recent life (approximately from 65 million years ago to present day) It is believed that the second super continent Pangea first split into a northern portion called Laurasia and a southern portion called Gondwanaland. Topic #10 – Fossil Fuels Petroleum is a type of oil found in rock formations in the Earth’s crust. It is refined into products such as gasoline or jet fuel (it is most often found in sedimentary rock). Fossil Fuels are fuels made of decomposed plants and other organisms that have been hardened and fossilized. Fossil fuels take millions of years to develop; examples of fossil fuels include oil, natural gas and coal. Bitumen is a heavy almost solid form of petroleum. Some bitumen deposits are found near the surface of the Earth and can be mined or heated and pumped to the surface (to be used as gasoline and or jet fuel).
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