Chemistry 101 Week 1
Which of the following is not a rule regarding significant figures? Select the correct answer below: -All trailing zeros to the right of a decimal mark are significant. -All nonzero digits are considered significant. -All zeroes between significant digits are significant. -All nonzero digits can be ignored.
Correct answer: -All nonzero digits can be ignored. All of the above are rules except that nonzero digits can be ignored.
Which of the following statements is/are example(s) of something that could be explained using chemistry? -The ripening of an apple ripens other apples. -Venus is the only planet that spins in the opposite direction to Earth. -A 200-pound person would only weigh 76 pounds on Mars. -A piece of cut potato turns brown when left out on the cutting board.
Correct answer: -The ripening of an apple ripens other apples. -A piece of cut potato turns brown when left out on the cutting board. The ethylene gas produced by a ripening apple ripens other apples. This is an example of a chemical process. The changes in the surface color of a potato when left exposed to air are another example of a process that changes the properties of matter.
A tentative explanation of observations that acts as a guide for gathering and checking information is called a: Select the correct answer below: -hypothesis -law -theory -scientific method
Correct answer: -hypothesis The hypothesis initiates further experimenting, which could lead to a theory or a law. The entirety of this process is called the scientific method.
Which is NOT a scientific discipline that chemistry is related to? Select the correct answer below: -toxicology -nutrition -philosophy -nanotechnology
Correct answer: -philosophy Knowledge of chemistry is central to understanding a wide range of scientific disciplines including toxicology, nutrition, and nanotechnology.
Which is NOT a scientific field that is requires a knowledge of chemistry? Select the correct answer below: -physics -sociology -astronomy -biology
Correct answer: -sociology Chemistry deals with atoms and subatomic particles, which have properties as dictated by particle physics. Astronomy deals with chemistry in the sense that stars produce all of their chemical elements through nuclear fusion. And biology is intimately linked with chemistry, as the large molecules that make up biological structures obey chemical principles. Sociology deals with factors that are emergent properties of large groups of humans, so there is little to do with chemistry.
The circumference of the earth is approximately 40 million meters. This is closest to: Select the correct answer below: -40 picometers -40 kilometers -40 megameters -40 gigameters
Correct answer: 40 megameters 1,000,000 meters is equal to 1 megameter. 40,000,000 meters is then equal to 40 megameters.
Which of the following units is a derived SI unit (not one of the SI base units)? Select the correct answer below: -meter -kilogram -second -newton
Correct answer: newton Newtons are defined to be kg ms2. The other three units are base SI units.
Which of the following temperatures are equivalent to absolute zero (0 K)? Select all that apply. Select all that apply: -74.93∘F -−100∘C -−273.15∘C -−459.67∘F
Correct answer: −273.15∘C −459.67∘F We can convert from Kelvin to Celsius using the following equation: ∘C=K−273.15 Therefore, 0K−273.15=−273.15∘C We can convert from Celsius to Fahrenheit using the following equation: ∘F∘F=95×∘C+32=95×−273.15∘C+32=−459.67∘F Therefore, −273.15∘C and −459.67∘F show absolute zero on the Celsius and Fahrenheit scales.
A liter is equivalent to: -1 cm3 -1 m3 -1 mm3 -1 dm3
Correct answer: 1 dm3 Use the fact that 1mL=1cm3 to determine the equivalent volume of 1L. If 1mL=1cm3, then 1L=1,000mL=1,000cm3. Now, convert 1,000cm3 into m3. 1,000cm3×(1m100cm)3=1×10−3m3 Now, use the fact that 1m=10dm to determine the volume of 1dm3 in m3. 1dm3×(1m10dm)3=1×10−3m3 Therefore, 1L=1×10−3m3=1dm3.
A speed limit in a U.S. city is 65.0 miles per hour. Canadian cities express speed limits in kilometers per hour. Express the value in km/hr. (1.609 km=1 mile) Select the correct answer below: -100kmhr -102kmhr -105kmhr -110kmhr
Correct answer: 105 km/hr To convert the speed from miles per hour to kilometers per hour, we must use the fact that 1 mi=1.609km. 65 miles 1 hour×1.609 km 1 mile=104.59 km/hr Therefore, the speed limit in a Canadian city would read about 105 km/hr.
35 gigatons equals __________. Select the correct answer below: 3.5×10−9 tons 3.5×10−10 tons 3.5×109 tons 3.5×1010 tons
Correct answer: 3.5×10^10 tons The prefix "giga" means 109, so it can be written as the following. 35 gigaton=35×10^9 tons To write the number in scientific notation, the decimal part must be between 1 and 10. Move the decimal point in 35 to the left one place, and, since this makes the number smaller by a power of 10, add 1 to the exponent on 10 to compensate.35×10^9 tons=3.5×10^10 tons.
The radius of a hydrogen atom is about 0.000000000037m. Select this value in scientific notation. Select the correct answer below: -3.7×10−10 -3.7×10−11 -3.7×10−12 -37×10−11
Correct answer: 3.7×10−11 The magnitude of this number is less than 1, so the exponent will be negative. Move the decimal point to the right until the number has a single digit in the ones place. In this case, the decimal point is moved 11 places to the right to get the number 3.7, so the exponent is −11. Therefore 0.000000000037=3.7×10−11
If we wish to convert a value in years into days, a conversion factor we could use would be: Select the correct answer below: -1 year/365 days -365 days/1 year -1 year/24 hours -24 hours/1 year
Correct answer: 365 days/1 year The top and the bottom must be equal to each other, so 365 days and 1 year, as those represent the same length of time. In addition, days must be on top and years on the bottom so that we can appropriately cancel out the existing unit.
Which measurement of the length of an object is the most precise? Select the correct answer below: -4.3 cm -4.30 cm -4.308 cm -4.3084 cm
Correct answer: 4.3084 cm The more significant figures there are in a value, the more precise of a measurement it represents.
Carbon dioxide has a density of 2.0gL. What mass will a 3.5 L sample of carbon dioxide have? Select the correct answer below: -7.0 g -0.57 g -1.8 g -1.1 g
Correct answer: 7.0 g If density is mass over volume, then mass is density times volume. m =d×v7.0g=2.0gL×3.5 L
Which of the following statements BEST describes the SI system of unit? Select the correct answer below: -An updated version of the English System of Measurement. -An expansion of the metric system. -Another version of the Imperial System of Measurement. -The only system of measurement that is used throughout the world.
Correct answer: An expansion of the metric system. The SI system is used in the scientific and medical fields and is an expanded form of the metric system.
In what temperature scale does water boil at 100∘? Select the correct answer below: -Fahrenheit -Kelvin -Celsius -Grams
Correct answer: Celsius Water boils at 100 degrees in Celsius, 373.15 degrees in Kelvin and 212 degrees in Fahrenheit. The gram is a unit of mass, not temperature.
Which word BEST completes the sentence below: _________ are any substance made up of matter and can be natural or man-made. Select the correct answer below: -Atoms -Chemicals -Molecules -Elements
Correct answer: Chemicals Everything around us is composed of varying chemicals.
Which is the shortest length of time? Select the correct answer below: -one microsecond -one nanosecond -one millisecond -one decisecond
Correct answer: one nanosecond A nanosecond is 10^−9 seconds, whereas a microsecond is 10^−6 seconds, a millisecond is 10^−3 seconds, and a decisecond is 10^−1 seconds.
The number of significant figures in a value is a display of the _________ of a measurement. Select the correct answer below: -precision -accuracy -both precision and accuracy -none of the above
Correct answer: precision Accuracy is a measure of how close a measurement is to a true or accepted value, whereas precision is a measure of how well consecutive measures of the same quantity agree with one another. The number of significant figures in a value will provide information regarding the precision of the value. For example, 15.000mL is a more precise value than 15mL. Significant figures alone will not provide evidence to suggest that a measured value is close to the true or accepted value.
Explain why chemistry is sometimes called "The Central Science" Select the correct answer below: -Chemistry is typically studied in the central years (tenth and eleventh grade) of a high school education. -Chemistry is the most important discipline in science. -Chemistry is highly interconnected with so many other scientific disciplines. -Other fields of science only connect to each other through chemistry.
Correct answer: Chemistry is highly interconnected with so many other scientific disciplines. Chemistry is sometimes referred to as “the central science†due to its interconnectedness with a vast array of other STEM disciplines (STEM stands for areas of study in the science, technology, engineering, and math fields). Chemistry and the language of chemists play vital roles in biology, medicine, materials science, forensics, environmental science, and many other fields, as illustrated in the following figure. A flowchart shows a box containing chemistry at its center. Chemistry is connected to geochemistry, nuclear chemistry, chemical physics, nanoscience and nanotechnology, materials science, chemical engineering, biochemistry and molecular biology, environmental science, agriculture, and mathematics. Each of these disciplines is further connected to other related fields including medicine, biology, food science, geology earth sciences, toxicology, physics, and computer science. Figure showing chemistry literally in the center, because of how highly interconnected it is to other disciplines.Â
Why is the term "chemical-free" when used to market cleaning products misleading? Select the correct answer below: -Only synthetically made cleaners are available to purchase. -Even naturally occurring substances are chemicals. -"Chemical-free" cleaners would not be effective. -All cleaners are made in laboratories and contain chemicals.
Correct answer: Even naturally occurring substances are chemicals. The term "chemical-free" is misleading because all substances are made up of chemicals. Even natural-based cleaners like vinegar or baking soda are chemical compounds. The term is used only to sell products and plays on the misconception that chemicals are toxic.
Which of the following must be true about a precise measurement? -It typically contains many significant figures. -It has very few significant figures. -It is very close to the true value. -It is far away from the true value.
Correct answer: It typically contains many significant figures. A precise measurement has a high degree of certainty, as indicated by having many significant figures.
In which temperature scale is the boiling point of water represented by the largest number? Select the correct answer below: -Celsius -Fahrenheit -Kelvin -The number stays the same in all units.
Correct answer: Kelvin The boiling point of water is 100 Celsius, 212 Fahrenheit, and 373 Kelvin. Therefore the boiling point of water is represented by the largest number on the Kelvin scale.
How are organic light emitting diodes (OLEDs), used in many modern displays, related to chemistry? Select the correct answer below: -Chemistry helped to discover what OLEDs were. -OLEDs use new materials that were developed using chemistry. -Chemistry is critical in marketing the new materials. -The displays are needed to continue to study chemistry.
Correct answer: OLEDs use new materials that were developed using chemistry. Organic light emitting diodes (OLEDs) are synthesized compounds that are now used in many displays. Chemistry played a role in determining methods for creating these compounds.
Many metals rust when exposed to a source of oxygen like air or water. Why does rusting fall under the study of chemistry? Select the correct answer below: -Rusting is an example of a property of matter. -Rusting is an example of an interaction of matter. -Rusting is an example of a composition of matter. -Rusting is not described by chemistry.
Correct answer: Rusting is an example of an interaction of matter. The rusting of a blade is due to a chemical reaction between the metal and oxygen. This is an interaction of matter, which is part of chemistry.
Which of the following defines mass? Select the correct answer below: -The basic unit for measuring distance -The amount of matter in an object -The force per unit area -The space occupied by any sample of matter
Correct answer: The amount of matter in an object Mass is the amount of matter in an object. The meter is the basic unit for measuring distance, pressure is the force per unit area, and volume is the space occupied by any sample of matter.
Dimensional analysis can be used to compute: Select the correct answer below: -the density of objects -the cost of a list of groceries -the distance a car can travel given the available funds -all of the above
Correct answer: all of the above Dimensional analysis can help us in a great number of every-day situations by simplifying seemingly complicated mathematical problems.
What is the SI unit of "mole" used to measure? Select the correct answer below: -mass of a substance -amount of a substance -temperature of a substance -time for substance to change phase
Correct answer: amount of a substance The mole is an SI unit used to measure amount of a substance. It's similar to how a 'dozen' is an amount that means 12 of something.
Which of the following substances will float when placed in pure water, which has a density of 1.00 g/mL? Select the correct answer below: -aluminum with a density of 2.70 g/mL -ethanol with a density of 0.81 g/mL -milk with a density of 1.03 g/mL -steel with a density of 7.80 g/mL
Correct answer: ethanol with a density of 0.81 g/mL Anything that has a density less than that of pure water will float on the surface of water. Ethanol is the only listed substance with the a density less than 1.00 g/mL
Which would NOT be an appropriate unit for density? Select the correct answer below: -g/mL -kg/m3 -g/s -all of the above are acceptable
Correct answer: g/s Density is an expression of mass per volume, and seconds are a unit of time, so this does not work for density.
"The higher the pH of the water in a pond, the higher the algae growth." This statement is an example of a _____________. -law -theory -fact -hypothesis
Correct answer: hypothesis A hypothesis is a proposed explanation for a set of observations. It is a statement that can be tested through experimentation.
Which of the following is not reliant on an understanding of chemistry? Select the correct answer below: geology biotechnology agriculture mathematics
Correct answer: mathematics Geology, biotechnology, and agriculture all rely on chemistry in their study and application.
The standard SI unit for the measurement of length is: Select the correct answer below: -the meter -the kilogram -the foot -the centimeter
Correct answer: the meter The foot and the centimeter are units of length but the standard SI unit for the measurement of length is the meter. The kilogram is a unit of weight.
A well-substantiated, comprehensive, testable explanation of a particular aspect of nature is called a(n): Select the correct answer below: -observation -hypothesis -theory -law
Correct answer: theory A hypothesis is testable, but not comprehensive. A law has already been sufficiently tested. An observation is not testable or comprehensive.
Which of the following has 3 significant figures? Select all that apply. Select all that apply: -123 -12.3 -123000. -1.23×10^4
Correct answer:123 12.3 1.23×104 -All of the answer choices have 3 significant figures except for 123000. The decimal point at the end of the number means that the trailing zeros are also significant, so it has 6 total.
Object A has a density of 2.0 g cm3 and a mass of 100 g. Object B a density of 0.8 g cm3 and a mass of 240 g. Object C a density of 5.0 g cm3 and a mass of 100 g. Which of the objects above (A, B, or C) has the smallest volume? Select the correct answer below: -Object A -Object B -Object C -all of the objects have the same volume
Correct answer:Object C volume=mass/density For A: 100 g/2.0 g/cm3=50 cm3. For B: 240 g/0.8 g/cm3=300 cm3. And for C: 100 g/5.0 g/cm3=20 cm3. Object C would have the smallest volume.
Why is it important to use a standard system of measurement across all science disciplines? Select the correct answer below: -Science has unique measurements that need to be taken. -Conversion factors are easily used between science disciplines. -So that scientists around the world can easily compare experimental results. -Science uses the oldest measurements to ensure accuracy.
Correct answer:So that scientists around the world can easily compare experimental results. Scientists use an international system of measurement and units so that they can easily compare their results and there is consistency.
The speed of light is around 6.706×108 miles per hour. What is the speed of light in units of miles per minute? Round the answer to four significant figures. Report your answer in scientific notation. Use the times symbol from the symbol palette.
Correct answers: 1.118*10^7 miles per minute To find the speed of light in units of miles per minute, we must use the fact that 60 min=1hr. 6.706×10^8 mi/hr×1hr 60min=1.118×107mimin Therefore, we find that the speed of light is approximately 1.118×10^7 miles per minute.
A cube with a mass of 250.0 g has sides measuring 5.00 cm each. What is the density of this cube in grams per cubic centimeter? Your answer should contain three significant figures.
Correct answers: 2.00grams per cubic centimeter Density is a mass to volume ratio: density=mass/volume First, calculate the volume of the cube. volume=(5.00 cm)3=125 cm3 Next, substitute in the mass and volume and simplify. density=250.0g/125cm3 = 2.00g/cm3
If 1 in.=2.54cm, calculate the number of inches in 75.0cm. Round the answer to three significant figures.
Correct answers: 29.5in Using the fact that 2.54cm=1 in. we can use dimensional analysis to calculate the number of inches in 75.0cm as follows. 75.0 cm×1 in.2.54 cm=29.53 in. Therefore, after rounding to three significant figures, we find that there are about 29.5 in. in 75.0 cm.
A thermometer reads 25∘C. If the temperature in the room is then increased by 16 K, what temperature will the thermometer read, in degrees Celsius? Round the answer to two significant figures (round to the nearest whole number). Provide your answer below:
Correct answers: 41 degrees Celsius The magnitude of 1K is equal to the magnitude of 1∘C. Therefore, this temperature can be found by adding the temperature change, in Kelvin, to the temperature in Celsius. 25∘C+16K=41∘C Notice that the freezing temperature of water in Kelvin is 273.15K, and its boiling temperature 373.15K. The numerical difference in these two reference temperatures is 100, the same as for the Celsius scale.
The wavelength of yellow light is approximately 0.000000580m. Convert this quantity from meters to nanometers. Write the answer in scientific notation, using the multiplication symbol, × not the letter x.
Correct answers: 5.80*10^2nm -The prefix "nano" means 10^−9. To convert meters to nanometers, move the decimal point to the right 9 times, filling in zeros as needed, and then use a prefix symbol, n, to represent 10−9. 0.000000580m=580×10−9m=580 nm -Now, to write 580 nm in scientific notation, move the decimal so that there is only one nonzero digit to the left of the decimal place. Therefore, the decimal should be moved two places to the left. The exponent on 10 will be equal to the number of places the decimal is moved. Therefore, the value written in scientific notation is as follows.580 nm=5.80×102 nm Recall that if a trailing zero is on the right side of a decimal point, it is significant and should be included in the scientific notation.
The number 0.0801 has how many significant figures? Provide your answer below:
Correct answers: significant figures=3 Non-zeros are significant, as well as zeros in between non-zeros, but leading zeros are not significant.
An object has a mass of 0.124kg and a volume of 1893mm3. What is its density in grams per cubic centimeter? Your answer should have three significant figures (round your answer to one decimal place).
Correct answers:65.5 grams per cubic centimeter Divide the mass by the volume in order to find the density, and then use conversion factors to cancel the given units and leave the desired units. density=0.124kg1893mm3 To convert from kilograms to grams, use the relationship 1kg=1000g. The conversion factor 1000g1kg cancels kilograms and leaves grams. In the denominator, use the relationship 1cm=10mm. Since these are cubic units, use the conversion factor (10mm1cm)3=1000mm31cm3 to cancel cubic millimeters and leave cubic centimeters. Now calculate the density with the converted units. density=0.124kg1893mm3×1000g1kg×1000mm31cm3=65.505gcm3 When we multiply or divide, our answer should have the same number of significant figures as the number with the fewest significant figures. In this calculation, the numbers in the unit conversions are exact numbers. The mass of 0.124kg has the fewest number of significant figures, so the answer has three significant figures. Round the answer to 65.5gcm3.
Saltwater covers approximately 361,900,000 square kilometers of the earth's surface. Write the number of square kilometers of saltwater in scientific notation. When using scientific notation to report your answer use the multiplication sign, ×, not the letter x.
correct answers: 3.619*10^8 square kilometers -To convert a number written in standard notation with a value of 10 or greater, move the decimal point to the left until the number has a single digit to the left of the decimal point. Then multiply the result by 10 raised to the power of the number of places that the decimal point was moved. In this case, the unwritten decimal point is to the right of the final zero in the number 361,900,000. It must be moved 8 places to the left to write the number as 3.619, so 3.619 is multiplied by 10^8.