Answer the Questions
What is matter?
Matter is anything that is made up of tiny particles called molecules. Each molecule is further made up of particles known as atoms.
Why do we need ventilators and exhaust fans in closed places?
• The air we breathe out is warmer and impure as it is rich in carbon dioxide. So, it rises and goes out through ventilators generally located at the top of the room.
• Air pollutants, unwanted smells of cooking, and foul smells also escape through ventilators.
• In kitchens, factories, chimneys and exhaust fans are used to assist in throwing out smoke and foul air out of the room so that fresh air can enter from the windows.
Solution
when two substances are combined in such a way that they evenly spread and mix with each other, it is called a solution.
Humidity
The amount of water vapour present in the air at a particular time is called humidity.
State the properties of solids, liquids and gases.
Properties of Solids
1. Solids have a fixed shape
2. Solids have a definite volume
3. Solids do not flow
Properties of Liquids
1. Liquids have a fixed volume
2. Liquids do not have a fixed shape. They take the shape of the container in which they are poured
3. Liquids only flow from higher to lower.
4. Particles in liquids are loosely packed and move around.
Properties of Gasses
1. Gases do not have a shape of their own. In an empty container, they occupy all the available space.
2. Gasses do not have a fixed volume. They take the shape of the container into which it is poured
3. Gasses can easily flow in all directions
4. The particles in gases are very loosely packed. The empty space helps the gas particles to move around freely.
Explain two methods to separate soluble substances
Boiling - The solution containing soluble impurities such as salt or sugar is heated till the water evaporates. Water is lost through boiling
Distillation - This method is generally done in laborataries. Pure water collected by the process of distillation is called distilled water. Distilled water is the purest form of water as it does not contain any impurities. Distilled water is not suitable for drinking as it does not contain minerals that are present in drinking water. However distilled water is used in laboratories, medicines and car batteries.
Solute
The substance that gets dissolved in a solution is called the solute.
Distinguish between miscible liquids and immiscible liquids.
Miscible Liquids
When two liquids are combined together, and they completely mix with each other, they are called miscible liquids.
Immiscible Liquids
Liquids that do not completely mix with each other are called immiscible liquids.
Explain two methods to separate insoluble substances.
1. Sedimentation - The process in which insoluble substances in a liquid settle down at the bottom of a container is called sedimentation.
2. Decantation - The process of removing clear water after the sediments have settled down is called decantation.
3. Filtration- the process of separating insoluble substances by passing the solution through filter paper is called filtration.
Solvent
The substance that dissolves the solute particles into it to make a solution is called the solvent.
What is air? State its composition
Air is a mixture of several gases-78% nitrogen and 21% oxygen. There are other gases present such as carbon dioxide, argon, helium, hydrogen, etc. Water vapour is also present in the air. Air also contains dust particles and smoke.
Soluble substances
Substances that dissolve completely in a liquid to form a solution are called soluble stances.
State the properties of air
• Air occupies space
• Air exerts pressure
• Air has weight
• Air is needed for burning
Insoluble substances
Substances that do not dissolve in a liquid are called insoluble substances.