Mixtures Chemistry
Chemistry
3.1 Types of mixtures
Mixtures
03
Let us pay our attention to the composition of the air around us. Air is composed
of gases like nitrogen, oxygen, argon and carbon dioxide, water vapour, and very
small particles such as dust. So, you may understand that air is a mixture of several
substances.
Therefore, if some matter contains two or more substances, such matter is referred
to as mixtures. You have already learnt that elements and compounds are pure
substances. But, mixtures are not pure substances. Natural environment mostly
contains mixtures, not pure substances. Air, soil, sea water, river water and rocks
around us are examples. The things that we drink such as cool drinks, fruit drinks,
tea, coffee and food items such as ice cream, yoghurt and fruit salad are also
mixtures. Let us do the following activity to study more about the components of
a mixture.
Activity 3.1.1
Materials required; - Hydrated copper sulphate, naphthalene, (moth balls), mortar
and pestle
Method; - Take some copper sulphate and naphthalene (moth balls) into a mortar,
grind them together with the pestle into a powder and mix well. Transfer the
powder onto a piece of paper and observe.
At a glance, you may not be able to see two substances, copper sulphate and
naphthalene but, you have a mixture of the two. A blend of two or more pure
substances is called a mixture and individual substances that form the mixture are
known as components.
Activity 3.1.2
Materials required ;- Two beakers, a glass rod, a funnel, a filter paper, hand lens.
Method ;- Transfer the mixture made in activity 3.1.1 above into a small 100 ml
beaker, add about 50 ml of water to it and stir well. Then, place a filter paper in a
funnel, glass and filter this solution into another beaker. Allow the residues on the
filter paper to dry and observe with a hand lens. Observe the filtrate as well.
For free distribution 30
,Mixtures Chemistry
From this activity, you would have understood that the remains on the filter paper
is naphthalene powder. Since the solution is blue in colour, the substance that
dissolved in water is copper sulphate.
The above activity clarifies another feature of a mixture. That is, even when the
components are in a state of being mixed, their chemical nature remains unchanged.
In other words, the identity of the components constituting a mixture does not change
even in the mixture. Moreover, the above activity shows that the components in a
mixture can be separated by physical methods.
How the components in a mixture can be separated by physical methods will be
discussed under the sub unit 6.3.
Thus mixtures can be defined as follows: Mixtures are matter consisting of two
or more components which are not chemically combined, and can be separated
by physical methods.
Table 3.11 shows the components of some commonly known mixtures.
Table 3.1.1
Mixture Components
Cement mortar Sand, cement, water
Cake Sugar, flour, water, colouring, butter
Well water Water, dissolved oxygen, dissolved carbondioxide
and various salts.
Sea water Water dissolved oxygen and salts such as sodium
chloride, magnesium chloride, magnesium sulphate,
calcium sulphate
When considering mixtures, it is very important that how well the components are
mixed. Understand this thoroughly with the help of the following examples.
Ex:- 1. When making colours by mixing paints, application of the paint will not
give a uniform colour unless they are mixed well.
2. If the components used to make cake are not mixed well, different parts of
the cake taste differently. Also, the rising will be different in different parts.
3. The medicinal property of tablets, capsules or liquid mixtures is not even in
all the parts if the components are not mixed well when producing medicines.
Investigate into more instances like the above examples.
Let us do activities 3.1.3 and 3.1.4 to study how the components are distributed in
a mixture.
31 For free distribution
,Mixtures Chemistry
Activity 3.1.3
Materials required ;- A beaker, clay, water, a piece of cloth
Method ;-
(i) Take about 500 ml of water into a beaker. Add about
10g of clayey soil to it, stir well and allow to stand still for
about one minute. Then filter the muddy coloured water
into another beaker using a piece of cloth. Allow to stand
still for about an hour and see whether the muddy colour Water containing
clay
is uniformly distributed throughout the solution. See if the
Figure 3.1.1
clearness of the solution is similar from top to bottom.
metal plate
A B
(ii) Take a piece of a metal sheet with a lustrous
A
surface. As shown in figure 3.1.2, take two
B
identical drops of the solution from two
places A and B with a pipette or glass rod,
place them on the spots marked as A and B
respectively, on the piece of metal and let
Figure 3.1.2 them vaporize. Check to see which water
sample contains more residual matter, See,
water obtained from which place contains
more residual matter.
The above activity leads to the following conclusions. In the mixture formed by
dissolving clay in water,
²² The colour/transparency is different from place to place.
²² The amount of clay particles in a unit volume is different from place to place.
Activity 3.1.4
Materials required ;- A beaker, water, common salt, a piece of cloth
Method ;- Take about 250 ml of water into a beaker add about 10 g of pure salt
into it, stir till the salt dissolves and filter the solution with a piece of cloth. Allow
to stand still for about one hour and see whether the clearness of the solution is
equal from top to bottom. Repeat what you did in activity 3.1.2 for this solution
as well.
For free distribution 32
, Mixtures Chemistry
Following conclusions can be drawn from the above activity. In the mixture formed
by dissolving salt in water,
²² The transparency is equal throughout the solution.
²² The amount of salt particles in a unit volume of the solution is equal throughout
the solution.
Pay your attention again to the mixtures you studied in activities 3.1.3 and 3.1.4.
According to the nature of the distribution of components, mixtures can be divided
into two categories.
²² Mixtures in which the composition of the components is uniform throughout
the mixture.
Ex: mixture prepared by dissolving common salt in water.
²² Mixtures in which the composition of the components is not uniform throughout
the mixture.
Ex: mixture prepared by dissolving clay in water
The mixtures in which the components are separated from one another are called
heterogeneous mixtures. The mixtures whose composition of the components are
uniformly distributed throughout are known as homogenous mixtures.
Homogeneous mixtures
The mixtures in which the components cannot be observed separately from one
another and the properties and composition are similar throughout are termed
homogenous mixtures. In a homogeneous mixture, the physical properties such as
colour, transparency and density are identical everywhere. Homogenous mixtures
are also known as solutions.
Examples: salt solution, sugar solution
Heterogeneous mixtures
The mixtures in which the components can be distinguished from one another
and their are known as a heterogeneous mixtures. The physical properties of the
mixture such as colour, transparency and density are different from place to place,
in a heterogeneous solution.
Examples: Water in which clay is dissolved, water in which laundry blue
(the powder used for whitening of clothes) is dissolved, cement mortar, sherbet
drinks, fruit salad
33 For free distribution
Chemistry
3.1 Types of mixtures
Mixtures
03
Let us pay our attention to the composition of the air around us. Air is composed
of gases like nitrogen, oxygen, argon and carbon dioxide, water vapour, and very
small particles such as dust. So, you may understand that air is a mixture of several
substances.
Therefore, if some matter contains two or more substances, such matter is referred
to as mixtures. You have already learnt that elements and compounds are pure
substances. But, mixtures are not pure substances. Natural environment mostly
contains mixtures, not pure substances. Air, soil, sea water, river water and rocks
around us are examples. The things that we drink such as cool drinks, fruit drinks,
tea, coffee and food items such as ice cream, yoghurt and fruit salad are also
mixtures. Let us do the following activity to study more about the components of
a mixture.
Activity 3.1.1
Materials required; - Hydrated copper sulphate, naphthalene, (moth balls), mortar
and pestle
Method; - Take some copper sulphate and naphthalene (moth balls) into a mortar,
grind them together with the pestle into a powder and mix well. Transfer the
powder onto a piece of paper and observe.
At a glance, you may not be able to see two substances, copper sulphate and
naphthalene but, you have a mixture of the two. A blend of two or more pure
substances is called a mixture and individual substances that form the mixture are
known as components.
Activity 3.1.2
Materials required ;- Two beakers, a glass rod, a funnel, a filter paper, hand lens.
Method ;- Transfer the mixture made in activity 3.1.1 above into a small 100 ml
beaker, add about 50 ml of water to it and stir well. Then, place a filter paper in a
funnel, glass and filter this solution into another beaker. Allow the residues on the
filter paper to dry and observe with a hand lens. Observe the filtrate as well.
For free distribution 30
,Mixtures Chemistry
From this activity, you would have understood that the remains on the filter paper
is naphthalene powder. Since the solution is blue in colour, the substance that
dissolved in water is copper sulphate.
The above activity clarifies another feature of a mixture. That is, even when the
components are in a state of being mixed, their chemical nature remains unchanged.
In other words, the identity of the components constituting a mixture does not change
even in the mixture. Moreover, the above activity shows that the components in a
mixture can be separated by physical methods.
How the components in a mixture can be separated by physical methods will be
discussed under the sub unit 6.3.
Thus mixtures can be defined as follows: Mixtures are matter consisting of two
or more components which are not chemically combined, and can be separated
by physical methods.
Table 3.11 shows the components of some commonly known mixtures.
Table 3.1.1
Mixture Components
Cement mortar Sand, cement, water
Cake Sugar, flour, water, colouring, butter
Well water Water, dissolved oxygen, dissolved carbondioxide
and various salts.
Sea water Water dissolved oxygen and salts such as sodium
chloride, magnesium chloride, magnesium sulphate,
calcium sulphate
When considering mixtures, it is very important that how well the components are
mixed. Understand this thoroughly with the help of the following examples.
Ex:- 1. When making colours by mixing paints, application of the paint will not
give a uniform colour unless they are mixed well.
2. If the components used to make cake are not mixed well, different parts of
the cake taste differently. Also, the rising will be different in different parts.
3. The medicinal property of tablets, capsules or liquid mixtures is not even in
all the parts if the components are not mixed well when producing medicines.
Investigate into more instances like the above examples.
Let us do activities 3.1.3 and 3.1.4 to study how the components are distributed in
a mixture.
31 For free distribution
,Mixtures Chemistry
Activity 3.1.3
Materials required ;- A beaker, clay, water, a piece of cloth
Method ;-
(i) Take about 500 ml of water into a beaker. Add about
10g of clayey soil to it, stir well and allow to stand still for
about one minute. Then filter the muddy coloured water
into another beaker using a piece of cloth. Allow to stand
still for about an hour and see whether the muddy colour Water containing
clay
is uniformly distributed throughout the solution. See if the
Figure 3.1.1
clearness of the solution is similar from top to bottom.
metal plate
A B
(ii) Take a piece of a metal sheet with a lustrous
A
surface. As shown in figure 3.1.2, take two
B
identical drops of the solution from two
places A and B with a pipette or glass rod,
place them on the spots marked as A and B
respectively, on the piece of metal and let
Figure 3.1.2 them vaporize. Check to see which water
sample contains more residual matter, See,
water obtained from which place contains
more residual matter.
The above activity leads to the following conclusions. In the mixture formed by
dissolving clay in water,
²² The colour/transparency is different from place to place.
²² The amount of clay particles in a unit volume is different from place to place.
Activity 3.1.4
Materials required ;- A beaker, water, common salt, a piece of cloth
Method ;- Take about 250 ml of water into a beaker add about 10 g of pure salt
into it, stir till the salt dissolves and filter the solution with a piece of cloth. Allow
to stand still for about one hour and see whether the clearness of the solution is
equal from top to bottom. Repeat what you did in activity 3.1.2 for this solution
as well.
For free distribution 32
, Mixtures Chemistry
Following conclusions can be drawn from the above activity. In the mixture formed
by dissolving salt in water,
²² The transparency is equal throughout the solution.
²² The amount of salt particles in a unit volume of the solution is equal throughout
the solution.
Pay your attention again to the mixtures you studied in activities 3.1.3 and 3.1.4.
According to the nature of the distribution of components, mixtures can be divided
into two categories.
²² Mixtures in which the composition of the components is uniform throughout
the mixture.
Ex: mixture prepared by dissolving common salt in water.
²² Mixtures in which the composition of the components is not uniform throughout
the mixture.
Ex: mixture prepared by dissolving clay in water
The mixtures in which the components are separated from one another are called
heterogeneous mixtures. The mixtures whose composition of the components are
uniformly distributed throughout are known as homogenous mixtures.
Homogeneous mixtures
The mixtures in which the components cannot be observed separately from one
another and the properties and composition are similar throughout are termed
homogenous mixtures. In a homogeneous mixture, the physical properties such as
colour, transparency and density are identical everywhere. Homogenous mixtures
are also known as solutions.
Examples: salt solution, sugar solution
Heterogeneous mixtures
The mixtures in which the components can be distinguished from one another
and their are known as a heterogeneous mixtures. The physical properties of the
mixture such as colour, transparency and density are different from place to place,
in a heterogeneous solution.
Examples: Water in which clay is dissolved, water in which laundry blue
(the powder used for whitening of clothes) is dissolved, cement mortar, sherbet
drinks, fruit salad
33 For free distribution
