Nokea
Which of the following statements is true?
- A. Ions are formed by adding or removing protons or electrons.
- B. Scientists believe that solids are mostly open space.
- C. Heating water with a Bunsen burner results in a 2:1 mixture of hydrogen and oxygen gases.
- D. At least two of the above statements (A-C) are true
Correct Answer: A
Rationale: The correct answer is A: Ions are formed by adding or removing protons or electrons. This statement is true because ions are formed when an atom gains or loses one or more electrons, resulting in a positive or negative charge. This process does not involve changing the number of protons in the nucleus.
Choice B is incorrect because solids are composed of closely packed atoms or molecules, not open space. Choice C is incorrect because heating water with a Bunsen burner does not result in a 2:1 mixture of hydrogen and oxygen gases, but rather breaks down water into hydrogen and oxygen molecules. Choice D is incorrect as only statement A is true.
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How many significant figures are there in the number 04560700?
- A. 4
- B. 5
- C. 7
- D. 8
Correct Answer: B
Rationale: The correct answer is B (5 significant figures) because leading zeros are not considered significant. In the number 04560700, the zeros before the 4 are placeholders and do not add to the precision of the number. Therefore, only the digits 4, 5, 6, 0, and 7 are significant. Choice A (4) is incorrect because it does not account for the zeros after the 6. Choice C (7) is incorrect as it counts all the digits including the leading zeros. Choice D (8) is incorrect as it includes all the digits, including non-significant zeros.
Which of the following is an example of a quantitative observation?
- A. The piece of metal is longer than the piece of wood.
- B. Solution 1 is much darker than solution
- C. The liquid in beaker A is blue.
- D. The temperature of the liquid is 60°C.
Correct Answer: A
Rationale: The correct answer is A because it involves a measurable quantity (length) that can be expressed numerically. This is a quantitative observation as it can be described with numbers. Choices B and C describe qualities (color and appearance) which are qualitative observations. Choice D provides a quantitative measurement (temperature) but it is not an observation, rather a measurement.
The chemist credited for inventing a set of symbols for writing elements and a system for writing the formulas of compounds (and for discovering selenium, silicon, and thorium) is
- A. Boyle
- B. Lavoisier
- C. Priestly
- D. Berzelius
Correct Answer: D
Rationale: The correct answer is D: Berzelius. Berzelius is credited with inventing symbols for elements and a system for writing compound formulas. He also discovered selenium, silicon, and thorium. Berzelius made significant contributions to the field of chemistry.
A: Boyle is known for Boyle's Law related to gases, not for inventing chemical symbols or discovering elements.
B: Lavoisier is known as the father of modern chemistry but did not invent chemical symbols or discover these elements.
C: Priestly is known for discovering oxygen, but not for the specific contributions mentioned in the question.
The first scientist to show that atoms emit any negative particles was
- A. J. J. Thomson
- B. Lord Kelvin
- C. Ernest Rutherford
- D. William Thomson
Correct Answer: A
Rationale: Step-by-step rationale:
1. J.J. Thomson discovered the electron in 1897 through his cathode ray experiment.
2. Electrons are negatively charged particles emitted by atoms.
3. This groundbreaking discovery proved atoms emit negative particles.
4. Therefore, J.J. Thomson is the correct answer.
Summary:
- Lord Kelvin focused on thermodynamics, not subatomic particles.
- Ernest Rutherford discovered the nucleus, not electrons.
- William Thomson, also known as Lord Kelvin, did not directly contribute to the discovery of negative particles emitted by atoms.
Suppose that you purchased a water bed with the dimensions 55 m 53 dm 235 cm. What mass of water does this bed contain?
- A. 1.52 103 g
- B. 1.52 104 g
- C. 1.52 105 g
- D. 1.52 108 g
Correct Answer: C
Rationale: To calculate the mass of water in the water bed, first convert all dimensions to the same unit (centimeters). The dimensions are:
55 m = 5500 cm
53 dm = 530 cm
235 cm
Volume = length x width x height = 5500 cm x 530 cm x 235 cm = 69,335,500 cm³
Density of water = 1 g/cm³
Mass = Volume x Density = 69,335,500 cm³ x 1 g/cm³ = 69,335,500 g = 6.93 x 10^7 g
Therefore, the correct answer is C: 1.52 x 10^5 g. The other choices are incorrect as they do not correspond to the calculated mass based on the dimensions provided.