Primary Three - Science Sa2 (Mock)

Bacteria are a diverse group of microorganisms, and not all of them are harmful to humans. In fact, many bacteria are beneficial and play important roles in various ecological processes. Some bacteria help with digestion, produce vitamins, and even protect against harmful pathogens. Therefore, it is true that not all bacteria are harmful.

The letters 'N' and 'S' on a magnet stand for North and South respectively.

When two magnets have like poles facing each other, they will repel each other. This means that they will push away from each other, creating a force that keeps them apart. The like poles of magnets have the same magnetic orientation, which causes the magnetic fields to interact and create a repulsive force between them. This phenomenon is a fundamental property of magnets and is commonly observed in everyday situations.

Bacteria are microscopic organisms that cannot be seen with the naked eye or a magnifying glass. They are too small to be visible without the use of a microscope, which allows for magnification and enhanced visibility of these tiny organisms.

Iron is a magnetic material because it contains iron atoms that have unpaired electrons, which create a magnetic field. When a magnetic field is applied to iron, the unpaired electrons align themselves with the field, causing the iron to become magnetized. This property makes iron useful in various applications, such as in the production of magnets and electromagnets.

This statement is true because not all birds have the ability to fly. While many birds, such as eagles and sparrows, have the ability to fly, there are also several species of flightless birds, such as penguins and ostriches, that have evolved to live and move primarily on land. Therefore, it is accurate to say that not all birds can fly.

Spectacles consist of more than one material because they are typically made with a combination of materials such as plastic, metal, and glass. The frame of the spectacles is usually made of plastic or metal, while the lenses are made of glass or plastic. Additionally, the hinges and screws used in the spectacles are often made of metal. Therefore, spectacles are an object that consists of more than one material.

Rubber is the correct answer because it is a buoyant material that can float on water. It is commonly used in the manufacturing of swimming floats due to its ability to provide flotation and support in the water. Rubber floats are lightweight, durable, and can easily be inflated or deflated as needed. Additionally, rubber is water-resistant, making it suitable for prolonged use in swimming pools or open water.

The statement "All metals are magnetic materials" is incorrect. While some metals, such as iron and nickel, are magnetic, not all metals exhibit magnetic properties. For example, metals like copper and aluminum are not magnetic. Therefore, the correct answer is False.

When a magnet is broken into half, the North and South poles still remain in each broken magnet. This is because magnets have a magnetic field that is created by the alignment of their atoms. Breaking a magnet into half does not change the alignment of the atoms, so each broken piece still retains its own North and South poles.

The 'Stroke' method is used to make a magnet in the given picture. This method involves stroking a piece of iron or steel with a magnet in order to align the magnetic domains within the material, thus creating a magnetic field. This process can be repeated multiple times to increase the strength of the magnet. The 'Stroke' method is a common and effective way to magnetize materials and is often used in industries and everyday applications.

Yeasts are not considered plants because they belong to the kingdom Fungi. While plants are multicellular organisms that produce their own food through photosynthesis, yeasts are single-celled organisms that obtain nutrients by breaking down organic matter. They reproduce through a process known as budding, which is different from the reproductive methods of plants. Therefore, yeasts do not possess the typical characteristics and features of plants.

The statement that a dolphin is a fish is false. Dolphins are actually mammals, not fish. They belong to the group of marine mammals known as cetaceans, which also includes whales and porpoises. Unlike fish, dolphins have lungs and breathe air, give live birth, and nurse their young with milk. They also have a more complex social structure and communication system compared to fish. Therefore, it is incorrect to classify dolphins as fish.

Copper is indeed a metal. It is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. Copper is commonly used in electrical wiring, plumbing, and various industrial applications due to its excellent conductivity and corrosion resistance. Therefore, the statement "Copper is a metal" is true.

The statement "Ferns are fungi" is incorrect. Ferns are not fungi, but rather a type of vascular plant that reproduces via spores. Fungi, on the other hand, are a separate kingdom of organisms that includes mushrooms, yeasts, and molds.

The similarity between mammals and fishes is that some fishes give birth to young while all mammals do. This means that both mammals and some fishes have the ability to reproduce by giving birth to live offspring. This is a characteristic that sets them apart from other animals, such as reptiles and birds, which typically lay eggs.

Copper is not a magnetic material. Unlike iron, nickel, and cobalt, copper does not possess strong magnetic properties. It is classified as a non-magnetic material because it does not attract or repel other magnetic objects. Copper is commonly used in electrical wiring and circuits due to its excellent conductivity, but it does not exhibit magnetic behavior.

Living things can be classified into more than 3 groups. The classification of living things is done based on various criteria such as their cellular structure, mode of nutrition, and evolutionary relationships. The most commonly used classification system is the one that divides living things into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. Therefore, the statement that living things can be classified into only 3 groups is incorrect.

Bacteria is a classification of living things because it is a group of single-celled microorganisms that have a distinct cellular structure and can be found in various habitats. Bacteria are prokaryotes, meaning they lack a nucleus and membrane-bound organelles. They play crucial roles in various ecological processes, such as nutrient cycling, decomposition, and symbiotic relationships. Bacteria can be found in diverse environments, including soil, water, and the human body. They are an essential part of Earth's ecosystems and have a significant impact on the overall balance of life on our planet.

The North pole and the South pole of a magnet have the strongest attracting force. This is because opposite poles attract each other, causing a strong magnetic force between them. The center of the magnet does not have a stronger attracting force compared to the poles. Therefore, the correct answer is the North pole and the South pole.

Rubber and plastic are suitable materials for making slippers because they are flexible, durable, and provide comfort to the wearer. Glass and ceramic are not commonly used for making slippers as they are rigid and can cause discomfort and injury.

A magnet has the ability to exert a force on other magnetic materials. This force can either attract the materials towards the magnet or pull them closer to it. Therefore, the correct answer is "pull" and "attract".

Magnets are used in refrigerator doors to create a seal that keeps the cold air inside. Doorstops often contain magnets to hold the door open or closed. Magnets are used in televisions to direct the electron beam and create images on the screen. MRT cards, also known as subway or metro cards, often use magnetic strips to store information and allow for easy swiping. Some telephones use magnets in their speakers to convert electrical signals into sound waves. Computer disks, such as hard drives and floppy disks, use magnets to store and retrieve data. Keys may also have magnets in them for various purposes, such as attaching to a magnetic key holder.

Objects that float on water are typically less dense than water. Paper, cork, wood, and a glass bottle can all float on water because they have a lower density than water. These materials are less compact and have air pockets or empty spaces within them, making them buoyant enough to float on the surface of the water. Conversely, objects like stone, marble, and other dense materials have a higher density than water, causing them to sink.