hey everyone welcome back to another video So today we're going be doing unit one of chemistry we'll be reviewing the unit through questions so you know I thought you could you know you could make those content reviews um but for just chemistry at the regions level there is a lot of fluff um and things you need to know for the regions um is sometimes just really dumbed down so to make it less overwhelming and more consumable I feel like the practice questions really get to the point um so that's why I think it that's what I'm going to be doing for these types of videos but yeah let's get in to the question so base your answers to the following question on the diagram of a molecule of nitrogen shown below so they just gave us this little diagram here of two circles connected together uh draw a particle diagram that shows at least six molecules of nitrogen gas um so for that we can just draw these um molecules together and you want them relatively far apart in spread out let's just pretend those two are connected it's kind of hard to draw these molecules with my mouse 1 2 3 4 5 um they won't be in a straight line like this cuz that's actually scientifically wrong um that you want them all spread out and stuff but you can also add arrows just to show that they are you know just random movement very IC uh B says draw a particle model that shows at least six molecules of liquid nitrogen so liquid nitrogen we're going to want them at least I will draw them in a container and they will be sort of like together right so they're going to be stuck not stuck together entirely but very very close to each other um and this will get a little messy but it's five and six all right those are some horrible drawings but I think you get the point um so let's move on to the next question base your answers to question two through five so these ones right here um on the information below and on your knowledge of chemistry a student prepares two 141 G mixtures A and B each mixture consists of nh4 nh4 Cl sand h2o at 15° cius both mixtures are thoroughly stirred and allowed to stand the mass of each component uh used to make the mixtures is listed in the data table blow I'm going to start typing my answers because I'm sick of drawing with my mouse the first question says describe one property of sand that would enable the student to separate the sand from the other components in mixture B um so when I hear sand I think filtration and you have your other components with the h 2 and nh4cl um and they're allowed to stand so yeah we can definitely uh talk about filtration here and the thing that makes filtration work is their different types of particle size um we can also talk about just solubility um if you were to use distillation but I'll just say particle size let me type particle size of the sand varies number three says determine the temperature which all of the nh4cl in mixture a dissolves to form a saturated solution so for this question you're going to want to have your reference table and let's see if I can find the table so if you go to table G uh find nh4 CL and then we want to dissolve what is this for mixture a so make sure a there's 40 gr of nh4cl so we just look on the right uh left side at 40 G lining up to the nh4 CL we can see it's in between 20 and 30 uh at the temperature so we can just say it's around 25° C which type of mixture is mixture B so mixture B here has 10 G of nh4cl 31 G of sand and 100 G of water um so it's either homogenous or heterogenous and this one one is heterogenous I don't think I spelled that right um but it's heterogenous because it is not the uniform distribution of molecules right because sand has a different density than water uh has a different density than nh4cl it's not going to be an equal distribution versus let's say we had like salt water that salt is going to evenly um dissolve in that water and when you draw the particle diagrams you can see that um number five says State evidence from the table indicating the proportion of the components in a mixture can vary so that was basically my explanation before um but we can say that there are different amounts of um you to mixture can vary okay so there are different amounts of nh4 Cl um and sand in each of the mixtures um so we can see that in mixture a we have 40 G of NH nh4cl versus mixture B we had 10 G um and then since they are the same 141 G in total the sand is going to have to vary based on that let's move on so based your answers um to this paragraph right here a few pieces of dry ice CO2 solid that's kind of important to know it's solid because it's dry ice at -78° C are placed in a flask that contains Air at 21° uh Celsius the flask is sealed by placing an uninflated balloon over the mouth of the flask as the balloon inflates the dry ice disappears and there's no liquid observed in the flask all right write the name of the process that occurs as dry ice under go a phase change in the flask so we know it starts as a solid I'll just write let's just write this to the side so it starts from a solid it says no liquid is observed and the balloon inflates so can you guess it goes from a solid to a gas um because you know the balloon is inflated by gas um so you're just going to have to know this solid to gas directly is called sublimation all right number seven State the direction of heat flow that occures between dry eyes uh in the air and the flow so heat flow this is another rule you need to know heat flows from high to low so we just look at which one had the higher heat to start with so the air was at 21° C CO2 dry ice was -78° C so the direction of heat flow is from the air to the dry ice all right let's move on uh final three questions here so student investigated the heat transfer using a bottle of water the student placed bottle in a room at 20.5 de C the stud student measured the the temperature of the water in the bottle at 7:00 a.m. and again at 3:00 p.m. the data from the investigation uh is shown in the table below so we can see that the mass of water didn't change so nothing really evaporated or anything um but the temperature did change there's a increase of 10° C uh let's see what the question asks here show a numerical set for calculating the change in thermal energy of the water in the bottle between 7:00 a.m. and 300 p.m. all right so we need to know um let's just write our equation it doesn't say to but it's always helpful so the change in energy is equivalent to mass times the specific heat heat capacity of our substance uh or in this case water and then we multiply this by the change in temperature uh so we don't need to calculate the actual value just uh the numerical calculation so Mass we know is 800 G cuz that's just constant and between um and I don't even think you need units here really so we just write this times the specific heat of water which is represented by C that is 4.18 and then the change in temperature like we said before is 10° C let's see what number n is saying so it says State the direction of heat transfer up between the surroundings and the water in the bottle between 7 a.m. and 300 p.m. so the water increased uh in temperature and therefore that means the heat must have come from the air so the heat um so the heat transfers from air to water all right um oh not from the air we can just say the surroundings because maybe it was something else uh oops I spell surroundings wrong compare the average kinetic energy of the water molecule in the bottle at 7 7 a.m. to the average kinetic energy of the water molecules in the bottle at 3 p.m. so what is average kinetic energy that is the exact definition of temperature so if you have a increased temperature that means you'll have a increased average kinetic energy so 3 P.M equals why am I still ready I'm just going to say 3 P.M has the um more average kinetic energy then and 7 a.m. yeah that uh concludes the unit one review for chemistry if you guys learned something make 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