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Matter in Our Surroundings
ACTIVITY 1
Objective
To prove that matter is made up of tiny particles (and have intermolecular space).
Materials Required
Beaker, water, salt or sugar, glass rod and marker.
Procedure
- Take a 100 mL beaker half-filled with water and mark the initial water level with the help of a marker.
- Then, add a teaspoonful of sugar (or salt) into it and stir with the help of the glass rod.
- Mark the water level after the disappearance of the solute.
Observation
Water level does not change.
Explanation
Matter is not continuous and is particulate in nature, i.e. it is made up of particles. When salt is dissolve in water then water level does not change. It indicates that there are some vacant spaces among the particles of water. These are known as interparticle spaces. The particles of salt have occupied some of them.
Conclusion
Matter is made up of tiny particles and intermolecular spaces are present in between them.
1. What happens to the sugar when it is dissolved in
water? CCE 2013 Ans When sugar is dissolved in water, its crystals separate into very fine particles.
2. Where does the sugar go?
Ans The sugar particles go into the spaces present between the particles of water and mix with them to form sugar solution.
3. Is there any change in water level after dissolving sugar/
salt in it? Ans There is no change in water level after dissolving sugar/salt in it.
4. What information do you get about the nature of
matter from the dissolution of sugar in water? Ans The dissolution of sugar in water shows that ( i ) the matter (sugar and water) is made up of small particles. ( ii ) the particles of matter (water) have spaces between them.
ACTIVITY 2
Objective
To prove that particles of matter :
- are very small in size (particulate in nature).
- move(diffuse) faster in gaseous state as compared to solid or liquid states.
- diffuse at a slower rate, if density is more.
- diffuse faster at a higher temperature.
Materials Required
Potassium permanganate, water, beakers, perfume, blue ink, honey and copper sulphate.
Observation Table
1
ACTIVITY ZONE
Stir Salt Salt
Add salt Particles of water magnified millions of times
Water Water Water
When we dissolve salt in water, the particles of salt get into the spaces between particles of water
Check Yourself
Step Experiment Observation Inference
- ( i ) Take 100 mL of water in a beaker and add 2- crystals of potassium permanganate into it.
The colour of the solution is quite dark. ( ii ) Transfer 10 mL of the above solution in another beaker and add 90 mL of clear water into it.
The colour becomes lighter in the second beaker.
After too much dilution, a slight shade of colour still remains in the solution.
( iii ) Repeat the above step thrice, i.e. dilute the solution as above.
The colour of the solution becomes lighter each time.
It shows that particles are too much small in size.
1. What conclusion can you draw after adding 2-3 crystals
of KMnO 4 in water? Ans After the addition of 2-3 crystals of KMnO 4 in water, it is concluded that a crystal of KMnO 4 is made up of millions of tiny particles. They keep dividing themselves into smaller particles.
2. When someone opens a bottle of perfume in one
corner of a room, its smell spreads in the whole room quickly. Why? Ans This happens because the particles of perfume (gas) move rapidly in all the directions and mix with the moving particles of air in the room. They do so by getting into the spaces between the air particles.
3. Why honey in step 3 dissolves at a slower rate?
CCE 2013
Ans In step 3, honey dissolves at a slower rate because it is more viscous i.e. has more density and has strong intermolecular forces of attraction.
4. From step 4, write the effect of temperature on
diffusion. Ans Diffusion becomes faster at a higher temperature.
5. Rate of diffusion is faster in gases, why? CCE 2014, 12
Ans The molecules of gases have large intermolecular space between them and have higher speed. So they diffuse faster.
ACTIVITY 3
Objective
To study the properties of solid and liquid.
Materials Required
Pencil, book, needle, thread, paper, hammer, some liquids (e.g. water, oil, milk etc), containers of different shapes and same volume.
Procedure
- Take a book, needle and a piece of thread. Draw their sketch on a paper with the help of a pencil. Observe their shapes and judge their volume. Now pull, drop and hammer these things one by one and record your observations.
- Take some liquids (50 mL each) and pour them in the containers of different shapes. Put a 50 mL mark on these containers using a measuring cylinder from the laboratory.
Observe the shapes of each liquid in each container.When a 50 mL of liquid is poured in another container, does its volume change?
Observation
- All these things (book, needle and thread) have sharp boundaries, i.e. definite shape and definite volume. When pulled, dropped or hammered, these things remain unaffected or do not break.
- Volume of the liquids remains the same but its shape depends upon the shape of the container.
Conclusion
Solids have definite shape and definite volume. Solids are hard and rigid and held together with greater force.
(^2) SCIENCE Class 9th Term I
Water level mark
Beaker
Water
Glass tumbler
Conical flask
Flat bottomed flask
( ) a ( ) b
( ) c ( ) d Water in different shapes of the container
Check Yourself
Step Experiment Observation Inference
- ( i ) Take a bottle of perfume. Smell it when it is closed.
No smell is obtained.
( ii ) Spray some perfume after opening the bottle. A strong smell is obtained. Particles of perfume reach in the gaseous state and diffuse fastly in air.
- Take equal amount of water in two beakers. Add a drop of blue ink in the first and a drop of honey in the second. Do not stir and keep these beakers undisturbed for a few hours.
Ink diffuses in water and the solution becomes blue in first beaker in a short time, but it takes a longer time to diffuse honey in the second beaker.
As the density of ink is less than that of honey, hence the rate of diffusion (movement of particles) is faster in the former case than in the latter.
- Dissolve a crystal of copper sulphate in two beakers- one containing hot water and other the cold water. Do not stir the solution.
The rate of dissolution is faster in hot water than in the cold water.
Higher is the temperature, faster is the movement of particles of matter.
- Note the temperature when most of the water vaporised.
Observation
- There is no change in temperature till all the ice melts though heating continues.
- Temperature remains constant at 0°C. Once the ice is converted to water, the temperature starts rising till the water begins to boil. Once the water starts boiling, the temperature remains constant at 100°C till all the water has changed to vapours.
Conclusion
During the change of state from solid to liquid or from liquid to gas, the temperature remains constant till all the solid has melted or all the liquid has vaporised. The heat energy supplied is used up in overcoming the forces of attraction and hence, the thermometer does not show any rise in temperature.
1. What is the change in temperature during this activity?
Ans The temperature remains constant during the complete melting and boiling process.
2. Is melting exothermic or endothermic process?
Ans Melting is an endothermic process because heat is absorbed during this process.
3. Under which condition, we can boil water at room
temperature? Ans We can boil water at room temperature under low pressure.
4. Draw temperature-time graph for the heating of ice.
Ans Graph of temperature - time for the heating of ice is given below:
5. In an experiment for studying the effect of heating on ice,
why do we use crushed ice? Ans Crushed ice will cover the thermometer bulb intimately and thus, would give correct temperature.
6. What do we call the temperature at which liquid starts
boiling? Ans The temperature at which liquid starts boiling is called its boiling point.
7. What would be the temperature when water starts
boiling? Ans As the water starts boiling, the temperature will be 100° C or 373K.
8. What is the temperature when all the water has boiled?
Ans The temperature remains constant, i.e. 100°C during the complete boiling process.
ACTIVITY 6
Objective
To study the process of sublimation.
Materials Required
Camphor or ammonium chloride, China dish, funnel, cotton plug and burner.
Procedure
- Take some camphor or ammonium chloride. Crush it and put it in a China dish.
- Put an inverted funnel over the China dish.
- Put a cotton plug on the stem of the funnel and set the apparatus as shown in figure.
Observation
Solid ammonium chloride changes into vapours without changing into liquid state and get condensed on the walls of the funnel.
(^4) SCIENCE Class 9th Term I
Check Yourself
Thermometer Glass stirrer
Beaker Ice
Burner
( ) a
Iron stand Iron stand
Burner
Water
Beaker
Glass stirrer
Thermometer
( ) b
A B
C D
Melting of ice is complete here
Water starts boiling here
Whole water gets vaporised at this point
Temperature/°C
Time
0
25
100
50
75
Cotton plug
Inverted glass funnel Vapours of ammonium chloride China dish
Wire gauze
Burner Tripod stand
Ammonium chloride
Ammonium chloride (Sublimate)
Sublimation of ammonium chloride
Matter in Our Surroundings
Conclusion
A change of state directly from solid to gas without changing into liquid state or vice-versa is called sublimation.
1. In an experimental set up for sublimation, a perforated
asbestos sheet is placed between the China dish and funnel. What is its purpose? Ans The asbestos sheet prevents direct heating of funnel.
2. What happens when solid ammonium chloride is heated?
Ans On heating, solid ammonium chloride changes into vapours without changing into liquid state and get condensed on the walls of the funnel.
3. Name the solid substance which is obtained by cooling the
vapour. Ans The solid substance obtained by cooling the vapour is known as sublimate.
4. Which substance is sublimate in this activity?
Ans Sublimate is pure ammonium chloride.
ACTIVITY 7
Objective
To study the factors which affect evaporation.
Materials Required
Test tubes, water, jar, China dish, thermometer and cupboard.
Procedure
- Take 5 mL of water in a test tube and keep it near a window or under a fan.
- Take 5 mL of water in an open China dish and keep it near a window or under a fan.
- Take 5 mL of water in an open China dish and keep it inside a cupboard or on a shelf in your class.
- Record the room temperature.
- Record the time or days taken for evaporation process in the above cases.
- Repeat the above three steps of activity on a rainy day and record your observations.
Observation
- In an open China dish kept near window or on a shelf, water evaporates very fast as compared to test tube.
- On sunny day, water evaporates very fast as compared to rainy day.
Conclusion
l (^) If surface area is increased, the rate of evaporation increases. l (^) If temperature is increased, the rate of evaporation increases because with the increase of temperature, more number of particles get enough kinetic energy to go into the vapour state. l (^) If wind speed is increased, the rate of evaporation increases because with the increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surroundings. l (^) If humidity is decreased, the rate of evaporation increases and vice-versa.
1. Why water evaporates faster in China dish as compared to
test tube? Ans China dish has more surface area as compared to test tube. So, the evaporation is faster in case of China dish.
2. Why evaporation is fast when water is kept under a fan?
Ans When water is kept under a fan, the rate of evaporation increases because with the increase in wind speed, the particles of water vapour move away with the wind.
3. What is the effect of humidity on evaporation?
Ans If humidity is decreased, the rate of evaporation increases and vice-versa.
4. What do you infer about the effect of temperature on
evaporation? Ans If temperature is increased, the rate of evaporation increases.
5. Why evaporation is slow on a rainy day?
Ans On a rainy day, humidity is increased, so rate of evaporation decreases.
5
Check Yourself
Check Yourself
