Kerala Syllabus Class 6 Basic Science: Chapter 07 The World of Changes - Questions and Answers

Study Notes for Class 6th Basic Science - മാറ്റങ്ങളുടെ ലോകം | Text Books Solution Basic Science (English Medium) Chapter 07 The World of Changes. ഈ യൂണിറ്റിന്റെ Teachers Handbook ലിങ്ക് ഈ പേജിന്റെ അവസാന ഭാഗത്തു നൽകിയിട്ടുണ്ട്. പഠന സഹായികൾ അയക്കാൻ താല്പര്യമുള്ളവർ ഈ നമ്പറിൽ വാട്സാപ്പ് ചെയ്യുക: 9497346250. പുതിയ അപ്‌ഡേറ്റുകൾക്കായി ഞങ്ങളുടെ Telegram Channel ൽ ജോയിൻ ചെയ്യുക.

ഈ ബ്ലോഗ് അഡ്‌മിൻറെ രേഖാമൂലമുള്ള അനുമതിയില്ലാതെ ഈ ബ്ലോഗിൽ നൽകിയിരിക്കുന്ന ചോദ്യോത്തരങ്ങൾ, ഇതേരീതിയിലോ പി.ഡി.എഫ് രൂപത്തിലോ, മറ്റേതെങ്കിലും ഡിജിറ്റലോ, പ്രിന്റഡ് ഉൾപ്പെടെയുള്ള ഏതെങ്കിലും രൂപങ്ങളിലേക്കോ മാറ്റി മറ്റൊരു വെബ്സൈറ്റിലോ, ബ്ലോഗിലോ, യുട്യൂബ്, സോഷ്യൽ മീഡിയാ ഗ്രൂപ്പുകളിലോ ഉൾപ്പെടെ ഒരിടത്തും പ്രചരിപ്പിക്കാൻ പാടില്ലാത്തതാകുന്നു.

Std 6: Basic Science Chapter 07: The World of Changes - Questions and Answers
♦ Observe the pictures given below. What changes do you notice in each pair?
• Jaggery: crumbles
• Bean seed: Germinates
• Cloud: Transforms into rain

♦ Observe your surroundings and find more examples for similar changes. Write them in your Science Diary. 
• Mango : Ripens
• Water: Boiling
• Ice: Melting
• Iron: Rusting
• Leaves: Drying 
• Wet clothes: Drying
• Milk: Curdling
• Butter: Melting

♦ Observe some handicrafts made from wax and paper. 
Aren't you interested in making such handicrafts? Let’s do it.  
Materials Required: Colour clay, colour paper, chart paper, beads, scissors, sketch pen 
Using the materials provided, try to make the objects shown in the picture.
Display them in the class. 
What changes have occurred to each of the materials you used?
Colour clay: shape changes
Colour paper: shape changes
Chart paper: shape and colour changes

In the case of colour clay, was it the substance or its shape that changed?
Only the shape changes

♦ Examine the pictures given below. What change happens to the object in each situation? 
• Cutting watermelon into pieces
• Making chair using wood  
• Expanding plastic pipe by heating
• Glass bottle was broken into pieces

♦ Write the situations where nature and other living organisms make use of the change in the state of water. 
• Formation of rain
• Snowfall – Water vapour freezes into ice crystals and falls as snow.
• Dew – Water vapour condenses on cool surfaces like grass and leaves.
• Human sweating – Sweat evaporates from skin, cooling the body.
• Ice in polar regions – Freezing water forms ice
• Glaciers melting – Melting ice provides fresh water to rivers and streams.
• Fog formation – Tiny droplets of condensed water float near the ground, creating fog.

♦ When the state of water changes, is there any change in water as a substance? Aren't ice and water vapour the two other states of water? Complete the illustration.
♦ Candle is a solid. Cut a candle into small pieces. Now what change has
occurred to the wax? Isn’t the wax still in the same state?
The wax is still in the solid state. Only the shape and size of the wax changed.

♦ Take a small piece of wax in a spoon and heat it. What change has occurred to the state of the wax? 
The state of the wax changed. The wax changed into molten state. 

♦ Allow the molten wax to cool for a while. Now, what change has occurred in its state? 
The molten wax changed into solid wax.
♦ Aren’t the solid wax and the molten wax the same substance? Did the change in wax result in the formation of a new substance? Did it become a new substance on cooling? Tabulate your observations.
♦ Write an experiment to observe the changes of state of wax on heating.
• Materials Required: Wax, boiling tube, test tube holder, cotton, lamp
• Procedure: Take a piece of wax in the boiling tube and heat it using the lamp as shown in the picture. The mouth of the boiling tube should be closed with cotton. Observe it. Heat the molten wax again. 
Remove the boiling tube from the lamp and observe it after a short while.
Take out the cotton from the boiling tube and observe.
• Observation: 
• The solid wax in the boiling tube melts while heating.
• On further heating, the melted wax turns into vapour, and this wax vapour collects on the cotton placed at the mouth of the tube.
• When the boiling tube is allowed to cool, the liquid wax inside the tube turns back into solid state.
• The wax vapour stuck to the cotton turned into solid wax.
• Conclusion: By heating and cooling, only the state of wax changes. No new substance is formed.

♦ Based on the indicators given below, analyse the change that occurred in each situation. Arrive at a conclusion. 
Indicators
In the experiment you conducted
• What was the state of the wax before heating? 
Answer: Solid state

• What change occurred in its state when heated? 
Answer: When heated, the wax melted and turned into liquid form.

• To which state did it change on heating further? 
Answer: On heating further, the liquid wax turned into vapour.

• To which state did the vapourised wax change on cooling? 
Answer: On cooling the vapourised wax changed into liquid state and then to solid state.

• Did the wax turn into a new substance when its state changed?
Answer: No, the wax did not turn into a new substance when its state changed

• Is the change that occurred to the wax permanent or temporary?
Answer: The change that occurred to the wax is temporary

• Observe the illustration of the change that occurred to wax. Fill in the missing parts.

♦ Physical Change
• Changes in the physical properties of substances such as size, shape, and state are called physical changes. 
• Expanding, melting, breaking and tearing are physical changes. No new substances are formed due to these physical changes. 
• In some physical changes energy is either absorbed or released. 

♦ What do we do with broken and unusable plastic items at home?
• Making decorative items 
• Giving them to the Haritha Karma Sena (Green Action Force)
• Used for planting plants
• Used for collecting waste materials

♦ Recycling 
Plastic carry bags and other plastic items thrown around carelessly cause major environmental issues. Most of them can be recycled into new items. Metals like iron, brass and aluminium can also be recycled in this way.

♦ Reuse 
Many items that are no longer useful can be used for other purposes. This is reuse. 

♦ What can we do with plastic instead of burning or throwing it away to protect the environment?
When plastic burns, poisonous gases harmful to living organisms are produced. Reusing and recycling plastic, instead of throwing it away or burning is an act of nature conservation. 

♦ Find more examples of physical changes being used in life situations.
Situation Physical Change
Grinding riceSize decreases, becomes powdered
Tearing paperShape and size change
Cutting vegetablesSize and shape change, no new substance formed
Stretching a rubber bandShape changes, returns to original form when released
Breaking a chalk stickSize and shape change, no new substance formed
♦ Find more examples of permanent changes.
• Paper burning
• Wood burning
• Resting of iron
• Cooking food
• Baking a cake 
• Lighting a match 
• Formation of curd from milk 
♦ Write an experiment showing a permanent change.
Materials Required: Sugar, spoon, matchbox, candle, coconut leaf midrib,lamp 
Procedure: Take a little sugar in a spoon and heat it using the lamp. Observe the change in sugar. Take the molten sugar on a coconut leaf midrib and taste it. heat it again. observe the colour change. After cooling, take this substance on another coconut leaf midrib and taste it. Heat it again until it turns black. Take this substance on another coconut leaf midrib, cool it and taste. Observe the change in taste. 
Observation: 
Tabulate the change that occurred to sugar at each stage.
Inference: Here, a new substance is formed. The black colour substance obtained at the end is Charcoal. This is a permanent change.

♦ Analyse the changes and characteristics of the substances formed here. Are charcoal, the black substance obtained at the end and the sugar the same? What is the reason for the change in taste? 
The black substance obtained at the end and the sugar are not the same. The new substance formed by heating sugar is charcoal. The change in taste is due to the chemical change.

♦ What are the characteristics of chemical changes? 
• When a chemical change occurs, the chemical properties of the substance change and new substances are formed. 
• Energy is usually absorbed or released when such a change occurs. 
• Chemical changes are permanent changes.

♦ Tabulate the differences between physical and chemical changes. 
Physical Change Chemical Change
The physical properties of substance changeThe physical and chemical properties of substance change
No new substances are formedNew substances are formed
It doesn't always have to absorb and release heat.Receives and releases heat
Only the shape, size and state of matter changeThe chemical structure of the substance changes
The change is temporaryChange is constant
♦ Some chemical changes that occur in daily life.
• Digestion of food 
• Verdigris on copper vessels 
• Rusting of iron 
• Souring of curd 
• Burning of sparklers 
• Cooking food 
• Colour change of sliced apple  
• Decomposition of waste
• Ripening of mango
• Curdling of milk

♦ Rust
Rust is formed by the reaction of iron with the moisture and oxygen in the air.

♦ What do we usually do to prevent rusting of iron? 
Rusting of iron objects can be controlled by greasing them with oil or by painting. By doing this, the contact of iron with air is prevented.

♦ Spoilage of food items is due to the chemical changes caused by the action of bacteria. What is usually done at home to prevent this? 
• Storing in a refrigerator  
• Freezing
• Drying
• Salting 
• Sugaring 
• Pickling
• Boiling 
• Vacuum sealing 

♦ Let's do some experiments using some substances available at home.
Materials to be kept in the Science Kit:
Vinegar, eggshell, baking soda, glass, spoon

• Crush the eggshell into small pieces. What kind of change is this? 
This is a physical change

• Put a few pieces of eggshell in a glass. Pour vinegar into it and observe the change. Discuss the changes taking place here. 
When eggshell pieces are placed in vinegar, bubbles of carbon dioxide gas form as the acid reacts with the calcium carbonate in the shell. This shows a chemical change, because a new substance (carbon dioxide) is produced and the shell slowly dissolves.

• Take a little vinegar in a glass and add one spoon of baking soda to it. What happens? What type of change is this?
When vinegar and baking soda are mixed, bubbles of carbon dioxide gas are released with fizzing and foaming. This is a chemical change, because a new substance (carbon dioxide) is formed during the reaction.

♦ Isn't it fascinating to watch a lighted sparkler? What are the things that attract you? 
• Sound 
• light
• Color
♦ When a sparkler is lit, forms of energy like sound, light and heat are produced. You know that sound, light and heat are forms of energy. What is the reason for the energy change when a sparkler is lit? 
There are chemical substances in a sparkler. It contains chemical energy. Chemical energy is present not only in the substances present in a sparkler, but in all substances. When the sparkler is lit, the chemical energy in the sparkler is converted into the forms of energy like sound, light and heat.

♦ Which are the energy changes that happen when a sparkler is lit? Complete the illustration given below.
♦ Some chemical changes are given in the table. Discuss the energy changes taking place in them. Put a tick (✔) mark in the appropriate columns. 
♦ Observe the picture. What is the process taking place in plants? 
Photo synthesis

• Which substances are being used here?
Carbon dioxide, sunlight, water, chlorophyll

• Which form of energy do plants use during photosynthesis? 
Light energy

• The food that plants produce through photosynthesis is -----------.
glucose

♦ What is Photosynthesis?
Photosynthesis is the process by which plants produce food using water and carbon dioxide, in the presence of sunlight, with the help of chlorophyll.

♦ Haven't you seen a mixer grinder working? Which energy is used to operate the mixer grinder?
Electrical energy

♦ Do any parts of the mixer grinder move? Which form of energy is required to move the machine parts? 
Moving machine parts possess mechanical energy.

♦ What are the energy changes that occur when a mixer grinder works?
When a mixer grinder works, electrical energy is converted into mechanical energy, sound energy and heat energy.

♦ Write the devices that convert electrical energy into mechanical energy.
• Fan 
• Mixer grinder
• Motor
• Grinder
• Drilling machines

♦ Observe the pictures given below. What energy transformations do we utilize in each device?
♦ Find more examples of utilising energy transformations and write them.
• Torch - Chemical energy → Light energy
• Washing machine - Electrical energy → Mechanical energy + Sound energy
• Electric kettle - Electrical energy → Heat energy
• Television - Electrical energy → Light energy + Sound energy
• Doorbell - Electrical energy → Sound energy
♦ We use an electric bulb to get light. But doesn't heat also get generated in the bulb? Heat generated like this is not utilised. The pictures below show three different types of bulbs we have used at different periods. The amount of light obtained in all three cases is almost the same. 
♦ Which of these do you use more in your house? Why? Analyse the energy transformations happening in each and find the reason. 
We use LED bulbs more in our house because LED bulbs use very less electricity and generate very less heat energy. We don't utilise the heat energy produced along with light energy when a bulb glows. Unutilised heat energy is energy loss. 

♦ What is the advantage of reducing the use of filament bulbs and increasing the use of LED bulbs? What could be the reason for the promotion of LED bulbs by the electricity board?
Filament bulbs use more electricity and generate more heat energy. But LED bulbs use very less electricity and generate very less heat energy. LED bulbs also last much longer, which saves money and reduces waste. Electricity boards promote LEDs to lower overall power demand and encourage energy conservation.

♦ Which forms of energy are produced in the following situations? Which form of energy among them is utilised? Which forms of energy are wasted? Complete the table. 
Let’s Assess
1. Find the odd one out.
a) Firecracker bursts  
b) Bottle breaks 
c) String of kite breaks  
d) Electric wire breaks
Answer: a) Firecracker bursts  

2. Examine the following changes and write whether they are chemical changes or physical changes. 
Change Chemical Change / Physical Change
Camphor burningChemical Change
Copper vessel getting verdigrisedChemical Change
Cutting firewood.Physical Change
Fermentation of dosa batterChemical Change
Melting of tarPhysical Change
Towel absorbing waterPhysical Change
Sugar dissolving in waterPhysical Change
Fish getting spoiledChemical Change
Green leaves turning yellowChemical Change
3. You know that electrical energy is being used by converting it into different forms. Write down the names of the devices that utilize the following energy transformations.
i. Electrical energy to heat energy -
• Iron box
• Toster 
• Induction cooker
• Water heater
• Electric kettle
• Hair dryer

ii. Electrical energy to chemical energy
• Battery charger 
• Electroplating unit
• Electrolysis apparatus 

iii. Electrical energy to sound energy 
• Loudspeaker
• Radio
• Doorbell
• Headphones
• Buzzer

iv. Electrical energy to light energy 
• LED bulb
• Tube light
• Torch 
• Television screen
• Street lamp

4. All changes that occur by absorbing heat are chemical changes. Is this statement correct? Why? 
This statement is not correct. Not all changes that occur by absorbing heat are chemical changes. Physical changes can also occur by absorbing heat. In physical changes, substances undergo a change of state by absorbing heat.


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