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#CellStructure #Biology #BasicConcepts Animal cell structure • The main features of animal cells: • They contain a nucleus with a distinct membrane • Cells do not have cellulose cell walls • Their cells do not contain chloroplasts (so they are unable to carry out photosynthesis) • They contain carbohydrates stored as glycogen Plant cell structure • The main features of plant cells: • They contain a nucleus with a distinct membrane • Cells have cell walls made out of cellulose • They contain chloroplasts (so they can carry out photosynthesis) • Carbohydrates are stored as starch or sucrose Bacteria cell structure • Bacteria, which have a wide variety of shapes and sizes, all share the following biological characteristics: • They are microscopic single-celled organisms • Possess a cell wall (made of peptidoglycan, not cellulose), cell membrane, cytoplasm and ribosomes • Lack a nucleus but contain a circular chromosome of DNA that floats in the cytoplasm • Plasmids are sometimes present - these are small rings of DNA (also floating in the cytoplasm) that contain extra genes to those found in the chromosomal DNA • They lack mitochondria, chloroplasts and other membrane-bound organelles found in animal and plant cells • Some bacteria also have a flagellum (singular) or several flagella (plural). These are long, thin, whip-like tails attached to bacteria that allow them to move • Examples of bacteria include: • Lactobacillus (a rod-shaped bacterium used in the production of yoghurt from milk) • Pneumococcus (a spherical bacterium that acts as the pathogen causing pneumonia)

#Excretion #Kidney #Biology The Kidney & the Nephron: Extended • The kidneys are located in the back of the abdomen and have two important functions in the body: • They regulate the water content of the blood (vital for maintaining blood pressure) • They excrete the toxic waste products of metabolism (such as urea) and substances in excess of requirements (such as salts) The Nephron  • Each kidney contains around a million tiny structures called nephrons, also known as kidney tubules or renal tubules • The nephrons start in the cortex of the kidney, loop down into the medulla and back up to the cortex • The contents of the nephrons drain into the innermost part of the kidney and the urine collects there before it flows into the ureter to be carried to the bladder for storage 1) Ultrafiltration  • Arterioles branch off the renal artery and lead to each nephron, where they form a knot of capillaries (the glomerulus) sitting inside the cup-shaped Bowman’s capsule  • The capillaries get narrower as they get further into the glomerulus which increases the pressure on the blood moving through them (which is already at high pressure because it is coming directly from the renal artery which is connected to the aorta)  • This eventually causes the smaller molecules being carried in the blood to be forced out of the capillaries and into the Bowman’s capsule, where they form what is known as the filtrate • This process is known as ultrafiltration • The substances forced out of the capillaries are: glucose, water, urea, salts • Some of these are useful and will be reabsorbed back into the blood further down the nephron  Components of filtrate:   2) Selective Reabsorption Reabsorption of Glucose • After the glomerular filtrate enters the Bowman’s Capsule, glucose is the first substance to be reabsorbed at the proximal (first) convoluted tubule • This takes place by active transport • The nephron is adapted for this by having many mitochondria to provide energy for the active transport of glucose molecules • Reabsorption of glucose cannot take place anywhere else in the nephron as the gates that facilitate the active transport of glucose are only found in the proximal convoluted tubule • In a person with a normal blood glucose level, there are enough gates present to remove all of the glucose from the filtrate back into the blood • People with diabetes cannot control their blood glucose levels and they are often very high, meaning that not all of the glucose filtered out can be reabsorbed into the blood in the proximal convoluted tubule • As there is nowhere else for the glucose to be reabsorbed, it continues in the filtrate and ends up in the urine • This is why one of the first tests a doctor may do to check if someone is diabetic is to test their urine for the presence of glucose Reabsorption of Water & Salts • As the filtrate drips through the Loop of Henle necessary salts are reabsorbed back into the blood by diffusion and active transport • As salts are reabsorbed back into the blood, water follows by osmosis • Water is also reabsorbed from the collecting duct in different amounts depending on how much water the body needs at that time

#EndothermicAndExothermicReactions #Chemistry #ChemicalEnergetics Heat exchange in reactions • Chemical reactions occur so that elements can achieve a more stable energy state by gaining a full outer shell of electrons • This is done by chemical bonding  • This process involves the transfer of thermal energy into and out of reaction mixtures • The terms used to describe this are: • System: the reacting chemicals  • Surroundings: anything other than the chemicals reacting • The energy within the system comes from the chemical bonds themselves which could be considered as tiny stores of chemical energy Exothermic reactions • In exothermic reactions, thermal energy is transferred from the chemical energy store of the chemical system to the surroundings • The energy of the system decreases, which means that the energy change is negative • The temperature of the surroundings increases because thermal energy is given out / released • The overall transfer is from the system to the surroundings • Typical examples of exothermic reactions include: • Combustion • Oxidation • Neutralisation  • Hand warmers used in the wintertime are based on the release of heat from an exothermic reaction • Self-heating cans of food and drinks such as coffee and hot chocolate also use exothermic reactions in the bases of the containers Endothermic reactions • In endothermic reactions, thermal energy is transferred from the surroundings system to the system surroundings • The energy of the system increases, which means that the energy change is positive • The temperature of the surroundings decreases because thermal energy is taken in / absorbed • The overall transfer is from the surroundings to the system • Endothermic reactions are less common than exothermic reactions • Typical examples of endothermic reactions include: • Electrolysis • Thermal decomposition • The first stages of photosynthesis  • Cold packs for sports injuries are based on endothermic reactions, designed to take heat away from a recently injured area to prevent swelling Reaction pathway diagrams • Reaction pathway diagrams are graphical representations of the relative energies of the reactants and products in chemical reactions • On a reaction pathway diagram: • Progress of the reaction is shown on the x-axis • Energy is shown on the y-axis • The difference in height between the energy of reactants and products is the overall energy change of a reaction • In exothermic reactions: • Energy is given out to the surroundings • The energy of the products will therefore be lower than the energy of the reactants • The overall energy change is negative • This is represented on the reaction profile with a downwards-arrow as the energy of the products is lower than the reactants • In endothermic reactions: • Energy is taken in from the surroundings • The energy of the products will be higher than the energy of the reactants • The overall energy change is positive • This is represented on the reaction profile with an upwards-arrow as the energy of the products is higher than the reactants

#MonohybridInheritance #Biology #Inheritance Inheritance: definitions • Inheritance is the transmission of genetic information from one generation to the next generation • A gene is a short length of DNA found on a chromosome that codes for a particular characteristic (expressed by the formation of different proteins) • Alleles are variations of the same gene • As we have two copies of each chromosome, we have two copies of each gene and therefore two alleles for each gene • One of the alleles is inherited from the mother and the other from the father • This means that the alleles do not have to ‘say’ the same thing • For example, an individual has two copies of the gene for eye colour but one allele could code for brown eyes and one allele could code for blue eyes • The observable characteristics of an organism (seen just by looking - like eye colour, or found – like blood type) is called the phenotype • The combination of alleles that control each characteristic is called the genotype • Alleles can be dominant or recessive • A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype • A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype. • If there is only one recessive allele, it will remain hidden and the dominant characteristic will show • If the two alleles of a gene are the same, we describe the individual as being homozygous (homo = same) • An individual could be homozygous dominant (having two copies of the dominant allele), or homozygous recessive (having two copies of the recessive allele) • If the two alleles of a gene are different, we describe the individual as being heterozygous (hetero = different) • When completing genetic diagrams, alleles are abbreviated to single letters • The dominant allele is given a capital letter and the recessive allele is given the same letter, but lower case • We cannot always tell the genotype of an individual for a particular characteristic just by looking at the phenotype – a phenotype associated with a dominant allele will be seen in both a dominant homozygous and a dominant heterozygous genotype • If two individuals who are both identically homozygous for a particular characteristic are bred together, they will produce offspring with exactly the same genotype and phenotype as the parents - we describe them as being ‘pure breeding’ as they will always produce offspring with the same characteristics • A heterozygous individual can pass on different alleles for the same characteristic each time it is bred with any other individual and can therefore produce offspring with a different genotype and phenotype than the parents - as such, heterozygous individuals are not pure breeding What is monohybrid inheritance? • Monohybrid inheritance is the inheritance of characteristics controlled by a single gene (mono = one) • This can be determined using a genetic diagram known as a Punnett square • A Punnett square diagram shows the possible combinations of alleles that could be produced in the offspring • From this the ratio of these combinations can be worked out • Remember the dominant allele is shown using a capital letter and the recessive allele is shown using the same letter but lower case Monohybrid Inheritance Example • The height of pea plants is controlled by a single gene that has two alleles: tall and short • The tall allele is dominant and is shown as T • The small allele is recessive and is shown as t • The term ‘pure breeding’ indicates that the individual is homozygous for that characteristic What is a monohybrid cross? • A monohybrid cross is the genetic mix between two individuals which determines a characteristic controlled by a single gene • A genetic diagram is used to predict the possible outcome of a cross How to construct Punnett squares • Determine the parental genotypes • Select a letter that has a clearly different lower case, for example: Aa, Bb, Dd • Split the alleles for each parent and add them to the Punnett square around the outside • Fill in the middle four squares of the Punnett square to work out the possible genetic combinations in the offspring • You may be asked to comment on the ratio of different allele combinations in the offspring, calculate a percentage chances of offspring showing a specific characteristic or just determine the phenotypes of the offspring • Completing a Punnett square allows you to predict the probability of different outcomes from monohybrid crosses Identifying an unknown genotype • Breeders can use a test cross to find out the genotype of an organism showing the dominant phenotype • This involves crossing the unknown individual with an individual showing the recessive phenotype - if the individual is showing the recessive phenotype, then its genotype must be homozygous recessive • By looking at the ratio of phenotypes in the offspring, we can tell whether the unknown individual is homozygous dominant or heterozygous • The short plant is showing the recessive phenotype and so must be homozygous recessive - tt Determining genotypes from offspring • If the tall plant is homozygous dominant, all offspring produced will be tall • If the tall plant is heterozygous, half the offspring will be tall and the other half will be short

#biology #organisms #mrsgren • Movement: an action by an organism or part of an organism causing a change of position or place. • Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism. • Sensitivity: the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses. • Growth: a permanent increase in size and dry mass by an increase in cell number or cell size or both. • Reproduction: the processes that make more of the same kind of organism. • Excretion: the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements. • Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds, ions and usually need water. MRS. GREN • Movement. • Respiration. • Sensitivity. • Growth and development. • Reproduction. • Excretion. • Nutrition.

#Mitosis #Inheritance #Biology Mitosis - Basics • Most body cells have two copies of each chromosome • We describe these cells as diploid • When cells divide their chromosomes double beforehand • This ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid) • This type of cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction and is known as mitosis • Mitosis is defined as nuclear division giving rise to genetically identical cells  Process: • Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x - shaped chromosomes) • Chromosomes line up along the centre of the cell where cell fibers pull them apart • The cell divides into two; each new cell has a copy of each of the chromosomes Importance: • All cells in the body (excluding gametes) are produced by mitosis of the zygote • Mitosis is important for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo) Occurs in: • Growth: mitosis produces new cells • Repair: to replace damaged or dead cells • Asexual reproduction: mitosis produces offspring that are genetically identical to the parent Mitosis & Stem Cells • Many tissues in the human body contain a small number of unspecialised cells • These are called stem cells and their function is to divide by mitosis and produce new daughter cells that can become specialised within the tissue and be used for different functions • The ultimate stem cell is the zygote • A zygote divides several times by mitosis to become a ball of unspecialised cells (around 200-300 cells) • These are embryonic stem cells • These cells are all the same and start differentiating as the fetus develops with recognisable features

#ExtractionOfAluminiumFromBauxite #Chemistry #ExtractionOfMetal Introduction • Aluminium is a reactive metal, above carbon in the reactivity series  • Its main ore, is bauxite, which contains aluminium oxide • Aluminium is higher in the reactivity series than carbon, so it cannot be extracted by reduction using carbon • Instead, aluminium is extracted by electrolysis   The process of aluminium extraction by electrolysis • Bauxite is first purified to produce aluminium oxide, Al2O3 • Aluminium oxide is then dissolved in molten cryolite  • This is because aluminium oxide has a melting point of over 2000 °C which would use a lot of energy and be very expensive • The resulting mixture has a lower melting point without interfering with the reaction • The mixture is placed in an electrolysis cell, made from steel, lined with graphite • The graphite lining acts as the negative electrode, with several large graphite blocks as the positive electrodes • At the cathode (negative electrode):  • Aluminium ions gain electrons (reduction)  • Molten aluminium forms at the bottom of the cell • The molten aluminium is siphoned off from time to time and fresh aluminium oxide is added to the cell Al3+ +  3e-   →  Al  • At the anode (positive electrode): • Oxide ions lose electrons (oxidation) • Oxygen is produced at the anode: 2O2- →   O2 + 4e- • The overall equation for the reaction is: 2Al2O3 → 4Al  +  3O2 • The carbon in the graphite anodes reacts with the oxygen produced to produce CO2 C (s) + O2 (g)   →   CO2 (g) • As a result the anode wears away and has to be replaced regularly • A lot of electricity is required for this process of extraction, this is a major expense

#EnthalpyChangeAndActivationEnergy #Chemistry #ChemicalEnergetics Introduction • For atoms or particles to react with each other in a chemical system they must collide together • A number of factors affect the success of a collision: • Energy • Orientation • Number of collisions per second - the frequency of collisions What is activation energy? • In terms of the energy of collisions, there is a minimum amount of energy required for a successful collision • A successful collision is where the particles in the reactant(s) are rearranged to form the products • This minimum amount of energy is called the activation energy, Ea  • Different reactions have different activation energies, depending on the chemical identities involved • Reactions with higher activation energies require more energy to start than those with lower activation energies What is enthalpy change? • The transfer of thermal energy during a reaction is called the enthalpy change, ΔH, of the reaction.  • ΔH is: • Positive for en endothermic reaction • Negative for an exothermic reaction Reaction pathway diagrams Exothermic reactions • A reaction is exothermic when more energy is released forming new bonds for the products than absorbed breaking the bonds in the reactants • So, the products have less energy than the reactants • This means that the change in energy is negative  • Therefore, an exothermic reaction has a negative value for enthalpy, ΔH  • The reaction pathway diagram for an exothermic reaction is: Endothermic reactions • A reaction is endothermic when more energy is absorbed breaking the bonds in the reactants than released forming new bonds for the products  • So, the products have more energy than the reactants • This means that the change in energy is positive  • Therefore, an endothermic reaction has a positive value for enthalpy, ΔH  • The reaction pathway diagram for an endothermic reaction is:

water pollution occurs when energy and other materials are released into the water, contaminating the quality of it for other users. Types Surface water pollution Found on the exterior of the Earth's crust , oceans, rivers and lakes . Groundwater pollution Found in soil or under rock structure or aquifers . Different causes of water pollution Marine dumping Industrial waste Sewage , mainly from households . Nuclear waste Oil pollution Underground storage leaks. Effects on environment Toxic water Thermal heating Our sources of water

#WaterTreatment #Chemistry #ChemistryOfTheEnvironment Introduction • Untreated water contains soluble and insoluble impurities • Insoluble impurities include soil, pieces of plants and other organic matter • Soluble impurities include dissolved calcium, metallic compounds and inorganic pollutants • The first step of water treatment is sedimentation / filtration • Water is pumped into sedimentation tanks and allowed to stand for a few hours • Mud, sand and other particles will fall to the bottom of the tank due to gravity and form a layer of sediment  • The water is then filtered through sand and gravel to remove smaller particles  • The second step is filtration / treatment with carbon (charcoal) • This removes unpleasant tastes and odours • The final step is chlorination • Bacteria and other microorganisms are too small to be trapped by the filters  • So, chlorine is carefully added to the water supply to kill bacteria and other microorganisms • Cholera and typhoid are examples of bacterial diseases which can arise from the consumption of untreated water

#ReactivitySeries #Chemistry #ExplainingReactivity What is the reactivity series of metals? • The chemistry of the metals is studied by analysing their reactions with water and acids • Based on these reactions a reactivity series of metals can be produced • The series can be used to place a group of metals in order of reactivity based on the observations of their reactions with water and acids • The non-metals hydrogen and carbon are also included in the reactivity series as they are used to extract metals from their oxides Reaction of metals with cold water • The more reactive metals will react with cold water to form a metal hydroxide and hydrogen gas • Potassium, sodium and calcium all undergo reactions with cold water as they are the most reactive metals: metal + water →  metal hydroxide + hydrogen •  For example, calcium and potassium: Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) Reactions of metals with steam • Metals just below calcium in the reactivity series do not react with cold water but will react with steam to form a metal oxide and hydrogen gas, for example, magnesium: Mg (s) + H2O (g)  →  MgO (s) + H2 (g) Reaction with dilute acids • Only metals above hydrogen in the reactivity series will react with dilute acids • Unreactive metals below hydrogen, such as gold, silver and copper, do not react with acids • The more reactive the metal then the more vigorous the reaction will be • Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids • When acids react with metals they form a salt and hydrogen gas: • The general equation is: metal + acid ⟶ salt + hydrogen Reaction with oxygen • Some reactive metals, such as the alkali metals, react easily with oxygen • Silver, copper and iron can also react with oxygen although much more slowly • When metals react with oxygen a metal oxide is formed, for example, copper: metal + oxygen → metal oxide  2Cu (s) + O2 (g) → 2CuO (s) • Gold does not react with oxygen Deducing the order of reactivity • The order of reactivity of metals can be deduced by making experimental observations of reactions between metals and water, acids and oxygen • The more vigorous the reaction of the metal, the higher up the reactivity series the metal is • A combination of reactions may be needed, for example, the order of reactivity of the more reactive metals can be determined by their reactions with water • The less reactive metals react slowly or not at all with water, so the order of reactivity would need to be determined by observing their reactions with dilute acid • Temperature change in a reaction can also be used to determine the order of reactivity • The greater the temperature change in a reaction involving a metal, the more reactive the metal is

#economics #factorsofproduction The mobility of factors of production refers to the extent to which resources can be changed for one another in the production process. For example, farming can be very traditional in some parts of the world and rely heavily on labour resources. However, in other countries, farming is predominantly mechanised, with a heavy reliance of capital resources. Economists usually talk about labour mobility, although factor mobility can apply to any factor of production. For example: • Land might be used for various competing purposes, such as to grow certain fruits and/or vegetables, or to construct buildings such as housing, hospitals or schools. • Capital equipment might be used for different purposes too. For example, the same machinery in the Coca-Cola factory can be used to produce Coca-Cola, Sprite and/or Fanta. • Entrepreneurs can also be mobile. For example, Meg Whitman, chief executive offi cer (CEO) of Hewlett-Packard, was previously a vice president of the Walt Disney Company and CEO of eBay. Labour mobility can be broken down into two categories. Geographical mobility Geographical mobility refers to the willingness and ability of a person to relocate from one area to another for employment purposes. Some people may not be geographically mobile for the following reasons: • Family ties and related commitments — people may not want to relocate as they want to be near their family and friends. There may be other commitments such as schooling arrangements for children (it can be highly disruptive to the education of children who have to move to a new school in a new town or country). • Costs of living — the costs of living vary between regions and countries, so may be too high in another location, making it uneconomical for a person to relocate. For example, a bus driver may fi nd it impossible to relocate from the countryside to the city because house prices are much higher in the city and he or she therefore cannot afford to purchase a home in the city. By contrast, a banker may be offered a relocation allowance to move to another country and the potential earnings are much higher, so the banker has greater geographical mobility than the bus driver. Occupational mobility Occupational mobility refers to the ease with which a person is able to change between jobs. The degree of occupational mobility depends on the cost and length of training required to change profession. Developing and training employees to improve their skills set improves labour occupational mobility (as workers can perform a greater range of jobs). Generally, the more occupationally and geographically mobile workers are in a country, the greater its international competitiveness and economic growth are likely to be.

Brownian motion is the random, erratic movement of microscopic particles suspended in a fluid (liquid or gas), caused by collisions with the molecules of the surrounding fluid. It is an important phenomenon in physics and chemistry. 1. Observation: • Discovered by Robert Brown in 1827 while observing pollen grains in water. • Under a microscope, he noticed that the pollen grains moved randomly, even in the absence of external forces like currents or shaking. 2. Cause: • The fluid's molecules are in continuous motion due to their thermal energy. • These molecules collide with the suspended particles, transferring momentum in random directions. • Because the collisions are not uniform or balanced, the suspended particle is "pushed" erratically, leading to zigzag or unpredictable movement. 3. Key Factors Influencing Brownian Motion: • Temperature: Higher temperature increases the motion, as fluid molecules move faster with greater energy. • Particle Size: Smaller particles exhibit more noticeable Brownian motion because they are easier to move by collisions. • Viscosity of Fluid: Higher viscosity reduces the intensity of motion by dampening collisions. • Density of the Fluid: More dense fluids cause more frequent collisions, affecting motion. • Molecules in a fluid are in continuous motion due to thermal energy. • These molecules collide with the suspended particles, transferring momentum and causing the particles to move in a zigzag pattern. • The motion is more noticeable in smaller particles because larger particles require more energy to move. Visualizing Brownian Motion: Imagine dust particles floating in sunlight. The erratic motion you observe is similar to Brownian motion but occurs on a microscopic scale. Each tiny particle is constantly "hit" by air molecules, causing the random motion.

#sreeshanphysics Pg:- 140,141,142,143 Ch:- 8 Work is the measure of energy transfer when a force is applied to an object, causing it to move in the direction of the force. Formula for Work: W = F ⋅ d Where: • W = Work (measured in joules, J) • F = Force applied (in newtons, N) • d = Displacement of the object (in meters, m) Key Points: 1. Work is only done if the object moves due to the force. 2. If the displacement is zero, no work is done, even if a force is applied. 3. The force must have a component in the direction of displacement. Power is the rate at which work is done or energy is transferred over time. It shows how quickly work is performed. Formula for Power: P = W/t Where: • P = Power (measured in watts, W) • W = Work done (in joules, J) • t = Time taken (in seconds, s) Key Points: 1. Power tells how fast energy or work is used or produced. 2. The SI unit of power is the watt (W), where 1 W=1 J/s Example: • If a machine does 100 joules of work in 5 seconds, the power is: P=100/5 = 20 W Related Concept: 1. Kilowatt (kW): 1 kilowatt = 1000 watts. 2. Horsepower (hp): Another unit of power, 1 hp ≈ 746 watts.

#AcidBaseTitration #Chemistry #ExperimentalTechniques Introduction • Titrations are a method of analysing the concentration of solutions • They can determine exactly how much alkali is needed to neutralise a quantity of acid – and vice versa • You may be asked to perform titration calculations to determine the moles present in a given amount or the concentration / volume required to neutralise an acid or a base • Titrations can also be used to prepare salts Apparatus • 25 cm3 volumetric pipette • Pipette filler • 50 cm3 burette • 250 cm3 conical flask • Small funnel • 0.1 mol / dm3 sodium hydroxide solution • Sulfuric acid of unknown concentration • A suitable indicator • Clamp stand, clamp & white tile Method 1. Use the pipette and pipette filler and place exactly 25 cm3 sodium hydroxide solution into the conical flask 2. Using the funnel, fill the burette with hydrochloric acid placing an empty beaker underneath the tap. Run a small portion of acid through the burette to remove any air bubbles 3. Record the starting point on the burette to the nearest 0.05 cm3 4. Place the conical flask on a white tile so the tip of the burette is inside the flask 5. Add a few drops of a suitable indicator to the solution in the conical flask 6. Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously 7. Quickly close the tap when the end-point is reached  • The endpoint is when one drop causes a sharp colour change 8. Record the volume of hydrochloric acid added, in a suitable results table as shown below • Make sure your eye is level with the meniscus 9. Repeat the titration with a fresh batch of sodium hydroxide 10. As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour 11. Record the volume to the nearest 0.05 cm3  12. Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy

1.) What is home science .Home science means the art of managing your resources efficiently and science of achieving healthy and happy home as well as successful career .Home science is concerned with the home,health and happiness of all member of the family and community Home science aims .Developing human skills and .Abilities suitable to the :needs and problems of the people .Home science empowers the women and youth to bring changes in their attitude and practices aiming at in creasing the literacy level standard of living ultimately support personal social and national development

#economics #economicproblem The nature of the economic problem: finite resources and unlimited wants In every country, resources are limited in supply and decisions have to be made by governments, fi rms (businesses) and individuals about how to allocate scarce resources to satisfy their unlimited needs and wants. This is known as the basic economic problem, which exists in every economy: how best to allocate scarce resources to satisfy people’s unlimited needs and wants. Essentially, economics is the study of how resources are allocated to satisfy the unlimited needs and wants of individuals, governments and fi rms in an economy. The three main economic agents (or decision makers) in an economy are: • individuals or households. • firms (businesses which operate in the private sector of the economy). • the government . The three basic economic questions addressed by economic agents are: 1. What to produce? 2. How to produce it? 3. For whom to produce it?. Firms and individuals produce goods and services in the private sector of the economy and the government produces goods and services in the public sector. For example, the government might provide education and healthcare services for the general public. All economic agents (governments, fi rms and individuals) produce and consume goods and services. Goods are physical items that can be produced, bought and sold. Examples are furniture, clothing, toothpaste and pencils. Services are non-physical items that can be provided by fi rms and paid for by customers. Examples are haircuts, bus journeys, education, concerts, telephone calls and internet access. Needs are the essential goods and services required for human survival. These include nutritional food, clean water, shelter, protection, clothing and access to healthcare and education. All individuals have a right to have these needs met and this is stated in Articles 25 and 26 of the United Nations Universal Declaration of Human Rights, drafted in December 1948. Article 25 Everyone has the right to a standard of living adequate for the health and wellbeing of himself and of his family, including food, clothing, housing and medical care and necessary social services, and the right to security in the event of unemployment, sickness, disability, widowhood, old age or other lack of livelihood in circumstances beyond his control. Article 26 Everyone has the right to education. Education shall be free, at least in the elementary and fundamental stages. Elementary education shall be compulsory. Technical and professional education shall be made generally available and higher education shall be equally accessible to all on the basis of merit. Wants are goods and services that are not necessary for survival but are human desires — that is, things we would like to have. Wants are unlimited as most people are rarely satisfi ed with what they have and are always striving for more. Wants are a matter of personal choice and part of human nature. World Bank fi gures suggest that over 3 billion of the world’s inhabitants live on less than $2.50 per day and more than 1.3 billion live in extreme poverty (less than $1.25 a day). These fi gures suggest that their basic needs are not being met. In contrast, the ten richest people on the planet have wealth equivalent to the poorest half of the world’s population. The study of economics can help to explain why this happens and offer possible solutions to the basic economic problem. Economic goods and free goods An economic good is one which is limited in supply, such as oil, wheat, cotton, housing and cars. It is scarce in relation to the demand for the product, so human effort is required to obtain an economic good. Free goods are unlimited in supply, such as the air, sea, rain water, sunlight and (to some extent) public domain webpages. There is no opportunity cost in the production or consumption of free goods. A free good is not the same as a good that is provided without having to pay (such as education or healthcare services provided by the government). The latter has an opportunity cost (the money could have been spent on the provision of other goods and services) and is funded by taxpayers’ money.

The 5 kingdoms classify all living organisms into groups based on their structure, how they live, and how they get energy. 1. Monera • Who are they? Bacteria. • Traits: • Very tiny, single-celled organisms. • No nucleus; their DNA floats freely inside the cell. • They can live almost anywhere, like in soil, water, or even inside your body. • Examples: E. coli, the bacteria in your gut. 2. Protista • Who are they? Single-celled organisms like amoebas and algae. • Traits: • They are larger than bacteria and have a nucleus (the brain of the cell). • They live in water or damp places. • Some make their own food, and others eat tiny particles. • Examples: Paramecium, giant kelp (a big algae). 3. Fungi • Who are they? Molds, mushrooms, and yeast. • Traits: • Cannot make their own food like plants. • They absorb nutrients from decaying plants, animals, or other organic matter. • Usually grow in damp, dark places. • Examples: Bread mold, mushrooms. 4. Plants • Who are they? Trees, flowers, and grass. • Traits: • They are multicellular and have a green pigment called chlorophyll. • Use sunlight, water, and carbon dioxide to make their own food through photosynthesis. • They cannot move around like animals. • Examples: Oak tree, sunflower. 5. Animals • Who are they? Humans, insects, birds, and more. • Traits: • Multicellular and eat food for energy. • Most can move to hunt, escape, or interact with their environment. • They rely on plants or other animals for survival. • Examples: Lion, butterfly, human. Why is this important ?This classification helps scientists understand how living things are related and how they survive in the world!

• the speed camera calculate the speed of each passing cars • Speed can be measured by: Speedometer (in vehicles) – measures in real-time. GPS – tracks position over time to calculate speed. Formula – using distance and time: Speed = Distance Time Speed= Time Distance ​ . Radar Gun – measures speed of moving objects (e.g., in sports or by law enforcement). Motion Sensors – detect changes in velocity or acceleration. Timing a Known Distance – measure time to travel a set distance and calculate speed. FRACTION OF A SECOND A fraction of a second refers to a portion or a small part of one second. Seconds can be divided into smaller units to measure very precise time intervals. Common fractions of a second include: Milliseconds (ms): One thousandth of a second (1/1000 of a second). 1 millisecond = 0.001 seconds. Microseconds (µs): One millionth of a second (1/1,000,000 of a second). 1 microsecond = 0.000001 seconds. Nanoseconds (ns): One billionth of a second (1/1,000,000,000 of a second). 1 nanosecond = 0.000000001 seconds. These units are used to measure extremely short durations of time, such as in high-speed processes, scientific experiments, or computing. LIGHT GATES OF SPEED . A light gate is a device used to measure the speed of an object. It works by using a light beam and a sensor. When an object passes through the beam, it breaks the light, and the sensor records the time. How it works: Place two light gates a certain distance apart. When the object passes through the first gate, it interrupts the light, starting the timer. The object breaks the light at the second gate, stopping the timer. Then, speed is calculated using the formula: Speed = Distance Time Speed= Time Distance ​ So, if the object travels 2 meters in 0.5 seconds, the speed is: Speed = 2  meters 0.5  seconds = 4  meters per second (m/s) Speed= 0.5 seconds 2 meters ​ =4 meters per second (m/s) Uses: In science experiments to measure speed. In sports to time runners or vehicles. In engineering to check the speed of machines.

#chemistry #bonding Diatomic Molecules And Single Elements • Elements with 2 atoms are called diatomic molecules, its because di means 2 and atomic means atoms thus 2 atoms molecule • Example Of Diatomic Molecules -: O2, This is one of the examples for diatomic molecules • There are certain elements which only have 1 atom, these types of elements come from the category from noble gases, cause elements from noble gases are very stable thus they are single Non-Metallic Bonding • Non-metallic bonding is called as covalent bonding as it does not have any type of attraction that metals have, non metals have a different type of attraction • Covalent bonding is a bonding that occurs with non metals and it bonds by sharing electrons, when 2 molecules are in the state of electronegative it tends to share electron rather than transferring it • The bonding of covalent bonding occurs from a nonmetal to a another non metal Main Features Of Covalent Bond • The bond is formed by a pair sharing a electron • Each atom contributes a electron at the bond • Molecules are formed when atoms like together by covalent bond Dot And Cross Diagram • A dot-cross diagram is a diagram represented as a diagram of bonding in a molecule • Its a diagram to represent bonds of molecules Simple Covalent Compounds • In covalent compounds bonds are made by sharing electrons between atoms • In simple molecules atoms combine to achieve a more stable arrangement • Example Of Covalent Bond -: Hydrogen chloride is a molecule that shares a single electron