Subject Knowledge Review - Science

The forces that hold atoms together are best described as "bonds". Bonds refer to the electrostatic forces of attraction between atoms, which can be covalent, ionic, or metallic in nature. These bonds are responsible for the formation of molecules and compounds, as they hold the atoms together in a stable arrangement. The terms "attachments," "joins," and "links" do not accurately describe the concept of the forces holding atoms together.

The correct answer is the first option: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. This answer lists the planets in the correct order of their distance from the Sun, starting with the closest planet (Mercury) and ending with the farthest planet (Pluto).

Mirrors are able to form a clear image because light is reflected by the mirror. When light hits a mirror, it bounces off the smooth surface of the mirror and creates a reflection. This reflection allows the light to maintain its original properties, such as direction and intensity, resulting in a clear image being formed.

This represents the biological feature of variation. The presence of different patterns and colors on the ladybirds indicates genetic diversity within the species. Variation is an important aspect of evolution as it allows for adaptation to changing environments and increases the chances of survival for a species.

A book resting on a table does not involve energy transfer because there is no movement or change in the book's position or state. Energy transfer occurs when there is a change in the form or location of energy. In the case of the other options, energy is being transformed or transferred. For example, in a candle burning, chemical energy is being converted into heat and light energy. In a person walking upstairs, mechanical energy is being transferred from the person's muscles to their movement. In a radio playing, electrical energy is being converted into sound energy.

In a complete circuit, the flow of electricity is the same through the switch, through the bulb, and along the wire. This is because in a series circuit, the current remains constant throughout the circuit. The switch, bulb, and wire are all connected in a series, so the current passing through them is the same.

Bacteria have a wide distribution because they can be found in various environments such as soil, water, and even in the human body. They are not limited to living or dead organisms, as they can exist in both. While some bacteria can cause diseases, not all bacteria are harmful, and many play important roles in various ecological processes. Therefore, the statement "They have a wide distribution" is correct.

Iron rusting is an example of a chemical reaction because it involves a chemical change. When iron reacts with oxygen and moisture in the air, it forms iron oxide, commonly known as rust. This process alters the chemical composition of iron, resulting in a new substance with different properties. Unlike physical changes such as melting or dissolving, chemical reactions involve the breaking and forming of chemical bonds, resulting in the creation of new substances.

A species is the correct answer because it refers to a group of organisms that share similar characteristics and are capable of interbreeding to produce fertile offspring. This is the fundamental concept in biology for categorizing and classifying living organisms. Clones, families, and genera are not specific enough to describe this particular characteristic of organisms.

In the reaction of hydrogen and iodine, new bonds are formed between hydrogen atoms and iodine atoms. This is because hydrogen and iodine atoms have a high tendency to form a covalent bond, where they share electrons to achieve a stable electron configuration. Therefore, the correct answer is that bonds between hydrogen atoms and iodine atoms are formed.

In order for characteristics to be inherited by living organisms, genetic material must be passed from one generation to another. This is because genetic material contains the instructions for the traits and characteristics of an organism. Through processes like sexual reproduction, where genetic material from two parents combines to form offspring, or asexual reproduction, where genetic material is passed down from a single parent, the genetic material is transferred and inherited by the next generation. Mutations occurring within the cell or the occurrence of asexual reproduction are not necessary for inheritance to take place, but the passing of genetic material is essential.

Scientists classify all living things into different groups based on their characteristics and evolutionary relationships. These groups are called kingdoms. The correct answer is "Plants, animals, fungi, and bacteria" because these are the four main kingdoms in which all living organisms are categorized. Plants are multicellular organisms that produce their own food through photosynthesis. Animals are multicellular organisms that consume other organisms for food. Fungi are multicellular or unicellular organisms that obtain nutrients by decomposing organic matter. Bacteria are unicellular organisms that can be found in various environments and have diverse metabolic capabilities.

In an ecosystem, there is interaction between plants, animals, and their physical environment. This means that plants and animals depend on each other for survival, as well as on the non-living components of their environment such as air, water, soil, and sunlight. Plants provide oxygen and food for animals, while animals help in pollination and seed dispersal for plants. The physical environment provides the necessary resources and conditions for both plants and animals to thrive. This interdependence and interaction between all these components is crucial for maintaining the balance and functioning of the ecosystem.

In option A, the bar magnets are aligned in opposite directions, causing them to attract each other. This attraction will cause the magnets to come to rest with their north poles facing each other. In options B, C, and D, the magnets are either aligned in the same direction or at different angles, which will not result in them coming to rest. Therefore, option A is the correct answer.

When sounds are produced, they cause the eardrums to vibrate. These vibrations are then transmitted through the middle ear bones to the inner ear. In the inner ear, the vibrations are converted into electrical impulses by the hair cells. These impulses are then carried by the auditory nerve to the brain, where they are processed and interpreted as sound.

The reading on the balance stays the same because mass is neither lost nor gained. When the ice cubes melt, they transform from a solid state (ice) to a liquid state (water). However, the total mass of the system remains constant. The water that is formed from the melted ice has the same mass as the ice cubes, so there is no change in the reading on the balance.

When the circuit is complete, the bulb acts as a load and converts the electrical energy stored in the battery into light and heat energy. This is possible because the bulb contains a filament that heats up when an electric current passes through it, producing light and heat as a result. The energy transfer occurs from the battery to the bulb, allowing the bulb to illuminate and generate heat. The potential energy in the circuit is not controlled by the length of the electrical wire, but rather by the voltage provided by the battery.

In the absence of air resistance on the Moon, both the hammer and the feather experience only the force of gravity. Since they are dropped from the same height, they will both fall with the same acceleration due to gravity. Therefore, they will both land at the same time.

Asexual reproduction (cloning) results in the least variation among offspring because it involves the production of genetically identical individuals. In this process, a single parent passes on its exact genetic material to its offspring, resulting in minimal or no genetic variation. On the other hand, sexual reproduction involves the combination of genetic material from two parents, leading to genetic recombination and increased variation among offspring. Mutation and recombination of genetic material can introduce new genetic variations, further increasing the variation among offspring.

Our current understanding of evolution is based on the idea that mutation of genes have led to beneficial changes. This means that changes in the genetic material of living organisms can result in advantageous traits or adaptations that improve their chances of survival and reproduction. These beneficial mutations can then be passed on to future generations, leading to the gradual accumulation of new traits and the formation of new species over time. This concept is supported by numerous scientific studies and observations in the field of evolutionary biology.

The question asks about the approximate number of elements that all materials are made up of. The correct answer is 100, which suggests that there are approximately 100 elements that make up all materials.

Day and night occur because the Earth rotates on its axis. As the Earth spins, different parts of it are exposed to the Sun's light, creating daytime, while other parts are in shadow, creating nighttime. This rotation causes the cycle of day and night that we experience on Earth.

Water evaporating is an example of a physical change because it involves a change in the arrangement and spacing of water particles without the formation of any new substances. During evaporation, water molecules gain enough energy to break their intermolecular bonds and escape into the air as water vapor. However, the chemical composition of water remains the same before and after evaporation. Therefore, no new substances are formed, making it a physical change.

Electrons are subatomic particles that are present in all forms of matter. They are negatively charged and are found orbiting around the nucleus of an atom. Electrons play a crucial role in determining the properties and behavior of matter. They are responsible for the flow of electricity in conductors, but their presence is not limited to conducting materials. Electrons are also found in non-conductive materials, such as liquids and solids. Additionally, electrons are present in matter even when there is no electrical charge passing through it. Therefore, the correct answer is that electrons are present in all forms of matter.

The mass of an object refers to the amount of matter it contains, which is measured in kilograms. Mass is a fundamental property of an object and is independent of its size or shape. It is different from volume (amount of space it takes up), capacity (measured in liters), or density (measured in kilograms per meters cubed). Mass can be thought of as a measure of the inertia of an object, determining how it responds to external forces.

When we alter the frequency of a sound, we change its pitch. Pitch refers to the perceived highness or lowness of a sound. The frequency of a sound wave determines its pitch, with higher frequencies corresponding to higher pitches and lower frequencies corresponding to lower pitches. Therefore, altering the frequency of a sound will result in a change in its perceived pitch.

A drop of water contains millions of molecules of water because water molecules are very small and compact. In a single drop of water, there are numerous water molecules tightly packed together. The exact number of molecules can vary depending on the size of the drop, but it is generally in the range of millions.

The electrical resistance of a conductor is a measure of the difficulty of the flow of electrons through the conductor. Resistance is caused by collisions between electrons and atoms in the conductor, which impedes the flow of current. A higher resistance means a greater difficulty for electrons to pass through the conductor, resulting in a lower current flow. Conversely, a lower resistance allows for easier electron flow and a higher current. Therefore, the correct answer is that the electrical resistance of a conductor is the measure of the difficulty of the flow of electrons through the conductor.

The correct answer is that the weight lifter uses energy to exert a force on the bar. This is because in order to lift the bar, the weight lifter needs to apply a force against the force of gravity. This force requires energy, which is provided by the weight lifter's muscles.

The correct answer is "Excrete, feed, grow, move, reproduce, respire and are sensitive to their surroundings." This answer includes all the essential characteristics of living organisms. Organisms excrete waste, feed to obtain energy, grow and develop, move to find resources or escape danger, reproduce to pass on their genetic material, respire to obtain energy, and are sensitive to their surroundings to respond to stimuli.

When a piece of rock is brought back to Earth from the Moon, its mass stays the same. Mass is a measure of the amount of matter in an object, and it remains constant regardless of the location. Similarly, the amount of matter the rock contains also stays the same because matter cannot be created or destroyed. Therefore, the correct answer is C - Stays the same.

The correct answer is B because it shows that when the solid ball is placed in the way of the torch's light, a shadow is formed on the screen behind the ball. This is because the ball blocks the light from reaching the screen, creating a dark area behind it.

Evaporation is the process by which molecules at the surface of a liquid gain enough energy to escape into the surrounding air as a gas. Molecules with higher than average energy have a greater chance of escaping from the surface, leading to evaporation. Therefore, the statement "Molecules with higher than average energy escape from the surface" is true.

Copper wire is a good electrical conductor because some electrons in the metal can move easily within the wire. In metals, such as copper, the outermost electrons of the atoms are loosely bound and can move freely. When a voltage is applied, these free electrons can easily flow through the wire, carrying electric current. This property of copper allows it to efficiently transmit electricity, making it a commonly used material in electrical wiring.

The circulatory system in humans plays a crucial role in carrying out various functions. It is responsible for carrying food to body cells, ensuring that they receive the necessary nutrients for energy and growth. Additionally, it carries oxygen around the body, which is essential for cellular respiration and the production of energy. Lastly, the circulatory system also carries waste products away from cells, helping to eliminate toxins and maintain overall health. Therefore, options 1, 2, and 3 accurately describe the role of the circulatory system.

The batteries in a torch push the electrons around the circuit in one direction. This is known as a direct current, where the flow of electrons is consistent and in a single path. As the electrons move through the circuit, they encounter the filament of the bulb, which offers resistance. This resistance causes the filament to heat up and emit light. Therefore, the batteries are responsible for creating a continuous flow of electrons that ultimately powers the light bulb in the torch.

When light falls on an object like a book, it interacts with the surface of the book. The molecules in the book scatter the light in different directions. Some of this scattered light enters our eyes and reaches the retina. The retina then sends signals to the brain, which interprets these signals as the image of the book. Therefore, we are able to see a book because light is scattered by the book and enters our eyes.

Substance Q could be a liquid on some days and solid on others because its melting point is 17°C, which is close to room temperature (20°C). This means that on colder days, the substance could be in a solid state, while on warmer days, it could transition into a liquid state.

When white light falls on a green t-shirt, the t-shirt appears green because it scatters green light. The molecules in the fabric absorb all the other colors present in white light, but reflect or scatter the green light back to our eyes. This selective scattering of green light is what gives the t-shirt its green appearance.

Diagram A correctly shows the forces acting on the ball after it leaves the child's hand. The force of gravity is acting downwards, represented by the arrow pointing downwards. There is no other force acting on the ball, so there are no additional arrows in the diagram.

When the engine of a moving boat is turned off, the boat slows down and stops due to the forces of air resistance and water resistance. Air resistance is the force exerted by the air on the boat as it moves through the atmosphere, which opposes its motion and causes it to slow down. Water resistance is the force exerted by the water on the boat, which also opposes its motion and further contributes to its deceleration. Together, these two forces act against the boat's forward motion, eventually bringing it to a stop.

The correct answer is that half the Moon is lit by the Sun but we see it from a different angle. This is because the Moon orbits around the Earth, and as it does so, the angle at which we see the illuminated portion of the Moon changes. This causes different shapes or phases of the Moon to be visible from Earth at different times of the month.

Gravitational attraction exists between all objects of any mass and depends on the mass of the objects and the distance they are apart. This means that the gravitational pull between two objects will be stronger if they have a larger mass and if they are closer together. Therefore, option D is the correct pair of statements.

When electrons travel through the filament of a light bulb, they collide with fixed atoms in the filament. This collision causes the atoms to vibrate, which in turn generates heat. As the temperature of the filament increases, it starts to emit light, resulting in the glow of the light bulb. Therefore, the correct answer is that the electrons collide with fixed atoms in the filament, causing them to vibrate, get hot, and emit light.

On the launch pad, forces are balanced because the shuttle is stationary and not moving. In space, the forces are also balanced because the shuttle is moving in a straight line at a constant speed.

The correct answer is "The rate at which energy is transferred to the bulb." Watts are a unit of power, which measures the rate at which energy is transferred or used. In this case, the table lamp is designed to handle a maximum of 100 watts, indicating that it can safely transfer energy to the bulb at a rate of up to 100 watts.