Chapter 1

What is meant by nanoscale? Why is structure at the nanoscale important?

Choose an object in your room, such as a cell phone or television set. Write down five qualitative observations and five quantitative observations regarding the object you chose.

How does a scientific theory differ from a law? How are theories and models related?

Give two examples of situations in which purity of a chemical substance is important.

Make a list of at least four issues faced by our society that require scientific studies and scientific data before a democratic society can make informed, rational decisions. Exchange lists with another student and evaluate the quality of each other's choices.

Make a list of at least four questions you have wondered about that may involve chemistry. Compare your list with a list from another student taking the same chemistry course. Evaluate the quality of each other's questions and decide how "chemical" they are.

Which of these statements are qualitative? Which are quantitative? Explain your choice in each case. (a) Sodium is a silvery-white metal. (b) Aluminum melts at \(660^{\circ} \mathrm{C}\). (c) Carbon makes up about \(23 \%\) of the human body by mass. (d) Pure carbon occurs in different forms: graphite, diamond, and fullerenes.

Which of the these statements are qualitative? Which are quantitative? Explain your choice in each case. (a) The atomic mass of carbon is \(12.011(12.011\) atomic mass units). (b) Pure aluminum is a silvery-white metal that is nonmagnetic, has a low density, and does not produce sparks when struck. (c) Sodium has a density of \(0.968 \mathrm{~g} / \mathrm{mL}\). (d) In animals the sodium cation, \(\mathrm{Na}^{+}\), is the main extracellular cation and is important for nerve function.

The melting point of gallium is \(29.76^{\circ} \mathrm{C}\). If you hold a sample of gallium in your hand, will it melt? Explain briefly.

These temperatures are measured at various locations during the same day in the winter in North America: \(-10^{\circ} \mathrm{C}\) at Montreal, \(28^{\circ} \mathrm{F}\) at Chicago, \(20^{\circ} \mathrm{C}\) at Charlotte, and \(40^{\circ} \mathrm{F}\) at Philadelphia. Which city is the warmest? Which city is the coldest?

A crystal of fluorite (a mineral that contains calcium and fluorine) has a mass of \(2.83 \mathrm{~g}\). What is this mass in kilograms? Give the symbols for the elements in this crystal.

Suppose a room is \(18 \mathrm{~m}\) long, \(15 \mathrm{~m}\) wide, and the distance from floor to ceiling is \(2.9 \mathrm{~m}\). What is the room's volume in cubic meters? In cubic centimeters? In liters?

The current world record for the \(100-\mathrm{m}\) dash is \(9.58 \mathrm{sec}-\) onds held by Usain Bolt of Jamaica. Calculate whether he could have been arrested for exceeding a \(25 \mathrm{mi} / \mathrm{h}\) speed limit while setting that record.

How many significant figures are present in these measured quantities? (a) \(1374 \mathrm{~kg}\) (b) \(0.00348 \mathrm{~s}\) (c) \(5.619 \mathrm{~mm}\) (d) \(2.475 \times 10^{-3} \mathrm{~cm}\) (e) 33 (f) \(2300 \mathrm{~m}\)

How many significant figures are present in these measured quantities? (a) \(1.022 \times 10^{2} \mathrm{~km}\) (b) \(34 \mathrm{~m}^{2}\) (c) \(0.042 \mathrm{~L}\) (d) \(28.2^{\circ} \mathrm{C}\) (e) \(323 . \mathrm{mg}\) (f) \(420 \mathrm{~g}\)

Perform these calculations and express the result with the proper number of significant figures. (a) \(\frac{4.850 \mathrm{~g}-2.34 \mathrm{~g}}{1.3 \mathrm{~mL}}\) (b) \(V=\frac{4}{3} \pi r^{3}\) where \(r=4.112 \mathrm{~cm}\) (c) \(\left(4.66 \times 10^{-3}\right) \times 4.666\) (d) \(\frac{0.003400}{65.2}\)

Perform these calculations and express the result with the proper number of significant figures. (a) \(2221.05-\frac{3256.5}{3.20}\) (b) \(343.2 \times\left(2.01 \times 10^{-3}\right)\) (c) \(S=4 \pi r^{2}\) where \(r=2.55 \mathrm{~cm}\) (d) \(\frac{2802}{15}-(0.0025 \times 10,000 .)\)

Calculate the volume of a \(23.4-\mathrm{g}\) sample of bromobenzene, density \(=1.49 \mathrm{~g} / \mathrm{mL}\).

In each case, identify the italicized property as a physical or chemical property. Give a reason for your choice. (a) The normal color of the element bromine is red-orange. (b) Iron is transformed into rust in the presence of air and water. (c) Dynamite can explode. (d) Aluminum metal, the shiny "foil" you use in the kitchen, melts at \(660^{\circ} \mathrm{C}\).

In each case, identify the italicized property as a physical or a chemical property. Give a reason for your choice. (a) Dry ice sublimes (changes directly from a solid to a gas) at \(-78.6^{\circ} \mathrm{C}\) (b) Methanol (methyl alcohol) burns in air with a colorless flame. (c) Sugar is soluble in water. (d) Hydrogen peroxide, \(\mathrm{H}_{2} \mathrm{O}_{2}\), decomposes to form oxygen, \(\mathrm{O}_{2},\) and water, \(\mathrm{H}_{2} \mathrm{O} .\)

In each case, describe the change as a chemical or physical change. Give a reason for your choice. (a) A cup of household bleach changes the color of your favorite T-shirt from purple to pink. (b) The fuels in the space shuttle (hydrogen and oxygen) combine to give water and provide the energy to lift the shuttle into space. (c) An ice cube in your glass of lemonade melts.

In each case, describe the change as a chemical or physical change. Give a reason for your choice. (a) Salt dissolves when you add it to water. (b) Food is digested and metabolized in your body. (c) Crystalline sugar is ground into a fine powder. (d) When potassium is added to water there is a purplishpink flame and the water becomes basic (alkaline).

While camping in the mountains you build a small fire out of tree limbs you find on the ground near your campsite. The dry wood crackles and burns brightly and warms you. Before slipping into your sleeping bag for the night, you put the fire out by dousing it with cold water from a nearby stream. Steam rises when the water hits the hot coals. Describe the physical and chemical changes in this scene.

Small chips of iron are mixed with sand (see photo). Is this a homogeneous or heterogeneous mixture? Suggest a way to separate the iron and sand from each other.

Identify each of these as a homogeneous or a heterogeneous mixture. (a) An asphalt (blacktop) road (b) Clear ocean water (c) Iced tea with ice cubes (d) Filtered apple cider

Devise and describe an experiment to (a) Separate table salt (sodium chloride) from water. (b) Separate iron filings from small pieces of magnesium. (c) Separate the element zinc from sugar (sucrose).

Devise and describe an experiment to (a) Separate sucrose (table sugar) from water. (b) Separate the element sulfur from table salt (sodium chloride). (c) Separate iron filings from granular zinc.

For each of the changes described, decide whether two or more elements formed a compound or if a compound decomposed (to form elements or other compounds). Explain your reasoning in each case. (a) Upon heating, a blue powder turned white and lost mass. (b) A white solid forms three different gases when heated. The total mass of the gases is the same as that of the solid.

For each of the changes described, decide whether two or more elements formed a compound or if a compound decomposed (to form elements or other compounds). Explain your reasoning in each case. (a) After a reddish-colored metal is placed in a flame, it turns black and has a higher mass.

Classify each of these as an element, a compound, a heterogeneous mixture, or a homogeneous mixture. Explain your choice in each case. (a) Chunky peanut butter (b) Distilled water (c) Platinum (d) Air

Classify each of these as an element, a compound, a heterogeneous mixture, or a homogeneous mixture. Explain your choice in each case. (a) Table salt (sodium chloride) (b) Methane (which burns in pure oxygen to form only carbon dioxide and water) (c) Chocolate chip cookie (d) Silicon

A black powder is placed in a long glass tube. Hydrogen gas is passed into the tube so that the hydrogen sweeps out all other gases. The powder is then heated with a Bunsen burner. The powder turns red-orange, and water vapor can be seen condensing at the unheated far end of the tube. The red-orange color remains after the tube cools. (a) Was the original black substance an element? Explain briefly. (b) Is the new red-orange substance an element? Explain briefly.

A finely divided black substance is placed in a glass tube filled with air. When the tube is heated with a Bunsen burner, the black substance turns red- orange. The total mass of the red-orange substance is greater than that of the black substance. (a) Can you conclude that the black substance is an element? Explain briefly. (b) Can you conclude that the red-orange substance is a compound? Explain briefly.

When you open a can of a carbonated drink, the carbon dioxide gas inside expands rapidly as it rushes from the can. Describe this process in terms of the kineticmolecular theory.

Sometimes, after clothes are washed, they are hung in the sun to dry. Describe the change or changes that occur in terms of the kinetic-molecular theory. Are the changes that occur physical or chemical changes?

Sucrose has to be heated to a high temperature before it caramelizes. Use the kinetic-molecular theory to explain why sugar caramelizes only at high temperatures.

Give a nanoscale interpretation of the fact that at the melting point the density of solid mercury is greater than the density of liquid mercury, and at the boiling point the density of liquid mercury is greater than the density of gaseous mercury.

Explain in your own words, by writing a short paragraph, how the atomic theory explains conservation of mass during a chemical reaction and during a physical change.

Explain in your own words, by writing a short paragraph, how the atomic theory explains constant composition of chemical compounds.

Explain in your own words, by writing a short paragraph, how the atomic theory predicts the law of multiple proportions.

The element chromium forms three different oxides (that contain only chromium and oxygen). The percentage of chromium (number of grams of chromium in \(100 \mathrm{~g}\) oxide) in these compounds is \(52.0 \%, 68.4 \%,\) and \(76.5 \%\). Do these data conform to the law of multiple proportions? Explain why or why not.

Write a chemical formula for each substance, and draw a picture of how the nanoscale particles are arranged at room temperature. (a) Water, a liquid whose molecules contain two hydrogen atoms and one oxygen atom each (b) Nitrogen, a gas that consists of diatomic molecules

Write a chemical formula for each substance and draw a picture of how the nanoscale particles are arranged at room temperature. (a) Iodine, a solid that consists of diatomic molecules (b) Ozone, a gas that consists of triatomic molecules (c) Helium (d) Carbon dioxide

Write a chemical formula for each substance and draw a picture of how the nanoscale particles are arranged at room temperature. (a) Iodine, a solid that consists of diatomic molecules (b) Ozone, a gas that consists of triatomic molecules (c) Helium (d) Carbon dioxide

Name and give the symbols for two elements that (a) Are metals. (b) Are nonmetals. (c) Are metalloids. (d) Are alkaline-earth elements.

Name and give the symbols for two elements that (a) Are gases at room temperature. (b) Are solids at room temperature. (c) Do not consist of molecules. (d) Consist of diatomic molecules.

Name and give symbols for three transition metals in the fourth period. Look up each of your choices in a dictionary, a book such as The Handbook of Chemistry and Physics, or on the Internet, and make a list of their properties. Also list the uses of each element.

Name two halogens. Look up each of your choices in a dictionary, in a book such as The Handbook of Chemistry and Physics, or on the Internet, and make a list of their properties. Also list any uses of each element that are given by the source.

How many elements are there in Group \(4 \mathrm{~A}\) of the periodic table? Give the name and symbol of each of these elements. Tell whether each is a metal, nonmetal, or metalloid.

How many elements are there in the fourth period of the periodic table? Give the name and symbol of each of these elements. Tell whether each is a metal, metalloid, or nonmetal.