Classify each change as physical or chemical. Even if

Why is chemistry often called the central science?

What is the difference between basic research and applied research?

What pledge has been made by members of the American Chemistry Council through the Responsible Care program?

It would take you 31,800 years to count to a trillion. About how many times would you have to do this to count all the atoms in a single grain of sand

Is a biological cell macroscopic, microscopic, or submicroscopic?

Are atoms made of molecules or are molecules made of atoms?

How are the particles in a solid arranged differently from those in a liquid?

How does the arrangement of particles in a gas differ from the arrangements in liquids and solids?

Which occupies the greatest volume: 1 g of ice, 1 g of liquid water, or 1 g of water vapor?

What happens to the chemical identity of a substance during a physical change?

What is a physical property?

What doesnt change during a physical change?

What is a chemical property?

What is a chemical bond?

What changes during a chemical reaction?

Why is the freezing of water considered to be a physical change?

Why is it sometimes difficult to decide whether an observed change is physical or chemical?

Why is the rusting of iron considered to be a chemical change?

What are some of the clues that help us to determine whether an observed change is physical or chemical?

Distinguish between an atom and an element.

How many atoms are in a sulfur molecule that has the elemental formula S8?

What is the difference between an element and a compound?

How many atoms are there in one molecule of H3PO4? How many atoms of each element are there in one molecule of H3PO4?

What does the chemical formula of a substance tell us about that substance?

Are the physical and chemical properties of a compound necessarily similar to those of the elements of which it is composed?

Which element within a compound is given first in the compounds name?

What is the IUPAC systematic name for the compound KF?

What is the chemical formula for the compound titanium dioxide?

Why are common names often used for chemical compounds instead of systematic names?

How soon will nanotechnology give rise to commercial products?

What are the two main approaches to building nanoscale materials and devices?

Who is the ultimate expert at nanotechnology?

A television screen looked at from a distance appears as a smooth continuous flow of images. Up close, however, we see that this is an illusion. What really exists are a series of tiny dots (pixels) that change color in a coordinated way to produce images. Use a magnifying glass to examine closely the screen of a computer monitor or television set.

Add a pinch of red Kool-Aid crystals to a still glass of hot water. Add the same amount of crystals to a second still glass of cold water. With no stirring, which would you expect to become uniform in color first: the hot water or the cold water? Why?

Air molecules stuck inside an inflated balloon collide continuously with the inner surface of the balloon. Each collision provides a little push outward on the balloon. All the many collisions working together keep the balloon inflated. To get a feel for whats happening here, add about a tablespoon of tiny beads to a large balloon (pellets, beans, BBs, or grains of rice also work). Inflate the balloon to its full size and tie it shut. Hold the balloon in the palms of both hands and shake rapidly. Can you feel the collisions? As you shake the balloon wildly, the flying beads represent the gaseous phase. How should you move the balloon so that the beads represent the liquid phase? The solid phase?

This activity is for those with access to a gas stove. Place a large pot of cool water on top of the stove, and set the burner on high. What product from the combustion of the natural gas do you see condensing on the outside of the pot? Where did it come from? Would more or less of this product form if the pot contained ice water? Where does this product go as the pot gets warmer? What physical and chemical changes can you identify?

When you pour a solution of hydrogen peroxide, H2O2, over a cut, an enzyme in your blood decomposes it to produce oxygen gas, O2, as evidenced by the bubbling that takes place. It is this oxygen at high concentrations at the site of the injury that kills off microorganisms. A similar enzyme is found in bakers yeast. Wear safety glasses and remove all combustibles, such as paper towels, from a clear countertop area. Pour a small packet of bakers yeast into a tall glass. Add a couple capfuls of 3% hydrogen peroxide and watch oxygen bubbles form. Test for the presense of oxygen by holding a lighted match with a tweezers and putting the flame near the bubbles. Look for the flame to glow more brightly as the escaping oxygen passes over it. Describe oxygens physical and chemical properties.

Rank the following in order of increasing volume: (a) bacterium, (b) virus, (c) water molecule

Rank the following in order of increasing force of attraction between its submicroscopic particles: (a) sugar, (b) water, (c) air.

Rank the physical and chemical changes in order of the amount of energy released: (a) the condensation of rain in a thunderstorm, (b) the burning of a gallon of gasoline in a car engine, (c) the explosion of a firecracker.

Rank the compounds in order of increasing numbers of atoms: (a) C12H22O12, (b) DNA, (c) Pb(C2H3O2)2.

While visiting a foreign country, a foreign-speaking citizen tries to give you verbal directions to a local museum. After multiple attempts, he is unsuccessful. An onlooker sees your frustration and concludes that you are not smart enough to understand simple directions. Another onlooker sympathizes with you because he knows how difficult it is to navigate through an unfamiliar city. Which onlooker is correct?

If someone is able to explain an idea to you using small familiar words, what does this say about how well that person understands the idea?

What is the best way to really prove to yourself that you understand an idea?

What is the best way to really prove to yourself that you understand an idea?

Is chemistry the study of submicroscopic, microscopic, macroscopic, or all three? Defend your answer.

You combine 50 mL of small BBs with 50 mL of large BBs and get a total of 90 mL of BBs of mixed sizes. Please explain how this occurs.

You combine 50 mL of water with 50 mL of purified alcohol and get a total of 98 mL of the mixture. Please explain how this occurs.

Which has stronger attractions among its submicroscopic particles: a solid at 25C or a gas at 25C? Explain.

The leftmost diagram below shows the moving particles of a gas within a rigid container. Which of the three boxes on the right(a), (b), or (c)best represents this material upon the addition of heat?

The leftmost diagram below shows two phases of a single substance. In the middle box, draw what these particles would look like if heat were taken away. In the box on the right, show what they would look like if heat were added. If each particle represents a water molecule, what is the temperature of the box on the left?

A cotton ball is dipped in alcohol and wiped across a tabletop. Explain what happens to the alcohol molecules deposited on the tabletop. Is this a physical or chemical change?

A skillet is lined with a thin layer of cooking oil followed by a layer of unpopped popcorn kernels. Upon heating, the kernels all pop, thereby escaping the skillet. Identify any physical or chemical changes.

A cotton ball dipped in alcohol is wiped across a tabletop. Would the resulting smell of the alcohol be more or less noticeable if the tabletop were much warmer? Explain.

Use Exercise 53 as an analogy to describe what occurs in Exercise 54. Does it make sense to think that the alcohol is made of very tiny particles (molecules) rather than being an infinitely continuous material?

Alcohol wiped across a tabletop rapidly disappears. What happens to the temperature of the tabletop? Why?

Red Kool-Aid crystals are added to a still glass of water. The crystals sink to the bottom. Twenty-four hours later, the entire solution is red even though no one stirred the water. Explain.

With no one looking, you add 5 mL of a cinnamon solution to a blue balloon, which you tie shut. You also add 5 mL of fresh water to a red balloon, which you also tie shut. You heat the two balloons in a microwave until each inflates to about the size of a grapefruit. Your brother then comes along, examines the inflated balloons, and tells you that the blue balloon is the one containing the cinnamon. How did he know?

In the winter Vermonters make a tasty treat called sugar on snow in which they pour boiled-down maple syrup onto a scoop of clean fresh snow. As the syrup hits the snow, it forms a delicious taffy. Identify the physical changes involved in the making of sugar on snow. Identify any chemical changes.

Oxygen, O2, has a boiling point of 90 K (-183C), and nitrogen, N2, has a boiling point of 77 K (-196C). Which is a liquid and which is a gas at 80 K (-193C)?

Each night you measure your height just before going to bed. When you arise each morning, you measure your height again and consistently find that you are 1 inch taller than you were the night before but only as tall as you were 24 hours ago! Is what happens to your body in this instance best described as a physical change or a chemical change? Be sure to try this activity if you havent already.

State whether each of the following is a physical or chemical property of matter. (a) Graphite conducts electricity. (b) Bismuth, Bi, loses its iridescence upon melting. (c) A copper penny is smushed into an embossed souvenir

State whether each of the following is a physical or chemical property of matter. (a) Carbon dioxide escapes when a soda can is opened. (b) A bronze statue turns green. (c) A silver spoon tarnishes.

Classify each change as physical or chemical. Even if you are incorrect in your assessment, you should be able to defend why you chose as you did. (a) Grape juice turns to wine. (b) Wood burns to ashes. (c) Water begins to boil. (d) A broken leg mends itself.

Classify each change as physical or chemical. Even if you are incorrect in your assessment, you should be able to defend why you chose as you did. (a) Grass grows. (b) An infant gains 10 lb. (c) A rock is crushed to powder. (d) A tire is inflated with air.

Each sphere in the diagrams below represents an atom. Joined spheres represent molecules. Which box contains a liquid phase? Why cant you assume that box B represents a lower temperature?

Is aging primarily an example of a physical or chemical change?

Octane is a component of gasoline. It reacts with oxygen, O2, to form carbon dioxide and water. Is octane an element or a compound? How can you tell?

Oxygen atoms are used to make water molecules. Does this mean that oxygen, O2, and water, H2O, have similar properties? Why do we drown when we breathe in water despite all the oxygen atoms present in this material?

Oxygen, O2, is certainly good for you. Does it follow that if small amounts of oxygen are good for you then large amounts of oxygen would be especially good for you?

Why isnt water classified as an element?

If you eat metallic sodium or inhale chlorine gas, you stand a strong chance of dying. Let these two elements react with each other, however, and you can safely sprinkle the compound on your popcorn for better taste. What is going on?

Which of the following boxes contains only an element? Which contains only a compound? How many different types of molecules are shown altogether in the three boxes?

What is the chemical formula for the compound dihydrogen sulfide?

What is the chemical name for a compound with the formula Ba3N2?

What is the common name for dioxygen oxide?

What is the common name for oxygen oxide?

Medicines, such as pain relievers and antidepressants, are found in the drinking water supplies of many municipalities. How did these medicines get there? Does it matter that they are there? Should something be done about it? If so, what?

Your friend smells cinnamon coming from an inflated rubber balloon containing cinnamon extract. You tell him that the cinnamon molecules are passing through the micropores of the balloon. He accepts the idea that the balloon contains micropores but insists that he is simply smelling cinnamon-flavored air. You explain that scientists have discovered that gases are made of molecules, but thats not good enough for him. He needs to see the evidence for himself. How might you lead him to accept the concept of molecules?

The British diplomat, physicist, and environmentalist John Ashton, in speaking to a group of scientists, stated (paraphrased): There has to be much better communication between the world of science and the world of politics. Consider the different meanings of the word uncertainty. To scientists, it means uncertainty over the strength of a signal. To politicians it means go away and come back when youre certain. Pretend you are a scientist with strong but inconclusive evidence in support of impending climate change. How might you best persuade politicians to take action?

The famous 20th-century physicist Richard Feynman (19181988) noted: The laws of science do not limit our ability to manipulate single atoms and molecules. What does?

A calculator is useful but certainly not exciting. Why would someone from 100 years ago vehemently disagree with this statement? We often marvel at a new technology, but how long does this marveling last? How soon before a new technology becomes assumed? Think of other examples. Is technology the source of happiness?

How might speculations about potential dangers of nanotechnology threaten public support for it? Consider Michael Crichtons 2002 science-fiction novel Prey, in which self-replicating nanobots run amok turning everything they contact into a gray goo.

In the past 20 years, the average life expectancy in most nations has risen by a couple of years. So has the healthy life expectancy, which is a measure of how long people remain in good health. Are the two necessarily related? How so?

What effects might a cure for aging have on the problem of overpopulation? How would society be able to support so many people living well into their 100s? What trends do you foresee in company retirement plans? Might there be a greater emphasis on privatized retirement accounts? Why?