Matter in Our Surroundings

Activity: 1.1

• Take a 100 mL beaker.
• Fill half the beaker with water and mark the level of water.
• Dissolve some salt/ sugar with the help of a glass rod.
• Observe any change in water level.
• What do you think has happened to the salt?
• Where does it disappear?
• Does the level of water change?

Solution:

(a) Salt is dissolved in water

(b) Particles of salt filled in the gaps between the particles of water.

(c) No, there is no change in level of water.

This activity shows that,

Matters are made of small particles. And there is space between these particles.

Activity: 1.2

• Take 2-3 crystals of potassium permanganate and dissolve them in 100 mL of water.
• Take out approximately 10 mL of this solution and put it into 90 mL of clear water.
• Take out 10 mL of this solution and put it into another 90 mL of clear water.
• Keep diluting the solution like this 5 to 8 times.
• Is the water still coloured ?

Solution:

Yes water is still colored.

This happens because matter is made of very small particles, which are spread in the water.

Activity: 1.3

• Put an unlit incense stick in a corner of your class.
• How close do you have to go near it so as to get its smell?
• Now light the incense stick. What happens?
• Do you get the smell sitting at a distance?
• Record your observations.

Solution :

One has to go very close to get the smell of the unlit incense stick.

After lighting the incense stick, smoke started to coming out of it.

Yes now, we can get smell of incense stick sitting at a distance.

This shows that,

Matters consist of small particles which are moving continuously. This means that particles of matter possess kinetic energy.

Smell of lighted incense stick diffuse with air present in air and reaches to us sitting at a distance.

Activity: 1.4

• Take two glasses/beakers filled with water.
• Put a drop of blue or red ink slowly and carefully along the sides of the first beaker and honey in the same way in the second beaker.
• Leave them undisturbed in your house or in a corner of the class.
• Record your observations.
• What do you observe immediately after adding the ink drop?
• What do you observe immediately after adding a drop of honey?
• How many hours or days does it take for the colour of ink to spread evenly throughout the water?

Solution :

Ink started mixing with water immediately after adding which is visible in the form of many thread like structures.

Honey slowly directed towards bottom of water.

It takes about one hour to spread colour of ink throughout the water.

This happens because

Ink has about equal or slightly higher density than that of water, so ink started immediately mixing with water, because particles of matters are moving continuously.

Density of honey is very high than that of water, so honey started to direct towards bottom.

Because particles of matters are continuously moving, thus after some time particles of ink and water get mixed with each other.

Activity: 1.5

• Drop a crystal of copper sulphate or potassium permanganate into a glass of hot water and another containing cold water. Do not stir the solution. Allow the crystals to settle at the bottom.
• What do you observe just above the solid crystal in the glass?
• What happens as time passes?
• What does this suggest about the particles of solid and liquid?
• Does the rate of mixing change with temperature? Why and how?

Solution :

Solid crystals starts mixing in the water in the form of thread like structures.

Coming of thread like structures in cold water is slower than that of in the hot water.

As time passes, crystal getting dissolved in water both hot and cold.

But it takes more time to get crystal dissolved in cold water than that of hot water.

This suggest that, matters are made up of tiny particles and these particles are in motion continuously.

Rate of mixing increases with increase in temperature. This is because of heat particles of matter gets more kinetic energy and they starts moving faster.

Activity: 1.6

• Play this game in the field? make four groups and form human chains as suggested:
• The first group should hold each other from the back and lock arms like Idu-Mishmi dancers (Figures given in book).
• The second group should hold hands to form a human chain.
• The third group should form a chain by touching each other with only their finger tips.
• Now, the fourth group of students should run around and try to break the three human chains one by one into as many small groups as possible.
• Which group was the easiest to break? Why?

Solution :

The fourth group of students was the easiest to break.

This is because students are not holding hands or bounded even with their finger tips.

This means that there was no bonding force present in forth group. And could be broken easily.

Activity: 1.7

• Take an iron nail, a piece of chalk and a rubber band.
• Try breaking them by hammering, cutting or stretching.
• In which of the above three substances do you think the particles are held together with greater force?

Solution :

Iron nail did not break, thus it particles of iron are held together with greater force.

Actitivy: 1.8

• Open a water tap, try breaking the stream of water with your fingers.
• Were you able to cut the stream of water?
• What could be the reason behind the stream of water remaining together?

Solution :

Now, we did not be able to cut the stream of water.

The reason behind the stream of water remaining together is that that particles of water are held together with force of attraction.

Activity: 1.9

• Collect the following articles? a pen, a book, a needle and a piece of wooden stick.
• Sketch the shape of the above articles in your notebook by moving a pencil around them.
• Do all these have a definite shape, distinct boundaries and a fixed volume?
• What happens if they are hammered, pulled or dropped?
• Are these capable of diffusing into each other?
• Try compressing them by applying force. Are you able to compress them?

Solution :

Yeas all these have a definite shape, distinct boundaries and a fixed volume.

Book is torn when pulled with strongly.

Pen and piece of wooden stick are broken when hammered.

None is capable of diffusing into each other.

None is compressible.

Activity: 1.10

• Collect the following:
  
• (a) water, cooking oil, milk, juice, a cold drink.
  
• (b) containers of different shapes. Put a 50 mL mark on these containers using a measuring cylinder from the laboratory.
  
• What will happen if these liquids are spilt on the floor?
  
• Measure 50 mL of any one liquid and transfer it into different containers one by one. Does the volume remain the same?
  
• Does the shape of the liquid remain the same ?
  
• When you pour the liquid from one container into another, does it flow easily?
  

Solution :

All the liquids flow after spilt on the floor.

Yes, volume remains same after transferring the liquid into different containers.

Liquid gets the shape of container.

Yes all liquids flow easily.

Activity: 1.11

• Take three 100 mL syringes and close their nozzles by rubber corks, as shown in Fig.1.4.
  
• Remove the pistons from all the syringes.
  
• Leaving one syringe untouched, fill water in the second and pieces of chalk in the third.
  
• Insert the pistons back into the syringes. You may apply some Vaseline on the pistons before inserting them into the syringes for their smooth movement.
  
• Now, try to compress the content by pushing the piston in each syringe.
  
• What do you observe? In which case was the piston easily pushed in?
  
• What do you infer from your observations?
  

Solution :

Syringe that left untouched is pushed easily.

This shows that, there was air in syringe left untouched, which is a gas and is compressible.

This shows, that

Gas is easily compressible while water (liquid) and solid (chalk) cannot be compressed, i.e. incompressible.

Activity: 1.12

• Take about 150 g of ice in a beaker and suspend a laboratory thermometer so that its bulb is in contact with the ice, as in Fig. 1.6.
  
• Start heating the beaker on a low flame.
  
• Note the temperature when the ice starts melting.
  
• Note the temperature when all the ice has converted into water.
  
• Record your observations for this conversion of solid to liquid state.
  
• Now, put a glass rod in the beaker and heat while stirring till the water starts boiling.
  
• Keep a careful eye on the thermometer reading till most of the water has vaporised.
  
• Record your observations for the conversion of water in the liquid state to the gaseous state.
  

Solution :

Temperature was `0^o\ C` when ice starts melting.

Temperature remained `0^o\ C` till all ice melted.

Temperature starts rising after melting of ice.

Temperature stopped rising after reaching at `100^oC`

Again temperature started rising after vaporization of all water.

This shows that supply of continuous heat while melting of ice is used in change of phase i.e. from solid to liquid.

And supply of continuous heat while vaporization of water is used in change of phase, i.e. from liquid to vapour of water.

Heat used in melting of ice is called Latent heat of Fusion.

And heat used in vaporization of water is called Latent heat of Vaporisation.

Activity: 1.13

• 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, as shown in Fig. 1.7.
  
• Now, heat slowly and observe.
  
• What do you infer from the above activity?
  

Solution:

After some time camphor or ammonium gets deposited on the inner surface of funnel.

This shows that camphor or ammonium chloride converted directly from solid to gas and from gas to solid.

This process is called sublimation.

A phenomenon or process in which matter is converted directly from solid to gas on heating and converted directly from gas to solid on cooling is called Sublimation.

Activity: 1.14

• 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 the evaporation process in the above cases.
  
• Repeat the above three steps of activity on a rainy day and record your observations.
  
• What do you infer about the effect of temperature, surface area and wind velocity (speed) on evaporation?
  

Solution :

Water kept in china dish near window evaporated in about half an hour.

While water kept in test tube took about one hour to get evaporated.

Water kept in china dish took more than one hour to get evaporated.

In rainy days, double time was taken to get water evaporated.

This activity shows that

Rate of evaporation increases with increase in surface are and wind speed and decreases with increase in humidity.