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What is a combustion reaction?
- A. It absorbs heat.
- B. It involves the replacement of one element by another.
- C. It involves the sharing of electrons.
- D. It is a reaction that involves oxygen.
Correct Answer: D
Rationale: A combustion reaction is a chemical process that involves a substance reacting with oxygen to produce heat and light. The key component in a combustion reaction is oxygen, making choice D the correct answer. Combustion reactions are typically exothermic, releasing energy in the form of heat and light, making choice A incorrect. Choices B and C describe different types of chemical reactions, not combustion reactions. Therefore, the correct answer is D.
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What is present in an emulsion?
- A. Water and salt
- B. Two or more immiscible liquids
- C. Any liquids
- D. All of the above
Correct Answer: B
Rationale: In an emulsion, two or more immiscible liquids are present. Immiscible liquids are those that do not mix together and form separate layers, such as oil and water. Emulsions are a type of colloid where one liquid is dispersed in another. Water and oil are a common example of an emulsion, where the two liquids do not mix naturally but can be forced to form a stable mixture with the help of an emulsifying agent.
What is a benefit of water's ability to make hydrogen bonds?
- A. Lack of cohesiveness
- B. Low surface tension
- C. Use as a nonpolar solvent
- D. High specific heat
Correct Answer: D
Rationale: The correct answer is D - High specific heat. Water's ability to make hydrogen bonds leads to a high specific heat capacity, which allows it to absorb and release large amounts of heat with minimal temperature change. This property is crucial for maintaining stable temperatures in living organisms and aquatic environments. High specific heat helps regulate body temperature in organisms and prevents sudden temperature fluctuations in water bodies, providing an essential benefit for various biological processes.
What is the term for the reactant that is entirely consumed by the reaction?
- A. limiting reactant
- B. reducing agent
- C. reaction intermediate
- D. reagent
Correct Answer: A
Rationale: The correct answer is A, limiting reactant. In a chemical reaction, the limiting reactant is the substance that is entirely consumed when the reaction reaches completion. It determines the maximum amount of product that can be formed. The reducing agent (choice B) is a substance that donates electrons to another chemical species, the reaction intermediate (choice C) is a molecule formed and consumed in different steps of the reaction, and a reagent (choice D) is a general term for any substance participating in a chemical reaction.
Which material has the smallest specific heat capacity?
- A. water
- B. wood
- C. aluminum
- D. glass
Correct Answer: C
Rationale: Specific heat capacity refers to the amount of heat energy needed to raise the temperature of a substance by a certain amount. In this context, aluminum has the smallest specific heat capacity among the materials listed. This means that aluminum requires the least amount of heat energy to increase its temperature compared to water, wood, and glass. As a result, aluminum is the material with the smallest specific heat capacity in this scenario.
Will solids always sink in liquids?
- A. True, because solids are hard while liquids are not.
- B. True, because solids are heavier than liquids.
- C. False, because solids have a smooth surface, so they will float.
- D. False, it depends on the density of the solid and liquid.
Correct Answer: D
Rationale: The statement 'solids will always sink in liquids' is not always true. Whether a solid sinks or floats in a liquid depends on the relative densities of the solid and the liquid. If the density of the solid is greater than the density of the liquid, the solid will sink. Conversely, if the density of the solid is less than the density of the liquid, the solid will float. Therefore, the correct answer is 'False, it depends on the density of the solid and liquid.'