JK-TK/GRADE-8-TERM-2 huggingface dataset:
O Frost formation: When the temperature drops below 0 C, water vapour in the air condenses directly into solid ice crystals. O Water boiling: When water is heated, it changes from liquid state to gas state steam . O Condensation of water vapour: When water vapour in the air cools below 100 C, it changes from gas state to liquid state and condenses to form liquid water droplets. O Sublimation: An example of sublimation is when solid dry ice frozen carbon dioxide changes into carbon dioxide gas without melting. Causes and Effects of Changing States of Matter The main cause of change in states of matter is due to the addition or loss of energy in the state of a substance that is altered physically. This phenomenon is connected with the movement of molecules. Solids possess very little kinetic energy, meaning that they only vibrate and keep the bonds of chemical strength. If the energy source is placed in e.g. heat energy, which can later be converted into kinetic energy then the molecules begin spinning and vibrating faster, which causes the strength of the bonds to diminish. If a certain amount of heating is applied this is different for each substance, for example, the melting point of the water is 0 C while the boiling point is 100 C those molecules will be moving towards the point of not remaining in their original form. When energy levels are reduced and reversed, the process begins again. Whereas, the effects of change in the state of matter are only two which are mentioned as well as explained below: o Change in Temperature: The temperature change occurs in states of a matter when it undergoes heat transfer to its surroundings. When a substance is placed in surroundings of a different temperature, heat is exchanged between the substance and the surroundings, causing both to achieve an equilibrium temperature. So when an ice cube is exposed to heat, its water molecules absorb heat energy from the surrounding atmosphere and begin to move more energetically, causing the water ice to melt into liquid water. O Change in Pressure: The change in pressure occurs in states of a matter only when it undergoes liquefaction. We can understand this effect from the examples of smoke rising all over the stage at performances or parties. Dry ice is the only thing that exists solid carbon dioxide . The solid carbon dioxide is kept at high pressure and instantly melts when pressure is reduced down to 1 bar. The space between particles of the material is what determines its physical state.
Dry ice is the only thing that exists solid carbon dioxide . The solid carbon dioxide is kept at high pressure and instantly melts when pressure is reduced down to 1 bar. The space between particles of the material is what determines its physical state. In the end, when pressure is applied to the gas, it is compressed into a liquid. Then, the pressure applied to liquids becomes solid. Pressure does not affect solids. If pressure is applied to the material and the chemical state of the substance shifts from liquid to gas and after that, liquid changes to solid. Experiments of Changing States of Matter Below are mentioned three experiments that depict all the five processes that take place during the change of state of matter: o If we take an ice cube and put it in a bowl then after some time it will melt into water. This depicts the conversion of a solid into liquid due to the process of melting which took place due to an increase in the temperature of the substance. Now if we put that bowl that has water in a freezer, then the water will again solidify into ice and again change its state. This phenomenon occurs due to the conversion of liquid into solid by the process of freezing. Freezing can only take place when the temperature of a substance is decreased. O Now if you put a bowl filled with water outside your home in the sun then after some days there will be no water. Due to an increase in the temperature, the liquid water changes its form into gaseous water vapour which depicts the process of evaporation taking place. Now to depict condensation we can take a bottle and fill it with some chilled water and as time goes by we can see small droplets of water outside of thebottle which occurred due to the process of condensation taking place. Condensation occurs when the gaseous water vapours come in contact with the cold water having a decreased temperature; they start to solidify and get converted into liquid water again. O If we take some dry ice and put it in a bowl then after some time we can see that the dry ice will disappear. This occurs due to the process of sublimation taking place in it. Sublimation converts the solid into a gaseous form and it occurs only when the temperature is increased. To reverse this process we can decrease the temperature as well as pressure and the atmospheric dry ice will again solidify. Applications of Changing States of Matter The phenomenon of change of states of matter can be found in the following examples: 1.
They are also called chemical changes There are many differences between physical and chemical changes and it is important to understand them to be able to understand these concepts clearly. The comparisons and differences between physical and chemical changes are given below along with their examples. To understand physical and chemical properties and changes better, it is important to know what they are. Differences between Physical and Chemical Change Physical Change Chemical Change When a substance undergoes a physical change, its composition remains the same despite its molecules being rearranged. When a substance undergoes a chemical change, its molecular composition is changed entirely. Thus, chemical changes involve the formation of new substances. Physical change is a temporary change. A chemical change is a permanent change. A Physical change affects only physical properties i.e. shape, size, etc. Chemical change both physical and chemical properties of the substance including its composition A physical change involves very little to no absorption of energy. During a chemical reaction, absorption and evolution of energy take place. Some examples of physical change are freezing of water, melting of wax, boiling of water, etc. A few examples of chemical change are digestion of food, burning of coal, rusting, etc. Generally, physical changes do not involve the production of energy. Chemical changes usually involve the production of energy which can be in the form of heat, light, sound, etc. In a physical change, no new substance is formed. A chemical change is always accompanied by one or more new substance s . Physical change is easily reversible i.e original substance can be recovered. Chemical changes are irreversible i.e. original substance cannot be recovered. Thus, it can be understood that the primary difference between physical and chemical changes is that physical changes are reversible, whereas chemical changes are usually not. Test your Knowledge on Difference Between Physical And Chemical Change QUESTIONS AND ANSWERS Q1 How can you tell the difference between physical and chemical changes? The appearance or form of matter changes during a physical change, but the type of matter in the substance does not. A chemical change, on the other contrary, results in the creation of at least one new substance with new properties. Q2. Why is it important to know the difference between physical and chemical changes? It s essential to recognise the difference between chemical and physical changes. Several changes are obvious, but there are some fundamental concepts to be aware of. Physical changes usually refer to changes in the physical state of stuff. When two or more molecules interact, chemical changes occur on a molecular level. Q3.
Physical changes usually refer to changes in the physical state of stuff. When two or more molecules interact, chemical changes occur on a molecular level. Q3. What are the examples of physical and chemical changes? Examples of chemical changes would be burning, cooking, rusting, and rotting. Examples of physical changes could be boiling, melting, freezing, and shredding. Most physical changes can be reversed if sufficient energy is provided. Q4. How to tell whether it s a physical or chemical change? Check for indications that a chemical change has taken place. The following are indications of a chemical change: Gas is created. Bubbles can occur in liquids. An odour is created. The colour of the substance changes. Sound is generated. There is a shift in the temperature. The environment either heats up or cools down. Light is generated. A precipitate develops. Reversing the change is difficult or impossible. Q5. What are three forces that can cause a physical change? Forces such as motion, temperature, and pressure can create physical changes. Oxygen in the air reacts with sugar, and the chemical bonds are destroyed. Elements and compounds Elements are pure substances which are composed of only one type of atom. Compound is substances which are formed by two or more different types of elements that are united chemically in fixed proportions. Elements and Their Symbols Chemical elements are the basic building blocks of matter. Elements are referred to by their names and their symbols. This makes it easier to write chemical structures and equations. Examples The first 20 elements of the periodic table are listed below. These elements include some of the most abundant in the universe hydrogen, oxygen, carbon as well as some of the most unusual phosphorus, boron . 1. H - Hydrogen 2. He - Helium 3. Li - Lithium 4. Be - Beryllium 5. B - Boron 6. C - Carbon 7. N - Nitrogen 8. O - Oxygen 9. F - Fluorine 10. Ne - Neon 11. Na - Sodium 12. Mg - Magnesium 13. Al - Aluminum 14. Si - Silicon 15. P - Phosphorus 16. S - Sulfur 17. Cl - Chlorine 18. Ar - Argon 19. K Potassium 20.
Cl - Chlorine 18. Ar - Argon 19. K Potassium 20. Ca - Calcium Notice that the symbols are one- and two-letter abbreviations for their names, with a few exceptions where symbols are based on old names. For example, potassium is K for kalium, not P, which is already the element symbol for phosphorusCommon Metals Magnesium: It has a symbol of Mg. Calcium: It has a symbol of Ca. Chromium: It has a symbol of Cr. Iron: It has a symbol of Fe. ... Zinc: It has a symbol of Zn. Mercurys-Hg Gold-Au Tin Sn Uses of elements 1. Hydrogen - Rocket propellant, chemical reagent, potential alternative fuel, coolant for electrical equipment, airship lifting gas. 2. Helium - Lifting gas for balloons airships, coolant for superconductors. Shielding gas for welding. 3. Lithium - Batteries, psychiatric medications, constituent in light structural metals. 4. Beryllium - Light, hard, strong structural metal, x-ray transparent materials. 5. Boron - Composite materials, cleaning agents, semiconductors, chemical reagents. 6. Carbon - Structural material, jewellery diamonds , basis for all organic compounds, adsorbent material, pencils. 7. Nitrogen - Primary component of the atmosphere, fertilizer production, rocket propellants, shielding gas for welding. 8. Oxygen - Primary active component of atmosphere, medical use, rocket propellant, steelmaking, support of combustion. 9. Fluorine - Toothpaste, pharmaceuticals, etching of glass, rocket propellant for use outside the atmosphere . 10. Neon - Electric signs, lasers. 11. Sodium - Table salt, glassmaking, baking soda, reducing agent. 12. Magnesium - Structural material, dietary supplement, flashbulbs, fireworks. 13. Aluminium - Structural material, ceramics aluminium oxide . 14. Silicon - Semiconductors, glassmaking, abrasives, structural material. 15. Phosphorus - Fertilizers, rust remover phosphoric acid , matches. 16. Sulphur - Primary starting material for sulphuric acid which has MANY uses , vulcanized rubber, detergents, odorant in natural gas, fungicide. 17.
What is an easy way to remember the first 20 elements? You just need to remember 2 sentences First Sentence - Hi Hello Listen Be. B.C. News On Friday Night. Hi-H-Hydrogen Hello-He-Helium Listen-Li- Lithium B.-Be-Beryllium B.-B-Boron C.-C-Carbon News-N-Nitrogen On-O-Oxygen Friday-F-Fluorine Night-Ne-Neon Second sentence - Natives Might All Sing Party Songs Clearly Arousing Kitty Cats Natives-Na-Sodium Might-Mg-Magnesium All-Al-Aluminium Sing-Si-Silicon Party-P-Phosphorus Songs-S-Sulfur Clearly-Cl-Chlorine Arousing-Ar-Argon Kitty-K-Potassium Cats-Ca-CalciumOXYGEN Preparation of oxygen One of the most common methods for the laboratory preparation of oxygen is by the method of preparation of oxygen by simply treating hydrogen peroxide in a particular manner so that it decomposes to form water and oxygen from which then, the oxygen can be extracted. Oxygen is one of the most important and basic elements found in the earth s atmosphere. All living animals need oxygen in the air to survive. Without oxygen, there would be no trace of life on earth. Apart from being one of the basic elements on earth for a living being to survive, it is important in a lot of other areas as well. Oxygen is used in medical applications, commercial and industrial practices all over the world. It is very much possible to manufacture oxygen in a laboratory. Apart from the necessary apparatus, the main ingredients required to make oxygen in a laboratory are hydrogen peroxide and manganese IV oxide. It must be noted that hydrogen peroxide is the main ingredient for the preparation and the manganese IV oxide acts as a catalyst to enhance the speed of the process. Laboratory Preparation of Oxygen https: www.youtube.com watch?v nkeniDKGs6Q There are a lot of laboratory processes for producing oxygen. Among them, one of the most common ways of preparation of oxygen is in a laboratory by the method of preparation of oxygen by simply treatinghydrogen peroxide in a particular manner so that it decomposes to form water and oxygen from which then, the oxygen can be extracted. Produce oxygen by heating potassium manganate VII , then identify it with a glowing splint This experiment should take 30 minutes.
Laboratory Preparation of Oxygen https: www.youtube.com watch?v nkeniDKGs6Q There are a lot of laboratory processes for producing oxygen. Among them, one of the most common ways of preparation of oxygen is in a laboratory by the method of preparation of oxygen by simply treatinghydrogen peroxide in a particular manner so that it decomposes to form water and oxygen from which then, the oxygen can be extracted. Produce oxygen by heating potassium manganate VII , then identify it with a glowing splint This experiment should take 30 minutes. Equipment Apparatus Eye protection Test tube holder Ceramic wool Test tube Spatula Bunsen burner Splints Heat-proof mat Chemicals Potassium manganate VII Health, safety and technical notes Always wear eye protection. When KMnO4 is heated, tiny particles shoot out. These are trapped by the ceramic wool. Potassium manganate is an oxidiser and harmful,Procedure 1. Place two spatula measures of potassium manganate VII in a test tube. 2. Place a small piece of ceramic wool near the top of the test tube. This stops fine dust escaping. 3. Gently heat the test-tube containing the potassium manganate VII . 4. Light a splint and extinguish it, to make a glowing splint . 5. Place the glowing splint just above the top of the test tube. Keep heating the test tube. The splint should relight. 6. Scrape out the ceramic wool. Let the test tube cool to room temperature and then wash it out. 7. Notice the colours produced when the test tube is washed out. 8. Record your observations. Conclusion Oxygen is one of the most important and basic elements found in the earth s atmosphere. All living animals need oxygen in the air to survive. Without oxygen, there would be no trace of life on earth. Over the years, scientists have discovered multiple ways of preparation of oxygen in laboratories and also identified other diverse uses of this gas. Oxygen is used in medical applications, commercial, and industrial practices. There are a lot of different methods of preparing oxygen and different methods may have different purity rates of the concerned gas.
Water extinguishers are coloured signal red. Other extinguishers will be predominantly signal red with a label, band or circle covering at least 5 of the surface area of the extinguisher in a second colour indicating the contents of the extinguisher. Fire Rating All extinguishers capable of extinguishing class A, B or F fires carry a fire rating which is indicated by a number and letter eg 13A, 55B . The number is indicating the size of fire it can extinguish under test conditions. The larger the number, the larger the fire it can extinguish. The letter indicates the fire classification as above. Class C, D and the electrical symbol do not carry a numerical rating. All extinguishers capable of extinguishing class F fires have a rating based on 4 benchmark tests using 5, 15, 25 and 75 litres of sunflower oil. The oil is heated to auto-ignition and allowed to pre-burn for 2 minutes. The fire is then extinguished and no re-ignition shall occur within 10 minutes of extinguishing the fire. Chosing Fire Extinguishers The following factors should also be considered when siting fire extinguishers: Extinguishers should normally be sited on escape routes on all floors at what is called fire points . They should be fixed in a location where the extinguisher can be reached quickly. The best place is near a door leading to a place of safety or near a specific fire risk. They should be fixed where they can be easily seen. Fixing them inside cupboards or behind doors will waste valuable time if a fire breaks out. Do not place them over cookers or heaters or in places of extreme temperatures, hot or cold. Extinguishers should be fixed at an elevated height, so that the carrying handle is 1m from the floor for heavier units heavier than 4kg and 1.5m for smaller units. Extinguishers should be within reasonable distance from any fire risk: 1. Class A: 30m 2. Class B: 10m 3. Class C: 30m 4. Class D: case-by-case basis, by expert advice 5. Class F: 10m If you have to travel through doorways, the maximum travel distances need to be reduced.
Only tackle a fire in its very early stages Always put your own and other peoples safety first On discovering the fire, immediately raise an alarm Make sure you can escape if you need to and never let a fire block your exitIf you cannot put out the fire or if the extinguisher becomes empty, get out and get everyone else out of the building immediately, closing all doors behind you as you go. Then ensure the fire brigade has been called Fire Triangle Trying to understand the seemingly endless list of fire safety regulations can be a complex and confusing task. Whether you are attempting to identify the different types of fire extinguisher and their appropriate uses or are learning about the benefits of a fire blanket, it is vital to remember that the various stringent rules are there for a reason and this reason ultimately relates to the fire triangle. Something usually taught in school, the fire triangle which is also known as the combustion triangle is a simple model for understanding the chemical reaction which must occur to create a fire. It is composed of three elements fuel, heat and oxygen which must all be present for a fire to ignite. It also demonstrates the interdependence of these ingredients in creating and sustaining a fire and teaches us that removing any one of these elements would prevent or extinguish the fire. The fire triangle is often used as a basic form of fire safety training and looks at the dynamics of fire itself. By looking at and understanding this in more detail, it is much easier to grasp the need for, and details of, fundamental fire regulations so let s get back to basics Fuel In order for a fire to start there must be a material to burn and this is referred to as the fuel. Fuel is any kind of combustible material, including paper, oils, wood, gases, fabrics, liquids, plastics and rubber. The fuel for a fire is usually characterised by its moisture content, size, shape and quantity and this will determine how easily the fuel will burn and at what temperature. Heat In addition to a fuel source, heat must be present in order for ignition to take place. All flammable materials give off flammable vapours which, when heat is present, combust. Heat is also responsible for the spread and maintenance of fire as it removes the moisture from nearby fuel, warming the surrounding area and pre-heating fuel in its path, enabling it to travel and develop with greater ease. Oxygen As well as fuel and heat, fires also need oxygen to stay alight.
All flammable materials give off flammable vapours which, when heat is present, combust. Heat is also responsible for the spread and maintenance of fire as it removes the moisture from nearby fuel, warming the surrounding area and pre-heating fuel in its path, enabling it to travel and develop with greater ease. Oxygen As well as fuel and heat, fires also need oxygen to stay alight. Ambient air is made up of approximately 21 oxygen and, as most fires only require at least 16 oxygen to burn, it acts as the oxidising agent in the chemical reaction. This means that when the fuel burns, it reacts with the oxygen to release heat and generate combustion. Extinction of the fire To stop a fire, one of the three elements of the fire triangle must be removed. So, if a fire runs out of fuel, it will smoulder out; if you can cool a fire down it will lose heat and go out; and if the oxygen is removed it will suffocate. Therefore, attempts at combatting a fire and also preventing a fire are based upon these principles. Fire blankets, for example, suppress a fire, removing the oxygen and, as a result, putting it out. Similarly, fire extinguishers are developed to eliminate one of the three elements such as water fire extinguishers which cool the fire down and remove any heat. By the same codes of practice, fire prevention methods are also developed in relation to the chemical reaction which occurs when fire takes place. Undertaking safety steps such as storing flammable liquids away andmaking sure piles of paper or fabric are not left near any possible heat sources are highly important. By using this fundamental fire safety knowledge, the prevalence of fires and the damage they cause can be significantly reduced.