Production of oxygen O2
Hydrogen peroxide ---manganese dioxide (catalyst)---> water + oxygen.
2H2O2 ---MnO2---> 2H2O + O2
Proof of oxygen: relights a glowing splint.
Carbon (charcoal) burned in oxygen:
C + O2 ---> CO2 : This is an acidic oxide.
Magnesium burned in oxygen:
2Mg + O2 ---> 2MgO : This is a basic oxide.
Production of CO2, carbon dioxide (denser than air, can be poured)
Calcium Carbonate (marble chips) + Hydrochloric acid ---> Calcium chloride + water + carbon dioxide
CaCO3 + 2Hcl ---> CaCl2 + H2O + CO2
Proof: quenches a lighted splint.
Limewater + carbon dioxide ---> Chalk + Water
Ca(OH)2 + CO2 --->CaCO3 +H2O
Carbon dioxide + water ---> Carbonic acid (acid rain)
CO2 + H2O ---> H2CO3
Production of hydrogen, H2 (colourless, odourless, highly reactive gas)
Zinc + Hydrochloric acid = Zinc chloride + Hydrogen
Zn + 2HCl = ZnCl2 + H2
Proof of hydrogen: Popping noise with a lighted splint.
Carbon dioxide in air dissolves in rainwater
CO2 + H2O ---> H2CO3 (carbonic acid)
Sulfur dioxide (SO2) from factories and cars burning fossil fuels SO2 then dissolves into rainwater
SO2 + H2O ---> H2SO3 (sulfurous acid)
Fossil fuels are hydrocarbons containing hydrogen and carbon.
Iron + oxygen + water = iron oxide
Speed : Distance(m) / Time(s)
Units: m/s (metres per second)
Memory Aid : Dads Silly Triangle (Distance / Speed X Time)
Velocity is speed in a given direction. The units for velocity is m/s.
Acceleration : Change in velocity(m/s) / time takenn(s)
Or V2 - V1 / t
V1 = initial velocity
V2 = final velocity
t - time taken
Units : m/s/s or m/s2
Density : mass(g) / volume(cm3)
Unit : g/cm3
Memory aid: My Dear Vera ( Mass / Density X Volume)
Work : Force(N) X Distance(cm)
Units : Joules
Power : Work done(j) / time taken(s)
Units W (Watts)
Weight : Weight is a forced measured in N
Mass(kg) X 10N/kg (earths gravity) (1.67 N/kg on moon) (O gravity in space)
Moment of a force : Force X Perpendicular distance from force to fulcrum
Units : Moments
Pressure : Force(N) / Area(m2)
Units : Pa / Pascals
Speed of Sound (340m/s) : Distance(cm) / Time (s)
Current, voltage, resistance:
V = Voltage (Volts)
I = Current (Amps)
R = Resistance (Ohms)
Memory aid : Very Important Rule (Voltage/ Current X Resistance)
Ohms law at constant temperature voltage is proportional to current in a circuit
The Periodic Table arranges the elements in order of increasing atomic number.
Atomic Number: The number of protons in the nucleus of an atom of an element.
Groups/Families - Vertical column.
All elements in a group are chemically similar.
All elements in a group have the same number of electrons in their outermost shell.
Group 1 - The Alkali Metals.
Group 2 - The Alkaline Earth Metals.
Group 7 - The Halogens.
Group 8 - The Noble Gases.
Period - Horizontal Row. (n=1, n=2, etc.)
All the elements in a period have the same number of electron shells.
Non-Metals are on the right.
Metals are on the left and center.
Elements, Compounds and Mixtures
An atom is the smallest part of an element that still has properties of that element.
An element is a substance which cannot be broken down into simpler substances by chemical means.
A compound is formed when two or more elements chemically combine. A compound is a completely new substance with its own properties.
A molecule is the smallest part of an element or compound that can exist on its own.
• Biology is the study of living things (organisms).
The seven characteristics of living things
• *For something to be alive it must possess all of these characteristics.
Animals can be divided into two main groups - Vertebrates and Invertebrates.
Vertebrates are animals that have a backbone
Invertebrates are animals that do not have a backbone
Vertebrates can be divided up into five groups - Fish, Amphibians, Reptiles, Birds and Mammals
A key is a set of questions used to identify a plant or animal.
Structures found in plant and animal cells
• Nucleus - controls the activities of the cell. Contains chromosomes made of DNA.
• Cell membrane - controls what substances enter and leave the cell.
• Cytoplasm - watery fluid. All other structures of the cell are suspended in it.
• Vacuoles - store substances.
Structures found in plant cells only
• Chloroplasts - contain chlorophyll for photosynthesis.
• Vacuole - contains cell sap.
• Cell wall - Supports the cell. Made of cellulose.
Tissues, Organs, Systems
• A tissue is a group of similar cells, e.g. nerve tissue, muscle tissue.
• An organ is a group of tissues, e.g. heart, brain.
• A system is a group of organs, e.g. digestive system, nervous system.
• The eyepiece is the piece you look through
• The objective lens is just above the stage.
• The stage is where you put the slide.
• The focus knob moves the objective lens up or down to focus the object you are looking at.
Preparing a microscope slide
1. Place a drop of water on a glass slide.
2. Place the object to be viewed on top of the water.
3. Gently lower the cover-slip onto the slide. Avoid trapping air bubbles.
4. Apply some drops of stain to one side of the cover-slip and draw it across the sample by soaking some fluid from the other side with paper.
• Growth results from cell division.
• Food is needed for growth energy, repair and protection against disease.
The five major nutrients
• Sugars: a fast supply of energy (fruit, chocolate, soft drinks)
• Starch: a slower supply of energy (bread, potatoes, rice)
• Fibre: prevents constipation (brown bread, cereals, vegetables)
• Store energy (butter, cream, milk)
• Growth & repair (lean meat, fish, cheese)
• Iron: maintain a healthy blood supply (red meat, green vegetables)
• Calcium: maintain strong bones (milk, cheese)
• Vitamin C: prevents scurvy (oranges, cabbages, kiwis)
• Vitamin A: prevents night blindness (carrots, milk)
A Balanced Diet
• The six constituents of a balanced diet are carbohydrates, fats, proteins, minerals, vitamins and water.
• A balanced diet is a diet which contains the right amounts of each of the six constituents.
• To test for starch add iodine solution to the food sample. It will turn blue-black if starch is present.
• To test for protein add copper sulfate and sodium hydroxide. It will turn violet if protein is present.
• To test for glucose, add benedict's solution and heat. It will turn brick red if glucose is present.
• To test for fats rub the food sample on brown paper. A translucent spot will appear if fats are present.
Stages of Digestion
• The five stages of digestion are ingestion, digestion, absorbtion, assimilation and egestion.
• Ingestion is the taking of food into the mouth
• Digestion is the breaking down of food
• Absorbtion is the absorbtion of molecules of food into the blood in the small intestine
• Assimilation is the taking of food molecules from the blood into body cells.
• Egestion is the passing of undigested food out of the body.
• Physical digestion involves the chewing of food in the mouth and churning of food in the stomach.
• The four types of teeth are incisors, canines, premolars and molars.
• Chemical digestion is the breaking down of food by enzymes.
The Digestive System
• The digestive system is a group of organs working together to break down food and absorb the nutrients from it.
• The mouth chews food and mixes it with enzymes, eg. amylase in saliva.
• The oesophagus carries food to the stomach by muscular action (peristalsis).
• The stomach stores and churns food and mixes it with digestive juices. It also produces hydrochloric acid to kill bacteria.
• The liver produces bile to break down fats.
• The small intestine contains enzymes to break down food. Food molecules are absorbed into the blood in the small intestine.
• The pancreas produces enzymes.
• The large intestine passes water into the blood.
• An enzyme is a chemical which speeds up a chemical reaction in the body without being used up in the reaction.
• An enzyme acts on a substrate to produce the product.
• Amylase is an enzyme which breaks down starch (substrate) into maltose (product).
Blood & The Circulatory System
• Plasma is the liquid part of the blood.
• Red blood cells are the most numerous blood cells. They are made in bone marrow and they contain haemoglobin to transport oxygen. They also give the blood its red colour.
• Iron is needed to make red blood cells.
• White blood cells fight disease.
• Platelets clot the blood to stop bleeding.
• Red blood cells have a biconcave shape and no nucleus.
The Circulatory System
• The circulatory system consists of the heart and the blood vessels.
• Veins bring blood to the heart. They have a wider lumen than arteries, and valves to prevent backflow of blood.
• Arteries carry blood away from the heart. They have a narrow lumen and have no valves.
• Capillaries are thin blood vessels (1 cell thick) that allow substances to pass into and out of the blood. They join veins to arteries.
• Made of cardiac muscle - never tires
• Contracts to pump blood around the body
• Consists of 4 chambers - right & left atriums, right & left ventricles.
• Right side of the heart pumps deoxygenated blood to the lungs
• Left side of the heart pumps oxygenated blood to the rest of the body. The heart wall is therefore thicker/stronger on the left.
• Has 2 valves to control the direction of the flow of blood.
Exercise and the rate of heartbeat
• The normal heartbeat rate of a resting human is 70 beats per minute.
• Exercise increases the heartbeat rate. This is because during exercise the cells need to produce more energy, so they require more food and oxygen.
• The normal body temperature in the human body is 37°C.
• Blood flow helps regulate body temperature.
• Respiration is the release of energy from food.
• Respiration produces energy, carbon dioxide and water vapour.
• Aerobic respiration requires oxygen.
• The word equation for aerobic respiration is: Glucose + Oxygen = Energy + Carbon Dioxide + Water Vapour.
The Breathing System
• The human breathing system consists of the nose, mouth, windpipe, lungs, bronchi, bronchioles, alveoli and diaphragm.
• Rings of cartilage surround the windpipe, bronchi and bronchioles to keep them open.
• Gas exchange takes place in the alveoli.
• Carbon dioxide is tested for by passing it through limewater. Limewater turns milky if carbon dioxide is present.
• Exhaled air contains more carbon dioxide than inhaled air.
• Smoking for a long time can cause lung cancer, but it can also have other harmful effects.
• Particles of smoke irritate the lungs and produce mucus, leading to diseases such as bronchitis.
• Smoking during pregnancy can damage the baby.
• Excretion is the removal of wastes from the body.
• The human excretory organs are the lungs, the skin and the kidneys.
• The lungs excrete carbon dioxide and water.
• The skin excretes sweat (water and salts).
• The kidneys excrete urine (urea, water and salts) .
The Urinary System
• The kidneys filter the blood and remove urea and salts. They also remove water if the blood is too dilute.
• Blood is brought to the kidneys in the renal artery.
• Blood exits the kidneys in the renal vein.
• Urine passes from the kidneys through the ureters, bladder and urethra.
Reproduction is the production of a new individual of the same species.
• A gamete is a sex cell.
• Sexual reproduction is the fusion of a male and female gamete.
• The male gamete is the sperm.
• The female gamete is the egg.
The Male Reproductive System
• Testes: produce sperm
• Sperm is mixed with seminal fluid to form semen.
• Seminal vesicle: produces the seminal fluid.
The Female Reproductive System
• The egg is made in the ovary
• Eggs are released every month until the menopause.
The Menstrual Cycle
• An egg is released from the ovary every 28 days.
• the release of an egg from the ovary is called ovulation.
• In days 1-5 of the menstrual cycle the lining of the uterus breaks down(menstruation).
• In days 6-12 the womb lining builds up again.
• In days 13-15 ovulation occurs.
• In days 16-28 the lining of the uterus stays built up.
• The fertile period is the time in the menstrual cycle when the woman is most likely to become pregnant if she has intercourse. The fertile period lasts from day 11 to day 18.
• Fertilisation is the fusion of a male and female gamete.
• The fusion of the male and female gametes forms a zygote.
• After an egg has been fertilised it attaches itself to the lining of the uterus. This is called implantation.
• The average length of human pregnancy is 40 weeks.
• During pregnancy the placenta allows food and oxygen to pass into the baby's blood, and wastes to pass into the mother's blood.
• The embryo is protected by amniotic fluid.
• Contraception is a means by which fertilisation is prevented.
• These are passed from parent to child.
• Examples: eye colour, facial shape, blood group.
• These are acquired during life and are not controlled by genes.
• Examples: scars, accent, muscle strength.
• These are strips of DNA wrapped around a protein.
• Every human cell contains 23 pairs of chromosomes except for the egg and sperm cells which contain 23 single chromosome.
• Genes are sections of chromosomes which determine the chemical make up of the body.
• When a cell divides exact copies of its chromosomes are formed.
• At fertilisation the sperm cell and the egg cell combine to create 23 pairs of chromosomes.
You actually are the best thank you ❤️
The Skeleton and Muscles
The Skeleton, Bone and Muscles
• The functions of the skeleton are support, protection and movement.
• Muscles are attached to bones. When they contract they allow us to move.
• All vertebrates have a spine made up of vertebrae.
• Bone is a living tissue so it can grow and repair.
• The presence of calcium in bones is what makes them hard.
• Fused joints do not allow movement, eg. the bones of the skull
• Ball and socket joints allow movement in any direction, eg the shoulder and the pelvis.
• Hinge joints allow movement in one direction only, e.g. the knee.
Ligaments and Tendons
• Ligaments join bone to bone.
• Cartilage acts as a shock absorber between bones.
• Synovial fluid acts as a lubricant.
• Tendons join muscle to bone.
• Antagonistic muscles are pairs of muscles that pull in opposite directions, e.g. the biceps and triceps of the arm.
• To raise the arm, the biceps contracts and the triceps relaxes. To lower the arm, the triceps contracts and the biceps relaxes.
Bones in the skeleton that you need to know
• Shoulder Blade
• Breast Bone
• Collar Bone
• Humerus (HL only)
• Ulna (HL only)
• Radius (HL only)
• Femur (HL only)
• Tibia (HL only)
• Fibula (HL only)
The Nervous System
The Central Nervous System
• The central nervous system consists of the brain, the spinal chord and the nerves.
• Sensory nerves carry messages to the brain.
• Motor nerves carry messages from the brain.
• In certain cases there is no time to decide what to do, e.g. if you place your hand on something hot. The message goes from your hand to the spinal chord. From there a message is sent to your arm telling it to pull your arm away.
• Sclera: a white protective layer (3rd layer from the inside).
• Choroid Layer: a dark layer rich in blood vessels (2nd layer from the inside).
• Retina: the light sensitive layer (1st layer from the inside).
• Cornea: this allows light into the eye.
• Aqueous Humour: liquid that helps focus light onto the retina (in the area between the cornea and the lens).
• Iris: a muscle that controls the amount of light entering the eye.
• Lens: this focuses light onto the retina.
• Ciliary Muscles: hold the lens in place and controls its shape to allow us to see objects near and far away.
• Optic Nerve: brings images to the brain in the form of electric pulses.
• Fovea/Yellow Spot: the most sensitive part of the retina.
• Blind Spot: the point where the retina joins the optic nerve.
• Vitreous Humour: jelly-like fluid that gives the eye shape (in the main part of the eye).
Ecology & Habitat Study
• Ecology is the study of the relationships of living things with one another and their environment (everything surrounding an organism).
• A habitat is a small part of an ecosystem where a plant or animal lives. Eg: a woodland
• An ecosystem is a large area with similar plants and animals. Eg: Desert & Rainforest.
Food Chains & Webs
• A food chain is a chain showing how organisms are linked by what they eat.
Solar energy is transferred through a food chain.
• The feeding level is the position of a particular organism in a food chain. Producers are at the first feeding level.
• A food web is a number of intersected food chains.
Producers, Consumers & Decomposers
• Producers are green plants that make their own food.
• Consumers are all organisms other than producers.
• Only animals can be consumers.
• There are two types of consumers: carnivores and herbivores.
• Carnivores only eat meat, eg. hawk, fox.
• Herbivores only eat plants, eg. cow, rabbit.
• Decomposers are organisms that feed on dead animals or plants.
• Adaption is a change that plants or animals make to help the survive better in their habitat.
• Example 1: Dandelions have a parachute mechanism to disperse seeds.
• Example 2: Hedgehogs have sharp spines to protect them from predators.
• Example 3: Ladybirds have a brightly coloured shell to warn of their bitter taste.
• Competition for scarce resources occurs in a habitat between organisms.
• Plants compete for light, eg. oak trees grow tall to catch more light.
• Animals compete for food, eg. hawks and foxes compete for the same food.
• When organisms in a habitat need each other for survival.
• Example: Flowers provide nectar for insects and insects pollinate flowers.
Conservation, Pollution & Human Activity
• Conservation is careful management of a habitat.
• Pollution is damage to the environment caused by the dumping of waste materials.
• Air pollution is caused by burning fossil fuels.
• Water pollution is caused by oil spillages and fertilisers being washed into rivers.
• Soil pollution is caused by acid rain, overuse of fertilisers and the dumping of waste.
• Human Activities have both positive and negative effects on the environment.
• Positive effects of Human Activity:
1) green spaces are maintained.
2) reducing our energy needs by increasing insulation in buildings.
3) using unleaded instead of leaded petrol and smokeless fuels.
• Negative effects of Human Activity:
1) global warming as a result of the burning of fossil fuels.
2) overuse of fertilisers on farms.
Tools for a Habitat Study
• Quadrat: a square frame with an area of 1 metre squared used to estimate plant & insect numbers. Used by placing randomly in a habitat multiple times and recording the number of plants/insects in the frame. This is then averaged to find the number of plants/animals per square metre.
• Pooter: used to suck up small insects to be examined.
• Pitfall Trap: small insects fall into a can in the ground which is covered by a board balancing on stones. The insects are then collected the next day and examined.
• Beating Tray: a tray is put under a shrub/tree and beat with a stick. Small insects are dislodged from the shrub/tree and fall onto the tray.
• Line Transect: a rope marked at regular intervals which is placed across a habitat. A plant directly underneath or touching a mark is recorded.
Photosynthesis & Tropisms
• Photosynthesis is the process by which plants make their food.
• Photosynthesis occurs in the leaves of a plant.
• The green chemical chlorophyll is needed for photosynthesis. It is found in the chloroplasts in a plant cell.
• Chlorophyll traps light energy and uses it to combine carbon dioxide and water. This forms glucose and oxygen.
• The water needed for photosynthesis is collected from the soil through the roots and is transported around the plant in xylem cells.
• Leaves have air spaces between their leaves called stomata. This is where the product Oxygen leaves the plant and Carbon Dioxide enters the plant.
• The three things needed for photosynthesis to occur are light, water and carbon dioxide.
• The word equation for photosynthesis is :
Carbon Dioxide + Water -----(Light & Chlorophyll)-----> Oxygen + Glucose
• A tropism is a growth of a plant in response to a stimulus, e.g. gravity, light.
• Geotropism is a plant's response to gravity. Geotropism causes the roots of a plant to grow downwards.
• Phototropism is a plant's response to light. Phototropism causes a plant's stem to grow towards the light.
Plant Structure, Transport & Transpiration
• All flowering plants consist of a shoot and a root.
• The root anchors the plant and absorbs water. It also absorbs minerals that are dissolved in the water.
• The stem holds the plant towards the sunlight, supports the flower, transports water and minerals up to the leaves and transports food down from the leaves.
• The leaf makes food by photosynthesis, loses water by transpiration, and exchanges carbon dioxide with oxygen.
• The flower forms the seeds for reproduction.
• Xylem Cells transport water and dissolved minerals up through the plant (Hint for remembering: Xylem = Water).
• Phloem Cells transport food down from the leaves to all the other parts of the plant (Hint for remembering: Phloem = Food)
• Water is absorbed through the roots of a plant.
• Xylem Cells transport water and dissolved minerals up through the plant (Hint for remembering: Xylem = Water).
• Phloem Cells transport food down from the leaves to all the other parts of the plant (Hint for remembering: Phloem = Food)
• Transpiration is the movement of water from the roots to the surface of the plant and the loss of water from the surface of the plant.
• Water is lost through stomata - tiny pores between cells on the undersurface of a leaf.
• Transpiration provides water for photosynthesis.
• Transpiration carries dissolved minerals up the plant.
• Transpiration also cools cools the plant.
• Transpiration is highest with bright sunlight, availability of soil water, and a low humidity.
Types of Plant Reprodction
• Sexual Reproduction in plants occurs when a male and female gamete fuse together. It involves two parents. Eg: buttercup.
• Asexual Reproduction is when new plants are formed from one parent only.
Parts of a Flower
• Petal: this attracts insects because of its appealing colour and scent.
• Sepals protect the flower before it blooms.
• Carpel: produces female sex cells (eggs).
• Stamen: produces male sex cells (pollen).
Parts of the Carpel
• Stigma: this is the landing place for pollen.
• Style: this connects the stigma to the ovary.
• Ovary: produces and contains the ovules which produce the female gamete (egg).
Parts of the Stamen
• Anther: this makes the grains of pollen.
• Filament: this is the stalk of the stamen which supports the carpel.
Stages of Sexual Reproduction
• This is the transfer of pollen from a stamen to a carpel.
• Pollen can be transfered by wind or by insects.
• Wind pollinated flowers have large amounts of pollen, stamens and carpels that hang outside the petals. Eg: grasses.
• Insect pollinated flowers have a nice smell, brightly coloured petals and nectar to attract insects. the stamens and carpels are often inside the petals. Eg: a rose.
• This is the joining of a male and a female gamete to form a zygote.
• A pollen grain grows a pollen tube through the style and down to the ovary.
• The male gamete passes through the tube into the ovule and fuses with the egg.
• The ovule becomes a seed.
• The ovary then swells to become the fruit and the petals, stamens and petals fall off the flower.
• This is a method of carrying seeds as far away as possible from a parent plant.
• This can be done by wind, water, animals or self dispersal.
• Wind dispersal: the seeds/fruits are light and might have wings or hairs. Example: dandelion, sycamore, grasses.
• Water dispersal: the seeds/fruit are light and buoyant so they will float. Example: water lily, coconut, alder, duck weed.
• Animal dispersal: fleshy and tasty, may have hooks. Examples: blackberry, strawberry, raspberry, goose grass (stick weed).
• Self dispersal: pods that explode to release the seeds. Examples: peas, lupin, wallflowers.
• The growth of a new plant from a seed.
• Conditions needed: water, oxygen, suitable temperature.
Parts of a Seed (HL only)
• Testa: protective outer coat
• Plumule: a baby shoot
• Radicle: a baby root
• A food supply
Length, Mass, Time & Temperature
• 1 kilometre (km) = 1000 metres (m)
• 1 metre (m) = 100 centimetres (cm)
• 1 centimetre = 10 millimetres (mm)
• Metre stick/ruler (avoid the error of parallax) (nearest mm)
• Measuring Tape (nearest mm)
• Callipers (nearest mm)
• Vernier Callipers (nearest 0.1mm)
• Opisometer (nearest mm when used with metre stick/ruler)
• Trundle Wheel (nearest cm)
• The mass of an object is the amount of matter in it.
• Electronic balance is used to measure mass.
• 1 kilogram = 1000 grams
• 60 seconds = 1 minute
• 60 minutes = 1 hour
• Watches / Clocks / Stopwatch / Electronic Timers
• The temperature of an object is a measure of how hot or cold the object is.
• Measured in Degrees Celsius (°C) using a thermometer.
• Body temperature is 37°C.
• There are 4 types of thermometers: mercury/alcohol thermometers, thermoscan ear thermometer, electronic digital thermometers, temperature sensors.
Area, Volume, Density & Floatation
• The area of a shape is the amount of surface enclosed within it’s boundary lines.
• m2 or cm2
• Area of a rectangle or square = length x width
• Area of a disc = ∏ x r x r
• Area of a triangle = ½ x base x perpendicular height
• The volume of the object is the amount of space it takes up.
• m3 or cm3
• Graduated cylinder / burette / pipette (liquids)
• Length x width x depth (regular solid)
• Overflow can (irregular solid)
• The density of a substance is its mass per unit volume.
• Electronic balance / Graduated cylinder & electronic balance.
• Density = Mass / Volume
• kgm−3 or cmg−3
• An object floats in a liquid if its density is less than the density of the liquid.
• An object sinks in a liquid if its density is greater than the density of the liquid.
Speed, Velocity & Acceleration
• Speed is distance travelled per unit time.
• Speed = Distance / Time
• ms-1 or m/s
• This is speed measured in a particular direction.
• Velocity is measured in ms-1 or m/s
• This is the rate of change of velocity.
• Acceleration is measured in m/s/s or m/s2 or ms-2
Force, Work & Power
• A force is a push or pull that can change the velocity of an object or make it move. Examples of the effects of forces: causing an object to move, speed up, slow down or stop, change direction, change shape.
• Force is measured in Newtons (N).
• For every force, an equal but opposite force is exerted.
Examples of Forces: Weight, Friction & Tension
• Weight: A force which pulls us towards the centre of the earth.
• Weight(N) = mass x 10
• The weight of an object on the moon is less than its weight on earth because the moon has a smaller mass and therefore has less pull on the object.
• Friction: A force that opposes movement between two surfaces.
• Friction is needed: between the soles of the shoes of a person and a path, between the tyres of a car and the road, between a ladder and the path.
• Friction is not wanted: in locks, in engines.
• Friction is reduced by lubrication.
• Tension: A force in a string or rope when it is pulled in opposite directions at the same time.
• The extension of a spring is in direct proportion with the force stretching it as long as this force does not exceed the elastic limit.
• Work is done when a force moves an object.
• Work is measured in Joules.
• Work (J) = Force (N) X Distance (M).
• Power is the work done per unit time.
• Power = work done / time
• Power is measured in watts.
• The average power(watts) is the work done(joules) divided by the time taken(seconds).
• Energy is the ability to do work.
• The Joule (J) is the unit of energy.
Moments, Levers & Centre of Gravity
• The measure of the turning effect of a force is called the moment of the force.
• Moment of a force = (force) x (perpendicular distance between the force and the fulcrum).
• Fulcrum: the fixed point or line through which something swings.
• Moments can be increased by increasing the size or the force or increasing the distance between the force and the fulcrum.
• A lever is any rigid body that is free to turn around a fixed point or axis called a fulcrum.
Law of the Lever
• When a lever is balanced by any number of forces, the sum of the clockwise moments equal to the sum of the anti-clockwise moments.
Centre of Gravity
• This is the point in a body where all its weight appears to act.
• The c.o.g. of a regularly shaped symmetrical objects are at their centre.
• The position of an object’s centre of gravity (c.o.g.) determines the stability of an object.
• A low centre of gravity makes an object more stable.
• A high centre of gravity makes an objects less stable.
• *A wide base increases stability, a narrow base decreases stability.*
• A body will topple if a vertical line through its c.o.g. falls outside its base.
• A body is in stable equilibrium if, when moved slightly its c.o.g. rises.
• A body is in unstable equilibrium if, when moved slightly its c.o.g. falls.
• A body is in neutral equilibrium if, when moved slightly its c.o.g. doesn’t move.
From this thread, just study on what you find most tricky to learn. Do not learn all these!
Air consists of 78% nitrogen, 21% oxygen, <1% argon, 0.03% carbon dioxide, and 0-4% water vapour.
Air is a mixture. This is shown by the fact that its composition varies (e.g. there is less oxygen in the upper atmosphere).
Preparing Oxygen & Carbon Dioxide
Oxygen is prepared by the breakdown of hydrogen peroxide using manganese dioxide as a catalyst.
2H2O2 + MnO2 -> 2H2O + O2.
Carbon Dioxide is prepared by the reaction between hydrochloric acid and marble chips.
2HCl + CaCO3 -> CaCl2 + CO2 + H2O.
Carbon dioxide is tested for by passing it through limewater. It turns limewater milky.
Oxygen is tested for using a glowing splint - it relights a glowing splint.
Water is tested for using cobalt chloride paper. It turns from blue to pink in the presence of water.
Properties of Oxygen
Physical Properties: Colourless, odourless, tasteless, heavier than air, slightly soluble in water.
Chemical properties: Supports combustion, very reactive, neutral pH.
Properties of carbon Dioxide
Physical Properties: Colourless, odourless, tasteless, heavier than air, moderately soluble in water.
Chemical properties: Does not support combustion, turns limewater milky, forms an acid in water (called carbonic acid).
Uses of Oxygen
Uses of Carbon Dioxide
A mixture consists of two or more elements which are mixed together but are not chemically combined.
Examples of mixtures are air (a mixture of gases) and seawater (a mixture of water & salt).
Crystillisation is when crystals are formed from a solution which is evaporated.
Filtration is used to separate insoluble solids from liquids. The mixture is passed through filter paper, which traps the solids and allows the liquid to pass through.
Evaporation is used to separate soluble solids from liquids. The liquid is evaporated, leaving the solid behind.
Distillation is used to separate two liquids with different boiling points, e.g. water and alcohol. It can also be used to separate soluble solids from liquids.
Chromotography is used to separate a mixture of dissolved substances in a solution.
A solution is a mixture of a solute (substance which is dissolved) and a solvent (liquid in which the solute is dissolved), e.g. copper sulfate dissolved in water.
The hotter the solvent, the more solute will dissolve in it.
A concentrated solution has a large amount of solute dissolved in a small amount of solvent. A dilute solution has a small amount of solute dissolved in a large amount of solute.
A saturated solution is one which has the maximum possible amount of dissolved solute at that temperature.
A dilute solution can be made concentrated by adding more solute or evaporating off some of the solvent. A concentrated solution can be made more dilute by adding more solvent.
When a saturated solution is cooled to a lower temperature, crystals of the solute form. This is known as crystallisation. For example, when a concentrated solution of copper sulfate in water is cooled, copper sulfate crystals form.
States of Matter
Matter is anything that takes up space and has mass.
The three states of matter are solid, liquid and gas.
Properties of Solids, Liquids and Gases
Solids Liquids Gases
Definite Mass Definite Mass Definite Mass
Definite Shape No Definite Shape No Definite Shape
Definite Volume Definite Volume No Definite Volume
Incompressible Incompressible Compressible
Does Not Flow Flows Diffuses
Melting is the changing of a solid to a liquid, e.g. when ice melts to form water.
Evaporation is the changing of a liquid to a gas. This happens when the liquid is heated, and the atoms in the liquid gain enough energy to become a gas.
The boiling point of a liquid is the point where evaporation occurs throughout the liquid. The boiling point of water is 100 degrees Celsius.
Condensation is the changing of a gas to a liquid, e.g. steam condenses into water when it hits a cold surface.
Bonding and the Octet Rule
Atoms combine to form compounds.
The octet rule states that atoms bond together so that each atom attains a stable outer shell of 8 electrons.
Ionic bonds are formed when electrons are transferred between atoms so that each atom has 8 electrons in its outer shell.
For example, NaCl is formed when Sodium (2, 8, 1) donates its outer electron to Chlorine (2, 8, 7). This way, sodium and chlorine both have 8 electrons in their outermost shell.
An ion is a positively or negatively charged atom.
An atom becomes positively charged when it loses an electron.
An atom becomes negatively charged when it gains an electron.
A covalent bond is formed when atoms share electrons.
A single covalent bond is formed when atoms share only one pair of electrons, e.g. Hydrogen(H2)
A double covalent bond is formed when atoms share two pairs of electrons, e.g. Oxygen(O2)
Properties of Metals
Usually solids(except for mercury)
Malleable - they can be hammered or pressed into shape
Good conductors of heat and electricity
Lustrous (shiny) appearance
Ductile - they can be stretched out into thin wires without breaking
Usually very dense
High melting points
Corrosion is when a metal reacts with oxygen to form an oxide
Rusting is the corrosion of iron or steel.
Rusting requires water and oxygen.
Corrosion can be prevented by painting, chrome plating, galvanising or greasing.
An alloy is a mixture of two or more metals.
Bronze is a mixture of copper and tin.
Steel is a mixture of iron and carbon.
Brass is a mixture of copper and zinc.
The Activity Series
The activity series is a list of metals in decreasing order of reactivity.
The order of reactivity (from most to least reactive) of the 4 metals on the Junior Cert course is: Calcium, Magnesium, Zinc, Copper.
Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen.
Metals react with acids to give off hydrogen gas (H2).
e.g. Zn + 2HCL -> ZnCl2 + H2.
Water is a compound made up of hydrogen and oxygen.
Water is tested for using cobalt chloride paper. It turns from blue to pink in the presence of water.
Water freezes at 0 degrees Celsius.
Water boils at 100 degrees Celsius.
Ice floats on water because it is less dense than water.
Water is an excellent solvent, and therefore it is very rarely pure because substances dissolve in it.
Water treatment has five stages - screening, settling, filtration, chlorination, fluoridation.
Screening involves using a wire mesh to filter out large, insoluble particles (e.g. twigs/branches).
Settling involves using settling beds to remove smaller insoluble particles.
Filtration involves filtering the water through beds of sand & gravel to remove small insoluble particles.
Chlorination involves adding chlorine to kill bacteria.
Fluoridation involves adding fluoride for healthy teeth.
Hardness in Water
Soft water is water that forms a lather easily with soap.
Hard water does not form a lather easily with soap.
Water hardness is caused by the presence of dissolved calcium ions.
Hardness in water is removed by distillation or using an ion exchange resin.
Ion exchange resin works by exchanging the calcium ions which cause hardness with hydrogen ions.
Advantages of hard water include that it tastes better, and provides calcium.
Disadvantages of hard water include that it causes limescale, and wastes soap.
Water can be broken down into hydrogen and oxygen by electrolysis. Hydrogen is formed at the negative electrode, oxygen is formed at the positive electrode.
Electrolysis of water produces twice as much hydrogen as oxygen because in water (H2O), there are 2 H atoms for every O atom.
A Hoffman voltameter is used in electrolysis of water.
Acids & Bases
An acid is a substance that turns blue litmus paper to red.
Acids can be strong (e.g. hydrochloric acid, sulfuric acid) or weak (e.g. vinegar, lemon juice).
A base is a substance that turns red litmus paper to blue.
Strong bases include sodium hydroxide and potassium hydroxide, weak bases include soap and baking soda.
Bases can also be called alkalis.
pH & Indicators
The pH scale is a scale ranging from 0 to 14. It is used to measure how strong an acid or base is.
Acids have a pH less than 7, bases have a pH above 7 and a substance with a pH of 7 is neutral.
pH can be measured using universal indicator paper. The colour of the paper gives the pH of the substance.
Acids and bases react to form a salt and water. This is known as a neutralisation reaction. The hydrogen in the acid is replaced with a metal from the base.
e.g. HCl + NaOH -> NaCl + H2O.
Acids and bases are neutralised in a titration reaction. The acid is placed in a burette, and the base is placed in a conical flask.
Acids and carbonates react to form a salt, water and carbon dioxide.
e.g. 2HCl + CaCO3 -> CaCl2 + H2O + CO2
SYRAN you need to sleep
Syran can you post the science answers please