Advertisements
Advertisements
प्रश्न
Which of the following are chemical changes and which physical ? Give reason.
- a glass bottle breaking
- coal burning in air
- making a cake
- wool being knitted into a sweater
Advertisements
उत्तर
- Breaking of a glass bottle is a physical change because each of the broken piece of bottle is still a glass and no new substance has been formed. In the process, only the shape and size of bottle change.
- Burning of coal in air is a chemical change because the burnt coal cannot be obtained back and it is an irreversible change.
- Preparation of a cake is a chemical change as all the raw materials that go inside the mixture get cooked after baking and the process cannot be reversed.
- Knitting sweater from wool is a physical change as we can obtain back the wool from the sweater. So, it is a reversible process.
APPEARS IN
संबंधित प्रश्न
Match the following
| Column A | Column B | ||
| (a) | Molecules | (i) | Water boils |
| (b) | 100° C | (ii) | Evaporation |
| (c) | 0° C | (iii) | Changes from solid to gas |
| (d) | At all temperatures | (iv) | Matter |
| (e) | Camphor | (v) | Water freezes |
Give one difference between atoms and molecules.
Fill in the blank
All matter is made up of tiny particles called ______
Fill in the blank
Liquids have a definite ______
When extremely small particles X derived from the anther of a flower were suspended in a liquid Y and observed through a microscope, it was found that the particles X were moving throughout the liquid Y in a very zig-zag way. It was also observed that warmer the liquid Y, faster the particles X moved on its surface.
- What could particles X be ?
- What do you think liquid Y is ?
- What is the zig-zag movement of X known as ?
- What is causing the zig-zag movement of particles X ?
- Name the scientist who discovered this phenomenon.
- What does this experiment tell us about the nature of liquid Y?
What is meant by saying that non-metals are brittle ?
What is the other name for impure substances ? Give two examples of impure substances.
Explain why, hydrogen and oxygen are considered elements whereas water is not considered an element.
A, B and C are all liquids. Liquid A has a comparatively low boiling point. On heating, liquid A vaporises completely without leaving behind any residue. Liquid A is being used increasingly as a fuel in motor vehicles either alone or by mixing with petrol. Liquid B has a very high boiling point. It also vaporises completely on heating, without leaving any residue. Liquid B is a conductor of electricity and used in making thermometers. Liquid C has a moderate boiling point. On heating, liquid C vaporises leaving behind a white solid D which is used in cooking vegetables. The condensation of vapours from C give a liquid E which turns anhydrous CuSO4 to blue.
(a) Which liquid could be an element ? Name this element.
(b) Which liquid could be a mixture ? Name this mixture.
(c) Which liquid could be a compound ? Name this compound.
(d) What could the solid D be ?
(e) What do you think is liquid E ?
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Which of the following contains less solute at a given temperature and pressure ? Unsaturated solution or Saturated solution.
Classify the following into true solutions and colloidal solutions:
Ink, Salt solution, Starch solution, Blood, Sugar solution
Fill in the following blanks with suitable words :
A mixture of kerosene and petrol can be separated by .....................
Fill in the following blanks with suitable words :
The gases of air can be separated by fractional distillation of liquid air because they have different..............
How will you separate a mixture of common salt, sulphur powder and sand ?
Explain how, impure copper sulphate can be purified by crystallisation.
A solid mixture contains four constituents P, Q, R and S. P consists of tiny grains and it is mixed with
cement for plastering the walls. Q is a white solid which is recovered on a large scale from sea water by the
process of evaporation. R is in the form of tiny particles of a material whose corrosion is called rusting. And
S is a white solid which is used in making ordinary dry cells.
- What could P, Q, R and S be ?
- How would you separate a mixture containing P, Q, R and S ?
Explain the meaning of the term ‘matter’.
Select the correct answer from A, B, C, D & E for the statement given below:
An atom or group of atoms _________ having a resultant charge.
______ is not made of matter.
