Matter
Exercises
BE PROMPT
A. Fill in the blanks.
1. The intermolecular force varies from material to material.
2. The particles of matter always show attraction towards each other.
3. The molecules of a Solid do not move around.
4. Heating causes expansion in liquids.
5. The different states of matter are interchangeable.
6. Ice melts to form water.
B. State whether the following statements are true (T) or false (F). Correct the false statements.
1. Some molecules can be seen with the help of naked eyes. [F]
= It is very difficult to observe the molecules even with a powerful microscope.
2. An element is a substance which cannot be subdivided into two or more simpler substances by any physical or chemical means. [T]
3. Solids can be beaten into thin sheets. [T]
4. Molecules can be made of same types of atoms only. [F]
= Molecules can either be made of same types or different types of atoms.
5. The intermolecular force is same in all kinds of materials. [F]
= The intermolecular force varies from material to material.
6. The different states of matter are interchangeable. [T]
C. Choose the correct option.
1. ________ are called the building blocks of matter.
a) Atoms. [ ]
b) Molecules. [✓]
c) Elements. [ ]
d) None of these. [ ]
2. Which of these do not have a fixed volume.
a) Solids. [ ]
b) Liquids. [ ]
c) Gases. [✓]
d) Both (b) and (c). [ ]
3. The molecules of a gas are _____ packed.
a) tightly. [ ]
b) loosely. [✓]
c) laterally. [ ]
d) none of these. [ ]
4. ______ cannot be compressed easily.
a) Solids. [✓]
b) Liquids. [ ]
c) Gases. [ ]
d) Both (b) and (c). [ ]
5. _________ take the shape of the container they are poured in.
a) Solids. [ ]
b) Liquids. [✓]
c) Gases. [ ]
d) Both (b) and (c). [ ]
6. The intermolecular forces are strongest in _____ .
a) solids. [✓]
b) liquids. [ ]
c) gases. [ ]
d) all of these. [ ]
D. Match the columns.
=
|
Column A |
Column B |
|---|---|
|
1. Most rigid. |
(a) Heating. [4] |
|
2. Fixed volume, indefinite shape |
(b) Gas. [3] |
|
3. Maximum intermolecular shape |
(c) Solid. [1] |
|
4. Solid to liquid |
(d) Cooling. [5] |
|
5. Liquid to solid |
(e) Liquid. [2] |
SHORT AND PRECISE
A. Show the following process in form of the flowcharts.
1. States of matter.
=
2. Interconversion of states of matter.
=
B. Give reasons for the following statements.
1. Solids have a fixed shape and size.
= Solids have a fixed shape and size because the molecules in solids are closely packed and the intermolecular distance between them is very less.
2. Solids expand very little on heating.
= Due to strong intermolecular force of attraction between the molecules, solids expand very little on heating.
3. The fragrance of incense stick spreads out in air to a distance.
= The fragrance of incense stick spreads out in air to a distance because of the zigzag motion of air molecules.
4. Molecules of gases move freely in all the directions.
= Molecules of gases move freely in all the directions because the molecules are not fixed at their positions.
5. Liquids expand more than solids.
= Liquids expand more than solids because liquids are less rigid compared to solids.
C. Answer in short.
1. How is an atom different from a molecule?
= An atom is the smallest unit of an element which may or may not have an independent existence but always take part in a chemical reaction. On the other hand, a molecule is the smallest unit of matter which can exist independently and retain all its physical and chemical properties.
2. Explain diffusion with the help of an example.
= We have to take a beaker containing clear water. Then we have to put a drop of blue ink into the beaker. Then we will see that soon the blue colour of the ink dissolves in the water and the entire water and the entire beaker appears slightly bluish in colour. This process is called diffusion and occurs due to continuous random motion of the molecules of ink and water.
3. Do gases have a fixed shape and size? Give reason.
= Gases do not have a fixed shape and size. The intermolecular distance in gases is large. The intermolecular force in them is almost negligible. Due to this, the molecules in gases are very loosely packed. And they do not have fixed shape or size.
4. Why can the molecules in a liquid move freely?
= The intermolecular force of attraction is lesser in liquids. That is why they are loosely packed. The molecules are not fixed at their positions and can move freely.
AT LENGTH
A. Explain the following terms.
1. Atom.
= Atom is the smallest unit of an element which may or may not have an independent existence but always takes part in a chemical reaction.
2. Matter.
= Matter is anything that has mass and occupies space.
3. Element.
= Element is a substance which cannot be subdivided into two or more simpler substances by any physical or chemical means.
4. Intermolecular force.
= Intermolecular force is the force of attraction between molecules of a material.
5. Intermolecular space.
= Intermolecular space is the distance between molecules of a substance.
B. Differentiate between the following.
1. Solids and liquids.
=
|
Solids |
Liquids |
|---|---|
|
The molecules in a solid are tightly packed, i.e., the intermolecular
distance among the molecules is the least. |
The molecules in a liquid are not very tightly packed, hence the
intermolecular distance is moderate. |
|
The intermolecular forces are the strongest in solids. |
The intermolecular forces are moderate in liquids. |
|
Solids have a fixed shape and size, a posses a definite volume. |
Liquids have a definite volume but not a fixed shape. |
|
Solids are rigid. |
Liquids are less very rigid. |
|
The molecules in a solid do not move, but only vibrate about their
mean positions. |
The molecules in a liquid can move in all directions but within the
boundary of the liquid. |
2. Liquids and gases.
=
|
Liquids |
Gases |
|---|---|
|
The molecules in a liquid are not very tightly packed, hence the
intermolecular distance is moderate. |
The molecules in a gas are loosely packed, i.e., the intermolecular
distance is the maximum. |
|
The intermolecular forces are moderate in liquids. |
The intermolecular forces are the weakest in gases. |
|
Liquids have a definite volume but not a fixed shape. |
Gases have neither a definite shape or a definite volume. |
|
Liquids are less very rigid. |
Gases are not rigid at all. |
|
The molecules in a liquid can move in all directions but within the
boundary of the liquid. |
The molecules in a gas can move freely and are in state of continuous
random motion. |
3. Solids and gases.
=
|
Solids |
Gases |
|---|---|
|
The molecules in a solid are tightly packed, i.e., the intermolecular
distance among the molecules is the least. |
The molecules in a gas are loosely packed, i.e., the intermolecular
distance is the maximum. |
|
The intermolecular forces are the strongest in solids. |
The intermolecular forces are the weakest in gases. |
|
Solids have a fixed shape and size, a posses a definite volume. |
Gases have neither a definite shape or a definite volume. |
|
Solids are rigid. |
Gases are not rigid at all. |
|
The molecules in a solid do not move, but only vibrate about their
mean positions. |
The molecules in a gas can move freely and are in state of continuous
random motion. |
C. Read the given experiment to show molecules have a very small size carefully. Identify the incorrect parts of the process.
❐ Take 3-4 crystals of potassium permanganate and dissolve them in 50 mL of water in a steel beaker A. A deep red coloured solution is obtained.
❐ Take 10 mL of the obtained solution and add it another beaker B containing 40 mL of kerosene. Due to this, the clear water turns purple but lighter than the previous case.
❐ Now take 10 mL of coloured water from beaker B and add it in another beaker C containing 40 mL of water. The water in beaker C turns coloured and darker in shade.
=
❐ Take 3-4 crystals of potassium permanganate and dissolve them in 50 mL of water in a beaker A. A deep purple coloured solution is obtained.
❐ Take 10 mL of the obtained solution and add it another beaker B containing 40 mL of water. Due to this, the clear water turns purple but lighter than the previous case.
❐ Now take 10 mL of coloured water from beaker B and add it in another beaker C containing 40 mL of water. The water in beaker C turns coloured and lighter in shade.
D. Answer in detail.
1. Write a short note on molecules.
= An English chemist, John Dalton experimentally found that matter is made up of very small particles called molecules. Two or more atoms are combined to form a molecule. A molecule is the smallest unit of matter which can exist independently and retain all its physical and chemical properties. A molecule can either be made of the same type of atoms like the molecules of oxygen and molecule of hydrogen, or different types of atoms like the water molecule and carbon dioxide molecule. The size of atoms and molecules is very small. It is very difficult to observe them even with a powerful microscope.
2. State important characteristics of molecules of matter.
= The important characteristics of molecules of matter are :
i) Molecules are very small in size - The size of molecules or particles is so small that it is difficult to see them with unaided eyes.
ii) Molecules have spaces between them - The space between the molecules of a substance is called the intermolecular space or intermolecular distance.
iii) Molecules are constantly moving - Molecules are never at rest, they are in constant random motion. By random motion, we mean that the molecules ate in zigzag motion rather than moving along a fixed defined path.
iv) Molecules attract each other - Molecules always show attraction towards each other. Due to this attraction, the molecules are bound together. This force of attraction between the molecules is known as intermolecular force of attraction.
3. Give the characteristics of solids.
= Solids have the following characteristics:
❐ The molecules in a solid are closely packed and the intermolecular distance between them is very less.
❐ The intermolecular force is very strong in solids.
❐ Solids have a fixed shape and size.
❐ Solids have a definite volume.
❐ Molecules in solids remain fixed and vibrate about their mean positions.
❐ Solids cannot be compressed easily when pressed.
❐ Due to strong intermolecular force of attraction between the molecules, solids expand very little on heating.
❐ Solids are hard and rigid, but can beaten either into sheets or into powdered form.
4. Give the characteristics of liquids.
= Liquids have the following characteristics:
❐ The intermolecular space between the molecules of liquids like water, mercury, etc. is more than that in solids.
❐ The intermolecular force of attraction is lesser in liquids. That is why they are loosely packed.
❐ The molecules are not fixed at their positions and can move freely.
❐ Liquids do not have a fixed shape and take the shape of the container they are poured in.
❐ Even though the intermolecular forces are weaker in liquids than in solids, the molecules are not completely free. That explains why they have a definite volume.
❐ Like solids, liquids are almost incompressible.
❐ Due to weak intermolecular forces, heating causes expansion in liquids.
❐ Liquids are less rigid as compared to solids.
5. Give the characteristics of gases.
= Gases have the following characteristics:
❐ The intermolecular distance in gases is large.
❐ The intermolecular force in gases is almost negligible. Due to this, the molecules in gases are very loosely packed.
❐ The molecules in a gas move freely in all directions, i.e., execute zigzag motion continuously.
❐ Gases have neither a fixed shape nor a fixed volume. They occupy all the space available to them.
❐ Gases can be compressed to a large extent. Gases also expand a lot on heating.
❐ Gases are not at all rigid.
6. Write a short note on change in states of matter with the help of an example.
= The three states of matter are interchangeable. This can be observed on heating matter. For example, water exists in all the three states of matter, i.e., ice(solid), water(liquid) and water vapour(gas). When ice is heated, it melts and turns into water. Similarly, when we take some water in a pan and heat it on a burner, it converts into water vapour. Also, water changes into ice on freezing.
Just like water, other materials can also change from one state to the other through processes like melting, boiling, evaporation and condensation.