Yearly Exam Revision Notes Science PDF

1. Chemical Reactions The Basics ➔ Atoms: The smallest unit of matter; is made of nucleus protons, neutrons and electrons. ➔ Elements: Are chemical substances; containing only one kind of atom ➔ Compounds: A chemical molecule; containing two or more different types of atoms....

1. Chemical Reactions The Basics ➔ Atoms: The smallest unit of matter; is made of nucleus protons, neutrons and electrons. ➔ Elements: Are chemical substances; containing only one kind of atom ➔ Compounds: A chemical molecule; containing two or more different types of atoms. ➔ Molecules: A group of atoms bonded together can include both elements and compounds Acids and Alkalis ➔ Weak acids are found in everyday items such as food, drinks and skincare products. It is safe to handle and in some cases even tastes like weak acids. ➔ Strong acids like those found in car batteries or the laboratory are too dangerous to taste or touch. Those acids are said to be corrosive as they can damage other materials by wearing them away, these are strong acids. What is an Alkali (base) ➔ Substances that are chemically the opposite of acids. ➔ Weak alkalis are found in soaps and other cleaning materials. They are also used in antacids to treat indigestion. ➔ Strong alkalies, like those used in laboratories, or cleaning materials such as bleach, are too dangerous to touch. These alkalis are said to be caustic because they can burn skin, and damage other materials. These are strong alkalis. ➔ Properties - taste bitter, turns red litmus blue, pH level over 7 What is an Acid ➔ An acid is a chemical compound, acids can be weak or strong ➔ Weak acids are found in everyday items like vinegar, lemons and soda. ➔ Strong acids are more dangerous, they can be found in a laboratory and a car battery. Stronger acids can be corrosive and wear away materials. ➔ Properties - taste sour, turns blue litmus red, has pH less than 7, can burn skin What is a Neutral Substance ➔ neither acidic nor alkaline ➔ pure water is a neutral substance ➔ saltwater, saliva and blood are all very close to neutral What is an Indicator ➔ an indicator is a chemical that turns into a different colour depending on whether it's an acid or base, eg Litmus can be blue or red, blue litmus turns red under acidic conditions and red litmus turns blue under alkaline conditions Universal Indicator ➔ has a range of colours how weak or strong that acid alkali is. ➔ red being strongly acidic then to a blueish purple being strongly alkaline ➔ A universal indicator is more useful than litmus, as it is more specific and definitive around the neutral area and also tells us how acidic or how alkaline the substance is with there being more colour options The pH scale ➔ The strength of an acid or alkali is measured by the pH scale. ➔ Each universal indicator is given a pH value, universal indicator can tell you the pH of a solution. ➔ A strong acid having a pH level of 1 and a strong alkali having a pH level of 14 1. Neutralisation reaction Mixing an acid with a base to form a salt and water: Acid + alkali —> salt + water ➔ Nitric acid + calcium hydroxide → calcium nitrate + water HNO3 +Ca(OH)₂→Ca(NO₃)₂+H2O ➔ Hydrochloric acid + sodium hydroxide → sodium chloride + water HCl + NaOH → NaCl + H2O ➔ Hydrochloric acid + potassium hydroxide → potassium chloride + water KOH + HCl→KCl + H2O Naming salts - ➔ When an alkali reacts with hydrochloric acid, the salt produced is a chloride. ➔ When an alkali reacts with sulfuric acid, the salt produced is a sulphate ➔ When an alkali reacts with nitric acid, the salt produced is a nitrate  2. Reaction of Acids with metals Acids react with metal to make a salt and a gas: Acid + Metal → Salt + Hydrogen gas. ➔ Hydrochloric acid + calcium —> calcium chloride + hydrogen Ca + 2HCl → CaCl₂ + H₂ ➔ Zinc + hydrochloride → Zinc chloride + Hydrogen gas HCl + Zn → Zn CL2 + H2 ➔ When an acid reacts with a metal, the gas produced makes a lighted splint pop. 3. Reaction of Acids with carbonates Acids react with carbonates to make salt, carbon dioxide and water: Acid + Carbonate → Salt + Carbon Dioxide + Water. ➔ Calcium carbonate + Hydrochloric Acid → Calcium Chloride + Water+ carbon dioxide CaCO3 + 2HCl → CaCl2 + H2O + CO2 4. Combustion A combustion reaction occurs when a substance reacts with oxygen gas, releasing energy in the form of light and heat: Fuel + oxygen ⟶ carbon dioxide + water + energy. ➔ Methane + oxygen → carbon dioxide + water CH₄ + 2 O₂ ⟶ CO₂ + 2 H₂O 5. Corrosion Corrosion is a natural process in which a refined metal is converted to a more chemically stable form, such as oxide, hydroxide, or sulphide. ➔ Iron + Oxygen + Water → Iron oxide-hydroxide 4Fe + 3O2 + 6H2O → 4Fe(OH)3 ➔ Metals behave differently when exposed to the environment  ➔ Gold (unreactive metal), doesn’t corrode easily ➔ In many cultures, gold is considered a precious metal, used to make scared and decorative objects ➔ Items of gold survive thousands of years, found in good condition underwater ➔ Objects made from metals that corrode easily do not survive for as long 6. Decomposition A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances. AB→A+B ➔ Calcium Carbonate → Calcium Oxide+ Carbon Dioxide CaCO3 →CaO(s)+CO2(g) 7. precipitation A precipitation reaction occurs when two different soluble salts are mixed and form one soluble salt and an insoluble salt. ➔ Sodium chloride + silver nitrate → sodium nitrate + silver chloride NaCl + AgNO3 → NaNO3 + AgCl ➔ The non-metal of the first compound binds to the metal of the second compound and vice versa Real Life examples: ➔ Acid-Base: Stomach acid is too high so tablets containing bases are injected to neutralise the stomach acid. ➔ Acid-Metal: Acid rain on metal structures or objects. ➔ Acid-Carbonate: Limestone dissolution due to acidic groundwater causing caves, sinkholes etc. ➔ Corrosion: Iron rusting ➔ Combustion: Combustion of lighter fluid, Combustion of petrol in car engine ➔ Decomposition: Carbonic acid in soft drinks decomposes to give off CO2 ➔ Precipitation: The formation of limestone caves. When rainwater, which is slightly acidic due to dissolved carbon dioxide, seeps through the soil and comes into contact with limestone rock, it can dissolve the calcium carbonate (𝐶𝑎𝐶𝑂3) present in the rock. ​ Exothermic and Endothermic Reactions ➔ Chemical energy is the energy stored in the chemical bonds of a surface ➔ chemical reactions always involve energy changes ➔ making bonds and breaking bonds involve energy changes Exothermic ➔ heat energy given off ➔ the temperature of the substances rises ➔ products feel hot Endothermic ➔ heat energy is taken in ➔ the temperature of the substance drops ➔ products feel cold ➔ reactants + energy → products ➔ reactants + heat → products Ways of Increasing the rate of reaction 1. Temperature: by increasing the temperature of the reactants in a chemical reaction, we increase the speed at which they move. This increases the likelihood of collisions occurring. 2. Surface Area: If we picture a cube that we want to dissolve in a liquid. The sides of the cube that are exposed to the liquid are the only places reactions (collisions) can occur. Therefore if we can increase the surface area of the cube we can increase the rate of reaction. 3. Catalyst: All chemical reactions require an input of energy to get started. This input energy is called “activation energy”. Catalysts work by lowering the required activation energy. They do this by providing an alternative pathway for the reaction to complete. 4. Concentration: When the amount of particles of a substance is increased in a solution there is a higher chance of collision occurring. More collisions then lead to a faster rate of reaction  2. Motion and Waves ➔ Law of conservation of energy: Energy cannot be created nor destroyed only transformed or transferred into other forms ➔ If a light globe uses 2000 of energy and 1000 of light energy is emitted, how much waste energy is there? 1000. How efficient is the light globe? Needs to be more efficient. ➔ Convection: The hot particles move upward because it's less dense and the cooler particles are thicker so they sink to the bottom. More particles go up than down and so after a point their density reduces and they start to sink again, but because of the particles coming from the bottom, they get pushed to the side. ➔ 3 types of heat transfer: Convection, Conduction and Radiation. Three main forms of heat transfer: 1. Convection: the density changes (less dense goes up, cools down comes down, more particles go up than the particles going down) 2. Radiations: These are energy waves like the sun, electromagnetic spectrum 3. Conduction: Particles vibrate. Transfer of heat through direct contact between particles in a solid. Energy moves from high to low-temperature areas. Equations of Motion 1. 𝑣 = 𝑢 + 𝑎 𝑡 2. 𝑣2 = 𝑢2 + 2𝑎𝑠 3. 𝑠 = 𝑢𝑡 + (1/2) 𝑎𝑡2 1. Newton's First Law (Law of Inertia) Summary: An object at rest stays at rest, and an object in motion continues in motion with the same speed and in the same direction unless acted upon by a net external force. Example: A book lying on a table will remain there until someone pushes it. Similarly, a soccer ball rolling on the ground will eventually come to a stop due to friction, but if there were no friction, it would keep rolling indefinitely. 2. Newton's Second Law (Law of Acceleration) Summary: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This is often expressed with the formula F=maF = maF=ma (Force = mass × acceleration). Example: If you push a shopping cart (force) and it accelerates, the more force you apply, the faster it will accelerate. If the cart is empty (less mass), it will accelerate more than if it is full of groceries (more mass) for the same amount of force applied. 3. Newton's Third Law (Action and Reaction) Summary: For every action, there is an equal and opposite reaction. This means that forces always come in pairs. Example: When you jump off a small boat into the water, you push down on the boat (action), and the boat pushes you up into the air (reaction), causing it to move backward. Wavelength (λ): Definition: The distance between successive crests (or troughs) of a wave. It is usually measured in meters (m). Significance: Wavelength is inversely related to frequency; as wavelength increases, frequency decreases, and vice versa. Frequency : ➔ Definition: The number of complete waves that pass a point in a given time period (usually one second). It is measured in hertz (Hz). ➔ Significance: Higher frequency means more waves passing a point in the same amount of time, which can affect the energy of the wave. Speed: ➔ Definition: The distance a wave travels in a given period of time. It is calculated using the formula: v=f⋅λv = f \cdot \lambdav=f⋅λ ➔ Significance: Wave speed varies depending on the medium through which the wave travels. For example, sound travels faster in solids than in liquids or gases. Transmission of Sound Using the Particle Model ➔ Particle Model Overview: According to the particle model, sound is a mechanical wave that propagates through a medium (solid, liquid, or gas) by causing the particles of the medium to vibrate. ➔ Transmission in Different Mediums: ◆ Solids: In solids, particles are closely packed and can transmit sound efficiently. When sound waves hit the material, they cause the particles to vibrate back and forth, passing the energy quickly from particle to particle. This is why sound travels fastest in solids. ◆ Liquids: In liquids, the particles are further apart than in solids, but they still transmit sound waves effectively. The sound waves compress and rarefy the liquid particles, allowing the sound to travel, though not as quickly as in solids. ◆ Gases: In gases, the particles are much more spread out, so sound travels more slowly compared to solids and liquids. The sound waves cause the gas particles to collide and transfer energy, but because of the larger distances between particles, this takes longer. The Electromagnetic Spectrum and Its Uses The electromagnetic spectrum encompasses all types of electromagnetic radiation, which vary in wavelength and frequency. Here’s a brief overview of its regions and uses: 1. Radio Waves: ○ Wavelength: Longest (from millimeters to kilometers). ○ Uses: Used for communication (radio, television signals), radar, and in wireless technology. 2. Microwaves: ○ Wavelength: Shorter than radio waves (from about 1 mm to 1 m). ○ Uses: Used in microwave ovens, satellite communications, and certain types of radar. 3. Infrared Radiation: ○ Wavelength: Between microwaves and visible light (from about 700 nm to 1 mm). ○ Uses: Used in remote controls, thermal imaging, and night-vision equipment. 4. Visible Light: ○ Wavelength: The range of wavelengths visible to the human eye (from about 400 nm to 700 nm). ○ Uses: Enables vision and photography, and is used in lighting. 5. Ultraviolet (UV) Radiation: ○ Wavelength: Shorter than visible light (from about 10 nm to 400 nm). ○ Uses: Used in sterilization, fluorescent lamps, and can cause sunburn. 6. X-rays: ○ Wavelength: Even shorter than UV radiation (from about 0.01 nm to 10 nm). ○ Uses: Used in medical imaging to view inside the body, and in security scanning. 7. Gamma Rays: ○ Wavelength: Shortest (less than 0.01 nm). ○ Uses: Used in cancer treatment (radiation therapy) and in nuclear reactions.  3. Genetics and Evolution ➔ DNA is present in the cells of all living organisms ➔ The process of extracting DNA from a cell is the first step for many laboratory procedures ➔ Each DNA contains 9 feet of DNA ➔ In an average meal, you eat approximately 55 million cells ➔ Using different chemicals to break down the outer membranes of the cells and the nucleus to reach the DNA effectively ➔ DNA is found in the nucleus of all eukaryotic cells ➔ Most cells have diploid 2n chromosomes ➔ Many plants are polyploid (containing several sets of chromosomes) ➔ Strawberries are octoploid 8n ➔ DNA is enclosed in a nuclear and a cell membrane made of phospholipids ➔ DNA is also coiled around proteins ➔ Both the phospholipid layer and the proteins must be removed to view the DNA ➔ Cell membranes are made of phospholipids ➔ Phospholipids won't dissolve in water ➔ One of Mendel's other conclusions was that genes work in pairs to determine which characteristic is shown or expressed. ➔ Gene: genetic code for a characteristic ➔ Alleles: different forms of the same gene/ alternate forms of a gene ➔ One copy of each allele from each parent, therefore, 2 alleles per characteristic ➔ Dominant (capital letter shows dominant allele shown regardless of number) and recessive alleles (lower case represents recessive allele and will only be expressed when there are 2 pairs of alleles) ➔ Recessive- allele that will only be expressed when there are 2 recessive copies (bb) ➔ Homozygous- BB, bb ➔ Heterozygous- Bb ➔ The only chromosomes not in pairs are the sex chromosomes Extra notes: ➔ There are 4 bases for DNA- adenine (A), cytosine (C), guanine (G), and thymine (T) ➔ A forms pairs with T and C forms pairs with G ➔ Karyotype- A karyotype is an individual's complete set of chromosomes. The term also refers to a laboratory-produced image of a person's chromosomes isolated from an individual cell and arranged in numerical order. A karyotype may be used to look for abnormalities in chromosome number or structure. Genetics Worksheet: 1. What is meant by homozygous, heterozygous and allele? ➔ Heterozygous: heterozygous means having two different alleles for a particular gene ➔ Homozygous: homozygous means having the same allele for a particular gene 2. In sheep, the gene for a white coat ⦗H⦘ is dominant over the gene for a black coat ⦗h⦘. If two white-coated sheep are bred explain how a black-coated offspring could be produced. H h H HH Hh h Hh hh As the above punnet square shows, the chance of there being a black-coated sheep is 25%. The black allele is only dominant in the bottom right square of the punnet square 3. The gene allele for a long nose ⦗N⦘ is dominant over the gene allele for a short nose ⦗n⦘. a. What are the possible genotypes for a long-nosed person? Nn, NN b. What are the possible genotypes for a short-nosed person? nn c. If a pure long-nosed person mates with a person with a short nose, what types of noses can their children have? Show your reasoning. N N n Nn Nn n Nn Nn The above punnet square shows that the offspring would have a long nose because the alleles will always be dominated by long-nose alleles. 4. Rabbits can have long or short ears. Long ears ⦗L⦘ are dominant over short ears ⦗l⦘. A pure long-eared rabbit is mated with a hybrid long-eared rabbit. L L L LL LL l Ll Ll a. What are all the possible genotypes of this offspring? Ll, LL b. What percentage of offspring would you expect to be long-eared? 100% of the offspring will be long-eared because the dominant allele is L.  5. The lack of pigment in humans is known as albinism. Albinism is known as caused by a recessive gene. Two parents, both ‘normal’ ⦗Not albino⦘ have an albino child. Explain how this can happen. Both parents whose appearance is normal ⦗A⦘ must contain the recessive gene for albino ⦗a⦘. Both parents must pass on the recessive gene to the offspring to get an albino child. A a A AA Aa a Aa aa Mitosis Meiosis ➔ Asexual reproduction ➔ Sexual reproduction ➔ Two daughter cells ➔ Four daughter cells ➔ The number of chromosomes is the ➔ The number of chromosomes is same halved ➔ One cell division cycle ➔ Two cell division cycles ➔ Daughter cells and parent cells are ➔ Genetic differences between parent genetically identical and daughter cells Phases Phases 1. Prophase 1. Interphase Chromosomes condense and 2. Prophase 1 become visible. Chromosomes condense, The chromosomes, which were homologous pairs form and crossing previously long, thin strands, coil up and become tightly packed. This over occurs. makes them easier to see under a In prophase I, the chromosomes microscope. The nuclear envelope condense and become visible, similar breaks down, and the centrioles to prophase in mitosis. Homologous (organelles involved in cell division) chromosomes pair up, forming move to opposite ends of the cell. structures called tetrads. This pairing 2. Metaphase is essential for crossing over, a Chromosomes align at the equator of the cell. process of exchanging genetic he chromosomes line up at the material between homologous middle of the cell, forming a chromosomes. The exchange of structure called the metaphase plate. genetic material is a key factor in This ensures that each daughter cell creating genetic diversity. This is a receives an equal number of unique feature of meiosis and is not chromosomes. found in mitosis. 3. Anaphase Sister chromatids separate and move 3. Metaphase 1 to opposite poles of the cell. Homologous pairs align at the The centromere of each equator.  chromosome splits, and the sister The tetrads line up at the middle of chromatids (identical copies of each the cell, forming the metaphase chromosome) separate. They are plate. This is similar to metaphase in then pulled to opposite ends of the mitosis but with homologous pairs cell by spindle fibres. 4. Telophase instead of individual chromosomes. Chromosomes decondense, nuclear envelopes form around each set of 4. Anaphase 1 chromosomes, and the cell begins to Homologous pairs separate and divide. move to opposite poles of the cell. The chromosomes begin to unwind The homologous chromosomes in and become less visible. Nuclear each tetrad separate and are pulled envelopes form around each set of chromosomes at the opposite poles to opposite ends of the cell by of the cell. The cell membrane starts spindle fibres. This is unlike mitosis, to pinch inward, preparing to divide where sister chromatids separate. the cell into two. 5. Telophase and Cytokinesis 1 5. Cytokinesis Nuclear envelopes form around each The cell divides into two daughter set of chromosomes, and the cell cells. divides into two. The cell membrane continues to pinch inward until it completely At the poles of the cell, nuclear divides the cell into two separate envelopes form around each set of daughter cells. Each daughter cell chromosomes. The cytoplasm contains a complete set of divides, forming two daughter cells, chromosomes, identical to the each with a haploid number of original cell. chromosomes (half the original number). This is unique to meiosis, as mitosis produces diploid daughter cells. 6. Prophase 2 Chromosomes condense and the nuclear envelope breaks down The chromosomes, which were previously relaxed, become tightly coiled and visible under a microscope. This condensation makes them easier to manipulate during cell division. The nuclear envelope, which surrounds the chromosomes, disintegrates. This allows the spindle fibres to access the chromosomes. 7. Metaphase 2 Metaphase II is a stage in meiosis where the chromosomes line up in the middle of the cell, similar to metaphase in mitosis but occurring  in haploid cells. At this point, the two sister chromatids of each chromosome are still attached and aligned at the metaphase plate. Spindle fibres from opposite poles of the cell attach to the centromeres, preparing the chromatids for separation. This phase ensures that, in the subsequent anaphase, the sister chromatids will be pulled apart to opposite ends of the cell, forming four genetically distinct haploid cells by the end of meiosis. 8. Anaphase 2 Anaphase II is the stage in meiosis where sister chromatids are finally separated and pulled to opposite poles of the cell. During this phase, the centromeres of the sister chromatids split, allowing the spindle fibres to pull the now individual chromosomes toward opposite ends of the cell. This ensures that each daughter cell will receive one complete set of chromosomes. Anaphase II is critical for reducing the chromosome number by half, essential for forming genetically diverse gametes during sexual reproduction. 9. Telophase 2 Telophase II is the final stage of meiosis, where the two haploid cells formed during meiosis I divide again to produce four genetically distinct haploid daughter cells. During this stage, the chromosomes, now single chromatids, reach the opposite poles of the cells, and the nuclear membranes re-form around each set of chromosomes. The chromosomes begin to decondense, reverting to their thread-like form, and the spindle fibres disappear. Cytokinesis follows, dividing the cytoplasm and completing the creation of four unique cells. Golden Rice ➔ Golden rice has been genetically modified to include elevated levels of vitamin A. Deficiency of Vitamin A leads to early blindness. ➔ Vitamin A deficiency is responsible for five hundred thousand cases of irreversible blindness and up to two million deaths each year ➔ The most vulnerable are pregnant women and children ➔ Worldwide, an estimated nineteen million pregnant women and two hundred and fifty million suffer from VAD-related disease ➔ Beta carotene Bt. Cotton ➔ Biotechnology refers to the use of cotton varieties with transgenic or genetically modified traits ➔ The use of biotechnology in cotton led to a 93% decrease in insecticide use since 1997 of insecticides applied to Australian cotton crops, coinciding with the introduction of strong Integrated Pest Management ➔ Bt cotton is an insect-resistant transgenic crop designed to combat the bollworm. Bt cotton has been genetically modified genetically altering the cotton genome, by the insertion of one or more genes of Bt to express a microbial protein from the bacterium Bacillus thuringiensis. ➔ Insecticidal cotton has inbuilt protection against insects, particularly Cotton bollworms.h