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문제 17
A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids A and B and gas C are elements or compounds?
문제 18
Zirconia, an oxide of zirconium, is often used as an affordable diamond substitute. Just like diamond, it is a colorless crystal which sparkles under sunlight. Which of the following physical properties do you think would help in differentiating between diamond and Zirconia—melting point, density, or physical state?
문제 19
In the process of attempting to characterize a substance, a chemist makes the following observations: The substance is a silvery white, lustrous metal. It melts at 649 °C and boils at 1105 °C. Its density at 20 °C is 1.738 g/cm3. The substance burns in air, producing an intense white light. It reacts with chlorine to give a brittle white solid. The substance can be pounded into thin sheets or drawn into wires. It is a good conductor of electricity. Which of these characteristics are physical properties, and which are chemical properties?
문제 19a
The radius of an atom of tungsten (W) is about 2.10 A . (a) Express this distance in nanometers (nm). Express this distance in picometers (pm).
문제 19b
The radius of an atom of tungsten (W) is about 2.10 Å. (b) How many tungsten atoms would have to be lined up to create a wire of 2.0 mm?
문제 20a
(a) Read the following description of the element zinc and indicate which are physical properties and which are chemical properties. Zinc melts at 420 °C. When zinc granules are added to dilute sulfuric acid, hydrogen is given off and the metal dissolves. Zinc has a hardness on the Mohs scale of 2.5 and a density of 7.13 g/cm3 at 25 °C. It reacts slowly with oxygen gas at elevated temperatures to form zinc oxide, ZnO.
문제 20b
(b) Which properties of zinc can you describe from the photo? Are these physical or chemical properties?
문제 21a,b
Label each of the following as either a physical process or a chemical process: (a) crushing a metal can (b) production of urine in the kidneys
문제 21c,d,e
Label each of the following as either a physical process or a chemical process: (c) melting a piece of chocolate (d) burning fossil fuel (e) discharging a battery.
문제 22
A match is lit and held under a cold piece of metal. The following observations are made: (a) The match burns. (b) The metal gets warmer. (c) Water condenses on the metal. (d) Soot (carbon) is deposited on the metal. Which of these occurrences are due to physical changes, and which are due to chemical changes?
- Which separation method is better suited for obtaining sugar from cane juice—filtration or evaporation?
문제 23
- A silvery metal is put inside a beaker of water. Bubbles form on the surface of the metal, and it dissolves gradually. (b) Do you expect the remaining solution to be a pure substance or a mixture?
문제 24
문제 24a
A silvery metal is put inside a beaker of water. Bubbles form on the surface of the metal and it dissolves gradually. (a) Is this an example of a chemical or a physical change?
- Convert this energy to calories. When the bullet is stopped by a bulletproof vest, which form of energy does the kinetic energy of the bullet convert to?
문제 25
문제 25a
(a) Calculate the kinetic energy, in joules, of a 15-g bullet moving at 120 m/s.
- A baseball weighs 145.4 g. What is the kinetic energy, in joules, of this baseball when it is thrown by a major league pitcher at 150 km/h?
문제 26
문제 27a
Two positively charged particles are first brought close together and then released. Once released, the repulsion between particles causes them to move away from each other. (a) This is an example of potential energy being converted into what form of energy?
문제 27b
Two positively charged particles are first brought close together and then released. Once released, the repulsion between particles causes them to move away from each other. (b) Does the potential energy of the two particles prior to release increase or decrease as the distance between them is increased.
문제 28
For each of the following processes, does the potential energy of the object(s) increase or decrease? (b) Water is pumped from ground level to the reservoir of a water tower 30 m above the ground.
문제 29
What is the kinetic energy and velocity of the aluminum sphere in Problem 1.4 at the moment it hits the ground? (Assume that energy is conserved during the fall and that 100% of the sphere's initial potential energy is converted to kinetic energy by the time impact occurs.)
문제 31a
Convert the following expressions into exponential notation: (a) 3 terameters (tm)
문제 31b,c
Convert the following expressions into exponential notation: (b) 2.5 femtoseconds (fs) (c) 57 micrometers (mm)
문제 31d
Convert the following expressions into exponential notation: (d) 8.3 megagrams (mg).
문제 32c
Use appropriate metric prefixes to write the following measurements without use of exponents: (a) 7.29×106 g (b) 6.1×10-10 m (c) 1.828×10-3 s
문제 32d
Use appropriate metric prefixes to write the following measurements without use of exponents: (d) 3.523×109 m3 (e) 9.62×102 m/s (f) 8.923×10-12 kg
문제 32g
Use appropriate metric prefixes to write the following measurements without use of exponents: (g) 3.552×1012 L.
문제 33a,b
Make the following conversions: (a) 83 °F to °C (b) 29 °C to °F
문제 33c
Make the following conversions: (c) 294 °C to K
문제 33d
Make the following conversions: (d) 832 K to °C
문제 33e
Make the following conversions: (e) 721 K to °F