Properties of Matter
- Anything that occupies space is called matter.
- There are three states of matter—solids, liquids and gases.
- Matter is composed of small microscopic particles called atoms.
- Atoms cannot be divided further and are made of subatomic particles called electrons, protons and neutrons.
- Different materials we see around us are made of matter with different properties.
- These materials can be grouped into different categories based on the properties of matter.
Atoms and Molecules
What Is Intermolecular Space? How Does It Vary in Solids, Liquids and Gases?
- Atoms combine to form molecules. The space between the adjacent molecules in a particular state of matter is called intermolecular space.
- The intermolecular space is the least in solids. Liquids have more intermolecular space than solids. Due to this reason, liquids can flow easily and assume the shape of a container.
- Gases have the maximum intermolecular spaces. As a result, gases do not have a fixed shape or volume.
- The hardness of a substance depends on the force of attraction between the atoms.
- The atoms of iron have strong intermolecular forces which hold them together. On the other hand, the intermolecular force between the atoms in chalk is relatively less, which makes it brittle.
Why Are Some Objects Hard Like Iron, but Some Are Brittle Like Chalk?
Solids, Liquids and Gases
How Do Solutes Dissolve in a Solvent?
- The substances used as solvents have sufficient intermolecular space between their molecules.
- When a solute is dissolved in a solvent, the intermolecular space among the solvent molecules gets occupied by the solute molecules.
- As a result, the solute dissolves in a solvent.
Why Can Solids Not Be Compressed Further?
- The atoms or molecules in solids are tightly packed with minimum intermolecular space.
- There is no space for the molecules to move closer; hence they cannot be compressed further.
Why Can Solids Not Be Compressed Further?
- The solubility of a solute increases with an increase in the temperature.
- It happens because, with the rise in temperature, the energy of the solute molecules increases and hence, they dissolve more.
Can We Keep Dissolving a Solute in a Solvent Forever?
- No, we cannot keep dissolving the solute in a solvent forever.
- The reason is that on continuous addition of a solute, the intermolecular space between the solvent particles gets fully occupied.
- Such a solution is called a saturated solution.
Solids Conduct Heat Quickly. Why Do You Think So?
- The molecules in a solid are closely packed.
- The transfer of heat takes place quickly as the molecules are touching each other, which provides a path for heat to pass.
- Hence, solids conduct heat quickly.
Which of the Three States of Matter Heats the Slowest? State the Reason for the Same.
- Gases heat the slowest.
- There is a large intermolecular space between the gas molecules, so heat does not get a continuous path to travel.
What Is a Mixture?
A mixture is a combination of two or more substances. These substances may be either miscible or immiscible.
State the Points You Should Consider Before Choosing the Method of Separation for Any Mixture.
The following points should be considered before choosing a separation method for any mixture—
- State of constituents of the mixture.
- Solubility of the components of the mixture.
Changing of States of Matter
Have You Heard About Compressed Gases? Are They of Any Use to Us? If Yes, Give Examples for the Same.
Yes, compressed gases are used by us for various purposes.
- LPG (Liquefied Petroleum Gas) used for cooking food is actually a mixture of gases that has been compressed into a liquid form.
- CNG (Compressed Natural Gas) is used as fuel in vehicles.
Why Do We Not See Any Liquid Gas Coming Out of Stoves As Soon as We Open the Knob?
- A gas is compressed using high pressure.
- The cylinders in which the gas is filled maintain the same pressure.
- As soon as the liquefied gas escapes the cylinder and reaches the stove, it changes into a gas due to a decrease in the pressure.
Properties of Elements
What Is an Element? Give Examples.
- An element is a group of one or more atoms which cannot be broken further using any force.
- For example, oxygen (comprises 2 atoms), hydrogen (comprises 2 atoms), etc.
Sodium Is Metal, but Unlike Other Metals, It Starts Burning When It Comes in Contact With Water. Why?
- Sodium is a highly reactive metal.
- As soon as it comes in contact with water, it produces a large amount of heat, making it catch fire.
What Is the Meaning of Lustre? How Can You Distinguish Between Materials Based on Their Lustre?
- The shiny appearance observed for some materials is called lustre.
- Materials are broadly classified into metals and non-metals based on their lustre.
- For instance, gold and silver are metals, whereas rubber and wood are non-metals.
Name Any Two Elements Which Are Used for Making Jewellery. State the Reason for the Same.
Gold and silver are used to make jewellery. These elements are less reactive and do not corrode easily; hence, they can be shaped to form jewellery.
Do elements play any role in our bodies? If yes, enlist them.
Yes, elements like potassium, calcium, iodine and iron play a vital role in our bodies. Their functions are as follows—
- Iron is required for the formation of haemoglobin, which is an essential pigment in our body.
- Calcium and phosphorus are required for healthy and strong bones.
- Iodine is required for the proper functioning of the thyroid gland which regulates the growth and development of our body.
An Iron Bell Creates a Ringing Sound When It Hits Any Surface. Can You State a Reason Behind It?
Iron is a metal. Metals are sonorous, i.e., they produce a ringing sound when they hit any surface.