CIE Science IGCSE Revision Cards

Blood is pumped away from the heart in the arteries and travels all around the body in the veins. There are two measurements of blood pressure: systolic and diastolic. A young, fit person should have a blood pressure of about 120 over 70 but many things can affect their blood pressure such as: 

• smoking or being overweight. 
• drinking excessive alcohol
• Stress

High blood pressure can cause

• kidney damage
• burst blood vessels
• brain damage, including strokes

Cigarette smoke contains many chemicals but the mains ones are: Nicotine, Carbon Monoxide and Tar. Nicotine is the addicitive substance that quickens your heart rate, carbon monoxide decreases your oxygen intake and tar blocks the arteries. 

The nutrients in food provide us with energy. Carbohydrates give us slow releasing energy, fats and sugars give us immediate energy, we use proteins for growth and repair and we use vitamins and minerals to keep our body functioning properly. 

People have to have a balanced diet in order to be healthy. Whether you are considered underweight or overweight depends of your BMI (body mass index) which can be calculated using the formula: BMI = mass in kg ÷ (height in m)²

Microorganisms that cause diease are known as pathogens. Living organisms that can cause disease are called parasites. Parasites make a home inside their host human or animal but do not tend to kill them, just feed off their food supply and make them very sick. Scurvy is caused becuase of a vitamin C deficiency. Anaemia is caused because of a lack of iron. Cancer is caused when cells begin to divide out of control. 

Our body fights these diseases in many ways such as producing white blood cells, skin protection, mucus, stomach acid and clotting blood when you get a cut. You can also be protected through drugs. 

Receptors in out eyes, ears, tongue, nose and skin are sensitive to light, souns, chemicals in food, chemicals in the air, touch, pressure, pain and temperature.

The Central Nervous System (CNS) consists of the brain and the spinal cord. When a receptor is stimulated is sends a signal along the neurones (nerves) to the brain which coordiantes a responce.  

Neurones carry messages to the brain via tiny electrical impulses. There are three types of neurone: They pass chemicals through a gap called the synapse. 

• Sensory Neurones - From receptors to the spinal cord and brain. 
• Relay Neurones - From one part of the CNS to another. 
• Motor Neurones - From the CNS to effectors.

Reflex actions are used when a quick responce is needed. They happen without us thinking, such as blinking or pulling your hand away from a flame. 

Maintaining a constant internal environment of the body is called homeostasis; the nervous system and hormones are responsible for this. Our body controls out carbon dioxide (a waste product of respiration) levels by breathing it out. It controls body temperature by sweating, shivering and altering blood flow to the skin. It also controls water content through breathing in our lungs, sweating and urinating. Body temperature is monitored by a part of the brain called the hypothalamus. When we are hot our blood vessels near out skin swell (known as vasodilation) causing more heat to be. When we are cold they shrink (known as vasoconstriction) causing less heat to be lost. 

Hormones are produced and secreted by glands. The thyroid gland produces thyroxine which controls metabolism, the adrenal glands produce adrenaline which gives the body energy to either fight back or run away from a dangerous situation (the fight or flight hormone), the pancreas produces insulin which controls blood sugar levels, testes produce testosterone which causes changes during puberty and stimulates sperm production, and the ovaries produce oestrogen which controls the menstrual cycle and female puberty changes. 

A tropism is a growth in response to stimuli. There are two main types:

• Geotropism - which is a growth against or in the direction of the force of gravity. 
• Phototropism - which is a growth towards or away from a source of light. 

Drugs are chemicals that alter the way that the body works. There are fur classifications:

• Depressant - slows down brain activity (e.g.alcohol)
• Hallucinogen - alters what we see and hear (e.g LSD)
• Painkiller - blocks nerve impulses (e.g.paracetamol) 
• Performance enhancer - improves muscle development (e.g. steroids)
• Stimlulant  - increases brain activity (e.g. caffeine) 

Drinking alcohol has both short-term and long-term effects. The short-term effects are sleepiness, impaired judgement, blurred vision, slurred speech and increased flow of blood to the skin. The long-term effects are damage to the liver and brain. 

The five organism kingdoms are animals, plants, fungi, prokaryotes and protoctists. We class animals in this order: 

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Phylum = vertebrate or invertebrate. Class = e.g. mammal. Order = place on the food chain e.g. carnivorous. Family = e.g. cat. Genus = e.g. big cat. Species = group of organisms that can successfully interbreed. 

Arthropods are a special group of invertebrates with legs (animals without a backbone/spine), they include: insects (6 legs), arachnids (8 legs), crustaceans (10-14 legs) and myriapods (more than 20 legs).  

There are seven characteristics of living organisms:

• Movement
• Respiration
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition

An organism that is missing any one of these characteristics isnot considered alive. E.g. A tree is alive, however a wooden mantelpiece is not considered alive because the tree has been killed to make it.

Alkenes can be used to make polymers. Polymers are very large molecules that are made when smaller molecules join together end-to-end. The smaller molecules are called monomers. Polymers are also known as macromolecules.

Alkenes are unsaturated and this is why they are used. Polymers are used for different things.

• Polythene is used for making plastic bags and bottles.
• Polypropene is used for making crates and ropes.
• Polychloroethene is used for making water pipes and insulation on electricity cables.

When drawing diagrams to show polymerisation you start with a monomer and change the double bond in the monomer to a single bond in the polymer and then add a bond to each end of the repeating unit. For polymerisation to take place you must have heat, pressure and a catalyst. The properties of a polymer include strength, stiffness, hardness, density and melting point.

Proteins contain the same (amide) linkages as nylon. However nylon is made up of linked amino-acids. Proteins can the hydrolysed into amino-acids in acid or alkaline conditions.

When ethene is but under pressure and heated with a catalyst with polymerise (make long chains of atoms) to form poly(ethene).

Depending on the reaction conditions and the type of catalyst used ethene can either make HDPE or LDPE. HDPE is high density poly(ethene) and has a higher crystallinity and a higher melting point than LDPE; which is low density poly(ethene). HDPE is stronger and stiffer than LDPE.

A polymer that is formed from monomers added together where no other substance is produced is called an addition polymer.

Animal cells have a different structure to plant cells. Animal cells have a cell membrane, and cytoplasm surrounding the nucleus. They are normally portrayed as circular. Plant cells and animals cells both have these along with mitochondria and ribosomes.

Plant cells are usually portrayed as rectangular, and they have a few parts that are different to that of animal cells. Plant cells have a cell wall to protect the cell more than just the cell membrane. They also have capsules known as chloroplasts which contain chlorophyll which absorbs light energy for photosynthesis. Plant cells also have a permanent vacuole which is filled with cell sap to keep the cell turgid (

Power = Voltage x Current (PIV)

Voltage = Current x Resistance (VIR)

 Charge = Current x Time (QIT)

Energy = Voltage x Current (EQV)

Energy = Voltage x Current x Time (E = ITV)

Voltage across primary coil  ÷ Voltage across secondary coil = Number of turns on primary coil ÷ Number of turns on secondary coil - Transformer Rule

Efficiency (%) = (Useful Energy Out ÷ Total Energy In) x 100

Gravitational Potential Energy = mass x gravity x height (GPE = mgh)

 Kinetic Energy = ½ mass x velocity ² (KE = ½mv²)

Work Done = Force x Distance (WD = FD)

Work Done = Energy Transferred (WD = E)

Power = Energy ÷ Time (P = E ÷ A)

Energy = Specific Heat Capacity x Mass x Change in Temperature

Speed = Distance ÷ Time

Acceleration = Change in Velocity ÷ Time

Force = Mass x Acceleration

Ohms law = Voltage across the resistor is directly proportional to current, V⋉ I provided if the physical conditions remains same

Hooke's law = force = extension in metres x the spring constant. 

Weight = Mass x Gravity

Momentum = Mass x Velocity

Change in Momentum = Force x Time

Density = Mass ÷ Volume

Moment = Force x Perpendicular Distance from Pivot

Pressure = Force ÷ Area

Velocity = Frequency x Wavelength

Speed of an echo = 2 x distance/time 

Pressure due to liquid = p x g x h (p is the density in kg/m³, h is the height or depth of the liquid in metres and g is the force of gravity)

Electrolysis is the process of decomposing ionic substances into simpler substances by passing an electric current through them. For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted. Therefore molten lead bromide can be broken down into lead and bromine using electrolysis.  

  In electrolysis the negatively charged particles are attracted to the positively charged electrode (anode) and the positively charged particles are attracted to the negatively charged electrode (cathode).

The + ions are reduced and receive electrons, the - ions are oxidised and lose electrons. OILRIG! Oxidation Is Loss Reduction Is Gain. The substance that is being broken down is known as the electrolyte.

When electroplating the cathode should be the object to be electroplated and the anode should be the metal that you want to coat the object in. And the electrolyte should be a solution of the chosen metal (e.g. sulfate or nitrate)

• Ionic substances form giant ionic lattices containing oppositely charged ions. They have high melting and boiling points, and they conduct electricity when melted or dissolved in water. 
• Simple molecular substances consist of molecules (atoms held together by strong covalent bonds). However the molecules are held together by weak bonds, low melting and boiling points. They do not conduct electricity. 
• Giant covalant structures contain many atoms joined together by covalent bonds to form a giant lattice, which are strong because of the many bonds.
• Ionic bonds form when a metal reacts with a non-metal. Metals = positive ions/Non-metals = negative ions. Ionic bonds are the electrostatic forces of attraction between the oppositely charged ions. 
• When a simple molecular substance melts or boils it is not the covalent bonds between atoms that break it is the weak bonds between molecules. 
• Metals form giant structures in which electrons in the outer shells of the metal atoms are free to move. The metallic bonds are the bonds between these free electrons and the metal ions. 

• All of the oxygenated blood is pumped from the lungs to the left atrium of the heart. This is where the arteries run out of to pump the blood to all of the parts of the body. 
• All of the de-oxygenated blood pumped from the body to the right atrium of the heart. 
• The right atrium then contracts forcing blood through the tricuspid valve into the right ventricle. 
• The left atrium also contracts forcing blood through the tricuspid valve into the left ventricle. 
• The right ventricle then contracts, the semi-lunar valve opens and the de-oxygenated blood travels back to the lungs to be oxygenated. 
• The left ventricle does the same only the oxygenated blood travels around the rest of the body. 

You must know all of the constituent parts of the human heart and the eye. You must also know how each works i.e. how blood is pumped by the heart and how the eye focuses on nearby and far away objects.  

• For nearby objects the ciliary muscles contract causing the suspensory ligaments to relax. This makes the lens become rounder, shortening the focal length allowing objects to be seen up close. 
• For far away objects the ciliary muscles relax causing the suspensory ligaments to tighten. This makes the lens flatten, lengthening the focal length allowing objects to be seen at a distance.
• Shortsightedness:  Someone with short-sightedness can see near objects clearly, but cannot focus properly on distant objects. This is because the lens focuses the sharpest image in front of the retina, instead of on it. 
• Longsightedness:  Someone with long-sightedness can see distant objects clearly, but cannot focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it.  

Ionic Bonding

• This normally occurs when a metal is reacted with a non-metal. Ionic bonding is the transfer of electrons from one atom to another to achieve a full outer shell.
• A good example is when sodium reacts with chlorine to form sodium chloride. Sodium has 11 electrons and therefore one extra. Chlorine has 17 electrons and is therefore missing one. So the sodium atoms "gives" one electon to the chlorine atom son that both atoms have a full outer shell.

Covalent Bonding

• This normally occurs when a non-metal reacts with a non-metal. Covalent bonding is the sharing of electrons between atoms. The easiest example to understand is the hydrogen molecule. Hydrogen atoms each have one electron in their outer shell. Therefore through a covalent bond these atoms share their electrons and each have a full outer shell with two electrons, forming a hydrogen molecule.

• The equation that converts mass into moles is: moles = mass/relative formula mass.
• This can be re-arranged to say that mass = relative formula mass x moles. 
• To calculate the mass of a product from a reaction you first have to find out how many moles are present in the reactant that you are told to measure. 
• Then write down the equation for the reaction ... to be continued at some point :P