Selina solutions

Selina solutions

Grade 8

Physical Quantities and Measurement | Numericals

Question 11

Q11) The mass of an empty density bottle is 30 g, it is 75 g when filled completely with water and 65 g when filled completely with a liquid. Find:

(a) volume of density bottle

(b) density of liquid: and

(c) relative density of liquid.

  • Solution

  • Transcript

Solution:

Mass of empty density bottle, M1 = 30g

Mass of bottle + Water, M2 = 75g

Mass of liquid + bottle, M3 = 65g

Mass of water = M2-M1 = 75 - 30 = 45g

(a) Volume of density bottle = Mass of water = 45g

(b) Density of liquid x = ? \frac{Mass\ of\ liquid}{Mass\ of\ water}=\frac{35}{45}=0.77\ g\ cm^{-3}

Mass of liquid = M3 - M1 = 65 - 30 = 35g

(c) Mass of water in the density bottle = 75 - 30 = 45g

Mass of equal volume of liquid in density bottle 65-30 = 35g

Relative Density of liquid = \frac{mass\ of\ 45\ cc\ ofliquid}{mass\ of\ 45\ cc\ of\ water}=\frac{35}{45}=\frac{7}{9}=0.77\

"hello students welcome to Lido learning's question and answer videos so before seeing the question here let's just understand the concept of density bottle so what do we mean by a density bottle this is a picture over here as you can all see so it has a stopper and a hole in it now what is the purpose of this hole so when you fill in any liquid in this density bottle all the a liquid comes out of this hole as a result the density bottle will always measure same volume for any liquid which you fill inside it so suppose you fill in water in it if it measures 20 centimeter cube then for the minimum of alcohol if you fill it with alcohol that also will be 20 centimeter cube so the volume density bottle is used to measure volume of liquids right okay having learned this let's now go to the question here so we have the mass of an empty density bottle given as 30 grams so here we have measured mass of the empty density bottle it is 30 grams let's just write that down as well so mass of empty density bottle let's write that that as db is 30 grams next thing is it is 75 grams when completely filled with water as you can see water is filled in the density bottle now so obviously the mass will increase which is 75 grams so mass when of the density bottle plus water that is empty density bottle plus water is 75 grams so how much is the mass of the then let's just calculate that so mass of water over here is equal to 75 minus 30 which is equal to 45 grams so we have found out the mass of water let's just calculate the mass of the liquid as well so now we know the third picture as you can see over here mass of the liquid in the density bottle is 65 grams so density bottle empty plus liquid gives you 65 grams therefore mass of the liquid liquid m let's write it like that is 65 minus 30 this is 5 okay so this will give this will give us 35 grams so we have the mass of the liquid as 35 grams now having calculated this let's move to the questions so the first one says have to calculate volume of the density bottle now we all know the formula for density density is given as mass upon volume let's calculate for we all also know that the density of water density of water is how much in cgs incidence it is one gram per centimeter cube so let's apply this to the other formula so 1 is equal to now mass of water was 45 grams so it's 45 upon volume we don't know the volume yet let's cross multiply we get volume as 45 centimeter cube now this is the volume of this particular density bottle and as i told you the volume of water is 45 centimeter cube so the volume of the liquid will also be 45 centimeter cube so let's just write down the volume over here so water is 45 centimeter cube and the liquid will also be of the same volume because we are using the same density bottle so the bottle is measuring volume of the two liquids as 45 centimeter cube so the first part is clear that is the answer to this is 45 centimeter cube let's move to the next part of the question that is density of the liquid now we all know the formula for density is mass upon volume so for doing the part b we know mass of the liquid is equal to 35 grams right so it becomes 35 let's just write it a bit more neater so yes so the mass of the liquid will be 35 upon the volume is we have just now calculated it is 45 so when we just do the calculation it becomes 7 upon 9 or we may write it as 0.77 grams per centimeter cube so this is the answer for the density of the liquid that is 0.77 grams per centimeter q now let's move ahead to the third question and a very interesting question indeed so it gives relative density of a liquid we have to calculate the relative density now to find the relative density we should know what it means right so let's look at the definition for relative density relative density is the ratio of density of a substance to dense of the water so here we have relative density let's denote it as rd it will be equal to ratio of the density of a substance that is density of the liquid was 0.77 let's write down the units as well i'll tell you why we are writing this down now so upon the density of water so density of water is 1 gram per centimeter cube so the relative density comes out to be 0.77 now will i stop here or will i put some unit here we will not put any unit relative density has no unit why because it's a ratio firstly and secondly look at this the units will also cancel out so the answer to this one is 0.77 that's it so i hope this question was clear if you have any further doubts please post your comments below thank you"

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Question 11

Q11) The mass of an empty density bottle is 30 g, it is 75 g when filled completely with water and 65 g when filled completely with a liquid. Find:

(a) volume of density bottle

(b) density of liquid: and

(c) relative density of liquid.

  • Solution

  • Transcript

Solution:

Mass of empty density bottle, M1 = 30g

Mass of bottle + Water, M2 = 75g

Mass of liquid + bottle, M3 = 65g

Mass of water = M2-M1 = 75 - 30 = 45g

(a) Volume of density bottle = Mass of water = 45g

(b) Density of liquid x = ? \frac{Mass\ of\ liquid}{Mass\ of\ water}=\frac{35}{45}=0.77\ g\ cm^{-3}

Mass of liquid = M3 - M1 = 65 - 30 = 35g

(c) Mass of water in the density bottle = 75 - 30 = 45g

Mass of equal volume of liquid in density bottle 65-30 = 35g

Relative Density of liquid = \frac{mass\ of\ 45\ cc\ ofliquid}{mass\ of\ 45\ cc\ of\ water}=\frac{35}{45}=\frac{7}{9}=0.77\

"hello students welcome to Lido learning's question and answer videos so before seeing the question here let's just understand the concept of density bottle so what do we mean by a density bottle this is a picture over here as you can all see so it has a stopper and a hole in it now what is the purpose of this hole so when you fill in any liquid in this density bottle all the a liquid comes out of this hole as a result the density bottle will always measure same volume for any liquid which you fill inside it so suppose you fill in water in it if it measures 20 centimeter cube then for the minimum of alcohol if you fill it with alcohol that also will be 20 centimeter cube so the volume density bottle is used to measure volume of liquids right okay having learned this let's now go to the question here so we have the mass of an empty density bottle given as 30 grams so here we have measured mass of the empty density bottle it is 30 grams let's just write that down as well so mass of empty density bottle let's write that that as db is 30 grams next thing is it is 75 grams when completely filled with water as you can see water is filled in the density bottle now so obviously the mass will increase which is 75 grams so mass when of the density bottle plus water that is empty density bottle plus water is 75 grams so how much is the mass of the then let's just calculate that so mass of water over here is equal to 75 minus 30 which is equal to 45 grams so we have found out the mass of water let's just calculate the mass of the liquid as well so now we know the third picture as you can see over here mass of the liquid in the density bottle is 65 grams so density bottle empty plus liquid gives you 65 grams therefore mass of the liquid liquid m let's write it like that is 65 minus 30 this is 5 okay so this will give this will give us 35 grams so we have the mass of the liquid as 35 grams now having calculated this let's move to the questions so the first one says have to calculate volume of the density bottle now we all know the formula for density density is given as mass upon volume let's calculate for we all also know that the density of water density of water is how much in cgs incidence it is one gram per centimeter cube so let's apply this to the other formula so 1 is equal to now mass of water was 45 grams so it's 45 upon volume we don't know the volume yet let's cross multiply we get volume as 45 centimeter cube now this is the volume of this particular density bottle and as i told you the volume of water is 45 centimeter cube so the volume of the liquid will also be 45 centimeter cube so let's just write down the volume over here so water is 45 centimeter cube and the liquid will also be of the same volume because we are using the same density bottle so the bottle is measuring volume of the two liquids as 45 centimeter cube so the first part is clear that is the answer to this is 45 centimeter cube let's move to the next part of the question that is density of the liquid now we all know the formula for density is mass upon volume so for doing the part b we know mass of the liquid is equal to 35 grams right so it becomes 35 let's just write it a bit more neater so yes so the mass of the liquid will be 35 upon the volume is we have just now calculated it is 45 so when we just do the calculation it becomes 7 upon 9 or we may write it as 0.77 grams per centimeter cube so this is the answer for the density of the liquid that is 0.77 grams per centimeter q now let's move ahead to the third question and a very interesting question indeed so it gives relative density of a liquid we have to calculate the relative density now to find the relative density we should know what it means right so let's look at the definition for relative density relative density is the ratio of density of a substance to dense of the water so here we have relative density let's denote it as rd it will be equal to ratio of the density of a substance that is density of the liquid was 0.77 let's write down the units as well i'll tell you why we are writing this down now so upon the density of water so density of water is 1 gram per centimeter cube so the relative density comes out to be 0.77 now will i stop here or will i put some unit here we will not put any unit relative density has no unit why because it's a ratio firstly and secondly look at this the units will also cancel out so the answer to this one is 0.77 that's it so i hope this question was clear if you have any further doubts please post your comments below thank you"

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