[Music] hi kids Welcome to our fourth week in our lesson in science grade four so are you ready so for this week we're going to discuss more about physical and chemical change so last time uh we already talked about it a little bit in our class last week and for this week we're going to focus on uh physical and chemical change are you ready okay so going back again uh we talked about materials and their uses and uh last week we focused on flammability uh degradable and bio degradable so let's have our objectives for this week's lesson first uh we need to describe changes in matter that involve physical change and chemical change investigate to show how changes in properties of materials occur when exposed to very high or very low temperatures and we are uh we need to side situations where in phase change is beneficial for day one we're going to review matter and its um faces matter is anything that has mass and takes up space it can exist in different states such as solid liquid or gas and can be composed of various elements and compounds matter is all around us from the air that we breathe to the food that we eat even objects that we may not be able to see like the atoms and molecules that make up those objects are still considered matter now let's take a look at it one by one let's start with solid imagine you have a bunch of marbles you can put them in a box and they'll stay in the shape of the box that's because marbles are solid solids have definite shape and volume solids have a fixed shape and volume their particles are tightly packed together in a regular repeating pattern called a crystal plaus so as you can see we have an example we have Pebbles and rocks as an example of solid so it has its own shape and volume now let's go and take a look at liquid liquids have a fixed volume but take the shape of their container their particles are close together but can move around more freely than in solids so they have a definite volume even though liquids can change shape they still take up the same amount of space if you pour the bouncy balls into a bigger bowl they'll still take up the same amount of space just spread out more so our example is water okay and for gas uh they don't have a definite shape the bouncy balls will fill up the whole room no matter what shape the room is gases do the same thing they spread out to fill whatever space they're in they don't have a definite volume if you add more Bouncy Balls to the roof they'll just spread out even more gases are like that too they can be squeezed into smaller spaces or spread out to fill larger [Music] spaces okay let's Ponder on this matter under goes various changes when exposed to changes in temperature which can be classified as either physical or chemical in the next phase of the lesson you will be able to know and understand how these changes in matter happen it could be a change in its internal structure or physical appearance it may also result in the formation of new materials when they are mixed but before we have head on to our lesson let's unscramble the words first although we have here the answer but then okay we are going to uh try to describe and explain quickly this minute okay so we have number one it is to make or become different and the answer is change then number two it is a measure of how hot or cold something is it is temperature and we all know that um some matter no can be affected by the temperature that they are in so if it's too cold they can freeze uh for example an ice cube it can be affected by the temperature of a place okay for example if it is too hot if you have an ice cube it will melt and if it's too cold it will freeze so we're going to talk more about that later on and uh for number three we have perishable is uh it's a type of food with a limited shelf life if it's not refrigerated okay so perishable it means um it will not it will not last long no if uh the food is not refrigerated it will be spoiled okay now uh the next one is it's a process in which one or more substances the uh reactants are converted to one or more different substances the products okay so it is the answer is chemical reaction okay and another one it is this chemical reaction that occurs between substances when materials burn and it is combustion okay so we have here change es in matter so we need to take uh a look at it and because this is also very important changes in matter refer to the physical or chemical Transformations that take place when a substance under goes a modification these changes can occur in any of the three states of matter uh if it um solid liquid or gas and they can be brought about by by a variety of factors including changes in temperature pressure or chemical composition so um these factors might affect all right the states of matter of an object so perhaps from solid it will turn to liquid from liquid it will turn to solid and uh for example from liquid it will turn to gas so fa so uh this could be temperature no you hotness or coldness we also have the pressure and chemical composition so let's talk about that more on day two for day two we're going to focus on the physical uh changes in matter okay when we talk about physical change uh in matter it involves a change in one or more physical properties of a substance such as its shape size or state of matter without changing its chemical composition meaning to say body composition chemical composition for example food for example banana into several pieces no shape and Si banana chemical composition or nutrients inside the banana is still the same same thing with Apple with carrots no Chin fruits and vegetables so change physical appearance but you composition chemical composition fruits and vegetables will never change okay unlike the chemical change which involve the formation of new substances physical changes can often be reversed by changing the cons condition that caused the change okay so P Para specific substance so let's further discuss we have the characteristics of physical change in matter so no new substances formed meaning to say one of the defining features of physical change is that they do not result in the creation of entirely new substance for example uh in this picture we have the carrots no CH carrots it will still be carrots Apple uh banana potato carrots no so no new substances uh uh was formed no upon chopping the carrots now in terms of change in state this occurs when substance transitions between solid liquid or gas States due to changes in temperature or pressure next change in appearance physical changes often involve alteration in the substances appearance texture or shape soain appearance no texture or shape per chemicals uh composition specific substance or for example the carrots or the vegetable or the fruits is still the same so substance once change into another vegetable so certain factors like heat or um coldness isang um B so we have here uh some examples of physical change okay we have here changing from solid to liquid state without altering its composition so for example butter melt butter per change state from solid to liquid chemical composition but is still the same another example is transforming from liquid to gaseous State through heat water water orquid gas but still chemical composition next altering the shape of the can without changing the materials it's made of so same thing no shape still chemical composition is the same okay now let's talk about melting so what is melting melting is a process where a solid turns into a liquid when it gets warm enough or uh when we um heat no okay so when something melts it becomes soft and turns into a liquid for example when ice cream melts it becomes liquid instead of being hard like ice so when we put something uh into heat heat is so especially solid like for example ice cubes butter or ice cream no it will turn into at first it becomes soft and eventually turns into a liquid state okay so let's have examples of melting so ice melting one common example of melting is when ice cubes are left outside on a warm day as The Sun Shines on them or the temperature gets warmer the ice cubes starts to melt and turn into water now chocolate melting another example is when you heat chocolate in a microwave or over a stove the solid chocolate turns into a liquid making it easier to spread or used for making desserts like chocolate covered strawberries and another example of melting is candle wax melting when you light a candle the heat from the flame melts the wa the melted wax then drips down the candle creating a pool of liid liquid wa that fuels the flame soil and Thena heat no it will turn again into a solid form now form or IM mold again into a new shape so definitely you're just going to hit it up no and then um for example molding uh cup or molding tray no or molding rubber or what do you call that and then lamig na it will become candle again okay so let's have real life applications of melting cooking melting is used in cooking to transform solid ingredients into liquid for example butter is melted before adding it to cake butter or melted cheese is used as a topping of four Naturals making popsicles melting is involved in making popsicles you pour liquid juice or flavored water into the molds and then freeze them when you take them out of the freezer and let them sit the popsicle starts to melt turning back into liquid another thing is recycling melting is used to recycle metals like aluminum and steel scrap metal is melted down at high temperatures to make new products like aluminum cans or steel beams instead of throwing it away and another one would be art and crafts melting can be used in art and craft projects for example crayons can be melted and poured into mold to make new crayons with different shapes or color understanding miling helps us understand how things change from solid to liquid when they get warm this process is useful in our daily lives whether we're cooking playing or even recycling now let's have evaporation so what is evaporation evaporation is when the liquid turns into gas no so Kina melting we have solid to liquid now we have here evaporation wherein liquid turns into gas this happens when the liquid gets warm enough so again apply heat and its molecules move so fast that they escaped into the air as Vapor you can think of it like tiny invisible water particles flying away from a bottle a cup of water or even wet clothes when they're left out to dry we have examples [Music] of for real life applications we have swimming pool evaporation we also have drying wet surfaces water cycle no uh we all know that evaporation is a crucial part of the water cycle when the sun heats up bodies of water like oceans rivers and lakes water evaporates into the air this water vapor Rises cools down and forms clouds later when the clouds get heavy with water it falls back to the ground as rain snow or hail we also have uh making salt no evaporation is also important in uh producing salt okay ever heard of sea salt is made by evaporating sea water when sea water is left out in the sun the water evaporates living behind salt crystals these crystals are collected and cleaned to make the salt we use use in cooking now understanding evaporation helps us know how water moves from one place to another changes form and even helps make some of the things we use every day so again uh uh we started with melting from solid to liquid and then evaporation liquid to gas now the next one is freezing okay so what is freezing freezing occurs when liquid turns into solid so from liquid state now it becomes solid by means of freezing so when it gets cold enough imagine water turning into ice when it's left in the freezer or outside on a cold winter day the cold slows down the molecules in the liquid making them stick together and form a solid so remember after we heated an ice cube or we left the Ice Cube Under the Sun so it melted right so from solid it becomes liquid now no okay now eventually uh uh this liquid will now turn into solid again so like butter or for example you fat for example M fat content bid right water liid fat but then now orid uh fat no coming from the beef no so parang ganun now uh that is when liquid turns into solid so once or environment we have examples of freezing making ice cubes melting ice making ice cubes one common example of freezing is making ice cubes you pour water into an ice cube tray and put it in the freezer the water freezes and turns into solid ice cubes as the water gets cold so same thing with freezing popsicles and ice cream no so have you ever seen an ice cream machine at an ice cream shop it works by freezing a mixture of cream sugar and flavors while steering it this makes creamy ice cream that you can enjoy on a hot day so for real life application we have preserving food so it is very important no a freezing is one way of preserving food and it keeps or it helps keep the food fresh for longer periods of time like fish and meat you can freeze fruits vegetables meat and leftovers to prevent them from spoiling this way you can enjoy your favorite foods even if you can't eat them right away so for example mama and papa they go to market on weekends anden that day so they will go to market to buy food good for one week for example and for the rest of the week I they will store it first in a freezer para fresh p on the next day or the day so that is um one of the examples of freezing so keeping cool transporting goods no in places where it's hard to keep fresh food like uh during long Journeys in remote areas so especially transport for example fish ocean s dag and then market so we need to apply um uh freezing no keep freshness fish then making Frozen treat so same thing like um you creating ice creams and popsicles understanding freezing helps us know how liquids can change into solids when they get cold and it's useful for keeping food fresh staying cool and making tasty treats no SOA freezing ice cream and it makes us cool no sometimes but of course not to the point all right so freezing is very important especially in preserving food now let's have some questions that I would like you to answer so what happened to the ice cubes when placed directly under the sun now what do you call this process no when you place Ice Cube Under the Sun it will melt now what do you call this process so again no for some solids apply heat it will turn into liquid and that process is called melting now what happened to the wet handkerchief when plac directly under the Sun so the wet handkerchief will dry and that process is called evaporation so evaporate you water from the wet handkerchief and evaporate you water dry dry handkerchief now what happened to the water inside the plastic bag after leaving in the freezer overnight so freeze no and the process is called freezing okay so let's have our day three and our day three on day three we're going to focus on chemical changes in matter now chemical changes in matter involved a change in the chemical composition of a substance resulting in the formation or one or more new substances no so uh physical change no outer appearance or appearance in size and shape but then when we talk about chemical change chemical composition substance and um resulting in forming a new or another substance chemical changes are usually irreversible when we see a reversible for example uh from solid liquid or gas State unlike physical change for example a while ago noid for example again no so and in uh chemical changes are usually irreversible and involve the breaking and forming of chemical bonds between atoms or molecules here are some of the characteristics of chemical change formation of new substances this is due to the breaking and forming of chemical bonds between atoms and molecules irreversibility the original substances cannot be restored through simple physical processes by means of physical or simple physical processes so uh if uh you need to reverse it no you need to apply some chemical processes complex into original state now change in properties this can in uh include alterations in color other taste and even the production of gas or precipitate okay for day four we're have are going to have our takeaways all right so for this uh activity you're going to create a graphic organizer on what you have learned in the lesson so just like the graphic organizer below so changes in materials we have physical and chemical change okay so it's the same for physical change we have melting solid to uh melting solid to liquid evaporation liquid to gas and freezing liquid to solid then for chemical change we have formation of charcoal rust formation production of smoke for of Ash and formation of bubbles which leads to formation of new materials so again these are some important uh terms that you need to remember for this lesson so for physical changes physical changes or alterations in the appearance or state of substance without changing its chemical compositions in other words the substance Remains the Same at the molecular level before and after the change physical change can involve changes in state solid liquid and gas and its shape size or face so now let's have again melting so this time you can now uh just read by yourself no uh it's just um again a while ago so this is just the summary of what we had a while ago so after melting no from solid to liquid we have the evaporation liquid to gas we also have and we also had freezing this time from liquid to solid [Music] we also discussed chemical changes okay we also have evidence of chemical change hey hey [Music] and for your assessment kindly read each question carefully and identify the letter of the correct answer he [Music] all right did you got the Perfect Score okay I hopefully so okay so uh here's some ice cream hey thank you for listening and sparing your 30 minutes with me and I hope you learn something new from our lesson for this week so this is teacher Isa I hope to be with you and I hope you'll be with me again for the next week so thank you and goodbye [Music]