1.
What can reverse a chemical change?
Correct Answer
A. Further chemical reaction
Explanation
Further chemical reaction can reverse a chemical change because it involves the formation of new chemical bonds and the breaking of existing ones, leading to the conversion of the products of the original chemical change back into the reactants. This process allows for the reversal of the chemical change and the restoration of the original substances.
2.
What are chemical changes that produce heat called?
Correct Answer
B. Exothermic reactions
Explanation
Exothermic reactions are chemical changes that release heat. In these reactions, the energy released from the breaking of chemical bonds is greater than the energy required to form new bonds. This excess energy is released in the form of heat, resulting in a temperature increase in the surroundings. Examples of exothermic reactions include combustion, oxidation, and neutralization reactions.
3.
What are chemical changes that require heat referred to?
Correct Answer
A. Endothermic reactions
Explanation
Chemical changes that require heat are referred to as endothermic reactions. In these reactions, heat is absorbed from the surroundings, resulting in a decrease in temperature. This absorption of heat is necessary for the reaction to occur and is usually accompanied by a feeling of coldness. Endothermic reactions are commonly observed in processes like photosynthesis, melting of ice, and evaporation of water.
4.
Which of these is a reaction to a chemical change?
Correct Answer
A. Hydrogen
Explanation
Hydrogen is a reaction to a chemical change because it is an element that can undergo various chemical reactions, such as combining with oxygen to form water or reacting with other elements to form compounds. In these reactions, the chemical composition of hydrogen changes, indicating a chemical change. Sodium, water, and air are not specific reactions but rather substances that can be involved in chemical reactions.
5.
What must a reaction have before it is referred to as undergoing a chemical change? It must be ___ from the initial chemical substances.
Correct Answer
D. All of the above
Explanation
Before a reaction can be referred to as undergoing a chemical change, it must be different, distinct, and separate from the initial chemical substances. This means that there should be observable changes in the properties, composition, or structure of the substances involved in the reaction. All of the options provided (different, distinct, separate) imply these changes, hence the correct answer is "All of the above".
6.
How many classes of chemical changes exist?
Correct Answer
B. 3
Explanation
There are three classes of chemical changes. This means that chemical changes can be classified into three different categories based on their characteristics and properties.
7.
Which of these is a class of chemical change not requiring carbon?
Correct Answer
A. Inorganic chemical changes
Explanation
Inorganic chemical changes refer to chemical reactions that do not involve carbon compounds. These reactions can occur between elements or compounds that do not contain carbon. In contrast, organic chemical changes involve carbon-containing compounds. Biochemical changes refer to chemical reactions that occur within living organisms, involving the transformation of organic molecules. Biological changes refer to any changes that occur within living organisms, including biochemical changes as well as other physiological and cellular processes. Therefore, the correct answer is inorganic chemical changes.
8.
Which of these classes of chemical changes is concerned with the chemistry of carbon?
Correct Answer
B. Organic chemical changes
Explanation
Organic chemical changes are concerned with the chemistry of carbon. Carbon is a unique element that forms the basis of organic compounds, which are essential for life. Inorganic chemical changes, on the other hand, do not involve carbon compounds. Biological changes and biochemical changes may involve carbon, but they are more specific to processes occurring in living organisms and their chemical reactions. Therefore, the correct answer is organic chemical changes.
9.
Which of these classes of chemical changes deals with living organisms?
Correct Answer
C. Biochemical changes
Explanation
Biochemical changes refer to chemical reactions that occur within living organisms. These reactions involve the transformation of organic molecules, such as proteins, carbohydrates, and lipids, into energy or other necessary substances for the organism's survival. Unlike inorganic and organic chemical changes, which can occur in non-living matter, biochemical changes are specific to living organisms and are essential for various biological processes, including metabolism, growth, and reproduction. Therefore, biochemical changes are the class of chemical changes that deal with living organisms.
10.
Which of these is a reaction to chemical change?
Correct Answer
D. All of the above
Explanation
All of the options listed - Methylation, Polymerisation, and Halogenation - are reactions to chemical change. Methylation refers to the addition of a methyl group to a molecule, which can alter its properties. Polymerisation is the process of combining monomers to form a polymer, resulting in a chemical change. Halogenation involves the substitution of one or more hydrogen atoms in a molecule with a halogen atom, leading to a chemical change. Therefore, all of these options are reactions to chemical change.