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?

For each of the following processes, would filtration, distillation, or chromatography be the most effective separation technique:

a. removing the pulp from freshly squeezed orange juice,

b. separating a food dye into its individual components,

c. desalinating seawater?

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?

A soccer ball is dropped out of a window on the second floor of a dormitory to the ground below. Which of the following statements is or are true?

i. The kinetic energy of the ball is greatest at the time it is dropped out the window.

ii. As the ball falls, potential energy is converted into kinetic energy.

iii. The potential energy of the ball is due to the force of gravity acting on it.

(a) Calculate the kinetic energy (in joules) of a 1200-kg automobile moving at 18 m/s.

The mass of a helium atom is roughly four times that of a hydrogen atom. The mass of an oxygen atom is roughly 16 times that of a hydrogen atom.

a. For each of the following pairs, choose the one that has the greater kinetic energy: (i) a H atom moving at 1000 m/s or a He atom moving at 400 m/s, (ii) a H atom moving at 1000 m/s or an O atom moving at 400 m/s, (iii) a He atom moving at 1000 m/s or an O atom moving at 400 m/s.

b. A He atom is moving at 800 m/s. What is the speed of an O atom that has the same kinetic energy as the He atom?

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?

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 electrostatic potential energy of the two particles increase or decrease as the distance between them is increased?

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.

Use appropriate metric prefixes to write the following measurements without use of exponents: c. 6.48×10^-7 L

Use appropriate metric prefixes to write the following measurements without use of exponents: d. 1.81×10^-2 s

Use appropriate metric prefixes to write the following measurements without use of exponents: g. 5.1×10² cm

Make the following conversions: a. 72 °F to °C

Make the following conversions: c. 233 °C to K

Make the following conversions: d. 315 K to °F

Make the following conversions: e. 2500 °F to K

Make the following conversions: f. 0 K to °F

The temperature on a warm summer day is 87 °F. What is the temperature in °C?

Many scientific data are reported at 25 °C. What is this temperature in kelvins and in degrees Fahrenheit?

(a) A sample of tetrachloroethylene, a liquid used in dry cleaning that is being phased out because of its potential to cause cancer, has a mass of 40.55 g and a volume of 25.0 mL at 25 °C. What is its density at this temperature? Will tetrachloroethylene float on water? (Materials that are less dense than water will float.)

(b) Carbon dioxide (CO₂) is a gas at room temperature and pressure. However, carbon dioxide can be put under pressure to become a 'supercritical fluid' that is a much safer dry-cleaning agent than tetrachloroethylene. At a certain pressure, the density of supercritical CO₂ is 0.469 g/cm³. What is the mass of a 25.0-mL sample of supercritical CO₂ at this pressure?

(a) To identify a liquid substance, a student determined its density. Using a graduated cylinder, she measured out a 45-mL sample of the substance. She then measured the mass of the sample, finding that it weighed 38.5 g. She knew that the substance had to be either isopropyl alcohol 1density 0.785 g/mL² or toluene (density 0.866 g/mL). What are the calculated density and the probable identity of the substance?

b. An experiment requires 78.1 g of benzene, a liquid whose density is 0.876 g/mL. Rather than weigh the sample on a balance, a chemist chooses to dispense the liquid using a graduated cylinder. What volume of the liquid should he use?

c. A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm³, what is the mass of the cube?

(d) A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm³, what is the mass of the cube?

a. After the label fell off a bottle containing a clear liquid believed to be a solvent called tetrahydrofuran, a chemist measured the density of the liquid to verify its identity. A 25.0-mL portion of the liquid had a mass of 22.08 g. A chemistry handbook lists the density of tetrahydrofuran at 25 °C as 0.8833 g/mL. Is the calculated density in agreement with the tabulated value?

b. An experiment requires 50.0 g of a substance called n-hexane, whose density at 25 °C is 0.6606 g/mL. What volume of n-hexane should be used?

The density of titanium metal is 4.506 g/cm³ at 20 °C. What is the mass of a spherical ball of titanium with a diameter of 2.00 cm. [The volume of a sphere is (4/3) πr³, where r is the radius.]

For January through April 2020, at the height of the global coronavirus pandemic, it is estimated that global emissions of carbon dioxide (CO₂) decreased by 940 million metric tons (1 metric ) compared to the same period in 2019. a. Express this mass of CO₂ in grams without exponential notation, using an appropriate metric prefix.

Indicate which of the following are exact numbers: (a) the mass of a 3- by 5-in. index card, (b) the number of ounces in a pound, (c) the volume of a cup of Seattle's Best coffee, (d) the number of inches in a mile, (e) the number of microseconds in a week, (f) the number of pages in this book.