1. What is matter?
Answer: Matter is anything that has mass and occupies space.
2. Which of the following is not a pure substance?
(a) Iron (b) Water (c) Soil
Answer: (c) Soil .
[ Iron → pure substance (an element)
Water → pure substance (H₂O)
Soil → not a pure substance .]
3. Who coined the term “atom” and what does it mean?
Answer: The term “atom” was coined by Democritus.
The word atom means “indivisible” .
INTEXT QUESTIONS 2.2
1. Which of the three states of matter has no definite volume? Give one reason for your answer.
Answer: (c) Gas
A gas has no definite volume because the intermolecular forces are very weak, so the gas molecules are far apart and move freely in all directions. Therefore, a gas expands to fill any container, no matter its size.
2. Why do solids have definite shape?
Answer: The molecules in solids have fixed positions, and strong intermolecular forces act between them. Therefore, solids have a definite shape.
3. Name a substance which exists naturally in all the three states.
Answer: Water exists naturally in all three states of matter:
(i) Solid → Ice
(ii) Liquid → Water
(iii) Gas → Water vapour (steam) ]
INTEXT QUESTIONS 2.3
1. Why gases are more compressible as compared to solids?
Answer: Molecules in solids are closely packed and any attempt to bring them closer results in strong repulsive forces and so solids cannot be compressed. In gases there are large spaces between their molecules and can be brought closer by applying pressure.
2. How can you change water into ice?
Answer: Water can be converted into ice by lowering its temperature . When water is cooled to 0°C or below, it changes from the liquid state to the solid state .
INTEXT QUESTIONS 2.4
1. Classify the following into element, compound and mixture:
aluminum, carbon, granite, water, silicon, carbon dioxide, air and sugar.
Answer: The classification are :
Element: Aluminium , Carbon and Silicon .
Compound: Water , Carbon dioxide and Sugar .
Mixture : Air and granite .
2. How does an element differ from a compound?
Answer: The differences between an element and a compound are:
|
Element |
Compound |
|
(i) An element consists of only one type of atom. |
(i) A compound contains two or more types of atoms chemically combined. |
|
(ii) It cannot be broken down into simpler substances by chemical methods. |
(ii) It can be broken down into its elements by chemical methods. |
3. Which is the most abundant element in the universe?
Answer: The most abundant element in the universe is Hydrogen (H).
INTEXT QUESTIONS 2.5
1. Say whether ethyl alcohol and water form a homogeneous mixture or heterogeneous mixture.
Answer: The mixture of ethyl alcohol and water is a homogeneous mixture because both substances mix completely and form a uniform composition throughout.
2. Give an example of homogeneous mixture obtained by mixing two solids.
Answer: An example of a homogeneous mixture obtained by mixing two solids is an alloy, such as brass (a mixture of copper and zinc).
INTEXT QUESTIONS 2.6
1. To make one kilogram of 40% sugar solution by mass, how much sugar and water will you need?
sugar ...................
water ...................
Answer: To make 1 kilogram (1000 g) of a 40% sugar solution by mass:
Sugar = 40% of 1000 g = 400 g
Water = 1000 g − 400 g = 600 g
Sugar: 400 g and Water: 600 g
2. What is the name given to a liquid which dissolves a solid to make a solution?
Answer: A liquid that dissolves a solid to make a solution is called a solvent.
3. To make a given solution more concentrated, what will you add ?
Answer: To make a given solution more concentrated, add more solute (the substance being dissolved).
1. Which physical property is used to separate iron granules from dust particles?
(a) Magnetic, (b) Electric, (c) Density
Answer: (a) Magnetic
[ The magnetic property is used to separate iron granules from dust particles because iron is attracted by a magnet, while dust is not.]
2. The separation of sugar in the form of Mishree is called
(a) evaporation (b) crystallization (c) distillation
Answer: (b) Crystallization
[ The separation of sugar in the form of Mishree is called crystallization because sugar crystals are formed from its solution.]
1. Indicate whether each of the following statements is true or false.
(i) A liquid has a definite shape true/false
(ii) An element cannot be broken into simpler substances by chemical means. true/false
(iii) A solid cannot be converted into liquid even by increasing temperature. true/false
(iv) A liquid can be converted into solid by lowering temperature. true/false
Answer: (i) A liquid has a definite shape → False
(ii) An element cannot be broken into simpler substances by chemical means → True
(iii) A solid cannot be converted into liquid even by increasing temperature → False
(iv) A liquid can be converted into solid by lowering temperature → True
2. Indicate the normal state (i.e. state at room temperature) of each of the following?
(i) iron (ii) water (iii) nitrogen (iv) carbon (v) gold (vi) oxygen
Answer:
|
Substance |
Normal state (at room temperature) |
|
(i) Iron |
Solid |
|
(ii) Water |
Liquid |
|
(iii) Nitrogen |
Gas |
|
(iv) Carbon |
Solid |
|
(v) Gold |
Solid |
|
(vi) Oxygen |
Gas |
3. In the table given below, a list of substances has been provided. Identify whether each of them is an element, compoind, mixture or soluton.
(i) Milk (ii) Sugar (iii) Silver (iv) Air (v) Water (vi) Sea water (vii) Iron (viii) Sugar (ix) Carbon dioxide
Answer:
|
Substance |
Type |
|
(i) Milk |
Mixture |
|
(ii) Sugar |
Compound |
|
(iii) Silver |
Element |
|
(iv) Air |
Mixture |
|
(v) Water |
Compound |
|
(vi) Sea water |
Solution |
|
(vii) Iron |
Element |
|
(viii) Sugar |
Compound |
|
(ix) Carbon dioxide |
Compound |
4. Why is it important to store cooking gas cylinder away from heat and flame?
Answer: It is important to store a cooking gas cylinder away from heat and flame because cooking gas is highly inflammable. Heat can increase the pressure inside the cylinder and may cause gas leakage, fire, or explosion. Therefore, cylinders should be kept in a cool and safe place.
5. Identify the most appropriate method to separate the following:
Substances Method of Separation
1. Separate water from yogurt
2. Separate clean water from muddy water
3. Separate oil from oil water mixture
4. Separate iron nails from saw dust
5. Separate sugar from saturated sugar solution
Answer:
|
Substances |
Method of Separation |
|
1. Separate water from yogurt |
Centrifugation (churning) |
|
2. Separate clean water from muddy water |
Filtration |
|
3. Separate oil from oil–water mixture |
Separating funnel |
|
4. Separate iron nails from saw dust |
Magnetic separation |
|
5. Separate sugar from saturated sugar solution |
Crystallization |
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