IS MATTER AROUND US PURE
milk
salt
ghee
Are these pure substances
A pure substance consists of a single type of particle, in which all the constituent particles of that substance are the same in their chemical nature.
Pure substance cannot be separated by physical process into its chemical constituents.
pure substance
Mixture
Mixtures are constituted by more than one kind of pure form of matter.
Can be separated from its constituents by the physical process.
TYPES OF MIXTURES
Homogeneous mixtures Heterogeneous mixtures
Homogeneous mixtures
Homogeneous mixtures can be defined as the mixtures which process the same properties and combination through out their mass
examples alloys ,salt water, alcohol in water ,lemonade etc
Heterogeneous mixtures
Heterogeneous mixtures poses different properties and composition in various parts of a mixture
Contain physically distinct parts and have non-uniform compositions.
Examples; oil in water, naphthalene in water, salt and sugar
Activity 2.2
GROUP A
Few crystals of copper sulphate
GROUP B
spratula of copper sulphate
GROUP C
Chalk powder / Wheat
GROUP D
Milk
Activity 2.2
GROUP A
Few crystals of copper sulphate
GROUP B
spratula of copper sulphate
GROUP C
Chalk powder / Wheat
GROUP D
Milk
GROUP A
Few crystals of copper sulphate
GROUP B
spratula of copper sulphate
GROUP C
Chalk powder / Wheat
GROUP D
Milk
solution.
solution.
suspension.
colloidal solution
1. What is meant by a substance?
Answer
A pure substance consists of a single type of particles.
2. List the points of differences between homogeneous and heterogeneous mixtures.�Answer
Homogeneous mixture
-It has uniform composition.
-no visible boundaries of
separation.
-They consist only one phase
examples alloys ,salt water,
alcohol in water ,lemonade etc.�
Heterogeneous mixture
-It does not have uniform composition.
-shows variable boundaries of separation.
-They consist more than one phase. examples oil in water, naphthalene in water, salt and sugar
Solution
A solution is a homogeneous mixture of two or more substances.
solvent + solute = solution
Solvent
The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent.
Solute
The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.
Properties of a Solution
. A solution is a homogeneous mixture.
• The particles of a solution are smaller than 1 nm (10-9 metre) in diameter. So, they cannot be seen by naked eyes.
• Because of very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
• The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.
Concentration of a Solution
Concentration of a Solution
Un Saturated Saturated
Adding Salt in water
Concentration of a Solution
Saturated
At any particular temperature , a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution.
Un Saturated
If the amount of solute present in the solution is less than the saturation level, it is called an un saturated solution
CONCENTRATION OF A SOLUTION
The concentration of a solution is the amount (mass or volume) of solute present in a given amount (mass or volume) of solution.
(i) Mass by mass percentage of a solution
= Mass of solute ×100 /Mass of solution
(ii) Mass by volume percentage of a solution
= Mass of solute ×100 / Volume of solution
(iii) Volume by volume percentage of a solution
= Volume of solute ×100 / Volume of solution
Example 2.1 A solution contains 40 g of common salt in 320 g of water.
Calculate the concentration in terms of mass by mass percentage of the solution.
Solution:
Mass of solute (salt) = 40 g
Mass of solvent (water) = 320 g
We know,
Mass of solution = Mass of solute + Mass of solvent
= 40 g + 320 g = 360 g
Mass percentage of solution = Mass of solute ×100 /Mass of solution
= 40 ×100/360 =11.1%
Alloys: Alloys are mixtures of two or more metals or a metal and a non-metal and cannot be separated into their components by physical methods. But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition. For example, brass is a mixture of approximately 30% zinc and 70% copper.
SUSPENSION
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.
Properties of a Suspension
• Suspension is a heterogeneous mixture.
• The particles of a suspension can be seen by the naked eye.
• The particles of a suspension scatter a beam of light passing through it and make its path visible.
• The solute particles settle down when a suspension is left undisturbed.
COLLOIDAL SOLUTION
The particles of a colloid are uniformly spread throughout the solution. Due to the relatively smaller size of particles, as compared to that of a suspension, the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture.
TYNDALL EFFECT
TYNDALL EFFECT
This scattering of a beam of light is called the Tyndall effect.
Tyndall effect can also be observed when a fine beam of light enters a room through a small hole. This happens due to the scattering of light by the particles of dust and smoke in the air.
TYNDALL EFFECT
Solution Colloid
Properties of a Colloid
• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is too small to be individually seen with naked eyes.
• Colloids are big enough to scatter a beam of light passing through it and make its path visible.
• They do not settle down when left undisturbed, that is, a colloid is quite stable.
• They cannot be separated from the mixture by the process of filtration.
1. Differentiate between homogeneous and heterogeneous mixtures with examples.
Homogeneous mixture
-It has uniform composition.
-no visible boundaries of
separation.
-They consist only one phase
examples alloys ,salt water,
alcohol in water ,lemonade etc
Heterogeneous mixture
-It does not have uniform composition.
-shows variable boundaries of separation.
-They consist more than one phase.
examples oil in water, naphthalene in water, salt and sugar
2. How are sol, solution and suspension different from each other?
3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.�Answer: Mass of solute (sodium chloride) = 36 g�Mass of solvent (water) = 100 g�Mass of solution = Mass of solute + Mass of solvent� = 36 g + 100 g = 136 g
Physical change
A change in composition and no change in chemical nature of substance.
Eg ; ice into water, melting wax.
Chemical Change
Chemical change brings change in the chemical properties of matter.
Eg ; burning of coal, respiration ,photosynthesis.
1 Classify the following as chemical or physical changes:
Answer:
Types of Pure Substances
ELEMENTS COMPOUNDS
Metals
Non metals
metalloids
Metals properties:
• They have a lustre (shine).
• They have silvery-grey or golden-yellow colour.
• They conduct heat and electricity.
• They are ductile (can be drawn into wires).
• They are malleable (can be hammered into thin sheets).
• They are sonorous (make a ringing sound when hit).
Non-metal properties:
• They display a variety of colours.
• They are poor conductors of heat and electricity.
• They are not lustrous, sonorous or malleable.
Metalloids
Some elements have intermediate properties between those of metals and nonmetals, they are called metalloids; examples are boron, silicon, germanium, etc.
COMPOUNDS
A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.
Mixtures
1. Elements or compounds just mix together to form a mixture and no new compound is formed.
2. A mixture has a variable composition..
3, A mixture shows the properties of the constituent substances.
4. The constituents can be separated fairly easily by physical methods.
COMPOUNDS
1. Elements react to form new compounds.
2. The composition of each new substance is always fixed.
3. The new substance has totally different constituent substances. properties.
4. The constituents can be separated only by chemical or electrochemical Reactions.
Mixtures and Compounds Mixtures
Question 1. Which separation techniques will you apply for the separation of the following?�(a) Sodium chloride from its solution in water.�(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.�(c) Small pieces of metal in the engine oil of a car.�(d) Different pigments from an extract of flower petals.�(e) Butter from curd.�(f) Oil from water.�(g) Tea leaves from tea.�(h) Iron pins from sand.�(i) Wheat grains from husk.�(j) Fine mud particles suspended in water.�Answer: (a) Evaporation (b) Sublimation�(c) Filtration (d) Chromatography�(e) Centrifugation (f) Separating funnel�(g) Filtration (h) Magnetic separation�(i) Winnowing/ sedimentation (j) Decantation and filtration
Question 2. Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.�Answer:
1. Take a cup of water in a container as solvent and heat it.�2. Add sugar in it which is solute. Heat it till all sugar dissolves.�3. You get a solution of water and sugar.�4. Sugar is soluble in water completely.�5. Add half a tea-spoon of tea-leaves, it is insoluble in water.�6. Boil the content, add milk which is also soluble in water, boil again.�7. Filter the tea with the help of strainer, the tea collected in cup is filtrate and the tea leaves collected on the strainer is residue.
Question 3. Pragya tested the solubility of three different substances at different temperatures and collected, the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).�
a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?�(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to coo! at room temperature. What would she observe us the solution cools? Explain.�(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?�(d) What is the effect of change of temperature on the solubility of a salt?
Question 4. Explain the following giving examples:�(a) Saturated solution�(b) Pure substance�(c) Colloid�(d) Suspension�Answer: (a) Saturated solution: In a given solvent when no more solute can dissolve further at a given temperature is called saturated solution.�(b) Pure substance: A pure substance consists of a single type of particles. E.g., gold, silver.�(c) Colloid: A colloid is a solution in which the size of solute particles are bigger than that of true solution. These particles cannot be seen with our naked eyes, they are stable, e.g., ink, blood.�(d) Suspension: It is a heterogeneous mixture in which the solute particles are big enough to settle down, e.g., chalk-water, paints, etc.
Question 5. Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air. soil, vinegar, filtered tea.�Answer: Homogeneous: Soda water, vinegar, filtered tea.�Heterogeneous: Wood, air, soil.
Question 6. How would, you confirm that a colourless liquid given to you is pure water?�Answer: By finding the boiling point of a given colourless liquid. If the liquid boils at 100°C at atmospheric pressure, then it is pure water. This is because pure substances have fixed melting and boiling point.
Question 7. Which of the following materials fall in the category of a “pure substance”?�(a) Ice (b) Milk (c) Iron�(d) Hydrochloric acid (e) Calcium oxide (f) Mercury�(g) Back (h) Wood (i) Air.�Answer: Pure substances are: Ice, iron, hydrochloric acid, calcium oxide and mercury.
Question 8. Identify the solutions among the following mixtures.�(a) Soil (b) Sea water�(c) Air (d) Coal�(e) Soda water.�Answer: Solutions are: Sea water soda water and air.
Question 9. Which of the following will show “Tyndall effect”?�(a) Salt solution (b) Milk�(c) Copper sulphate solution (d) Starch solution.�Answer: Milk and starch solution.
Question 10. Classify the following into elements, compounds and mixtures.�(a) Sodium (b) Soil (c) Sugar solution�(d) Silver (e) Calcium carbonate (f) Tin�(g) Silicon (h) Coal (i) Air�(j) Soap (k) Methane (l) Carbon dioxide�(m) Blood�Answer: Elements – Compounds – Mixtures�Sodium – Calcium carbonate – Sugar solution�Silver – Methane – Soil�Tin – Carbon dioxide – Coal�Silicon – Soap – Air ,Blood
Question 11. Which of the following are chemical changes?�(a) Growth of a plant (b) Rusting of iron�(c) Mixing of iron filings and sand (d) Cooking of food�(e) Digestion of food (f) Freezing of water�(g) Burning of a candle.�Answer: Chemical changes are:�(a) Growth of a plant (b) Rusting of iron�(c) Cooking of food (d) Digestion of food�(e) Burning of a candle
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