Chapter Test 5 - Chemical Bonds (30questions)

In a chemical reaction, energy can be either absorbed or released. This is because chemical reactions involve the breaking and forming of chemical bonds, which requires energy. Some reactions require an input of energy to break bonds and form new ones, resulting in energy absorption. On the other hand, some reactions release energy as bonds are broken and new ones are formed. Therefore, energy can be either absorbed or released during a chemical reaction.

Exothermic reactions release heat energy. This means that during an exothermic reaction, energy is being released to the surroundings in the form of heat. This can be observed by an increase in temperature in the surroundings or the production of light or sound. In contrast, endothermic reactions absorb heat energy from the surroundings, causing a decrease in temperature. Molecular reaction and high heat are not specific types of energy that release heat.

Using a home fire extinguisher is the best way to put out a small kitchen fire. Fire extinguishers are specifically designed to combat fires and are equipped with the necessary chemicals to extinguish different types of fires. They are easy to use and can quickly suppress the flames, preventing the fire from spreading and causing further damage. Using a fire extinguisher is safer and more effective than other options like blowing out the fire, using a garden hose, or simply turning off appliances, as these methods may not effectively extinguish the fire or could potentially worsen the situation.

Combustion is the rapid reaction between oxygen and a fuel, resulting in the release of heat and light. During combustion, the fuel undergoes oxidation, combining with oxygen to produce carbon dioxide, water vapor, and other combustion products. This process is exothermic, meaning it releases energy in the form of heat. Combustion is a common chemical reaction that occurs in various natural and human-made processes, such as burning wood, gasoline in car engines, or natural gas in stoves.

When chemical bonds break and new bonds form, it indicates a chemical change. In a chemical change, the composition and properties of the substances involved are altered, resulting in the formation of new substances with different chemical properties. This process involves the rearrangement of atoms and the breaking and forming of chemical bonds, leading to the creation of entirely new molecules or compounds. It is different from a physical change, where no new substances are formed, and the matter remains the same.

A chemical change is a process that transforms matter into one or more new substances. During a chemical change, the atoms of the original substances rearrange themselves to form different molecules or compounds. This is different from a physical change, where the matter may change its state or appearance, but the chemical composition remains the same. Conservation refers to the preservation or protection of resources, and freezing is a physical change where a substance changes from a liquid to a solid state due to a decrease in temperature.

An endothermic reaction is a reaction that absorbs energy in the form of heat from its surroundings. In this type of reaction, the products have a higher energy level than the reactants. This means that energy is being taken in or absorbed during the reaction, resulting in a decrease in temperature of the surroundings. This is why an endothermic reaction feels cold to the touch.

To bring a fire under control, removing oxygen is necessary. Oxygen is one of the three components of the fire triangle, along with heat and fuel. By removing oxygen, the fire is deprived of the necessary element to sustain combustion. This can be achieved by using fire extinguishers or smothering the fire with a fire blanket or sand. Removing oxygen effectively suppresses the fire and prevents it from spreading or causing further damage.

A decomposition reaction is a type of chemical reaction where a compound breaks down into two or more simpler substances. In this case, the hydrogen peroxide (H2O2) is breaking down into water (H2O) and oxygen (O2). Therefore, the given reaction of hydrogen peroxide turning into water and oxygen is an example of a decomposition reaction.

Enzymes are biological catalysts that speed up reactions in living things. They are composed of proteins and act by lowering the activation energy required for a reaction to occur. Enzymes are highly specific and can only catalyze a particular reaction or group of reactions. They are essential for various biological processes, such as digestion, metabolism, and DNA replication. Enzymes are not consumed or altered during the reaction, making them reusable and efficient catalysts in living organisms.

Activation energy is the minimum amount of energy that needs to be supplied to start a reaction. It is the energy required to break the bonds between reactant molecules and initiate the formation of new bonds in the products. Without reaching this threshold energy, the reaction will not proceed. Therefore, activation energy is crucial in determining the rate at which a reaction occurs.

When water vapor in the air condenses and turns into liquid water in the form of rain, it is considered a physical change. This is because the substance (water) undergoes a change in its physical state, from a gas to a liquid, but its chemical composition remains the same. No new substances are formed during this process, so it is not a chemical change.

Water most affects fires by cooling the fire and preventing contact between oxygen and fuel. When water is applied to a fire, it absorbs heat and lowers the temperature, which helps to extinguish the flames. Additionally, water creates a barrier between the fire and the surrounding oxygen and fuel, effectively cutting off the fire's source of oxygen and preventing it from spreading. This cooling and smothering effect of water makes it an effective tool for firefighting.

In this chemical reaction, copper oxide (CuO) and carbon (C) react to produce copper (Cu) and carbon dioxide (CO2). This type of reaction is known as a replacement reaction. In a replacement reaction, one element replaces another element in a compound. In this case, carbon replaces oxygen in copper oxide to form copper and carbon dioxide. This can be visualized in the analogy provided, where the guy in the orange shirt (carbon) "steals" the date (oxygen) of the other guy (copper oxide), resulting in a rearrangement of the reactants and products.

The process described in the question, where two or more substances combine to make a more complex compound, is known as a synthesis reaction. This is because the reactants are being synthesized or combined to form a single product. In the given example, the skinny bird and the worm combine to form a fat bird, which is a more complex compound than the individual reactants. Therefore, the correct answer is synthesis reaction.

Carbon dioxide is not one of the three things necessary to start and maintain a fire. The three essential components for a fire are fuel, heat, and oxygen. Fuel provides the material that can burn, heat raises the temperature of the fuel to its ignition point, and oxygen supports the combustion process. Carbon dioxide, on the other hand, is a byproduct of the combustion process and can even be used to extinguish fires by displacing oxygen.

The principle of conservation of mass in chemical reactions states that matter is not created or destroyed. This means that the total mass of the reactants before the reaction is equal to the total mass of the products after the reaction. The atoms are rearranged and bonded differently, but no atoms are lost or gained in the process. This principle is a fundamental concept in chemistry and is supported by experimental evidence.

A chemical equation is a shorter and easier way to represent chemical reactions using symbols instead of words. It shows the reactants and products involved in the reaction and uses chemical formulas and symbols to represent them. By using a chemical equation, it becomes more concise and efficient to communicate the details of a chemical reaction.

An inhibitor is a substance that is used to decrease the rate of a chemical reaction. It works by interfering with the reaction process, either by binding to the reactants or the catalyst, and preventing the reaction from proceeding at its normal rate. Inhibitors are commonly used in various industries and processes to control the speed of reactions and prevent unwanted side reactions or damage to equipment. They are especially useful in situations where a reaction needs to be slowed down or stopped altogether.

Adding a catalyst does not increase the number of particles of a substance available to react in a chemical reaction. A catalyst works by lowering the activation energy required for the reaction to occur, but it does not change the number of particles present. Increasing the concentration, increasing the surface area, and increasing the mass all involve increasing the number of particles available for the reaction, thus increasing the likelihood of a successful reaction.

A solid that forms from a solution during a chemical reaction is called a precipitate. This occurs when two or more substances in a solution react to form a new substance that is insoluble and falls out of the solution as a solid. The formation of a precipitate is often a visual indicator that a chemical reaction has occurred. It is different from a bond, reactant, or chemical, which are not specific to the formation of a solid during a chemical reaction.

In every chemical reaction, energy is either absorbed or released. This is because chemical reactions involve the breaking and formation of chemical bonds, which requires energy. The change in energy can be in the form of heat, light, or electricity. Therefore, energy is an essential component of chemical reactions and is involved in the overall transformation that occurs.

In the given question, the analogy is being made between the symbols of elements being used to write the formula of compounds and letters being used to write words. Just like letters are the building blocks of words, the symbols of elements are the building blocks of compound formulas. Therefore, the correct answer is "letters are used to write words".

The production of a new material as ash from a burnt log is sure evidence of a chemical reaction. When a log burns, it undergoes a chemical change known as combustion. During this process, the log reacts with oxygen in the air, resulting in the formation of ash as a new material. This change in composition and the formation of a new substance is a clear indication of a chemical reaction taking place.

In order to balance the chemical equation, the number of atoms on both sides of the equation must be equal. The equation currently has two hydrogen atoms on the left side (H2) and two hydrogen atoms on the right side (H2O). To balance this, the coefficient of H2 must be changed to 2, resulting in 4 hydrogen atoms on both sides. Additionally, the coefficient of H2O must also be changed to 2, resulting in 4 oxygen atoms on both sides. Therefore, the correct answer is to change the coefficient of both H2 and H2O to 2.

The correct answer is 2 Fe2O3 + 3 C yields 4 Fe + 3 CO2. This equation is balanced because the number of atoms of each element is the same on both sides of the equation. There are 2 Fe atoms on the left side and 4 Fe atoms on the right side, 6 O atoms on the left side and 6 O atoms on the right side, and 3 C atoms on the left side and 3 C atoms on the right side. Therefore, the equation is balanced.