Olympiad Test Level 2: Science and Technology - 2 - Class 2 MCQ

Solids have definite shape, so the particles are tightly packed.

Everything around us is made up of matter. Matter is something that has mass and takes up the space.

Some gases like air, oxygen are not colored but some gases like chlorine is visible.

Liquid does not have its own shape and takes the shap of the container, because it’s particles are loosely packed.

Explanation:
To determine which of the given options is not an input device, we need to understand what an input device is. An input device is any hardware device that allows users to input data into a computer system. Examples of input devices include keyboards, mice, scanners, and light pens.
Let's analyze each option to determine if it is an input device:
A: Optical scanner
- Optical scanners are input devices that use light to capture images or text and convert them into digital data. They are commonly used to scan documents or images and input them into a computer system.
B: Mouse
- A mouse is a common input device that allows users to move a cursor on a computer screen and interact with graphical user interfaces. It is used to input positional data into a computer system.
C: Light pen
- A light pen is an input device that allows users to point to or select objects on a computer screen by directly touching the screen with the pen. It is used to input positional data and perform selections or actions.
From the analysis above, we can conclude that all the given options (A, B, and C) are indeed input devices. Therefore, the correct answer is:
D: None of the above
None of the given options is not an input device.

Oxygen is essential for human beings to survive.

Surface of metal is shiny in appearance.

Stars are made up of plasma. Plasma is not a common matter on earth, but is a common matter in universe.

To determine the substance that has definite volume but no definite shape, we need to understand the properties of different states of matter.
1. Liquids: Liquids have definite volume but no definite shape. They take the shape of the container they are placed in but maintain the same volume. The particles in a liquid are close together but not arranged in a regular pattern. Examples of liquids include water, oil, and milk.
2. Solids: Solids have both definite volume and definite shape. The particles in a solid are tightly packed and arranged in a regular pattern. Examples of solids include rocks, metals, and wood.
3. Gases: Gases have no definite volume or shape. They expand to fill the entire space available to them. The particles in a gas are far apart and move randomly. Examples of gases include air, oxygen, and carbon dioxide.
Based on the above information, we can conclude that the substance with definite volume but no definite shape is liquid (option A).

Non-metals are poor conductors of electricity. Here is a detailed explanation:
Conductivity of Non-metals
- Non-metals are elements that lack the characteristics of metals, such as metallic luster, malleability, and good conductivity of heat and electricity.
- Unlike metals, non-metals have high ionization energies and electronegativities, which means they tend to gain or share electrons rather than lose them.
- The valence electrons in non-metals are tightly bound to the nucleus, making it difficult for them to move freely and carry an electric current.
- As a result, non-metals have a high resistance to the flow of electric charge and are poor conductors of electricity.
Comparison with Metals
- Metals, on the other hand, have loosely held valence electrons that can move freely through the atomic lattice, allowing for efficient conduction of electricity.
- The presence of delocalized electrons in metals enables the flow of electric charge, making them good conductors.
- This is why metals, such as copper and aluminum, are commonly used in electrical wiring and circuits.
Exceptions
- While most non-metals are poor conductors of electricity, there are exceptions. For example, graphite, which is a form of carbon, exhibits some degree of electrical conductivity due to its unique structure and the presence of delocalized electrons.
- Additionally, certain non-metallic substances can conduct electricity when they are dissolved in water or melted. These substances are called electrolytes and include acids, bases, and salts.
In conclusion, non-metals are generally poor conductors of electricity due to the tight binding of valence electrons to the atomic nucleus. Metals, on the other hand, are good conductors because of their ability to freely move valence electrons. However, there are exceptions to this rule, such as graphite and certain electrolytes.