JK-TK/GRADE-8-TERM-2 huggingface dataset:
Steel is a combination of iron and carbon. Steel is important in construction. Gold and silver:They are precious metals elements that occur naturally and have high market value. In some cases, Gold and silver can be used as currency. In other cases, these precious metals have various uses such as in electronics, medical technology and awards therefore gold and silver valuable to many businesses. Gold is more valuable because it is rare than silver. Information on Packaging labels. Substances purchased contain various elements that are part of ingredients. The elements present are usually indicated in the information found on the packaging labels. Few examples are given below. Toothpaste- contains sodium flouride, zinc sulphate and sodium hydroxide. Body lotion contains sodium hydroxide and other compoundsLiquid handwash contains sodium chloride. Baking powder contains sodium hydroxide carbonate. Curry powder contains sodium. Tomato source contains a compound of sodium. Margarine-contains a preservative that is a compound of potassium. Beef cubes-contains a compound of iron and a compound of sodium. Bottled water-contains calcium, sodium, potassium, magnesium and other common elements. 1.2 -Physical and Chemical changes. Matter is anything that occupies space and has mass. All solids, liquids and gases are made up of matter. The three states of matter have different physical properties. These properties depend on intermolecular forces. Intermolecular forces are forces that hold the particles of matter together. Properties of different states of matter. Solids have a definite shape which does not change on its own unless use of external forces such as breaking it into smaller pieces. For example, when a stone is place on a table, or a plate or a tin, it does not change its shape according to the item it is place in or on. A liquid has no definite shape. That means a liquid changes its shape to take the shape of the container or vessel in which it is put. A liquid also changes its shape when spilled on the floor. For example, when a liquid id poured in two different containers, the liquid will display two different shapes that resemble or are similar to the container they are placed in. This means liquids lack a definite shapeGases-a gas has no definite shape. A gas changes its shape to look like that of container in which it is held in. For example, when a balloon is inflated with air, the air inside takes the shape of the balloon.
This means liquids lack a definite shapeGases-a gas has no definite shape. A gas changes its shape to look like that of container in which it is held in. For example, when a balloon is inflated with air, the air inside takes the shape of the balloon. Solids, liquids and gases are different in terms of their volumes. Solids. When a solid is totally immersed in a liquid, the volume of the displace liquid is equivalent, equal to the volume of the solid. The volume of the stone remains the same when place in two different measuring cylinders. Therefore, solids have a definite shape. Liquids. The volume of water poured in a measuring cylinder remains unchanged even when it is transferred from one measuring cylinder to other measuring cylinders of different capacities. For example, if you pour 30ml of water in a 50mli measuring cylinder, its reading will be 30ml. If the same water is transferred to a 100ml measuring cylinder, the reading will still remain 30ml. Therefore, liquids have a definite shape just like solids. Gases. A given mass of a gas can occupy different volumes in different containers. This is an indication that gases, do not have a fixed volume. Solids, liquids and gases are different in terms of their Compressibility. Compressibility is the ability of a substance to be reduced in volume or size by applying force or pressure on it. Compressibility can also be defined as how much a given volume of matter decreases when pressed. When a bottle id filled with air, it can easily be squeezed compared to one filled up with water. If the two are replaced with sand, we cannot squeeze the bottle anymore. This experiment proves that gases are highly compressible, liquids have little compressibility while solids are incompressible. Occupies entire volume of container. Their particles move freely because the intermolecular forces are very weak. This makes particles to move far apart from each other and can be brough closer when pressure is applied. This is the reason gases are highly compressible. Their properties lie between those of gases and solids. Their intermolecular forces in liquids are weaker than in solids but stronger than in gases. The particles in liquids do not move freely as in gases, therefore, it is difficult to compress liquids since the liquid particles can move but keep same volume. Particles in solids are very close to each other closely packed and the intermolecular forces between the particles are very strong.
Their intermolecular forces in liquids are weaker than in solids but stronger than in gases. The particles in liquids do not move freely as in gases, therefore, it is difficult to compress liquids since the liquid particles can move but keep same volume. Particles in solids are very close to each other closely packed and the intermolecular forces between the particles are very strong. The strong forces keep the particles in fixed position. This is the reason why solids are hard, firm and rigid. Therefore, solids are incompressible. C. Solids, liquids and gases are different in terms of their ability to flow. Particles in liquids can move from one place to another, therefore, a liquid can flow and change shape. This makes liquids such as water to flow from a tap to fill a jar or a bucket. This is applied when pouring tea in a cup. Solids have particle that do not move therefore solids cannot flow. Gases have freely moving particles which can be moved from an area. For example, when you breathe, you force air gas into and out of your lungs. This is an indication that gas flow in and out of the body. This is also applied when cooking gas flows from the gas cylinders to the burners when cooking. Therefore, liquids and gases can flow while solids cannot flow. Summary of properties of different states of matter. Pure and Impure substances. When two pure substances are mixed together, they form a mixture. A mixture is an impure substance. Therefore, a pure substance is any material that is not a mixture at all. The melting and boiling points of pure and impure substances can be determined. Melting point of pure substances Ice . It is the temperature at which a solid change into liquid state. The melting point of ice is the temperature at which ice is converted from its solid state to its liquid state. Heat from a heat source is used to melt the ice. The thermometer helps to note the temperature at which the ice melts. After the initial and final readings are taken, it will be observed that once the ice attained its melting temperature 0oC , the temperature remains the same until all the ice is converted into liquid state. Pure solids have specific melting points. Therefore, it means that ice is a pure substance. Melting point of Impure substances Candle wax . The melting point of candle wax is the temperature at which the solid materials turns into liquid by heating it .
Therefore, it means that ice is a pure substance. Melting point of Impure substances Candle wax . The melting point of candle wax is the temperature at which the solid materials turns into liquid by heating it . The melting point of candle wax ranges between 46oC to 68 oC. Therefore, it means that candle wax is an impure substance. Impure substances do not have specific melting points. The presence of impurities affects the melting point of the substances. Determining Boiling points of Pure and Impure substances. Procedure for the experiment above. Put about 10cm3 of distilled water on a boiling tube. Close the tube with a stopper that has two holes. Pass a thermometer through one hole. Immerse the thermometer bulb into the water. Push and L shaped tube through the other hole as shown above. Heat the apparatus using a small flame. Observe the changes in temperature and record your observations. Cool the apparatus and remove the stopper. Add a spoonful of salt to some water stir to dissolve all the salt to form a salty water solution. Repeat the above experiment using a salty water solution in place of pure distilled water. Observe changes in temperature, record your observation. What conclusion have you made. At what temperature does water pure water boil? At what temperature does water with dissolved salt impure water boil Compare your observations. Observations and conclusion Explanation. When distilled water is heated, the temperature of the water rises to about 100oC. After this, the temperature remains constant not changing for some time. The heat absorbed changes liquid water into water vapour or steam. Pure water has a definite or specific boiling point. Salty impure water has a range of boiling temperatures above 100oC. Impurities cause a rise in temperatures of the boiling point of liquids. The greater the impurities in the given solution, the higher the boiling point. Therefore, we can use the boiling point to determine the purity of a liquid. Temporary and Permanent Changes in SubstancesTemporary Physical changes. Experiment to demonstrate physical change. Requirements:A pair of tongs. An iron pin. A source of heat such as burning candle or Bunsen burner and writing materials. Procedure:Hold iron pin using a pair of tongs over a burning flame from either a candle or Bunsen burner for sometime. Remove the pin from the flame after noticing any changes you can observe.
A source of heat such as burning candle or Bunsen burner and writing materials. Procedure:Hold iron pin using a pair of tongs over a burning flame from either a candle or Bunsen burner for sometime. Remove the pin from the flame after noticing any changes you can observe. Observations, Explanation conclusion. Iron pin becomes red-hot when heated. After sometime the iron pin regains its original colour on cooling. This indicates that the iron pin went through a temporary change on heating. Any change in properties such as shape, size, colour and state of a substance is called a physical change. Physical changes are reversible. When a change is reversible is said to be temporary. This is demonstrated when the heated red-hot iron pin regains its original colour after cooling. Temporary chemical changesExperiment to demonstrate temporary chemical changes. Requirements:Safety googles. Two test tubes. Delivery tube right-angled Beaker 250ml . Bunsen burner. Clamp. Stand. 5g of hydrated copper II sulphate. Procedure:- Put 5g of powdered blue hydrated copper II sulphate in the test tube. -. Set up the experiment as shown below. Heating blue hydrated copper II sulphateObservation, Explanation and Conclusion. When blue hydrated copper II sulphate is heated in the test tube as show above, it turns colour from blue to white. This because it loses water which was making it hydrated. After losing water, it become white anhydrous copper II sulphate. When water is added to the white anhydrous copper II sulphate, it turns back to its original blue colour. The chemical change that had occurred is reversed. Some chemical changes are therefore temporary and can be reversed easily. These changes are referred to as temporary chemical changes or reversible chemical changes. Other examples of temporary chemical changes include the following;On mixing baking soda and vinegar, a chemical reaction produces carbon IV oxide gas. This gas causes the mixture to bubble. Once the gas escapes into the air, the reaction stops and the mixture returns to its original state. Freezing, melting and vapourisation of waterPermanent Chemical changesExperiment to demonstrated permanent chemical change. Requirements:5cm magnesium ribbon. A source of heat. Sand paper. A pair of tongs. Writing materials. Procedure:Clean the magnesium ribbon by rubbing it with sand paper. Examine the appearance of the magnesium ribbon.
Writing materials. Procedure:Clean the magnesium ribbon by rubbing it with sand paper. Examine the appearance of the magnesium ribbon. Hold the ribbon with a pair of tongs over a burning candle or Bunsen burner for a few minutes. Caution:Burning magnesium ribbon produces a very bright flame that can damage your eyes. Avoid looking directly at the flame. Observation, Explanation Conclusion. Magnesium ribbon burns with a bright light forming a white ash. If the magnesium ribbon is not shining it may take long to ignite. Therefore, is advisable to clean the ribbon by rubbing it with sand paper since it is coated with an oxide layer that prevents it from burning. Burning magnesium ribbon form a substance called magnesium oxide. A change in which one or more substances are formed is known as chemical change. A chemical change is also known as permanent change. Most chemical changes are irreversible in nature. Chemical changes are important in life. Example of chemical changes include:Digestion of food in the body. O Ripening of fruits. Fermentation of grapes. Applications of changes of state of matter in day-to-day life. Change of state of matter has many applications in day-to-day life. Some of these changes are:Refrigerators. -. Liquids evaporate and absorbs heat in the process. A refrigerator works by using a liquid to remove heat from the food items inside and transfer it to the surrounding. The liquid is first heated and then cooled at the back of the fridge where the heat is removed. The process of changing liquid to gas cools the food. Ice cream vendor. -. Ice cream vendors place ice inside their ice cream carts. The ice absorbs heat from the container surrounds and change to a gas. This leaves the inside of the ice cream cart cold, thus maintaining the ice cream in frozen state. Melting metals. -. Metals are heated to a molten state making it possible to shape and form them into desired objects or structures. Generating electricity. -. Water can be converted to steam, which can in turn be used to drive turbines to generate electricity. Fog formation. -. Fog forms when water vapour gaseous state condenses. During condensation, molecule of water of water vapour combine to make tiny liquid water droplets that are suspended in the air. Fog reduces visibility. Some animals such as insects, depend on fog as a source of water, especially in desert climate. -Classes of Fire. Fires can be classified between four and seven classes.
Some animals such as insects, depend on fog as a source of water, especially in desert climate. -Classes of Fire. Fires can be classified between four and seven classes. The following are six classes of fire mostly widely used and accepted. Fire control measures. To prevent the start and spread of fire, one or more components should be removed from the fire triangle. A fire triangle in a simple model of understanding the components of fire which are fuel, heat and oxygen. Therefore, to control fire one or more components should be removed from the fire triangle as follows: Removing fuel:Use fire-resistant materials where possible. This will help to prevent the fire from starting and spreading. Removing heat:Water is mostly used to remove the heat from fire. A water fire extinguisher would be the safest way of doing this. However, these extinguishers cannot be used on all types of fire. Removing oxygen:It is important to remove oxygen gas from fore triangle to prevent spread of a fire. This can be achieved by using either a carbon IV oxide or a form fire extinguisher. Fire extinguisher come in different types depending on the kind of environment you are in. Some places such as school, work or home, one or more types of fire extinguishers may be required. The following are different types of fire extinguishers and the classes of fire they put. Other items that can be used to control fire. In addition to the fire extinguishers, the following items can also be used to control fire. Sand-it absorbs heat and cuts off the supply of oxygen. Sand can be used to put out class A, D and F fires. Fire blanket-it is useful in putting out class F fires and wrapping around a person whose clothing is on fire. Rights to safety and access to information. At school, home and workplace you are supposed to be safe. These paces should take the following precautions for our safety:Avoid build up of rubbish that can fuel fire. Put measures in place to detect fires and warn people quickly in case fires start. This can be done successfully by installing smoke detectors and fire alarms or bells. Have correct fire fighting equipment to put out a fire quickly. Keep fire exits and escape routes clearly marked and unobstructed at all times. Give proper training on emergency procedures to follow, including fire drills. Access to information on flammable substances is important for the following reasons.
Keep fire exits and escape routes clearly marked and unobstructed at all times. Give proper training on emergency procedures to follow, including fire drills. Access to information on flammable substances is important for the following reasons. It makes us aware of all hazards fire and explosion of the materials we are handling. Helps us to know which of the materials or products we are working with are flammable. Helps us to remove sources of ignition sparks, smoking, flames or hot surfaces when working with flammable and combustible products. Helps to use approved equipment, including labelled safety containers, for flammable liquids. Helps to know the proper personal protective equipment to use when handling hazardous liquids. Helps us to know how to handle emergencies fires, spills, personal injury involving the hazardous materials we work with. Fire safety posters we should be aware in the environment we are in. Strand 2 LIVING THINGS THEIR ENVIRONMENT. 2.1 The Cell. Cells make up the structure of living organisms and carry out various biological processes. Organisms such as amoeba are composed of a single cell hence are said to be unicellular. Organisms such as plants and animals are composed of many cells hence are said to be multicellular. Therefore, a cell is defined as the basic unit of structure and functions in organisms. To observe the cell, a powerful magnifying instrument called a microscope is used. A microscope enlarges the image of objects when observed and improves the resolution of the image. Plant and animal cell structures as seen under a light microscope. The following diagram shows the components of a plant cell as seen under a light microscope. Components of a plant cell. The following diagram shows different components of the animal cell as seen under a light microscope. Components of an animal cell. Comparing plant and animal cells. Plant and animal cells have slight differences in their internal structures while sone features are common in both. The figures below show the components of both plant and animal cells as seen under a light microscope. Similarities between a plant cell and an animal cell. They both have the cell membrane. Both have nucleus within themFunctions of the cell structures found in plants and animals cells. Magnification of Cells. Magnification of a specimen is the measure of how much bigger a specimen is when it is viewed through a hand lens or microscope compared to its original size. Magnification is usually expressed using X before the digits, for example, X2, X10 and X20.
Writing materials. Procedure:pour some water in a beaker. Put a drop of the dye or ink in the water. What observations do you make after a few minutes? Observation, explanation and conclusion. After a few minutes, the ink or dye spread throughout the water in the beaker. The ink pr dye spread from the region where it was highly concentrated to region in water where it was in low concentration. Diffusion is defined as the movement of molecules from a region of high concentration to a region of low concentration. Experiment demonstrating diffusion in gases. Requirements: A bottle of perfume of scented flowers. Procedure:Place the scented flower in a corner of the classroom. Remove the stopper of the perfume, hold it a few centimetres away from your friend s nose. Observation, explanation and conclusion. After a few seconds, you and your classmates will be able to smell the scent of the flower or perfume. This is due to diffusion. The scent of the flower and perfume molecules diffuse the air to their nose. Molecules in the scent of flower or perfume moved from the region of high concentration and spread evenly towards the region of low concentration. Diffusion in gases also makes it possible for us to smell things, for example, flower, food being cooked and also foul smells. Roles of diffusion in Living things. Plants absorb minerals salts from soil through diffusion. Nutrients such as glucose and amino acids move from the small intestines into bloodstream of animals by diffusion. Cells and unicellular organisms such as amoeba get rid of waste substance through diffusion. Gaseous exchange is the process through which gases are transferred across cell membrane to either enter or leave the blood. This process is done by diffusion in human beings in the alveoli in lungs. Oxygen gas moves from alveoli where is it is highly concentrated to the blood capillaries where it is lowly concentrated. On the other hand, carbon IV oxide moves from the capillaries where it is highly concentrated into the alveoli where it is lowly concentrated to be exhaled out. Factors that affect the rate of diffusion. Concentration gradient-molecules move from region of high concentration to that of low concentration. The greater the difference in concentration between high and low regions, the faster the rate of diffusion. 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.