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प्रश्न
Write a few lines on the blackboard with a chalk. Now observe the chalk. What changes do you see in the chalk?
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उत्तर
The chalk reduces in size after writing on the blackboard. It becomes flat on the side from which we use it for writing.
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संबंधित प्रश्न
Which of the following materials fall in the category of a “pure substance”?
- Ice
- Milk
- Iron
- Hydrochloric Acid
- Calcium oxide
- Mercury
- Brick
- Wood
- Air
Out of solids, liquids and gases, which one has :
- maximum movement of particles ?
- maximum interparticle attractions ?
- minimum spaces between particles ?
What are the three groups into which all the elements can be divided ? Name two elements belonging to each group.
There are three substances X, Y and Z. The substance X does not have a fixed melting point or boiling point and it still shows the individual properties of its constituents. The substance Y is a pure substance which occurs in nature as such. The substance Y has a fixed melting point and boiling point but it cannot be broken down into simpler substances by any chemical means. The substance Z is also a pure substance whose properties are entirely different from those of its constituents. The substance Z can, however, be divided by electrolysis into two substances which belong to the same class of substances as Y.
- What type of substance could X be ? Name one substance like X.
- What type of substance could Y be ? Name one substance like Y.
- What type of substance could Z be ? Name one substance like Z.
- Which process involves absorption or release of an appreciable amount of energy : formation of substance X or formation of substance Z ?
- Name the three groups into which all the substances like Y are divided on the basis of their properties.
What is the name of the clear liquid formed when a solid dissolves in a liquid ?
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
How is the impurity of iron present in several substances removed in industries ?
How is water purified on a large scale at water works ? Explain with the help of a labelled diagram. Name the substance which is added to kill germs in the drinking water supply ?
Which one of the following scrap metal cannot be separated by magnetic separation ?
______ is not made of matter.
