Science Practice Test - 4 - Class 5 MCQ

How to put out a fire caused by petrol:
To safely extinguish a fire caused by petrol, it is important to follow the correct steps. Here's a detailed solution on how to handle such a situation:
1. Ensure safety:
- Prioritize your safety and the safety of others around you.
- Evacuate the area if necessary or move to a safe distance from the fire.
- Call emergency services to report the fire.
2. Switch off the electricity supply:
- Locate the main electrical switch or circuit breaker.
- Turn off the electricity supply to the affected area to prevent any electrical sparks that could worsen the fire.
3. Turn off the gas supply:
- If the fire is near any gas lines or appliances, turn off the gas supply.
- Locate the gas shut-off valve and close it to prevent the fire from spreading.
4. Use sand to smother the fire:
- Sand is a suitable material for extinguishing petrol fires as it helps to smother the flames and cut off the oxygen supply.
- If available, grab a bucket or container filled with sand.
- Stand at a safe distance and carefully throw the sand onto the base of the fire, covering it completely.
5. Do not use water:
- Petrol fires should never be extinguished with water, as this can spread the flames and potentially cause an explosion.
- Water is denser than petrol, so it can sink to the bottom and spread the burning liquid, making the situation more dangerous.
6. Wait for professional assistance:
- Even if you have successfully smothered the fire with sand, it is crucial to wait for professional firefighters to arrive and ensure the fire is fully extinguished.
- They have the necessary equipment and expertise to handle the situation safely.
Remember, it is always best to prioritize safety and leave the firefighting to professionals whenever possible.

The backbone protects the spinal cord.The backbone, also known as the vertebral column or spinal column, is a series of bones called vertebrae that extends from the skull to the pelvis. It provides support and protection to the spinal cord, which is a long, thin bundle of nerves that runs through the vertebral column.The spinal cord is a crucial part of the central nervous system and carries messages between the brain and the rest of the body. It is responsible for transmitting sensory information, coordinating movement, and controlling bodily functions.
Some key points to note about the backbone and its protection of the spinal cord:

 

 

 

 

 

 

 

 

 

 

 

 

• The backbone consists of 33 vertebrae, including cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and coccygeal (tailbone) vertebrae.
• Each vertebra has a hollow space called the vertebral foramen, which collectively forms the vertebral canal that houses and protects the spinal cord.
• The vertebrae are connected by ligaments and cushioned by intervertebral discs, which help absorb shock and provide flexibility.
• In addition to protecting the spinal cord, the backbone also supports the weight of the body and helps maintain an upright posture.

 

Thus, the backbone plays a vital role in protecting the spinal cord, allowing it to function properly and facilitating communication between the brain and the body.

 

Fats and carbohydrates are called energy giving foods.

The forces of attraction between molecules is greatest in the solid state.
Explanation:
In the solid state, molecules are closely packed together and have strong intermolecular forces of attraction. These forces include:
1. Van der Waals forces: These forces arise from temporary shifts in electron density within molecules, creating temporary dipoles. These temporary dipoles induce dipoles in neighboring molecules, leading to attractive forces.
2. Hydrogen bonding: This type of intermolecular force occurs when a hydrogen atom is bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) and is attracted to another electronegative atom in a neighboring molecule. Hydrogen bonding is stronger than Van der Waals forces.
3. Dipole-dipole interactions: These forces occur between polar molecules. The positive end of one molecule is attracted to the negative end of another molecule, resulting in attractive forces.
In contrast, the intermolecular forces in the liquid and gaseous states are weaker because the molecules are further apart and have more freedom of movement. While these states also exhibit Van der Waals forces, hydrogen bonding, and dipole-dipole interactions, the forces are not as strong as in the solid state.
Therefore, the forces of attraction between molecules are greatest in the solid state.

Reasons for including protein in a healthy diet:

• Raw material for cell growth and repair: Protein is essential for building and repairing tissues in the body. It provides the necessary amino acids that are used to create and maintain cells, muscles, organs, and other body structures.


• Muscle development and maintenance: Protein is crucial for the development, growth, and maintenance of muscles. It helps to build and repair muscle tissues, which is important for overall strength and physical performance.


• Enzyme production and function: Many enzymes in the body are made up of protein, and these enzymes play a vital role in various metabolic processes. They help to catalyze chemical reactions, break down food, and support overall digestion and nutrient absorption.


• Hormone synthesis: Certain hormones, such as insulin and growth hormone, are made up of protein structures. These hormones regulate important functions in the body, including metabolism, growth, and development.


• Immune function: Protein is necessary for a healthy immune system. It helps to produce antibodies, which are proteins that play a key role in fighting off infections, diseases, and foreign substances in the body.

Therefore, the best reason for including protein in a healthy diet is because it serves as the main source of raw material for cell growth and repair. Protein provides the necessary building blocks for the body to create and maintain its structures, ensuring optimal growth, development, and overall health.

Head Movement Joint:

Meena uses the pivot joint to move her head.

Explanation:

A pivot joint is a type of synovial joint that allows rotational movement.

It consists of a rounded or pointed surface of one bone fitting into a ring formed by another bone and a ligament.

This joint allows for rotation around a single axis, such as shaking or nodding the head.

Meena's head is connected to her neck through a pivot joint, enabling her to turn her head from side to side and up and down.

Example:

When Meena wants to look to her right, she rotates her head using the pivot joint, allowing her to face in that direction.

Similarly, when she wants to tilt her head up or down, she uses the pivot joint to achieve the desired movement.

Conclusion:

Therefore, Meena uses the pivot joint to move her head, allowing for rotational movements such as turning and tilting.

Similarities between Penguins and Turtles:
- Tippers for Movement in Water: Both penguins and turtles have adapted to their aquatic environments and possess structures that aid in their movement through water. Penguins have flippers, which are modified wings that enable them to swim efficiently. Similarly, turtles have flippers that help them navigate and propel themselves through water.
- Lungs for Oxygen Breathing: Penguins and turtles are air-breathing animals that possess lungs to extract oxygen from the air. This allows them to stay submerged underwater for extended periods while resurfacing to breathe.
- Egg-laying Reproduction: Both penguins and turtles reproduce by laying eggs. They have evolved to lay their eggs on land, and the females take great care in finding suitable nesting sites to ensure the survival of their offspring.
Therefore, the correct answer is D: All of these. Penguins and turtles share these common characteristics, which are essential for their survival in their respective aquatic habitats.

To determine whether a car jack is a screw or a lever, we need to understand the characteristics and functions of both.
Screw:
- A screw is a simple machine that consists of an inclined plane wrapped around a cylinder.
- It is used to convert rotational motion into linear motion.
- Screws are designed to hold objects together or to lift heavy loads by applying a twisting force.
Lever:
- A lever is a simple machine consisting of a rigid bar that rotates around a fixed point called a fulcrum.
- Levers are used to amplify or redirect force.
- There are three classes of levers: first, second, and third.
Now let's analyze the characteristics of a car jack and a see-saw to determine their classification:
Car Jack:
- A car jack is a mechanical device used to lift vehicles off the ground for maintenance or tire changes.
- It consists of a long rod or screw that is turned to raise or lower the lifting platform.
- The rod or screw in the car jack can be considered as an inclined plane wrapped around a cylinder, which aligns with the characteristics of a screw.
- Therefore, a car jack can be classified as a screw.
See-saw:
- A see-saw is a playground equipment consisting of a long plank balanced on a fulcrum.
- It is designed for two or more people to sit on opposite ends and take turns pushing off the ground to go up and down.
- The fulcrum in a see-saw acts as the pivot point, and the force applied by the users creates a rotational motion around the fulcrum.
- Based on the description, a see-saw can be classified as a first-class lever, where the fulcrum is located between the effort (force applied by the users) and the load (people sitting on the plank).
Therefore, the answer is b. First class lever, as a car jack is a screw and a see-saw is a first-class lever.

The Moon Blocking the Sun: Solar Eclipse
- When the moon blocks the sun, it is known as a solar eclipse.
- A solar eclipse occurs when the moon passes between the sun and the Earth, casting a shadow on the Earth's surface.
- This phenomenon can only happen during the new moon phase when the moon is positioned directly between the Earth and the sun.
- There are three types of solar eclipses - total, partial, and annular.
- Total solar eclipse: Occurs when the moon completely covers the sun, creating a brief period of darkness on Earth.
- Partial solar eclipse: Occurs when the moon only partially covers the sun, resulting in a partial shadow or dimming effect on Earth.
- Annular solar eclipse: Occurs when the moon is at its farthest distance from the Earth, resulting in the appearance of a ring of fire around the edges of the moon.
- Solar eclipses are rare events and can only be observed from specific locations on Earth where the alignment of the sun, moon, and Earth is in perfect synchronization.
- It is important to note that looking directly at a solar eclipse without proper eye protection can cause serious damage to the eyes.
- Solar eclipses have been studied by scientists and astronomers for centuries, providing valuable insights into the dynamics of celestial bodies and our understanding of the universe.

When a solid is heated, it undergoes a phase change called melting, which results in the formation of a liquid. This process can be explained in detail as follows:
1. Introduction:
- When a solid is heated, the energy is transferred to its atoms or molecules, causing them to vibrate more rapidly.
- As the temperature continues to increase, the kinetic energy of the particles also increases.
2. Melting Point:
- Every substance has a specific temperature at which it changes from solid to liquid. This temperature is known as the melting point.
- When the temperature reaches the melting point of a solid, its particles gain enough energy to overcome the attractive forces holding them together.
3. Breaking of Bonds:
- The heat energy supplied breaks the intermolecular forces or bonds between the particles.
- These forces can be ionic, covalent, or metallic in nature, depending on the type of solid.
4. Arrangement of Particles:
- In a solid state, the particles are arranged in a regular pattern, which gives them a fixed shape and volume.
- As the solid is heated and melts, the particles gain enough energy to move more freely, leading to an increase in disorder.
5. Liquid Formation:
- Once the bonds are broken, the solid transforms into a liquid state.
- In the liquid state, the particles have more kinetic energy and are able to move past one another, resulting in a fluid substance.
6. Properties of the Liquid:
- The liquid formed from the melted solid has a definite volume but takes the shape of its container.
- It exhibits properties such as surface tension, viscosity, and the ability to flow.
In conclusion, when a solid is heated, it melts to form a liquid. This phase change occurs when the particles gain enough energy to break their bonds and transition into a more disordered state.

Explanation:
In the third class of lever, the effort is applied between the fulcrum and the load. This means that the effort is closer to the fulcrum than the load. Here is a detailed explanation:
Definition:
A lever is a simple machine that consists of a rigid beam or bar that pivots around a fixed point called the fulcrum. There are three classes of levers based on the relative positions of the effort (force applied), the fulcrum, and the load (resistance).
Third Class Lever:
In a third class lever, the fulcrum is at one end, the load is at the other end, and the effort is applied in between. The effort is closer to the fulcrum than the load. This type of lever is commonly found in various everyday objects and tools, such as brooms, tweezers, and fishing rods.
Characteristics of Third Class Lever:
- The effort is applied between the fulcrum and the load.
- The effort arm (distance between the fulcrum and the effort) is shorter than the load arm (distance between the fulcrum and the load).
- The mechanical advantage of the lever is always less than 1, which means the effort force must be greater than the load force to achieve equilibrium.
Examples:
- Using a broom to sweep the floor: The fulcrum is the point where the broom handle rests on the floor, the load is the weight of the dirt on the floor, and the effort is applied by the person holding the broom handle.
- Using tweezers to pick up small objects: The fulcrum is the point where the two arms of the tweezers meet, the load is the object being picked up, and the effort is applied by squeezing the arms of the tweezers.
In conclusion, in the third class of lever, the effort is applied between the fulcrum and the load. This type of lever is characterized by having the effort closer to the fulcrum than the load.

What can happen if we touch electric things with wet hands?
When we touch electric things with wet hands, several things can happen:
1. Electric shock:
- Water is a good conductor of electricity, so when we touch electric objects with wet hands, the electrical current can flow through our body, causing an electric shock.
- The severity of the shock can range from mild to severe, depending on the voltage, current, and duration of exposure.
- Electric shocks can cause muscle contractions, burns, cardiac arrest, and even death in extreme cases.
2. Increased risk of burns:
- Wet skin reduces the body's resistance to electric current, increasing the risk of burns.
- The combination of electricity and moisture can lead to thermal burns that can be painful and cause tissue damage.
3. Damage to electrical equipment:
- When we touch electrical appliances or devices with wet hands, the moisture can cause short circuits or damage the internal components.
- Water can corrode the electrical contacts and circuitry, rendering the equipment non-functional or unsafe to use.
4. Fire hazards:
- Wet hands can introduce moisture into electrical outlets, switches, or other electrical components, increasing the risk of short circuits and electrical fires.
5. Trip and fall accidents:
- Electric shocks from touching wet electrical objects can cause muscle contractions and startle reactions, potentially leading to falls or other accidents.
In summary, touching electric things with wet hands can result in electric shocks, increased risk of burns, damage to electrical equipment, fire hazards, and potential accidents. It is crucial to always keep our hands dry when dealing with electricity to ensure our safety.

Answer:
Ribcage:
- The ribcage is responsible for protecting the heart and lungs.
- It consists of curved bones called ribs.
- These ribs are fused firmly together to provide stability and protection to the organs.
- The ribcage forms a cage-like structure around the thoracic cavity.
Skull:
- The skull protects the brain, not the heart and lungs.
- It is a bony structure that encases the brain and provides support and protection.
Spine:
- While the spine does provide support and protection to the spinal cord, it does not directly protect the heart and lungs.
- The spine consists of a series of vertebrae that are stacked on top of each other to form the vertebral column.
Sternum:
- The sternum, also known as the breastbone, is a flat bone located in the center of the chest.
- It forms the front part of the ribcage and helps to protect the heart and lungs.
- However, it is not the primary structure responsible for their protection.
Therefore, the correct answer is Ribcage (B) as it specifically protects the heart and lungs with its curved, fused ribs.

Answer: Vitamin A

• Prevents night blindness: Vitamin A is essential for good vision, particularly in low light conditions. It helps prevent night blindness, which is the inability to see in dim lighting or darkness.


• Helps to keep skin healthy: Vitamin A plays a crucial role in maintaining healthy skin. It promotes the production of skin cells, helps repair damaged skin, and supports the overall health and integrity of the skin.


• Found plentiful in carrots: Carrots are known for their high content of beta-carotene, which is a precursor to vitamin A. The body converts beta-carotene into vitamin A, making carrots a great source of this essential nutrient.

In conclusion, the information provided suggests that the vitamin being referred to is Vitamin A. It is responsible for preventing night blindness, maintaining healthy skin, and can be found in abundance in carrots.