Year 8 Science Study Guide PDF
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This study guide covers the basics of body systems, including cells, tissues, organs, and organ systems, for Year 8 science students. It details fundamental concepts about how cells are organized and work together to keep organisms alive.
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Year 8 Science s >/ Study guide BODY SYSTEMS ells To Organ Systems C Cellsare the smallest unit of living things. Tissuesare made of t he same types of cell...
Year 8 Science s >/ Study guide BODY SYSTEMS ells To Organ Systems C Cellsare the smallest unit of living things. Tissuesare made of t he same types of cells. Muscle tissue is made of muscle cells. Organsare made of different types of tissues. The stomach is an organ made of glandular tissue that produces chemicals to digest the food, muscle tissue to churn the food and connective tissue to hold the other tissues together. Organ systemsare made of different types of organs.The digestive system is made of several organs including the mouth, oesophagus, stomach and intestine. ulticellular organisms contain many cells that are specialised for particular roles. They are M organised together in organs and systems which all work together to keep the organism alive. igestive System D The digestive system digests food for the body. It is made of several parts. ∙ Mouth– chews, moistens and swallows the food. ∙Oesophagus– transfers the food from the mouth tothe stomach ∙Stomach– digestion of the food continues here ∙Small Intestine– digestion of the food finishesand then the digested food is absorbed into the bloodstream to be taken to al parts of the body ∙Large Intestine– excess water is reabsorbed intobloodstream and undigested food is formed into faeces ∙Rectum– the faeces are stored here until they areremoved through the anus.2 ĂŶŬƐƚŽǁŶ 'ŝƌůƐ ,ŝŐŚ ^ĐŚŽŽů irculatory System C The circulatory system transports blood around the body. It is made of several parts. ∙ Heart– pumps blood out into the blood vessels. Ithas four chambers – the left atrium, left ventricle, right atrium and right ventricle. The diagram below shows the four chambers and the direction of blood flow through them. ∙Blood vessels– carry blood to all parts of thebody and then back to the heart.Arteries carry blood away from the heart. They have thick, muscular walls because blood flows through them under pressure. ∙ Veins carry bloodbacktotheheart.Theyhavethinnerwallsthanarteriesbecausethe bloodisflowingthroughthemwithoutpressurebuttheyhavevalvestostoptheblood flowing backwards. ∙Capillariesconnect arteries to veins. They deliverfood and oxygen to cells and take away carbon dioxide and other wastes. Their walls are one cell thick so that materials can pass between them and the cells. Blood travels to the lungs to drop off carbon dioxide and pick up oxygen. It then travels to all parts of the body to deliver the oxygen and collect carbon dioxide. ∙ Blood– is made of red blood cells that carry oxygen,white blood cells that fight infection and platelets that help blood to clot. 3 4 T he Respiratory System The respiratory system delivers oxygen to the blood and collects carbon dioxide from it. It is made of several parts. ∙ Trachea– also called the windpipe, takes in airfrom the mouth and nose. ∙Bronchi– the trachea branches into two tubes called the bronchi that enter the lungs. There they branch into smaller and smaller tubes. ∙Alveoli– also called the air sacs, are at the endof the small tubes. They are surrounded y capillaries. Oxygen passes from the alveoli into the blood in the capillaries and b carbon dioxide passes from the blood in the capillaries into the alveoli. T he Excretory System The excretory system removes wastes from the body. Excretion is carried out by the ∙ Lungs– which remove carbon dioxide and water vapourwhen we breathe out ∙ Skin– which removes salts and water in sweat ∙ Kidney system– which removes urine; It is madeof several parts. ∙ Kidneys– filter urea and excess salts from theblood and mix them with water to form urine. ∙ Ureters– are two tubes take the urine from thekidneys to the bladder. ∙ Bladder– stores urine until it is removed. ∙Urethra– is a tube that removes urine from thebladder 5 T he Skeletal System The skeletal system is composed of 206bones. It hasseveral roles in the body. ∙ It allows the body to stand upright and supportits weight ∙ It protects vital organs such as the heart and lungs ∙ It allows movement ∙ It makes red and white blood cells The skeletal system also contains ∙ Ligaments– which join bones together ∙Cartilage– which prevents bones from grinding againsteach other ∙Tendons– which join muscles to bones ∙Muscles– which move the bones 6 lossary G specialisedcell,tissue,organ,digestive,oesophagus,intestine,circulatory,artery,vein, capillary, respiratory, trachea, bronchi, alveoli, excretory,urea,kidney,ureter,bladder, urethra, skeleton S tudy Questions 1. Explain why multicellular organisms require specialised organs and systems. 2. Describe the role of these organs in the digestive system: i) Mouth ii) Oesophagus iii) Stomach iv) Small intestine v) Large intestine v i) Rectum vii) Anus 3. Draw a simple labelled diagram of the heart showing the four chambers, the valves, arteries and veins and use arrows to show the direction that blood flows through it. 4. Describe the structure and function of arteries, veins and capillaries 5. What is blood made of? What does each part do? 6. Describe the role of these parts of the respiratory system: i) trachea ii) bronchi iii) the alveoli in the lungs 7. Which gas does the blood a) pick up at the lungs ? b) take back to the lungs? 8. Name the excretory organs of the body. 9. Describe the role of these parts of the excretory system: i) Kidneys ii) Ureters iii) Bladder iv) Urethra 10. Draw a labelled diagram showing the arrangement of the kidneys, ureters, bladder and urethra. 11. Describe the roles of the skeleton, ligaments, cartilage, tendon and muscles.7 Elements and Compounds E lements Allmatteriscomposedofelements.Therearemorethan110knowndifferenttypesof elementsandtheirnamesareshowninthePeriodicTable.Elementscannotbebroken down into simpler substances. etals And Non-Metals M There are two main groups of elements – metals and non-metals – and they have specific properties. etals M ∙ have a shiny, metallic lustre ∙have high melting point and boiling point ∙ are solids at room temperature, except mercury whichis a liquid ∙ conduct heat and electricity ∙are malleable, which means that they can be easilybent and formed into thin sheets Examples of metals (Gold) (Mercury) (Copper) 8 on-metals N ∙ have a dull lustre ∙ have either low melting point and boiling pointor very high melting point and boiling point ∙ do not conduct heat and electricity, except forcarbon ∙ are brittle, which means that they break easily Examples of non – metals (Carbon) (Neon) (Sulfur) ompounds C A compound is made of two or more different elements joined together Compounds have properties that are different to the elements that they are made of. The names of the e lements come from the elements that are in them. For example, the elements called sodium and chlorine make the compound called sodium chloride. There many different compounds on Earth with many different uses. ∙ sodium chloride is table salt ∙ water is essential for the survival of all livingthings ∙ methane is found in natural gas and is used forcooking ∙ sucrose, also called sugar, is used in cooking ∙octane is found in petrol and is used as a fuelin cars 9 ompounds And Mixtures C Acompoundcontains elements joined together. Theamount of each element in the compound is always the same. For example, water is always H2O and carbon dioxide is always CO2. Amixturecontains elements and/or compounds mixedtogether but not joined together. The amounts of each substance in the mixture are not always the same. Air is a mixture of gases and sea water is a mixture of water and dissolved salts. hemical Reactions C A chemical reaction occurs when elements and/or compounds join together to form different elements and/or compounds. There are several observable signs that a chemical reaction has occurred. ∙the temperature of the mixture increases or decreases ∙a gas is produced ∙a colour change occurs ∙a solid is formed 10 Glossary element, melting point, boiling point, density, compound, chemical reaction, temperature S tudy Questions 1. What is an element? 2. Complete this table for the properties of metals and non-metals. Property Metals Non-metals Lustre Heat conduction Electricity conduction Malleability 3. What are the chemical symbols for a) hydrogen c) oxygen b) magnesium d) zinc 4. What is a compound? 5. Name the compounds formed from these elements. a) silver + chlorine c) lead + oxygen b) tin + sulphur d) magnesium + iodine 6. Name the elements contained in these compounds. a) magnesium oxide c) zinc chloride b) aluminium sulphide d) nickel iodide 7. Name two common compounds and describe one use for each one. 8. Identify three changes that commonly take place during a chemical reaction. 9. What is an ore? 10. Explain how froth flotation is used to separate ores from rocks. 11. Identify two ways that metals are separated from ores and give an example for each one. 11 Energy T ypes Of Energy There are several types of energy found around us. ∙ Potential energy – is stored energy to be used later.It is found in a stretched elastic band, a wound up spring and an object raised above the ground. ∙ Kinetic energy – is found in moving objects. ∙ Light energy – is produced by the sun, artificiallights, burning chemicals and very hot objects. ∙ Heat energy – is found in hot objects such as roomheaters. ∙ Sound energy – is produced by vibrating objectssuch as musical instruments. ∙ Electrical energy – is changed by electrical appliances into other types of energy. (Light energy) (Kinetic and Potential energy) E NERGY CHANGES Energy can change from one type to another. Electrical appliances change electrical energy into different types of energy. For example, ∙ a toaster changes electrical energy into heat energyto toast the bread ∙an iPod changes electrical energy into sound energy so that you can listen to music ∙a fan changes electrical energy into kinetic energy so that you can keep cool 12 L aw Of Conservation Of Energy The Law of Conservation of Energy states that energy cannot be created or destroyed. It can only be changed from one type to another. F ossil Fuels Coal and petroleum are called fossil fuels because they are formed from the remains of ancient living things. They take millions of years to form and are non-renewable, which means that once they are used they cannot be replaced. They are used as fuel in vehicles. They are also used as fuels in power stations to generate electricity. S olar Energy Solar energy comes form the sun. It is renewable which means that as it is used it can be replaced because it is continually being supplied to Earth by the sun. It is used in solar cells to produce electricity and in solar water heaters to heat water. 13 onduction Of Heat C Heat travels through solids by conduction. At the point where the object is heated, its particles gain energy and vibrate faster, which causes them to collide with the particles next to them and pass on their energy. When the neighbouring particles receive the energy, it makes them also vibrate faster and pass the energy on to more particles. In this way, heat travels through the solid. Metals are conductors of heat. This means that heat energy can travel though them from one place to another. For example, saucepans are made with a metal base to conduct heat from the stove into the food. Plastics are insulators of heat. This means that heat energy cannot travel through them. For example, the handle of a saucepan is made of plastic because it will not conduct heat and so you can pick up the saucepan without burning your hand. onvection Of Heat C When liquids and gases are heated, the heat travels in a circular motion called a convection current. The diagram below shows how convection currents warm a room. 14 adiation Of Heat R Radiation is the transfer of heat energy by waves called infrared radiation. It does not need a medium to travel through and so can travel through a vacuum. Heat travels by radiation from the sun to earth and it travels the same way outwards from a fire. Light coloured surfaces reflect more heat while dark coloured surfaces absorb more heat. This is why light coloured clothes and cars are cooler in summer than dark coloured ones. The absorbing panels of solar water heaters are painted black so that the copper water pipes inside them absorb heat from the sun to heat the water. 15 Glossary k inetic, potential, fossil fuels, solar energy, renewable, electric current, conduction, convection, radiation S tudy Questions 1. Define these types of energy and identify objects or situations in which these types of energy exist: a) potential energy b) kinetic energy c) light energy d) heat energy e) sound energy f) electrical energy 2. Energy can change from one type into another. What energy changes occur in these electrical appliances: a) heater b) CD player c) stove d) light globe e) battery operated toy car f) TV 3. What does the Law of Conservation of Energy state? 4. Coal and petroleum are non-renewable fossil fuels. a) What does ‘non-renewable’ mean? b) What does ‘fossil fuels’ mean? 5. What are coal and petroleum used for? 6. Solar energy is renewable. What does ’renewable’ mean? 9. What is solar energy used for? 8. Describe some situations in which heat is transferred by conduction. 9. Metals are heat conductors. What does this mean? 10. Plastics are heat insulators. What does this mean? 11. Describe some situations in which heat is transferred by convection. 12. Describe some situations in which heat is transferred by radiation. 16 Force and Electricity F orces Aforceis something that changes motion. This meansthat a force can get something to ∙stop ∙go faster ∙ go slower ∙ change direction ∙change shape force can be a push, a pull or a twist. A Contactforces touch the object they are acting on.Some contact forces are friction, air resistance and buoyancy. Non-contactforces do not touch the object. Some non-contactforces are gravity, magnetic forces and electric forces. Force is measured on a spring balance in units called Newtons (N). F RICTION Friction is a force between two rolling or sliding objects. It is caused by the roughness of surfaces and it acts to slow the objects down. Friction always acts in the opposite direction to the object’s movement. Rough surfaces have more friction than smooth surfaces. Friction causes surfaces to wear away. Rubber wheels on skateboards and bikes become thinner as they rub against the road. Friction also produces heat. A car engine becomes hot as the pistons move up and down in the cylinders. 17 E lectrostatic Forces Electrostatic forces occur on objects that have become electrically charged after being rubbed. Some objects become positively charged and others become negatively charged. When electrostatically charged objects are brought near to each other ∙ two positively charged objects will repel each other ∙ two negatively charged objects will repel each other ∙a positively charged object and a negatively charged object will attract each other E lectrostatic forces can be useful. They are used ∙ to produce images in photocopiers ∙ in paint spray guns to make paint stick to surfaces ∙ to remove solid particles from smoke in chimneys Electrostatic forces can be a nuisance. They ∙ cause lightning ∙ cause electric shocks when we touch door handlesand cars ∙ cause sparks that lead to explosions Anelectric fieldis the area around an electric charge. 18 agnetic Forces M Magnetic forces are produced by magnets. These forces attract metals containing iron, steel, nickel and cobalt. The ends of a magnet are calledpoles– the northpole and the south pole. When two unlike(different) poles – north and south – are broughttogether, theyattracteach other. When twolike(same) poles – north and northorsouthand south – are brought together, theyrepeleach other. Amagnetic fieldis thearea around a magnet agnets are used M ∙ to keep refrigerator doors closed ∙ to hold notes on the refrigerator door ∙ in speakers 19 E lectric Current An electric current is the movement of electric charges through a metal wire. The charges carry electrical energy to appliances that then change the energy into other types of energy. The diagram below shows a simple electric circuit containing a power supply, a lamp and electrical wires. E lectromagnets Anelectromagnetcontains an iron core surroundedby electric wires. It is a temporary magnet because the iron core is magnetic only when electricity runs through the wires. Electromagnets are used ∙in scrap-yard cranes to lift cars ∙ in hospitals to remove a piece of steel from a patient’seye ∙ in the mouthpiece of a telephone ∙in metal detectors at airports 20 Glossary force, spring balance, Newton, friction, electrostatic, field, magnetic, pole, electromagnet S tudy Questions 1. Describe one example of a force that is changing a) shape b) direction c) speed 2. Which instrument is used to measure force in Newtons? . What is friction? 3 4. Describe two examples of friction occurring in everyday situations. 5. What must you do to an object to give it an electrostatic charge? 6. What happens when the following types of electrostatic charges are brought together? a) two positive charges b) two negative charges c) one positive charge and one negative charge 7. Identify two everyday situations in which electrostatic forces are a) useful b) a nuisance 8. What is the meaning of the term “magnetic substance”? 9. Name two magnetic substances. 10. What happens when the following types of magnetic poles are brought together a) two north poles b) two south poles c) one north pole and one south pole 11. Identify two everyday situations in which magnets are used. 12. What do electric charges do in an electric circuit? 13. Identify some common electrical appliances and the energy changes that occur in them. 14. Identify two everyday situations in which electromagnets are used21 Investigating Scientifically Laboratory Equipment Equipment 2D diagram Beaker Measuring Cylinder Conical Flask Test Tube Tripod and wire gauze Bunsen Burner 22 C. Spirou (LMC) Retort stand with clamp x Filter funnel Test tube rack with test tubes Test tube holder Evaporating dish Crucible with lid 23 Bunsen Burner Bunsen burner has two flames. A ∙ Yellow flame is the safety flame because it is easilyseen when the Bunsen burner is not being used. ∙Blue flame is the heating flame because it is hotterthan the yellow flame and it does not leave black soot on the glassware. ypothesis H A hypothesis (pl. hypotheses) is an intelligent guess or probable answer to a question. It is based on previous experience, information gained from other sources and the results of other experiments. A scientist plans and conducts an experiment to test a hypothesis. For this reason, a hypothesis is written as a statement that can be proved or disproved by experiment. Some hypotheses are: ∙ Watering plants with soapy water stunts their growth ∙ Tall students jump higher in high jump competitionsthan short students. 24 Planning And Conducting A Valid, Reliable Experiment variable is a factor in an experiment that can change, eg, temperature, light. Avalid A experiment tests the independent variable and keeps all other variables constant /the same. In a valid experiment … ∙ one variable is changed during the experiment. Itis called theindependent variable.∙ one variable is measured or observed as it responds to the independent variable. It is called thedependent variable. ∙ all other variables are kept constant/the same. The aim of the experiment is to investigate the effect of the independent variable on the dependent variable. controlis the part of an experiment that is designedto show that the independent A variable being tested is responsible for the results observed. It is used as a standard against which the results from the experiment can be compared and judged. It ensures that that the results are due to the independent variable and nothing else. The control has everything the same except that the independent variable is not included. For example, when testing the effect of a fertiliser on plant growth, the control will have the same type of plants growing under exactly the same conditions but without fertiliser. Note that in some experiments a control is not possible. reliableexperiment repeats the method numeroustimes to minimise errors and A inaccuracies. Planning A Method hen you are planning an experiment, ask yourself these questions:- W 1. Which variable will I make different? 2. Which variables must I keep the same? 3. What will I measure or observe? What measuring instrument will I use? 4. What safety precautions must I take? 5. How will I record the results? 6. How many times will I repeat the experiment? 7. How will I analyse the results? Will I calculate averages? Will I draw a graph? 25 riting A Method W To write a method for an experiment, number each step and use this format:- VERB NOUN CONDITION (when, where, how, how long?) simple way to write a method is to A a) write the steps for ONE form of the independent variable b) write the phrase “Repeat steps 1-?” for the other forms of the independent variable F or example… 1. Put 500g of sandy soil into a pot. 2. Plant 20 seedlings in the pot. 3. Place the pot in constant light. 4. Add 100ml of water to the pot every day. 5. Measure the height of the seedlings with a ruler every day for 10 days. 6. Record results. 7. Repeat steps 1-6 four times. 8. Repeat steps 1-7 in 12 hours of light and 12 hours of darkness. 9.Repeat steps 1-7 in constant darkness. bservations O Scientists collect information from experiments by making observations using their senses and measuring instruments. There are two types of observations. )Qualitative observations– are descriptions inwords, eg, the colour of a chemical. We use 1 our senses to make these observations. However the senses are limited and can be unreliable. )Quantitative observations– are measurements involvingnumbers, eg, the temperature 2 of a liquid. We use measuring instruments to make these observations. Measuring instruments increase our powers of observation. Where possible, scientists make quantitative observations because they are more accurate. ∙ a thermometer is used to measure temperature ∙ a stopwatch is used to measure time ∙ a balance is used to measure mass ∙ a measuring cylinder is used to measure volume 26 T ables Data is presented in tables because this makes the data easy to understand, easy to see relationships and easy to make comparisons. L ine Graphs A line graph is used to show a relationship between two variables that are measured. To draw a line graph: 1. draw the axes. 2. label each axis with the name of the variable and a unit of measurement eg, mass (g). 3. choose a suitable scale for each axis. Mark numbers at regular intervals along the axis. 4. plot each point with a cross. 5. join crosses with a ruled line or a freehand line. Graphs can be used to extract information, make calculations, show trends, make comparisons, recognise patterns, make conclusions and predictions. onclusions C Making a conclusion from an experiment involves comparing experimental results with those predicted from the hypothesis. If the experimental results agree with the predicted results then the conclusion is that the hypothesis is supported. If the experimental results disagree with the predicted results then the conclusion is that the hypothesis is rejected. Glossary laboratory, Bunsen burner, test tube, beaker, tripod, gauze, measuring instrument, thermometer, stopwatch, balance, measuring cylinder, hypothesis, valid experiment, reliable experiment, independent variable, controlled variable, dependent variable, qualitative observation, quantitative observation, procedure, table, graph, conclusion 27 S tudy Questions 1. What must you do to a Bunsen burner to get the a) yellow flame? b) blue flame? 2. Why is the yellow flame called the safety flame? 3. When do you use the safety flame? 4. Why is the blue flame on the Bunsen burner used for heating? 5. What is the difference between qualitative and quantitative observations? 6. Which measuring instrument would you use to measure a) time? b) temperature? c) volume of a liquid? 7. Identify the three types of variables in a valid, reliable experiment. 8. What is a control? Describe one example. 9. What must be done to make an experiment a) valid? b) reliable? 10. Explain how to write a procedure. 11. Using examples, explain the difference between a qualitative and a quantitative observation. 12. Which type of observation is more accurate – a qualitative observation and a quantitative observation? 13. State two reasons why data is presented in tables. 14. What is a line graph used for? 15. How are crosses joined on a line graph? 16. State two reasons why data is presented in line graphs. 17. Explain how to make a conclusion from an experiment. 28 Living Things ells C All living things are made of cells. The parts of a cell are ∙ nucleus – controls everything that happens insidethe cell ∙cell membrane – protects the cell and gives it itsshape. It has tiny holes that allow materials to enter and leave the cell ∙ cytoplasm – a jelly-like substance that fills thecell. Most cell functions occur here. ∙cell wall – in plant cells only. It is located on the outside of the cell membrane gives the plant its shape and stiffness ∙chloroplasts – in plant cells only. They contain chlorophyll for making food for the plant. (Animal Cell) (Plant Cell) nicellular And Multicellular Organisms U Aunicellularorganism is made of one cell only. Bacteriaare unicellular organisms. Unicellular organisms reproduce by cell division. This means that their cells divide in half to produce two new cells. Bacteria can be either helpful of harmful. Helpful bacteriaare used to ∙ break down human faeces in sewage ∙treat industrial waste ∙ decompose dead plants and animals ∙ make yoghurt and cheese ∙ produce drugs for treating diseases Harmful bacteriacause diseases. 29 (Bacteria) Amulticellularorganism is made of more than onecell. Most organisms are multicellular. lassification Keys C Scientists use classification keys to identify unknown objects and organisms. The most common type of key is the dichotomous key which has two choices at every point. It starts at the top with one group and slowly subdivides until no more choices are possible. 30 ertebrate Groups V Vertebratesare animals with backbones. There arefive groups of vertebrates. )Mammals 1 ∙ are endothermic (warm-blooded) ∙ have hair or fur over their skin ∙ have lungs for breathing ∙ feed their young with milk from mammary glands 2) Birds ∙ are endothermic (warm-blooded) ∙ have feathers over their skin ∙ have lungs for breathing ∙ lay eggs )Reptiles 3 ∙ are ectothermic (cold-blooded) ∙ have dry scaly skin ∙ have lungs for breathing ∙lay eggs 31 )Amphibians 4 ∙ are ectodermic (cold-blooded) ∙have ∙ are ectodermic (cold-blooded) ∙have moist, scaly skin smooth, moist skin ∙ have lungs for ∙have gills for breathing ∙lay eggs lay eggs breathing ∙ Ad aptations In Vertebrates 5)Fish any vertebrates have special features in their appearance or behaviour to help them live M in their environment. These features are called adaptations. For example, ∙desert foxes are the same colour as the desert sandand they have very large ears that lose heat to keep the body cool. It rests in its cool underground den during the day and comes out at night to hunt for food. ∙ polar bears have layers of fat under the skin andthuick white fur on top to keep them warm. The white fur also helps them to blend in with their surroundings. They have fur covering the soles of their feet to protect them from the snow and long curved claws to help them grip the ice and their prey. 32 lant Groups P There are four main groups of plants. 1)Mosses ∙ have simple leaves and very simple roots but nostem ∙ reproduce by spores )Ferns 2 ∙ have leaves, roots and stem ∙ the leaves are called fronds ∙reproduce by spores )Conifers 3 ∙ have leaves, roots and stems ∙reproduce by seeds in cones 33 )Flowering Plants 4 ∙ have leaves, roots and stems ∙reproduce by seeds produced in flowers daptations In Plants A Many plants have special features to help them live in their environment. These features are called adaptations. For example, ∙desert plants have a variety of adaptations in theirleaves to reduce water loss. Some leaves are rolled into spikes, some leaves are covered in shiny hairs or have a shiny surface to reflect the Sun’s heat, some leaves hang vertically so that the Sun does not hit their surface. ∙ mangrove plants grow in muddy, salty water. Theyhave a dense mass of rots that help t o stabilise the mud. Also, the roots are adapted so that they do not take in too much salt with the water and the leaves remove salt from the plant. lossary G cell, nucleus, cytoplasm, cell membrane, unicellular, multicellular, microorganism, bacteria, classification, classify, characteristics, features, vertebrate, mammal, reptile, amphibian 34 S tudy Questions 1. Draw a labelled diagram of a plant cell showing the nucleus, cytoplasm, cell membrane and cell wall. 2. Describe the function of the following cell structures a) nucleus b) cytoplasm c) cell membrane d) cell wall 3. What is the difference between a plant and an animal cell? 4. What is a unicellular organism? Give an example. 5. What is a multicellular organism? Give an example. 6. How do unicellular organisms reproduce? 7. Identify one way that bacteria can be harmful. 8. Identify one way that bacteria can be helpful. 9. Name the five vertebrate groups. 10. Describe the features of the five vertebrate groups. 11. Describe some adaptations of vertebrates to their environment. 12. Describe the features of these plant groups – mosses, ferns, conifers, flowering plants. 13. Describe some adaptations of plants to their environment. 35 Matter atter, Mass, Volume And Density M Matteris all of the substances that make up objectsin the universe. Massis the amount of matter in a substance or object.Mass is measured on a balance and is given in grams (g) and kilograms (kg). Volumeis the amount of space that a substance orobject takes up. The volume of a liquid is measured with a measuring cylinder and is given in millitres (mL) and litres (L). Densityis the mass of 1cubic centimetre (cm3) of a substanceor object. Density is measured in grams per cubic centimetre (g/ cm3). S tates Of Matter All matter is made of tiny particles that are too small to be seen. The three states of matter are solids, liquid and gases. ∙Insolids, the particles are packed closely togetherand they are held tightly together. They cannot move around but can only vibrate from side to side. This is why solids have a definite volume and a definite shape and they cannot be compressed into a smaller volume. An example of a solid is steel. ∙ Inliquids, the particles are close together andthey are held loosely together. They can roll over each other. This is why liquids have a definite volume but take the shape of their container. They cannot be compressed into a smaller volume. An example of a liquid is water. ∙ Ingases, the particles are a long way apart andare free to move anywhere in the container. This is why gases have no definite volume and no definite shape and they can be compressed into a smaller volume. An example of a gas is oxygen. 36 E xpansion And Contraction ∙ Expansionoccurs as follows. When a substance isheated, its particles gain energy and so they move faster. This causes the particles to collide more often and push each other apart so that they take up more space. As a result, the substance expands. Railway tracks are laid with gaps between them. When they are heated, they expand and fill the gaps. Without the gaps, they would buckle. ∙ Contractionoccurs as follows. When a substanceis cooled, its particles lose energy and so they move slower. This causes the particles to collide less often and come closer together so that they take up less space. As a result, the substance contracts. Overhead electricity cables hang loosely between the poles. When they are cold, they contract and become shorter. If they did not hang loosely, they would snap. hange Of State C When substances are heated and cooled they often change state. There are five changes of state. ∙ melting– a substance is heated and changes fromsolid to liquid ∙ evaporation– a substance is heated and changesfrom liquid to gas ∙ sublimation– a substance is heated and changesfrom solid to gas ∙ condensation– a substance is cooled and changesfrom gas to liquid ∙freezing– a substance is cooled and changes fromliquid to solid elting Point And Boiling Point M Water ∙ melts at 0OC ∙ freezes at 0OC ∙ evaporates at 100OC ∙ condenses at 100OC 0O C is the melting point of water 100OC is the boiling point of water 37 T hemelting pointof a substance is the temperatureat which it changes from solid to liquid or liquid to solid. Theboiling pointof a substance is the temperatureat which it changes from liquid to gas or gas to liquid. Glossary balance, measuring cylinder, matter, mass, volume, solid, liquid, gas, particle, compressibility, expansion, contraction, evaporation, condensation, melting, freezing, S tudy Questions 1. What is matter? 2. What is the meaning of the word “mass”? 3. Which piece of equipment is used to measure the mass of an object? 4. What is the meaning of the word “volume”? 5. Which piece of equipment is used to measure the volume of an object? 6. Name the three states of matter. 7. Describe the movement of particles in solids, liquids and gases. 8. Using the particle model, describe and give reasons for the volume, shape and compressibility of a) solids b) liquids c) gases 9. Using the particle model of matter, explain why a metal expands when it is heated and contracts when it is cooled. 10. Describe an example of a situation in which a substance a) expands b) contracts 11. Which change of state occurs when a substance freezes? 12. Which change of state occurs when a substance melts? 13. Which change of state occurs when a substance evaporates? 14. Which change of state occurs when a substance condenses? 15. What is the melting point of water? 16. What is the boiling point of water? 17. Complete this table of changes of state to show whether particles gain or lose energy and move faster or slower. Change of State Energy Move Gain Lose Faster Slower melting evaporation condensation freezing 38 Mixtures ure Substances And Mixtures P The materials around us can be grouped into pure substances and mixtures. ∙ Pure substancescontain only one substance. Theyalways have the same properties no matter where they come from. Examples are sugar, gold, pure water and helium gas. ∙Mixturesare substances that have several differentpure substances mixed together. Examples are lipstick, concrete, soft drink and air. S olute, Solvent And Solution Asolublesubstance is a substance that dissolves.An insoluble substance is a substance that does not dissolve. When asolutedissolves in asolvent, it forms asolution.In a sugar solution, the sugar is the solute and the water is the solvent. 39 Some solutions are coloured and some are colourless but all solutions are transparent. ∙ Adilutesolution contains a small amount of solutein the solvent. ∙ Aconcentratedsolution contains a large amountof solute in the solvent. ∙ Asaturatedsolution is a solution that cannot dissolveany more solute T he Importance Of Water As A Solvent Wateris a very important solvent because it dissolvesmany substances in a wide variety of situations. For example, ∙ many drinks, such as fruit juice and soft drink,are water solutions ∙ almost all chemical reactions in the human bodyoccur between substances dissolved in water in the cells and the blood ∙ water dissolves minerals in the soil and carriesthem into plants through the roots ∙ many industrial chemicals, such as acids, are made by dissolving chemicals in water. F iltration And Sieving Filtrationis a method of separation that uses a filterto separate an insoluble substance from a mixture. A filter contains tiny holes that trap the insoluble substance but let the rest of the mixture pass through. Filters are used to separate ∙ dirt from water in swimming pools ∙ dirt from petrol and oil in cars ∙ dust from air in vacuum cleaners ∙ coffee grounds from coffee in a coffee machine ∙ solid particles from air in a mask sieveis also a filter but with larger holes. Sievesare used to separate A ∙ spaghetti from water in a colander ∙ tea leaves from tea in a tea strainer 40 E vaporation And Crystallisation Evaporationandcrystallisationare used to separatesoluble substances from solutions. In this process, the solvent evaporates and the solute crystallises. Evaporation and crystallisation are used to obtain salt from seawater. istillation D Distillation is used to separate pure water from solutions. In this process, the solution is boiled, the steam is collected and then cooled and turned back into liquid water. This water is pure and is called distilled water. Distillation is used to obtain pure water from sea water and is called desalination. agnetic Attraction M Magnetsattract substances made of iron. Magneticattraction is used to separate iron and steel from mixtures. For example, it is used in can recycling centres to separate iron cans from aluminium cans. 41 hromatography C Chromatographyis used to separate small amounts ofchemicals from a solvent. In this process, the chemicals are dissolved in a solvent and then the solvent is allowed to soak through a material such as filter paper. Some chemicals are carried through the filter paper faster than others. This means that they travel different distances along the filter paper and so they are separated. If the chemicals are different colours, they can be clearly seen on the filter paper. Chromatography is used to detect ∙ colours in ink ∙ harmful pesticides in food ∙drugs in urine samples lossary G pure substance, mixture, dissolve, soluble, insoluble, solute, solvent, solution, dilute, concentrated, filtration, sieving, evaporation, crystallisation, magnetic attraction, chromatography S tudy Questions 1. Sugar is soluble in water. What does “soluble” mean? 2. In a saltwater solution, what is the a) solute? b) solvent? 3. What is the difference between a dilute solution and a concentrated solution? 4. How would you separate these mixtures in a lab: a) salt from saltwater? b) iron nails from sawdust? c) powder from water? d) colours in ink? 5. Describe one use of a) filtration or sieving b) evaporation and crystallisation c ) distillation d) magnetic attraction 42 e) chromatography Planet Earth S tructure Of The Earth The Earth is a huge ball of rock. It is made of four layers. – ∙ crust– made of solid rock ∙mantle– mostly made of solid rock with some moltenrock in a layer called the asthenosphere ∙ outer core– made of molten iron and nickel ∙ inner core– made of solid iron and nickel Thelithosphereis the name given to the layer ofsolid rock in the crust and upper mantle. inerals M A mineral is a chemical compound that is found in the Earth’s crust, either on its own or with other minerals in rock. Therefore every rock is made of two or more minerals. T ypes Of Rocks There are three types of rocks. 1)igneous rocks– are formed when magma and lavacool 2)sedimentary rocks– are formed when sediments arecompacted or cemented together 3)metamorphic rocks– are formed when igneous rocksand sedimentary rocks are put under intense heat or pressure 43 eathering And Erosion W Weatheringis the breaking down of rocks into smallfragments called sediments. Two types of weathering are ∙physical weathering– rocks are broken down intosmall fragments by physical factors in the environment such as extreme temperature changes ∙chemical weathering– rocks are changed into newsubstances by chemical factors in the environment such as acid rain. E rosionis the process of moving fragments of weatheredrock to other places. This is done by agents of erosion such as wind, rivers, waves and glaciers. ater Cycle W The water cycle continually supplies Earth with fresh water. It is called a cycle because it has no beginning and no end and so it never stops. The three stages of the water cycle are ∙ evaporation– water on Earth’s surface changes fromliquid to vapour and rises into the atmosphere ∙condensation– water vapour in the atmosphere changesfrom vapour to liquid and forms clouds ∙precipitation– liquid water in the atmosphere fallsto the Earth’s surface as rain, snow or hail. 44 T he Atmosphere The atmosphere is a mixture of gases surrounding the Earth. It is made of several layers – the troposphere, stratosphere and ionosphere. About 78% of the atmosphere is nitrogen and 21% is oxygen. The remaining 1% is a mixture of numerous gases including carbon dioxide, neon, helium, methane, hydrogen and ozone. The carbon dioxide in the atmosphere traps heat from the sun to keep the Earth warm but if the amount of carbon dioxide increases too much, the Earth will heat up. This called the greenhouse effect. The layer of ozone in the atmosphere blocks out more than 95% of the sun’s UV rays. If the ozone layer is damaged so that it has holes in it, then too much UV light will reach the Earth’s surface causing sunburn and skin cancer. lossary G core, mantle, crust, lithosphere, mineral, weathering, erosion, deposition, sedimentary, igneous, metamorphic, evaporation, condensation, precipitation, atmosphere, ozone, greenhouse S tudy Questions 1.Draw a labelled diagram showing the core, mantle,crust and lithosphere. 2.What are minerals? 3.Explain how these rocks form: a) igneous b) sedimentary c) metamorphic 4.Rocks are weathered by physical change and chemicalchange. Explain one example of each. 5.Draw a labelled diagram of the water cycle showingwhere evaporation, condensation and precipitation occur. 6.In the water cycle, what happens in 7.evaporation 8.condensation 9.precipitation? 10.Which two gases make up most of the atmosphere? What is the percentage of each one in the air? 11.What is ozone needed for? 12.What is carbon dioxide needed for? 45 Producers and Consumers ater Transport In Plants W Therootsof a plant take in water. Thestemof a plant transports water from the rootsto the leaves through tubes called xylem. Theleavesof a plant have tiny holes calledstomatathat release excess water into the air in a process calledtranspiration. any Australian plants have adaptations that allow them to live in high temperature, low M water environments. These include ∙ Leaves rolled into spikes to reduce the number ofstomata ∙ Leaves that hang vertically to keep the leaf coolby reducing the amount of sunlight striking the surface of the leaf ∙Leaves that have a shiny, waxy covering that keepsthe leaf cool by reflecting sunlight hotosynthesis P Photosynthesis is the process in which plants make their own food. They combine water and carbon dioxide in a series of chemical reactions driven by energy absorbed from sunlight by the chlorophyll in the leaves. The products of photosynthesis are glucose and oxygen. The glucose is used as food for the plant and the oxygen is released into air to be used by plants and animals. 46 espiration R Respiration is the process in plants and animals that uses glucose and oxygen to produce energy. The energy is used for growth, repair and reproduction. Respiration is closely linked to photosynthesis because photosynthesis in plants provides the glucose to be used in respiration in plants and animals. roducers, Consumers And Decomposers P Plants make their own food in photosynthesis. Animals obtain their food by eating plants and/or other animals. Plants are calledproducersbecause they make theirown food. Animals are calledconsumersbecause they obtain theirfood by eating plants and other animals. There are three types of consumers. ∙ Herbivores– eat plants only ∙ Carnivores– east animals only ∙ Omnivores– eat both plants and animals Some organisms, such as bacteria, aredecomposers.They feed on the wastes and dead remains of plants and animals. They break down the wastes and remains into carbon dioxide, water and minerals which then go back into the air and soil to be reused by plants. 47 F ood Chains And Food Webs Afood chainshows how energy is passed on from oneorganism to another. Each organism in the chain obtains food by eating the organism before it. The first organism is a producer, such as a plant, because it makes its own food. The other organisms are consumers. The first consumer is a herbivore and then the others following it are either carnivores or omnivores. A food chain is shown below. In any place there are numerous food chains. They can be combined into afood webto show the complete picture of feeding relationships in that place. A food web is shown below. Bushfires, Drought And Flood ushfireshave both negative and positive effects on the environment. They destroy large B areas of vegetation and many of the animals living in those areas. With the vegetation removed, the soil is exposed to wind and water and so it is easily eroded. However, some Australian plants need fire for their seeds to begin growing and so they regenerate quickly 48 after fires. Ashes from the fire provide nutrients for the soil that allow plants to recover and seeds to grow quickly. Some Australian animals survive fires by either quickly moving away from fires or sheltering in burrows or logs, allowing them to return to the area after the fire and quickly repopulate it. Drought Drought creeps up over a number of years when rainfall is low. The effects can be devastating to wildlife as well as to farmers. Drought kills native plants and animals as well as crops and livestock and the destruction of vegetation leads to soil erosion. Drought depletes lakes and rivers, causing the death of many aquatic plants and animals. Finally, drought increases the chance of bushfire, dust storms and toxic algal blooms in rivers. F lood Floods cover vast areas of land, submerging plants and animals and causing their destruction. They also wash away soil, causing soil erosion. However, floods can also have positive effects on ecosystems. They replenish ground water and soil water, they wash excess salt from the soil and they provide water for fish and other animals in arid areas to breed. lossary G xylem, stomata, transpiration, photosynthesis, respiration, ecosystem, producer, consumer, decomposer S tudy Questions 1. Describe the role of roots in water absorption. 2. Describe the role of the stem in water movement. 3. What are xylem? 4. Describe the role of the leaves in transpiration. 5. What are stomata? 6. In which part of the plant does photosynthesis occur? 7. Which materials are needed by plants for photosynthesis? 8. Which materials are produced by plants for photosynthesis? 9. Which materials are needed by plants for respiration? 10. Which materials are produced by plants for respiration? 11. Why are photosynthesis and respiration important for all living things? 12. Name one Australian ecosystem. 13. Using an example of a food web, describe how the producers, consumers and decomposers are related. 14. Discuss some effects on Australian ecosystems of a ) bushfires b) drought c) flood 49 Space odels Of The Universe M Earth-centred model In ancient times when there was no technology for looking at the universe, people could only use their eyes to make observations. They saw the Sun rise in the East and set in the West and concluded that the Sun was moving across the sky. Aristotle used his observations of planets and stars in the night sky to propose an Earth-centred model of the universe. In this model, the Earth was the centre with the planets and stars moving in circular orbits around it. Sun-centred model Aristarchus was the first astronomer to suggest that the Sun was at the centre of the universe. He used his observations and estimates of the relative sizes of the Sun, Earth and Moon and their distances from each other to argue that it was more logical to place the largest object, the Sun, at the centre rather than the smaller Earth. He claimed that the apparent motion of the planets and stars was due to the Earth rotating on its axis once per day. ith the invention of the telescope, more accurate observations could be made which W confirmed the Sun-centred model. Earth centred model Sun centred model 50 ay And Night D Earth has day and night because of Earth’s rotation on its axis. As it spins, one side of the Earth faces the sun and the other side does not. The side facing the sun receives sunlight and so it has day. The other side does not receive sunlight and so it has night. One rotation of the Earth takes 24 hours. ne Year O The earth revolves around the sun. One revolution of the Earth around the sun takes one year. S easons The Earth has seasons because Earth is tilted on its axis. When a hemisphere is tilted towards the sun it has summer and when it is tilted away from the sun it has winter. In between, it has autumn and spring. 51 ravity G Gravity is a force that attracts objects. All bodies in space have gravity that attracts other objects in space towards them. For example, the Sun’s gravity attracts the planets and keeps them in orbit around it. The Earth’s gravity keeps the Moon in orbit around it. It also keeps objects on the surface of the Earth. For an object to leave Earth, it must exert a force greater than the Earth’s gravitational force. T ides Tides are periodic rises and falls of large bodies of water. They are caused by the gravitational pull of the Moon and the Sun on the Earth. T he gravitational pull of the Moon on the Earth causes the oceans to bulge out in the direction of the Moon. They bulge out on the other side because the Earth is being pulled towards the Moon and the water in the oceans is left behind. The Sun has less effect on the tides but when the Sun and the Moon line up (New Moon and Full Moon), very high tides, called king tides or spring tides, occur. L ight And Sound Light is a form of energy that does not need a medium (material) to travel through. It travels at 300,000 km/s and it can travel through a vacuum. Light from the Sun travels 150 million kilometres through the vacuum of space to Earth in 8 ½ minutes. S ound is a form of energy that does need a medium to travel through and so it cannot travel through a vacuum. It travels through air at 340 m/s. Because there is no air on the Moon, sound does not travel on the Moon as it does on Earth. 52 S olar System The solar system is one small part of the universe. The sun is at the centre and the planets orbit it. The eight planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The Solar System also contains comets, asteroids, meteors and meteorites. cometis a small mass made of ice mixed with dust,frozen carbon dioxide and organic A matter. Comets orbit the Sun in a long, narrow orbit. As a comet approaches the Sun, some of the mass evaporates and forms two tails that point away from the Sun. Asteroidsare small rocky objects left over from theformation of the solar system. They orbit the Sun in the asteroid belt which is located between Mars and Jupiter. 53 hen a chunk of space rock enters the Earth’s atmosphere the friction between it and the W air causes it to burn up. This burning rock is called ameteor. S pace rock that lands on the Earth’s surface without completely burning up is called a meteorite. S tars Beyond the solar system are galaxies of stars. Astaris a sphere of gas, mainly hydrogen and helium,that produces its own heat and light by nuclear reactions. Agalaxyis a group of millions or billions of starsheld together by gravity. Anebulais a cloud of gas and dust in space thateventually becomes a star. 54 L ight Year A light year is equal to the distance travelled by light in one year. Large distances in space are measured in light years rather than kilometres. lossary G axis, rotation, revolution, hydrosphere, solar system, star, galaxy, nebula, light year S tudy Questions 1. What is the difference between an Earth-centred model of the universe and a Sun centred model? 2. Describe the observation/s that led Aristotle to propose an Earth-centred model of the universe. 3. Describe the observation/s that led Aristarchus to propose a Sun-centred model of the universe. 4. Which technology provided evidence for the Sun-centred model? 5. Explain why Earth has day and night. 6. What is the name given to the time taken for the earth to revolve once around the sun? 7. Explain why Earth has the seasons. 8. Explain why Earth has tides. 9. Explain why light energy travels on Earth and in space but sound energy only travels on earth and not in space. 10. Name the eight planets in our solar system in order from the sun. 11. What is a a) comet? b) asteroid? c) meteor? d) meteorite? 12. What is the role of gravity in our Solar System? 13. What is a a) galaxy? b) star? c) nebula? 14. What is a light year? 55
