Changes Around Us Questions & Answers

Hi Everyone!! This article will share Changes Around Us Questions & Answers.

In my previous post, I have shared the Objective Type Questions & Answers of Changes Around Us so, you can check these posts as well.

Changes Around Us Questions & Answers

Question 1: List three main causes of change.

Answer: The three main causes of change are:

  • Pressure
  • Heat
  • Mixing

Question 2: List the properties that undergo a change during a physical change.

Answer: Physical change alters the physical properties such as size, shape, colour, density, odour without causing any change in its composition.

Question 3: State one difference between physical and chemical changes.

Answer: A physical change is a change to a sample of matter in which some properties of the material change but the identity of the matter does not.
A change in which a new substance is formed and shows different properties than the ones we started with is called a chemical change.

Question 4: State one difference between natural and man-made change.

Answer: Some changes around us take place without any human efforts; such changes are natural changes.
Some other changes occur only with human activity or human efforts. Such changes are called man-made or artificial changes.

Question 5: State one difference between desirable changes and undesirable changes.

Answer: Changes that are useful are called desirable changes. Ripening of fruits and occurrence of day and night are examples of desirable changes. 
Changes that are not useful and may even be harmful are called undesirable changes. Rotting of food and drastic changes in weather are examples of undesirable changes. 

Changes Around Us Questions & Answers

Question 6: Give two examples for each of the following.

(a) Man-made changes 

Answer: Cutting of wood and making of paper.

(b) Reversible changes 

Answer: Burning of fuel and setting milk into curd.

(c) Undesirable changes 

Answer: Rotting of food and drastic changes in weather

Question 7: Define the following:

(a) Irreversible changes

Answer: Changes which cannot be reversed simply by changing the conditions are called irreversible changes. These changes are permanent and we cannot get back the original substance.
Examples: Setting milk into curd, Germination of a seed

(b) Fast changes

Answer: The changes that occur in a short time are called fast changes.
Examples: Burning of fire crackers, Earthquakes

(c) Chemical changes

Answer: A chemical change is a change in which new substances are formed which have properties that are different from the original substances. Both the physical and chemical properties of a substance change during a chemical change.
Examples: Digestion of food, leaves changing colours during fall.

Question 8: Neha mixes all the materials required to make a chocolate cake and then she bakes the mixture in the oven. List different types of changes taking place while making the cake.

Answer: Chemical, irreversible, slow and desirable.

Question 9: What is a change? Explain why water cycle is considered as an example of reversible change.

Answer:

  • The transformation either in the appearance, properties or functions of a substance is called a change.
  • The water cycle is based on the interconversion of the three physical states of water.
  • Processes such as melting, boiling, evaporation, freezing, condensation that are part of the water cycle are reversible changes.
  • In these changes, there is a change in the state of matter but a new substance is not formed.

Question 10: Give reasons for the following:

(a) Melting of ice is a reversible process.

Answer: Ice kept out of the refrigerator, begins to melt and changes into water. If the same water is put back into the freezer, it changes back to ice. Hence, melting of ice is a reversible process.

(b) Gaps are left between railway tracks.

Answer: Heat causes metals to expand. Gaps are left between railway tracks to allow the expansion of the metal during summer. Otherwise, the tracks would bend and may cause accidents. Hence, gaps are left between the railway tracks.

(c) Metals are used for making tools. 

Answer: The property of solids to expand and contract on cooling is used in making tools. So, Metals are used for making tools. Also they can be strong and easy to shape too.

(d) Digestion is a chemical change as well as a physical change. 

Answer: Digestion is another example of physical and chemical changes occurring simultaneously. Food is physically broken down by chewing and chemically broken down by digestive enzymes in the saliva and the acid in the stomach.

Changes Around Us Questions & Answers

Question 11: Parveen sharpens pencil to draw sketches on a paper.

(a) Is sharpening a pencil a reversible or irreversible change?

Answer: Irreversible change

(b) Is this change a physical or chemical change? Why?

Answer: It’s a physical change because no chemical reaction takes place. There is no new substance formed.

Question 12: How will you separate two steel vessels that are stuck to each other?

Answer: The two steel vessels can be separated from each other by heating since heating results in the expansion of metal vessel.

Question 13:

Changes Around Us Questions & Answers

(a) What causes the change in the object as seen in the picture?

Answer: Pressure

(b) Describe the changes in the object at the molecular level.

Answer: When we apply pressure, the molecules of a substance undergo a change in terms of their position.
In most cases, the substance regains its original state or shape as soon as the pressure is released.

Question 14:

Changes Around Us Questions & Answers

Why does the metal ball slip through the ring in picture A but not in picture C?

Answer: On heating, the ball expands and increases in diameter. This restricts the ball from slipping through the ring in picture C. After cooling, the metal ball contracts and slips through the ring in picture A.

Question 15: How is the melting of wax different from the burning of wax? 

Answer: The melting of wax is a physical change. The production of carbon dioxide and water vapour (new substances) during the burning of wax is a chemical change.

Question 16: How does mixing bring about a change? Explain with the help of an example. 

Answer: When two or more substances are mixed, they may form a mixture or react with each other to form a new substance. 
Some examples of changes due to mixing are: 

  • When salt is mixed with water, it forms a salt solution. The salt can be recovered back from the solution by evaporation. 
  • When we add baking soda to vinegar, it results in the release of carbon dioxide which is an entirely a new substance and the initial substances cannot be recovered back.

So, these were Changes Around Us Questions & Answers.

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