JK-TK/GRADE-8-TERM-2 huggingface dataset:
Temperature-high temperature increases energy and therefore faster movement of molecules. This increases the rate of diffusion. Mass of particles- heavy particles move slowly hence slower rate of diffusion. Light particles on the other hand move fast hence faster rate of diffusion. -Diffusion distance- rate of diffusion depends on distance that particles have to travel in order to be evenly distributed within available space. Medium of diffusion- particles diffuse faster through gases than liquids. Surface area to volume ration- diffusion occurs faster in smaller organisms as compared to larger organisms. This is because small organisms have a large surface area to volume ratio. OSMOSIS. Experiment to demonstrate osmosis process. Requirements:Procedures:Moisten a piece of visking tube and rubber between your fingers to open it. O Tie one end of the visking tubing tightly with a thread. Put the dye concentrated sugar solution in the Visking tubing using a measuring cylinder. O Insert one end of capillary tube to the open end of the visking tubing and tie that end. Slowly lower it into a beaker containing distilled water and hold the capillary tube with a clamp. O Mark the level of dyed concentrated sugar solution in the capillary tube at the beginning of the experiment. Leave the experiment for about 20 minutes. Observe and record your resultsQuestions to answer. What happens to the level of the dye concentrated sugar solution in the capillary tube after 20 minutes? The level of the dye concentrated sugar solution increases in the capillary tube. Why did the above change take place? Water is highly concentrated in the beaker than in the visking tubing. Water moves from where is it more into the visking tubing across the visking tubing where it is less hence making the visking tubing to swell. Explain the biological process taking place in the experiment. Osmosis takes place since water moves from the beaker where it is highly concentrated to the visking tube where is lowly concentrated. What is the role of the visking tubing in the experiment? The visking tubing acts as a semipermeable membrane. What can we compare the visking tubing with in living cells? The cell membrane. Observation and explanation. The concentration of water outside the visking tubing is higher than the concentration of water inside the visking tubing. Water moves in through the pores in the semi-permeable membrane of the Visking tubing by osmosis because of the differences in concentration inside and outside the visking tubing.
Observation and explanation. The concentration of water outside the visking tubing is higher than the concentration of water inside the visking tubing. Water moves in through the pores in the semi-permeable membrane of the Visking tubing by osmosis because of the differences in concentration inside and outside the visking tubing. Osmosis is the random movement of water solvent molecules from there they are more to where they are less through a semi-permeable membrane. Osmosis can also be defined as the random movement of water solvent molecules from a dilute solution to a more concentrated solution through a semi-permeable membrane until the concentration on each side is equal. Visking tubing is similar to the cell membrane. It is also a semi-permeable membrane, it has tiny holes pores that allows small molecules through but prevents large molecules from passing through. Investigating the process of Osmosis using plant materials. Requirements:Raw potato tuber. -. Distilled water. Table salt. -. A measuring cylinder. Boiled potato. -. A scalpel. Labels. -. A spatula. Petru dishes. -. Writing material. Clock or wrist watch. Procedure:Label two petri dish A and B. Half fill each petri dish with equal volume of distilled water. Using a scalpel, peel a raw potato tuber and trim both if its ends. Make a scoop cavity in one of the ends. Using a scapula, place a given amount of salt in the cavity. Carefully place the set-up in petri dish labelled A and note the time. Repeat step 3 and 5, this time using a previously boiled potato. Place it in a petri dish and label it B. Leave the set up for 40 minutes. Observe and record. Questions to answer. Why is it necessary to peel off the potato tuber before carrying out this experiment? Explain the changes in the petri dish A and B. What biological process is being investigated? Observation and explanation. It is necessary to peel off potato tubers so as to expose large surface area and expose the inner cells that are permeable for osmosis. Petri dish A-water moves up by osmosis through the potato cells then dissolves the table salt in the cavity. Petri dish B-the slat did not dissolve because no water moved by osmosis in to the cavity.
It is necessary to peel off potato tubers so as to expose large surface area and expose the inner cells that are permeable for osmosis. Petri dish A-water moves up by osmosis through the potato cells then dissolves the table salt in the cavity. Petri dish B-the slat did not dissolve because no water moved by osmosis in to the cavity. This is because the boiled potatoes have destroyed semi-permeable cells membranes that cannot carry out osmosis. The process being investigated is osmosis in living cells. Factors affecting the rate of osmosis. Temperatures -rate of osmosis increases with increase in temperature. This is because increase in temperature increases energy of the molecules. Concentration gradient- osmosis increases where the difference in concentration of water molecules is higher. Type of semi-permeable membrane- larger number of pores, the faster the rate of osmosis. Role of osmosis in living things. In plants Osmosis plays the following roles:Absorption of water from the soil-roots absorb water from the soil by osmosis. Support-some plants have cells that absorb water, become turgid hence providing support to the plants. Feeding in insectivorous plants-insectivorous plants such as pitcher plant prey on insects. They trap insects when there is a sudden change in their stiffness when disturbed by the insect. Trapped insects are digested to provide the plant with nitrogen. In animals, Osmosis plays the following roles:Absorption of water in the human body. Excretion-this is the removal of waste products from the body. Urine is the main product through which excess water is excreted from the body. Kidneys filter urine to control the amount of water lost. This happens through osmosis. Similarities and difference between osmosis and diffusion. Similarities. Both are mean to equalize concentration of two solutions. Both are passive transport processes, i.e., they do not require any energy to occur. In both, particles move from an area of higher concentration to an area of low concentration. Differences. Osmosis happens in liquid medium while diffusion happens in liquids, gases and even solids. Semi-permeable membrane is required in osmosis while in diffusion no membrane is needed. Osmosis requires water for movement of particles while diffusion does not require water. In osmosis there is only one way for particles to flow while in diffusion particles can flow in any direction.
Semi-permeable membrane is required in osmosis while in diffusion no membrane is needed. Osmosis requires water for movement of particles while diffusion does not require water. In osmosis there is only one way for particles to flow while in diffusion particles can flow in any direction. 2.3 Reproduction in Human Beings. Menstrual cycle. Menstrual cycle consists of natural changes that occur to the body of a female human being every month in preparation to pregnancy. A menstrual cycle lasts between 28-35 days. However, this can vary between female and from one cycle to the next. The cycle depends on hormones. Hormones are chemical messengers in the body. They direct the body on what to do and when to do it. The menstrual cycle is a process controlled by hormones in the female body. The menstrual cycle is divided in to the following phases:Challenges related to the Human menstrual cycle. Irregular periods. This can be determined by finding out how long your menstrual cycles are. You can determine your personal menstrual length by counting from day 1 of your period to day 1 of your next period. Day 1 means the first day of the actual flow. It is normal to have menstrual cycles that are between 21 and 35 says. Your periods are irregular if it tends to come more frequently than every 21 days or less often than 35 days. If the circle length falls in the normal range but varies by 7 to 9 days from the cycle to cycle that is a sign of an irregular period too. For example, if one is 25 days and the next is 33 days, your cycles would be considered irregular. Absent periods. In some cases, some females may fail to get periods. Others might not get their first period by the age of 16 years. Other cases when some females stop getting their regular periods for 6 months or more. Irregular bleeding. Bleeding very little or no bleeding at all with each menstrual cycle is another challenge related to the menstrual cycle. Light or lack of bleeding can result from being extremely underweight or overweight. If you are overweight, losing weight might help to make your periods regular. If you are underweight, slow and steady weight gain may help to regulate your menstrual circle. Excessive bleeding is another challenge related to the menstrual cycle. Bleeding is considered heavy if it interferes with normal activities.
If you are underweight, slow and steady weight gain may help to regulate your menstrual circle. Excessive bleeding is another challenge related to the menstrual cycle. Bleeding is considered heavy if it interferes with normal activities. However, though common, you should see a doctor. Heavy periods can be a sign of a health problem. Painful periods. Most women experience menstrual cramps before or during their period at some point in their lives. For some of them it is part of the regular monthly routine. However, if the cramps are painful and persistent, you should see a doctor. A doctor can prescribe hormonal medication that can help control heavy bleeding. If one experiences heavy bleeding, an iron supplement might help to prevent anaemia. Mild to moderate pain or cramps can be lessened reduced by taking an appropriate pain reliever. Taking a warm bath might also help to relieve cramps. Surgery can also be performed. If symptoms persist, always visit a doctor. Fertilization and Implantation. Fertilization is the fusion of a sperm with an ovum in the oviduct also called the fallopian tube. During sexual intercourse, thousands of sperms are released into the vagina by the penis. Sperms swim through the cervix into the uterus up to the oviduct. Few sperms that reach the ovum try to penetrate it. Only one sperm penetrates the ovum. When the sperm penetrates the ovum, the surface of the sperm fuses with the nucleus of the ovum to form a zygote. The zygote moves from the oviduct and enters the uterus, attaching itself to the uterus walls. This process is called implantation. Once implantation has taken place, the zygote is now referred to as an embryo. Symptoms and prevention of common STIs. HIV aid. Symptoms. Chronic diarrhea. High fever and night sweating. Weight loss. Patient becomes very thin and weak. Prevention. Abstain from unnecessary sex. Self control in drinking. Carry out blood transfusion only in extreme need and consider safety. Gonorrhea. Symptoms. Vaginal discharge with bad odours. Penis becomes sore at the tip. Urination is difficult and painful. If untreated it spreads to rest of the organs blocking passages. Prevention. Avoid unnecessary sexual behaviours. Abstain from sexual intercourse. Faithfulness in marriage is encouraged. Syphilis.
Abstain from sexual intercourse. Faithfulness in marriage is encouraged. Syphilis. Symptoms. Sore resembling blisters appear at site of infection. Rashes appear on the skin. Patient feels feverish, suffers body pains and loses hair. Can be prevented by using same measures as in gonorrhea. HerpesSymptoms. Painful sores on the genitals. Blisters may disappear. Can be prevented by;Not indulging in promiscuous sexual behavior. Being faithful in marriage. Avoiding sexual contact with an HSV-II infected personStrand 3 FORCE ENERGY. 3.1 Transformation of energy. Energy is the ability to do workEnergy is not visible, has no mass and neither does it occupy space. Energy exists in different forms. Energy transformation is the process of changing one form of energy to another. Forms of energy in nature. Forms of energy in nature include:Heat or thermal energy. Sound energy. Electromagnetic energy. Nuclear energy. Electrical energy. Chemical energy. Mechanical energy- divided into potential and kinetic energy. Heat energy. Heat is a form of energy transferred from one body to another due to difference in temperature. In an experiment where a metal rod on which different pins are attached using candle wax is heated on a source of heat, the pins start to fall starting with one closest to the source of heat. This means heat flows through the metallic rod from the burning candle to the other end of metallic rod. Sound energy. Sound energy is the energy associated with vibration or disturbance of bodies or particles. Such as striking a drum with a piece of wood or plucking the wire. Nuclear energy. Nuclear energy is the energy that results from nuclear reactions in the nucleus of atom. Very large amounts of energy can be released when changes take place within the nucleus of an atom. Examples of these changes are nuclear fission in which a nucleus breaks down to give two smaller nucleus or nuclear fusion where two small nuclei join to form one big nucleus and radioactive decay in which the nucleus of an element change to different nucleus by releasing certain particles. Electrical energy. Electrical energy is energy produced by flow of electric charges electrons Chemical energy. Is a type of energy stored in atoms and molecules that make up a substance. For example, a thermometer records a higher temperature reading after the steel and vinegar are mixed. This reaction of vinegar and steel wool produces heat.
Is a type of energy stored in atoms and molecules that make up a substance. For example, a thermometer records a higher temperature reading after the steel and vinegar are mixed. This reaction of vinegar and steel wool produces heat. People and other living things get their energy needs from the chemical energy stored in food. Other sources are dry cells and fuels. Mechanical energy. Mechanical energy is the energy possessed by a body due to its motion or due to its position. It can either be kinetic or potential energy or both. When an object is falling down through air, it possesses both potential energy PE and kinetic energy KE due to its speed as it falls. The sum of its PE and KE is its mechanical energy. Mechanical energy kinetic energy potential energy. In conclusion. Kinetic energy is possessed by a moving body while potential energy is possessed by a body due to its position. The sum of an object s kinetic energy and potential energy is its mechanical energy. Potential energy. When a stone is held and released to fall on the ground, this indicates that the stone had stored energy due to its position that made it to start moving down after it had been released. The energy possessed by a body e.g., the stone due to its position above the ground is known as gravitational potential energy. In the same way, when a compressed spring or a stretched catapult is released, it goes back to its original shape and size. This indicates that the spring had stored energy due to compression. The energy possessed by a body dur to compression for example the spring or stretch for example a catapult is called elastic potential energy. Kinetic energyKinetic energy is the energy possessed by a moving object. Examples of objects that possess Kinetic energy KE include:Moving air. Rotating windmills. Falling water. A person running. Any moving object in general. Classifications of energy sources. Energy sources are classified either as renewable sources and non-renewable sources. Renewable energy sources-this are energy sources that cannot be depleted or they can be used again and again. Examples are solar energy, water and wind. Non-renewable energy sources are energy sources that can be depleted and are limited. That means they are completely used and can not be replaced such as fossil fuels like coal and petroleum. Demonstrating energy transformation in nature. Using a flash light. When using a flashlight, the circuit closes. Chemical energy is transformed into electrical energy in the dry cells.
Using a flash light. When using a flashlight, the circuit closes. Chemical energy is transformed into electrical energy in the dry cells. The electrical energy is then converted into light energy. The torch bulb therefore lights which is light energy. Chemical energy to Electrical energy to Light energyUsing a basketball. When you dribble a basketball, the ball had potential energy at its starting point above the ground. The potentials energy is converted to kinetic energy as the ball starts o fall to the ground. Some of the energy is lost on impact as it produces sound and generate heat as it hits the floor When the ball bounces back, it may not return to its starting height. If your hand is there to put more energy into the ball by pushing it down again , the ball can continue to bounce up and down and the energy will shift back and forth between potential and kinetic energy. Potential energy to kinetic energy to potential energy. Appliances whose working rely on energy transformation. Bulb electrical energy -light energy. Solar panels-solar energy to electrical energy. Hammer-potential energy to kinetic energy. Diodes-electrical energy to light energy. Moving coil microphone-electrical energy to sound energy. Electrical heater-electrical energy to heat energy. Dynamo-mechanical energy to electrical energy. Motor-electrical energy to mechanical energy. Safety measures associated with energy transformation. Road accidents. In case an accident, a moving vehicle has kinetic energy that is transformed into other forms incase of head-on collision with another vehicle or a stationery object. Most of kinetic energy is converted to other forms of energy as the vehicle undergoes permanent deformation that causes it to bend and twist. This is a destructive mechanical energy. Some kinetic energy is converted to heat energy and sound energy. Accidents caused by fire. Heat is produced during energy transformation from one form to another. Heat can cause fire accidents, especially when electrical energy is transformed to thermal energy through the use of various appliances. Accidental fires can also be caused by lighting when electrical energy is transformed into heat energy. We should take precaution when handling electrical appliances. We should also observe safety measures during a thunderstorm. Accident associated with the use of electricity. At home various appliances that transform electrical energy into other forms of energy such as light, sound and heat. These appliances include:Electrical heater. Television sets. Iron boxes etc. Risks or accidents associated with use of electricity include electrical shocks, electrical burns and electric fires.
Television sets. Iron boxes etc. Risks or accidents associated with use of electricity include electrical shocks, electrical burns and electric fires. To reduce electricity accidents the following should be done:Move electrical appliances away from water. Repair any faulty wirings. Replace faulty appliances. Health hazard from bright light. Some energy transformation produces very bright light that can damage the eyes, for example in welding Electrical energy is transformed into heat and light energy. This produces a very bright spark of flame that is a health hazard. Welders and other people nearby should wear protective welding shield to avoid exposure to the bright light from the flame. Loud sounds. Various transformations of energy results in production of sound. For example, a motor converts electrical energy into mechanical energy. The mechanical rotation of the fan, blenders and other appliance produces sound. In our environment, sound can be classified into loud or soft sound. Loud sounds such as loud music and shouting or screaming are not good for the environment. Loud soud affect living things by:Causing irritation. Damaging our eardrumsTo reduce loud sounds, we should do the following:Use more efficient appliances that minimise production of loud sound. Wear hearing protection devices to protect our ears from loud sounds. Common types of hearing protection devices include: Earplugs. Earmuffs3.2 Pressure I. Meaning of pressure. Pressure is defined as the force acting normally per unit area. Normally here means at a right angle or perpendicularly. For example,If two leaners of equal mass walked on mud and the boy pus on flat-sole shoes while the girl wears sharp-high heeled shoes, which of the two would make deeper impression on the muddy ground? In the scenario above, the girl makes deeper impressions on the muddy ground than the boy. This is because the weight of the boy is spread over a large surface area than that of the girl. The greater the force weight acts on, the less the effect or impression made on the muddy surface. The sharp heel shoes of the girl have a small surface area in contact with the ground. The smaller the area the deeper the impressions or more sinking than the shoes of the boy for the same weightExample 2,If a leaner has two identical bags, but one has wider shoulder strap and the other has narrow shoulder straps. If the learner places same books with similar weight in the two bags, which bag will the learner feel the straps squeezing more into their shoulder?
The sharp heel shoes of the girl have a small surface area in contact with the ground. The smaller the area the deeper the impressions or more sinking than the shoes of the boy for the same weightExample 2,If a leaner has two identical bags, but one has wider shoulder strap and the other has narrow shoulder straps. If the learner places same books with similar weight in the two bags, which bag will the learner feel the straps squeezing more into their shoulder? In this case, the bag with narrow straps will produce more squeezing effect than that one with wider straps for the same force weight of books carried. This is because, pressure is high when the surface area is small, and it is low when the surface area is large. Therefore, pressure is the force acting normally per unit area. Pressure in liquids. Pressure is represented by a symbol P It is defined as force acting normally per unit area applied to the surface of an object. Pressure increases as the force increases. In mathematical terms, pressure can be expressed as:Pressure ForceAreaSI unit for Force is measured in Newtons N SI unit for Area is measured in m2. ThereforePressure Force F N Area A m2 Form the equation, we obtain unit of pressure as N m2 Pressure can also be measured in Pascal Pa where1N m2 1 Pascal Pa Experiment to demonstrate pressure in solids. Use two different knives. One that is sharp and one that is blunt to cut an orange. Make an observation of the process. From the observation, It is easier to cut an orange with a sharp knife than with a blunt knife. This is because, while cutting, the sharp knife has very small area of contact with the orange. When using the blunt edge of the knife, the force requires to apply for cutting the orange is over a large area. The sharp knife has a smaller area that produces a greater cutting effect. The blunt knife has a large area that produces a lesser cutting effect. The cutting effect is equivalent to pressure. For the same applied force, pressure is higher with a smaller area and it is less with a large area. It is easier to cut with a sharp knife, axe, panga than trying to cut with a blunt knife, axe or panga. A farm tractor has wide wheels that prevent it from sinking into the soil because pressure is distributed over a large area of the wide wheels.