Chapter 1: The Chemical World
According to the scientific method, what is a law? (a) A short statement that summarizes a large number of observations. (b) A fact that can never be refuted. (c) A model that gives insight into how nature is. (d) An initial guess with explanatory power.
(a) A short statement that summarizes a large number of observations.
What is the difference between a hypothesis and a theory?
A hypothesis is an explanation of a single or small number of observations. A theory is an explanation that extends beyond individual observations to an understanding of the underlying causes for the way nature is or behaves.
What is the difference between a law and a theory?
A law is simply a general statement that summarizes and predicts behavior. Theories seek to explain the causes of observed behavior.
experiment
A procedure that attempts to measure observable predictions to test a theory or law.
theory
A proposed explanation for observations and laws. It presents a model of the way nature works and predicts behavior that extends well beyond the observations and laws from which it was formed.
scientific law
A statement that summarizes past observations and predicts future ones. They are usually formulated from a series of related observations.
hypothesis
A theory or law before it has become well established; a tentative explanation for an observation or a scientific problem that can be tested by further investigation.
atomic theory
A theory stating that all matter is composed of tiny particles called atoms.
Examine the opening figure of this chapter. Use the information in Section 1.1 to identify the two molecules sitting next to the cola glass and identify each of the atoms within each molecule.
Carbon dioxide contains one carbon atom and two oxygen atoms. Water contains one oxygen atom and two hydrogen atoms.
What are chemicals? Give some examples.
Chemicals compose virtually everything in our world: a soda, a book, your pencil; indeed, even your own body. Everything that we can hold or touch is made of chemicals.
How is chemistry connected to everyday life? How is chemistry relevant outside the chemistry laboratory?
Chemistry is connected to everyday life because molecules are interacting with you to produce all the experiences you have, from your dreams while asleep to watching the stars at night. Chemistry is not confined to a laboratory. As you experience the world around you, molecules are interacting to create your experience. Imagine watching a sunset. Molecule are involved in every step (Pg. 5 for detailed description).
Define: chemistry
Chemistry is the science that seeks to understand what matter does by studying what atoms and molecules do.
What do chemists try to do? How do they understand the natural world?
Chemists study molecules and interactions at the molecular level to learn about and explain why ordinary things are as they are.
law of conservation of mass
In a chemical reaction, matter is neither created nor destroyed.
A student prepares several samples of the same gas and measures their mass and volume. The results are tabulated as follows. Formulate a tentative law from the measurements. Mass of Gas (in g) --> Volume of Gas (in L) 22.5-->1.60 35.8-->2.55 70.2-->5.00 98.5-->7.01
Mass of Gas (in g) --> Volume of Gas (in L) 22.5-->1.60 = 22.5 / 1.6 = 14 35.8-->2.55 = 35.8 / 2.55 = 14.0 70.2-->5.00 = 70.2 / 5.00 = 14.0 98.5-->7.01 = 98.5 / 7.01 = 14.1 The ratio of mass to volume is constant.
observation
Often the first step in the scientific method. It must measure or describe something about the physical world.
Why does soda fizz?
Soda fizzes due to the interactions between carbon dioxide (CO2) and water under high pressure. At room temperature, carbon dioxide is a gas and water is a liquid. Through the use of pressure, the makers of soda force the CO2 gas to dissolve in the water. When the can is opened, the pressure is released and the CP2 molecules escape in bubbles of gas.
What is the atomic theory, and who formulated it?
The atomic theory states that all matter is composed of small, indestructible particles called atoms. John Dalton formulated this theory.
What is the law of conservation of mass, and who discovered it?
The law of conservation of mass states that, "In a chemical reaction matter is neither created nor destroyed". This law was founded by French chemist Antoine Lavoisier.
Examine Figure 1.1 and, from a molecular point of view, explain why soda pop fizzes. What molecules are inside the bubbles in a glass of soda pop?
The makers of soda pop use pressure (the result of collisions between gaseous molecules and the surfaces around them) to force gaseous carbon dioxide molecules to mix with liquid water molecules. As long as the can of soda is sealed, the carbon dioxide molecules remain mixed with the water molecules, held there by pressure. When the can is opened, the pressure is released and carbon dioxide molecules escape out of the soda mixture. As they do, they create bubbles - the familiar fizz of soda pop.
chemistry
The science that seeks to understand the behavior of matter by studying what atoms and molecules do.
Explain the scientific method.
The scientific method is the way chemists investigate the chemical world. the first step consists of observing the natural world. Later observations can be combined to create a scientific law, which summarizes and predicts behavior. Theories are models that strive to explain the cause of the observed phenomenon. Theories are tested through experiment. when a theory is not well established, it is sometimes referred to as a hypothesis.
scientific method
The way that scientists learn about the natural world. It involves observations, laws, hypotheses, theories, and experimentation.
What is wrong with the statement, "It is just a theory"?
To say "It is just a theory" makes it seem as if theories are easily discardable. However, many theories are very well established and are as close to truth as we get in science. Established theories are backed up wutg years of experimental evidence, and they are the pinnacle of scientific understanding.
What are three things you need to do to succeed in this course?
To succeed as a beginning chemist, you must be curious and imaginative, be willing to do calculations, ad be committed to learning the material.
Cite an example from this chapter of the scientific method at work.
An example of the scientific method being used from this chapter is the discovery of what happens during the combustion reactions which required proving the phlogiston theory as incorrect by Lavoisier.
What is meant by the statement, "Matter does what molecules do"? Give an example.
Because matter is made up of molecules, the behavior of matter is dictated by the behavior of the molecules. For example, water expands when it freezes because the distance between water molecules gets farther apart during the freezing process.
A chemist in an imaginary universe does an experiment that attempts to correlate the size of an atom with its chemical reactivity. The results are tabulated as follows. Size of Atom --> Chemical Reactivity small --> low medium --> intermediate large --> high (a) Formulate a law from this data. (b) Formulate a theory to explain the law.
(a) All atoms contain a degree of chemical reactivity. The larger the size of an atom, the higher the chemical reactivity of that atom. (b) There are many correct answers. One example is: Conceivable, when the size of an atom is increased, the surface area of the atom is also increased; an atom with a greater surface area is more likely to react chemically.
Classify each statement as an observation, a law, or a theory. (a) When a metal is burned in a closed container, the sum of the masses of the container and its contents does not change. (b) Matter is made of atoms. (c) Matter is conserved in chemical reactions. (d) When wood is burned in a closed container, its mass does not change.
(a) Observation (b) Theory (c) Law (d) Observation
Classify each statement as an observation, a law, or a theory. (a) The star closest to Earth is moving away from Earth at high speed. (b) A body in motion stays in motion unless acted upon by a force. (c) The universe began as a cosmic explosion called the Big Bang. (d) A stone dropped from an altitude of 450 m falls to the ground in 9.6 s.
(a) Theory (b) Law (c) Theory (d) Observation
Which statement best defines chemistry? (a) The science that studies solvents, drugs, and insecticides. (b) The science that studies the connections between the properties of matter and the particles that compose that matter. (c) The science that studies air and water pollution. (d) The science that seeks to understand processes that occur only in chemical laboratories.
(b) The science that studies the connections between the properties of matter and the particles that compose that matter.
Which statement most resembles a scientific theory? (a) When the pressure on a sample of oxygen gas is increased 10%, the volume of the gas decreases by 10%. (b) The volume of a gas is inversely proportional to its pressure. (c) A gas is composed of small particles in constant motion. (d) A gas sample has a mass of 15.8 g and a volume of 10.5 L.
(c) A gas is composed of small particles in constant motion.
Which statement is an example of an observation? (a) In a chemical reaction, matter is conserved. (b) All matter is made of atoms. (c) When a given sample of gasoline is burned in a closed container, the mass of the container and its contents does not change. (d) Atoms bond to one another by sharing electrons.
(c) When a given sample of gasoline is burned in a closed container, the mass of the container and its contents does not change.
Where can you find chemicals? (a) In a hardware store (b) In a chemical stockroom (c) All around you and even inside of you (d) All of the above
(d) All of the above
Which characteristic is necessary for success in understanding chemistry? (a) Curiosity (b) Calculation (c) Commitment (d) All of the above
(d) All of the above
