8th Grade Final Exam Practice Test

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The correct answer is CaCO3 because it represents the chemical formula for calcium carbonate. Calcium carbonate is a compound composed of one calcium atom (Ca) and three carbonate ions (CO3). The formula CaCOOO is incorrect as it does not follow the proper chemical notation. CaCO5 is also incorrect as it suggests the presence of five carbonate ions, which is not the case. CaCO is also incorrect as it does not specify the number of carbonate ions present.

During an endothermic reaction, energy is absorbed. Endothermic reactions require an input of energy in order to proceed. This means that the reactants have a lower energy level compared to the products, and energy is absorbed from the surroundings to make up for this difference. As a result, the surroundings become cooler, and the reaction is characterized by a decrease in temperature.

The given state of matter is liquid. This is because liquids have a definite volume but no definite shape. They can flow and take the shape of their container. The other options, solid and gas, do not fit the description given in the question.

The roller coaster has the most gravitational potential energy at point A because it is at the highest point of the track. At this point, the roller coaster has the maximum height and therefore the maximum potential energy due to gravity. As the roller coaster moves downwards, its potential energy decreases and is converted into kinetic energy.

The correct answer is Yes, because the reactants are different from the products. In a chemical reaction, the reactants are transformed into different substances, which are the products. The fact that the reactants and products are different indicates that a chemical reaction has occurred. The presence of an arrow in the equation also suggests a chemical reaction, as it represents the direction of the transformation.

The image indicates that the iron shavings are clustering around certain areas. These areas are most likely the magnetic poles of the magnet. Magnetic poles are the regions of a magnet where the magnetic field is strongest, and they attract magnetic materials like iron. Therefore, it can be inferred that the majority of the iron shavings are collecting around the magnetic poles of the magnet.

The correct answer is No, because chemical bonds were NOT broken and/or formed. This means that there was no chemical reaction occurring. Chemical reactions involve the breaking and/or forming of chemical bonds, so if no bonds were broken or formed, it indicates that there was no chemical reaction taking place in the diagram.

The given question is asking about the state of matter being represented. The answer is "Solid" because solids have a definite shape and volume, and their particles are tightly packed together and vibrate in fixed positions.

During an endothermic reaction, temperature decreases because the reaction absorbs heat from the surroundings. This means that the reactants have a higher energy level than the products, causing a decrease in temperature.

The correct answer is "Yes, because chemical bonds were broken and/or formed." This is because chemical reactions involve the breaking and/or forming of chemical bonds between atoms. In the diagram, if there is evidence of broken or formed chemical bonds, it indicates that a chemical reaction has occurred.

The correct answer is insoluble because they are not mixing. When two liquids are soluble, they are able to mix together completely, forming a homogeneous solution. In this case, since the liquids are not mixing and one is floating on top of the other, it suggests that they are not soluble and therefore insoluble.

The answer is correct because polyester is indeed synthetic as it is manufactured in a factory using chemical processes. On the other hand, cotton is natural as it is derived from the cotton plant.

During an exothermic reaction, the reactants release energy in the form of heat to the surroundings. This increase in energy causes the temperature to rise, resulting in an increase in temperature. Therefore, the correct answer is "Increases."

During an exothermic reaction, energy is released. This means that the reaction releases heat or energy into its surroundings. Exothermic reactions typically involve the formation of new bonds, resulting in the release of energy that was previously stored in the chemical bonds of the reactants. This release of energy is often observed as an increase in temperature or the production of light.

The given state of matter is gas. This is because gases have no fixed shape or volume, and they can easily expand to fill the space available to them.

The diagram includes two terms: compound and molecule. A compound refers to a substance made up of two or more different elements chemically bonded together. On the other hand, a molecule refers to a group of two or more atoms held together by chemical bonds. Both terms are related to the combination of elements, but a compound specifically involves different elements while a molecule can involve the same or different elements.

The diagram likely represents a collection of individual atoms, as indicated by the term "single atoms." These atoms are most likely representing elements, which are substances made up of only one type of atom. Therefore, the two terms that best describe the diagram are "element" and "single atoms."

As temperature increases, atoms move more quickly because an increase in temperature corresponds to an increase in the kinetic energy of the atoms. This increase in kinetic energy causes the atoms to vibrate and move more rapidly. On the other hand, as temperature decreases, atoms move more slowly because a decrease in temperature corresponds to a decrease in the kinetic energy of the atoms. This decrease in kinetic energy causes the atoms to have less vibrational and translational motion, resulting in slower movement. Therefore, both statements accurately describe the relationship between temperature and the speed of atoms.

The reactants in a chemical reaction are the substances that undergo a chemical change. In the given options, H2O (water) and NH3 (ammonia) are the reactants because they are the substances that are present before the reaction takes place. NH4+ (ammonium) and OH- (hydroxide) are not reactants in this context as they are not mentioned in the question or diagram.

NH4+ and OH- are the products according to the diagram. This can be determined by analyzing the chemical reactions depicted in the diagram. NH4+ is a positively charged ion formed by the combination of NH3 (ammonia) with a hydrogen ion (H+). OH- is a negatively charged ion formed by the dissociation of H2O (water) into a hydroxide ion (OH-) and a hydrogen ion (H+). Therefore, NH4+ and OH- are the products indicated in the diagram.

When Charles heats the helium inside the balloon, the atoms inside the balloon will gain energy and move faster. This increased kinetic energy causes the atoms to spread out more, leading to an expansion in volume. As a result, the balloon will get bigger.

The diagram likely represents a combination of single atoms and molecules. An element refers to a substance that is composed of only one type of atom, while a molecule is formed when two or more atoms are chemically bonded together. Therefore, the terms "element" and "molecule" accurately describe the components in the diagram.

The melting point, boiling point, density, and solubility are all physical properties that can be used to identify a substance. The melting point is the temperature at which a substance changes from a solid to a liquid state, while the boiling point is the temperature at which a substance changes from a liquid to a gas state. Density is a measure of how much mass is contained in a given volume of a substance. Solubility refers to the ability of a substance to dissolve in a solvent. By analyzing these properties, scientists can determine the identity of a substance.

As the temperature of a substance increases, the kinetic energy of its particles also increases. This increased kinetic energy causes the particles to move more rapidly and spread out, resulting in an increase in the volume of the substance. Therefore, the statement "As temperature increases, volume increases" correctly describes the relationship between temperature and volume of a substance.

The roller coaster has the least gravitational potential energy at point B. This is because gravitational potential energy is directly proportional to the height of an object above the reference point. At point B, the roller coaster is at its lowest height, which means it has the least gravitational potential energy compared to points A and C.

The first statement is false because not all chemical reactions result in the formation of new substances. Some reactions may only involve a rearrangement of atoms or molecules without producing new compounds. The third statement is also false because chemical reactions can indeed result in the formation of new substances, such as when two or more elements combine to form a compound.

The diagram shows a balanced chemical equation, where the number of atoms on both sides of the reaction is equal. This indicates that in a chemical reaction, atoms are neither gained nor lost. Additionally, the law of conservation of mass states that the mass of the reactants is equal to the mass of the products, further supporting the answer choice.