8sg2 Yearly Science Exam

Fossil fuels, such as coal, oil, and gas, began forming millions of years ago. During that time, when dinosaurs roamed the Earth, trees fell into swamps and were covered by silt and mud. Over time, these organic materials transformed into the fossil fuels that we use today. The advantages of using fossil fuels are that they are readily available, cheap, and can be used for various purposes, such as generating electricity and heating homes. However, the disadvantages are that fossil fuels will eventually run out and they also contribute to pollution as they are burnt in power stations and vehicles.

The law of conservation of energy states that energy cannot be created or destroyed, but can only change forms. There are many different forms of energy. Potential energy is stored energy and kinetic energy is the energy of motion. Take for example the motion of a roller coaster on its tracks: at the start of the loop, the roller coaster has high potential energy. At the bottom of the loop, it has high kinetic energy. If energy is conserved why does the roller coaster eventually slow down and stop at the bottom of the roller? That's because the force of friction changes the kinetic energy into sound and heat energy, especially when the brakes are applied. As the roller coaster moves around the track, its potential and kinetic energy change back and forth.

The picture shown is likely a physical change because physical changes involve a change in the appearance or form of a substance without altering its chemical composition. Since the question does not provide any specific details about the picture, it is difficult to determine the exact nature of the change. However, physical changes can include processes like melting, freezing, or dissolving, which do not involve a chemical reaction.

Coal is the correct answer because it is one of the primary sources of electricity generation worldwide. Coal-fired power plants burn coal to produce steam, which then drives turbines connected to generators, converting mechanical energy into electrical energy. Despite the environmental concerns associated with coal combustion, it remains a significant contributor to global electricity production due to its abundance and relatively low cost compared to other sources such as oil and natural gas.

Without the picture, it is impossible to determine the specific physical or chemical change being referred to.

A natural fuel formed in the geological past from the remains of living organisms is known as a fossil fuel. Fossil fuels, such as coal, oil, and natural gas, are formed over millions of years from the decomposition of organic matter, such as plants and animals, that lived millions of years ago. These fuels are non-renewable resources and are widely used for energy production due to their high energy content.

Oil is a fossil fuel because it is formed from the remains of ancient plants and animals that were buried and subjected to high heat and pressure over millions of years. This process transformed the organic matter into hydrocarbons, which make up crude oil. Fossil fuels are non-renewable resources and are widely used for energy production due to their high energy content.

Line A in the picture represents the atomic number. The atomic number of an element is the number of protons in the nucleus of an atom of that element. It is a unique identifier for each element and determines its position on the periodic table. The atomic number also determines the chemical properties and behavior of an element.

The main disadvantage of a coal-fired power plant is that it is a non-renewable energy source. This means that coal is a finite resource and once it is depleted, it cannot be replaced. Unlike renewable energy sources such as solar or wind power, which can be replenished naturally, coal takes millions of years to form. Therefore, relying on coal for energy production contributes to the depletion of a valuable resource and increases our dependence on fossil fuels, which have negative environmental impacts such as air pollution and greenhouse gas emissions.

The question asks for the letter that best describes the characteristics of a metal. Since the table is not provided, it is impossible to determine the specific characteristics associated with each letter. Therefore, without further information, it is not possible to provide a meaningful explanation for why answer C is correct.

The picture shown is most likely depicting a physical change. Physical changes involve a change in the appearance or state of a substance without altering its chemical composition. In the absence of further information about the picture, it is difficult to provide a specific explanation. However, examples of physical changes could include changes in shape, size, or state of matter, such as melting, freezing, or dissolving.

Based on the information given, the letter A is the best description of the characteristics of a non-metal. However, without further information or context from the table, it is not possible to provide a more specific explanation.

In the given picture, line B represents the symbol for the element.

The chemical formula for salt is NaCl, which indicates that it is composed of sodium (Na) and chlorine (Cl) atoms. Sodium and chlorine combine to form an ionic bond, resulting in the formation of the compound salt.

The box labelled C represents a pure element, where only one type of atom is present. This means that the substance in the box consists of only one type of atom and is not combined with any other elements or compounds.

The main advantage of wind power is that it is a renewable energy source. Unlike fossil fuels, which are finite and will eventually run out, wind power relies on the natural movement of air currents and is therefore sustainable in the long term. This makes it an environmentally friendly alternative to traditional forms of energy production that contribute to climate change and pollution. Wind power also has the potential to reduce dependence on non-renewable energy sources and promote a more sustainable and cleaner energy future.

The particle of an atom with a positive charge is known as a proton. Protons are found in the nucleus of an atom and have a positive electrical charge. They are responsible for determining the atomic number of an element and contribute to the overall mass of the atom. Neutrons, on the other hand, have no charge, while electrons have a negative charge and orbit around the nucleus. The term "particle" is too general and does not specifically refer to the positively charged particle in an atom.

Food is a source of chemical energy because it contains molecules that can be broken down through chemical reactions in the body. These reactions release energy that can be used for various functions such as growth, movement, and metabolism. The energy stored in the chemical bonds of food molecules, such as carbohydrates, proteins, and fats, is converted into a usable form of energy called ATP (adenosine triphosphate) through cellular respiration. This ATP is then used by cells to carry out their functions. Therefore, food serves as a source of chemical energy for the body.

Atoms are composed of three basic components: electrons, protons, and neutrons. Electrons are negatively charged particles that orbit around the nucleus. Protons are positively charged particles found in the nucleus. Neutrons are neutral particles also located in the nucleus. These three components together determine the properties and behavior of an atom.

Plants obtain the energy to make food from the sun through a process called photosynthesis. During photosynthesis, plants use sunlight, along with carbon dioxide from the air and water from the soil, to produce glucose (food) and oxygen. The sun's energy is captured by chlorophyll in the plant's leaves, which converts it into chemical energy that can be used for growth and development. Therefore, the sun is the ultimate source of energy for plants, enabling them to carry out their vital life processes.

The picture is a chemical change because it involves a transformation at the molecular level, resulting in the formation of new substances. Physical changes, on the other hand, do not alter the chemical composition of a substance.

Electrons are the particles that move around the nucleus of an atom. They have a negative charge and are much smaller in size compared to protons and neutrons. Electrons play a crucial role in determining the chemical properties and behavior of an atom, as they are involved in chemical bonding and the formation of molecules.

This statement is false. Elements cannot be broken down into simpler substances. Elements are the fundamental building blocks of matter and cannot be further broken down by any chemical means. They are made up of only one type of atom and retain their unique properties.

Natural gas is a non-renewable resource because it is formed over millions of years from the remains of plants and animals buried deep in the earth. Once extracted and burned for energy, it cannot be easily replenished within a human lifetime. In contrast, wind, solar energy, and hydroelectricity are considered renewable resources as they are naturally replenished and can be harnessed without depleting the earth's finite reserves.

Potential Energy (PE) is the energy that is stored in an object due to its position or state. It is not caused by the movement of an object, but rather by its potential to do work. This type of energy can be found in various forms, such as gravitational potential energy, elastic potential energy (like compressed springs), or chemical potential energy. When the object's position or state changes, this stored energy can be converted into other forms of energy, such as kinetic energy.

The image depicts a solid object in direct contact with another solid object, suggesting the transfer of heat through direct contact or conduction. Conduction is the process of heat transfer between objects that are in direct contact with each other, where heat energy flows from a region of higher temperature to a region of lower temperature. This image does not show any fluid movement or electromagnetic waves, ruling out convection and radiation as methods of heat transfer.

Coal is formed from the remains of plants that lived millions of years ago. These plants absorbed energy from the sun through photosynthesis and converted it into chemical energy, which was stored in their tissues. Over time, these plants were buried and subjected to heat and pressure, transforming them into coal. Therefore, the energy stored in coal originally came from the sun.

Heat is being transferred mainly by radiation from a hot clothes iron to your hand held close to it. Radiation is the transfer of heat through electromagnetic waves, and in this situation, the heat from the clothes iron is being transferred to your hand without any direct contact or movement of particles.

Dissolving sugar in tea is not a chemical change because it does not result in the formation of new substances. It is a physical change where the sugar molecules disperse evenly throughout the tea, but the chemical composition of both the sugar and the tea remains the same. In contrast, burning a match, ripening a banana, and cooking a cake involve chemical reactions that result in the formation of new substances.

The box labelled A represents a mixture of two compounds, as indicated by the presence of two types of compounds.

The image shows convection as the method of heat transfer. Convection is the transfer of heat through the movement of fluids, such as liquids or gases. In the image, there is a clear depiction of fluid movement, indicating the transfer of heat through convection. This method occurs when warmer fluid rises and cooler fluid sinks, creating a continuous flow of heat transfer.

Batteries are stores of chemical energy. This is because batteries store energy through a chemical reaction that occurs within them. When a battery is connected to a circuit, the chemical reaction takes place, converting the stored chemical energy into electrical energy, which can then be used to power devices. Therefore, the correct answer is chemical energy.

The box labelled B represents a pure compound because it contains only one type of compound. A pure compound is composed of two or more elements that are chemically bonded together in a fixed ratio. In the given picture, there are no other compounds or elements present in box B, indicating that it is a pure compound.