Nokea
Will solids always sink in liquids?
- A. True, a solid is hard, and liquids are not.
- B. True, solids are heavier than liquids.
- C. False, 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: Solids will not always sink in liquids. 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 that of the liquid, it will sink. If the density of the solid is less than that of the liquid, it will float. Therefore, it is incorrect to state that solids will always sink in liquids without considering their respective densities. The weight or hardness of the solid and the smoothness of its surface do not determine whether it will sink or float in a liquid. The critical factor is the density relationship between the solid and the liquid.
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In the chemical reaction CH₄ + 2O₂ → CO₂ + 2H₂O, what are the reactants?
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'A: CHâ‚„ and Oâ‚‚.' Reactants are the substances that undergo a change to form the products in a chemical reaction. In the given reaction, CHâ‚„ (methane) and Oâ‚‚ (oxygen) are the reactants, as they transform into COâ‚‚ and 2Hâ‚‚O, which are the products. Therefore, the correct answer is A.
What is the density of a block on your desk that acts as a paperweight? The block measures 3cm by 4cm by 6cm and has a mass of 184.32g.
- A. 13.27 g/cm3
- B. 2.56 g/cm3
- C. 0.39 g/cm3
- D. None of the above.
Correct Answer: B
Rationale: To calculate density, you use the formula: Density = Mass/Volume. First, calculate the volume of the block by multiplying its dimensions: 3cm x 4cm x 6cm = 72 cm3. Next, divide the mass (184.32g) by the volume (72 cm3) to find the density. Density = 184.32g / 72 cm3 = 2.56 g/cm3. Therefore, the correct answer is B, with a density of 2.56 g/cm3.
What is the name for a reaction in which electrons are transferred from one atom to another?
- A. combustion reaction
- B. synthesis reaction
- C. redox reaction
- D. double-displacement reaction
Correct Answer: C
Rationale: A redox reaction, also known as a reduction-oxidation reaction, involves the transfer of electrons from one substance to another. During this process, one substance is oxidized (loses electrons) while another is reduced (gains electrons). This transfer of electrons is a key characteristic of redox reactions, making choice C the correct answer. Combustion reaction (choice A) involves a substance reacting with oxygen to produce heat and light, but it does not necessarily involve electron transfer. Synthesis reaction (choice B) involves the combination of two or more substances to form a new compound, without necessarily involving electron transfer. Double-displacement reaction (choice D) involves the exchange of ions between two compounds, but not the transfer of electrons from one atom to another.
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 the name for the horizontal rows of the periodic table?
- A. groups
- B. periods
- C. families
- D. sets
Correct Answer: B
Rationale: In the periodic table, the horizontal rows are called 'periods.' These periods represent the number of electron shells an element has. Each period starts a new energy level, indicating the elements' properties and atomic structure. 'Groups' refer to the vertical columns of the periodic table, each containing elements with similar chemical properties. 'Families' can also be used interchangeably with groups. 'Sets' is a vague term and not specifically related to the layout of the periodic table. Understanding the distinction between 'periods' and 'groups' is crucial in comprehending the organization and properties of elements in the periodic table.