GED Science Extra Prep: Characteristics of Matter
Each type of matter has a defining set of characteristics, and you can expect some questions on the GED Science exam to test your knowledge of what these characteristics are.
- Which of the following always stays the same when a chemical reaction takes place?
A. the amount of gas
B. the number of molecules
C. the number of atoms
D. the temperature
- Which of the following correctly lists the atoms in the following compounds?
A. CO2 has 1 chlorine atom and 2 oxygen atoms.
B. H2O has 1 hydrogen atom and 2 oxygen atoms.
C. C6H12O6 has 6 chlorine atoms, 12 hydrogen atoms, and 6 oxygen atoms.
D. CH4 has 1 carbon atom and 4 hydrogen atoms.
Answers and Explanations
- The correct answer is C.
The law of conservation of mass states that matter is always conserved. For chemical equations, this means that the number of atoms of each type of element is the same at the end of the reaction as it was before the reaction; hence, Choice (C) is correct.
Choice (A) is not true because chemical reactions can produce gases. Choice (B) is tempting but incorrect. It’s the number of atoms, not the number of molecules, that stays the same. Choice (D) is incorrect because exothermic reactions give off heat, causing the temperature of the surroundings to rise, and endothermic reactions take in heat, causing the temperature of the surroundings to fall.
- The correct answer is D.
Choice (A) is incorrect because CO2 has 1 carbon atom (not chlorine) and 2 oxygen atoms.
Choice (B) is incorrect because H2O has 2 hydrogen atoms and 1 oxygen atom (not the other way around).
Choice (C) is incorrect because C6H12O6 has 6 carbon atoms (not chlorine), 12 hydrogen atoms, and 6 oxygen atoms.
Choice (D) is correct. CH4 has 1 carbon atom and 4 hydrogen atoms.