SCIENCE
School Certificate Notes
YRLY SCI NOTES
Chapter 1-Forces at work
1. A machine is a device that makes a physical task easier.
2. A lever is a simple machine that uses the turning effect of a force to make a task easier.
3. Force multipliers reduce the effort needed to perform a task while speed multipliers increase the speed at which a load is moved.
4. Ramps, wedges, and screws are all inclined planes which are force-multiplying machines.
5. A wheel and axle is a rotating lever. It can be used as a force multiplier when the effort is applied at the wheel rim and as a speed multiplier when the effort is applied at the axle.
6. In order to reduce the effort needed to perform a task the effort needs to move through a greater distance. In order to increase the speed at which a load is moved, a greater effort must be used.
7. A pulley is a grooved wheel and axle around which a rope or cable can be used to change the direction of the effort needed to move a load.
8. A block and tackle consists of two or more pulleys which can be used to move a large load with a small effort.
9. Gears are wheels and axles with teeth. Two or more gears can be used to make wheels turn faster or slower, change direction or multiply a force.
10. Compound machines consist of two or more simple machines.
11. Robots are machines that perform physical tasks without human assistance.
12. Bridges are structures which are designed to support a large load. Features like trusses and arches are used to increase the load that can be supported by a bridge.
13. Bridge design depends on many factors, including the size of the load that need to be supported, the distance the bridge must span and the type of surface under the bridge.
14. The balancing point of an object is at its centre of gravity.
15. An object will fall over if its centre of gravity is not above its base.
16. The lower the centre of gravity of an object, the less likely it is to fall over.
Chapter 2-Reproduction
1. Sexual reproduction occurs when offspring result from the joining together (fusion) of a male reproductive cell and a female reproductive cell. These special reproductive cells are called gametes.
2. The joining of a sperm and egg cells is called fertilisation. The cell resulting from this cell is called a zygote.
3. In some animals, fertilisation occurs outside the females’ body. This is called external fertilisation. In other animals, for example those that live and breed on land, internal fertilisation occurs.
4. Human sperm travels through the vans deferens from the testes to the urethra.
5. Human ova are produced in the ovaries whereas sperm are produced in the testes.
6. In humans, the male’s penis is placed in the female’s vagina during sexual intercourse. Fallopian tubes are the tunnels in which the sperm and the egg meet, and house the site of fertilisation.
7. The uterus is the site of implantation of the embryo and the ‘house’ of the developing fetus.
8. Changes that you may be currently aware of are indication that you are becoming an adult. These physical changes are called puberty. The changes are due to substances which travel through your bloodstream called hormones.
9. The release of ovum from the ovary is called ovulation.
10. The monthly discharge or shedding of the uterus lining is called menstruation or a period. A menstrual cycle is the time from the first day of one period to the first day of the next.
11. The fetus obtains its nutrients and oxygen through a special organ cell called the placenta. The total time spent in the uterus is often called the gestation period
12. Asexual reproduction does not require the sex cells of another organism. Examples include vegetative propagation, parthenogenesis, budding, binary fission and regeneration. The scientific name for the development of new individuals from an unfertilised egg is parthenogenesis.
13. There are a variety of different strategies used by organisms to increase the chances of fertilisation occurring. Due to environmental factors and predators, not all fertilised eggs survive.
Chapter 3-The Body At War
1. A disease is a condition which prevents or stops the body or any of its parts from working.
2. The skin is a physical barrier to microbes. Saliva and stomach acid are chemical barriers to microbes.
3. Inflammation is an example of the body’s internal defences at work. White blood cells can act like scavengers and destroy foreign particles.
4. The lymphatic system is one of the body’s last lines of defence against disease.
5. All of the small organisms that prevent the body from working properly are called pathogens.
6. Viruses can only live and reproduce inside a host cell.
7. Bacteria reproduces by dividing in two in a process called binary fission.
8. Parasites are organisms that depend upon their host for food and shelter.
9. Tinea, thrush and ringworm are diseases caused by fungi.
10. Contagious diseases are those that are spread by contact.
11. Vectors such as mosquito carry diseases from host to host.
12. Diseases such as cholera and gastroenteritis are spread by contaminated water.
13. Personal hygiene and care with food preparation are two of the most effective ways of fighting the spread of disease.
14. Disinfectants are used to kill pathogenic organisms on many surfaces.
15. Antiseptics are not as powerful as disinfectants and can be used safely in the skin.
16. Antibodies are special chemicals that the body makes to fight pathogens.
17. A vaccine is a substance taken or injected to produce an immunity to a disease.
18. Nutritional, chemical, inherited diseases and cancer are all examples of non-infectious diseases. They cannot be spread from person to person.
Chapter 4-It’s A Material World
1. Synthetic materials can be moulded into different shapes.
2. Polymer is a word to describe the materials we commonly call plastic.
3. Polymers are large molecules made up of repeating units called monomers.
4. 19th Century chemists divided the study of chemistry into organic and inorganic chemistry.
5. Polymers which softer when heard are called thermoplastic polymers. Rigid polymers which char when heated are called thermosetting polymers.
6. Nylon and polyester are examples of synthetic fibres.
7. Fibres made from cellulose are called regenerated fibres.
8. Most ceramics are made from clays, which consist largely of silicates, (compounds of silicon and oxygen).
9. Glazing is used to make the surface of pottery more attractive and less porous.
10. Colloids contain particles which are too small to remove by filtering.
11. Emulsions are colloids consisting of two liquids such as water and oil.
12. A mixture consisting of a solid dispersed in water is known as a gel.
13. Most metals are malleable, ductile, lustrous and good conductors of electricity.
14. An alloy is formed by nixing a metal with other metals or non-metals.
15. Using electricity to coat objects with a layer of metal is called electroplating.
16. Two reasons for recycling plastics are that they are made from our dwindling oil reserves and that they are non-biodegradable.
Chapter 5-Chemical Energy
1. Chemical reactions which absorb energy from the surroundings and lower the temperature are called endothermic reactions.
2. Reactions which increase the temperature of the surroundings are called exothermic reactions.
3. Stored chemical energy is transformed into other forms of energy when a chemical reaction takes place.
4. Whether energy is released or absorbed during a chemical reaction can be observed by comparing the temperature of the reactants before the reaction with the temperature if the products after the reaction.
5. Explosions are chemical reactions in which a large amount of energy is released very quickly.
6. When an atom loses an electron it forms a positive ion.
7. Salt solutions conduct electricity well because ions are able to carry the current through the solution.
8. A solution that conducts electricity is called an electrolyte.
9. Metals are good conductors of electricity because free electrons can move freely towards the positive terminal of a battery.
10. A battery consists of several cells connected together.
11. Chemical reactions in a cell cause electrons to flow from the negative electrode through the device being powered, and back to the cell.
12. Coal, natural gas and oil are fossil fuels.
13. Crude oil is a mixture of many hydrocarbons.
14. An increase in the amount of greenhouse gases is largely responsible for global warming.
15. Fuels that consist of plant and animal wastes are called biofuels.
16. Chemical energy is stored in the carbohydrates, fat and protein that we eat.
17. Energy is transformed inside each body cell by a chemical reaction called cellular respiration in which glucose reacts with oxygen to form carbon dioxide and water.
18. Energy is measured in a unit called the joule.
Chapter 6-Electrical Circuits
1. All electrical circuits consist of three essential items. They are:
i. a power supply to provide the electrical energy;
ii. a load, in which electrical energy is converted into other forms of energy;
iii. a conducting path which allows electric charge to flow around the circuit.
2. The electrical energy is transformed into other forms of energy when the conducting path of an electric circuit is complete. A switch in the circuit allows you to control whether or not electrical current flows.
3. Electric current is a measure of the movement of the amount of electric charge passing a particular point in an electric circuit every second. Electric current can be measures with an ammeter.
4. Voltage is a measure of the amount of electrical energy gained or lost by electric charge as it moves through an electric circuit. The voltage across any two points in an electric circuit can be measures with a voltmeter.
5. Electrical resistance is a measure of how difficult it is for electric charge to flow through part of a circuit.
6. Conductors of electricity have very little resistance.
7. In metallic conductors, as long as the temperature remains fairly constant, a graph of voltage drop versus electric current for the conductor yields a straight line. Its resistance is ohmic.
8. A variable resistor can be used to change the voltage across and electric current flowing through parts of electric circuits.
9. When three light globes are connected to a power supply so that they are in series, if one light globe ‘blows’, the others stop glowing. When, on the other hand, the dame three light globes are connected in parallel, if one globe ‘blows’ the others remain glowing.
10. A short circuit could make a battery go flat very quickly
11. The electric current supplied by a cell or battery is direct current. The electric current provided to your home is called alternating current.
12. Fuses or circuit breakers inside a meter box at home stop the flow of electric current if it gets high enough to cause a fire risk.
13. Electrical power is a measure of how constant electrical energy is transformed into other forms of energy. It can be measured in watts.
14. Resistors, capacitors, diodes and transistors are examples of components that make up electronic circuits.
15. The circuits etched onto the silicon chips inside electronic devices are called integrated circuits.
Chapter 7-Keeping An Eye On Light
1. You can see beams of light only when particles in the substance like air scatter some of the light towards your eyes.
2. When light meets a boundary between two different substances, it can be reflected, absorbed or transmitted.
3. Everything that you see is an image.
4. When light travels from one medium to another, it changes speed and, unless it crossed the boundary at right angles, changes direction as well. This process is called refraction.
5. When light travels from water into the air, it bends away from the normal.
6. A diverging lens is curved outwards on both sides. It converges light toward a point called a focus.
7. A biconvex lens spreads light out.
8. The action of the lens in obtaining a sharp image on the retina is called accommodation.
9. Most of the bending of light done by the human eye occurs at the cornea.
10. if the combined focusing power of the lens and the corneas is too weak for the length of the eye, images of nearby objects become blurry. This condition is commonly known as long-sightedness.
11. Endoscopes, which include bundles of optical fibres, can be used to look inside the human body.
12. The total reflection of light when it travels from glass into air is called total internal refraction.
13. The separation of white light into its colours, called dispersion occurs because different colours of light are bent by different amount as they refract.
14. RGB can be combined together to produce white light.
15. The colours yellow, magenta, and cyan are used in printing, paints and dyes because they can be combined into different proportions to produce a wide range of colours, including white.
16. The receptor cells on the retina detect the brightness and colour of light. It is the cone cells that respond to colour.
Chapter 8-Dynamic Earth
1. The crust of the Earth varies in thickness between about 5km and 70km.
2. A volcano erupts when magma moves upward through the Earth’s crust.
3. The theory of plate tectonics provides and explanation of the patterns of volcanic activity on Earth.
4. The plates which males up the earth’s crust move slowly and can slide past each other, push against each other or move away from each other.
5. The forces below the Earth’s surface are large enough to cause solid rock to fold or crack.
6. When movement occurs along a crack in rocks, the crack is called a fault.
7. Movements along faults are responsible for many earthquakes.
8. All living matter on Earth is referred to as the biosphere.