What can you tell about two of these, namely, bursting of a balloon and ripening
of a fruit, from the point of view of their duration i.e. the time they take to happen?
Answers
Answer:
1) What are the causes of the changes occurring in surroundings?
Ans. When there is a change in the structure and state of the substances that
surround us, them there are changes caused in the surroundings. There are Physical
chemical and biological changes occurring around us. Some of the changes are
natural while some are man – made changes.
2) What is meant by man-made changes? Which are these changes?
Ans. When man wishes to produce things of his own use, he changes the substances
around him. Such changes are called man-made changes. These changes can be
physical or chemical changes.
Observe and discuss.
What changes have taken place in the materials seen in the following pictures? What
kind of changes are they?
Which points will you consider while classifying the following changes into two groups –
a fruit falling from a tree, rusting of iron, raining, lighting an electric bulb, cutting
vegetables?Can you tell?
Which of the above changes have occurred of their own accord or naturally?
Changes like the ripening of a fruit, spoiling of milk occur naturally. These are called
natural changes.
Can you tell?
We see many man-made materials in our day-to-day life. For what purposes are they
produced?
Many changes such as sharpening a pencil, baking bread, cooking food are useful to
us and these are, therefore, called useful changes. The changes that are not useful or
changes that do us harm are called harmful changes.
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Explanation: