1.E: Introduction to Chemistry (Exercises)

Exercises

Macroscopic vs Microscopic World

PROBLEM 1-1 Identify each of the underlined items as a part of either the macroscopic domain, the microscopic domain, or the symbolic domain of chemistry. For any in the symbolic domain, indicate whether they are symbols for a macroscopic or a microscopic feature.

1. (a) The mass of a lead pipe is 14 lb.
2. (b) The mass of a certain chlorine atom is 35 amu.
3. (c) A bottle with a label that reads Al contains aluminum metal.

Scientific Method

PROBLEM 1-2 Identify each of the following statements as being most similar to a hypothesis, a law, or a theory. Explain your reasoning.

1. Falling barometric pressure precedes the onset of bad weather.
2. All life on earth has evolved from a common, primitive organism through the process of natural selection.
3. My truck’s gas mileage has dropped significantly, probably because it’s due for a tune-up.

States of Matter

PROBLEM 1-3 What state or states of matter does each statement, describe?

1. This state has a definite volume, but no definite shape.
2. This state has no definite volume.
3. This state allows the individual particles to move about while remaining in contact.
4. This state has individual particles in a fixed position with regard to each other.
5. This state has individual particles far apart from each other in space.
6. This state has a definite shape.

Classification of Matter

PROBLEM 1-4 Define:

a- Element. How does it differ from a compound?

b- Compound. How does it differ from an element?

PROBLEM 1-5 Give two examples of a heterogeneous mixture and two examples of a homogeneous mixture.

PROBLEM 1-6 Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

1. xenon, a substance that cannot be broken down into chemically simpler components
2. blood, a substance composed of several types of cells suspended in a salty solution called plasma
3. water, a substance composed of hydrogen and oxygen

PROBLEM 1-7 Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

1. sugar, a substance composed of carbon, hydrogen, and oxygen
2. hydrogen, the simplest chemical substance
3. dirt, a combination of rocks and decaying plant matter

PROBLEM 1-8 Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

1. air, primarily a mixture of nitrogen and oxygen
2. ringer’s lactate, a standard fluid used in medicine that contains salt, potassium, and lactate compounds all dissolved in sterile water
3. tartaric acid, a substance composed of carbon, hydrogen, and oxygen

PROBLEM 1-9 Identify each material as an element, a compound, a heterogeneous mixture, or a solution.

1. equal portions of salt and sand placed in a beaker and shaken up
2. a combination of beeswax dissolved in liquid hexane
3. hydrogen peroxide, a substance composed of hydrogen and oxygen

Energy

PROBLEM 1-10 Classify each of the following energies as kinetic energy or potential energy:

1. The energy in a chocolate bar.
2. The energy of rushing water used to turn a turbine or a water wheel.
3. The energy of a skater gliding on the ice.
4. The energy in a stretched rubber band.

PROBLEM 1-11 You mix two chemicals in a beaker and notice that as the chemicals react, the beaker becomes noticeably colder. Which chemicals have more chemical potential energy, those present at the start of the reaction or those present at the end of the reaction?

PROBLEM 1-12 Explain how you could experimentally determine whether the outside temperature is higher or lower than 0 °C (32 °F) without using a thermometer.

Physical and Chemical Properties

PROBLEM 1-13 In the following paragraph, there are six properties of Fluorine. Classify them as chemical or physical:

Fluorine is a pale yellow gas that reacts with most substances. The free element melts at −220 °C and boils at −188 °C. Finely divided metals burn in fluorine with a bright flame. Nineteen grams of fluorine will react with 1.0 gram of hydrogen.

PROBLEM 1-14 Does each statement refer to a chemical property or a physical property?

1. Balsa is a very light wood.
2. If held in a flame, magnesium metal burns in air.
3. Mercury has a density of 13.6 g/mL.
4. Human blood is red.

PROBLEM 1-15 Does each statement refer to a chemical property or a physical property?

1. The elements sodium and chlorine can combine to make table salt.
2. The metal tungsten does not melt until its temperature exceeds 3,000°C.
3. The ingestion of ethyl alcohol can lead to disorientation and confusion.
4. The boiling point of isopropyl alcohol, which is used to sterilize cuts and scrapes, is lower than the boiling point of water.

Physical and Chemical Changes

PROBLEM 1-16 What word describes each phase change?

1. solid to liquid
2. liquid to gas
3. solid to gas
4. liquid to solid
5. gas to liquid
6. gas to solid

Selected Answers

PROBLEM 1-1 (a) microscopic; (b) macroscopic; (c) macroscopic.

PROBLEM 1-2 (a) law (states a consistently observed phenomenon, can be used for prediction); (b) theory (a widely accepted explanation of the behavior of matter); (c) hypothesis (a tentative explanation, can be investigated by experimentation)

PROBLEM 1-4

a- An element is a substance that cannot be broken down into chemically simpler components. Compounds can be broken down into simpler substances.

b- A compound is composed of two or more elements combined in a fixed ratio. An element is the simplest chemical substance.

PROBLEM 1-5 heterogeneous mixture: a salt and pepper mix and a bowl of cereal (answers will vary)

homogeneous mixture: vinegar and rubbing alcohol (answers will vary)

PROBLEM 1-6 element heterogeneous mixture compound

PROBLEM 1-7 compound element heterogeneous mixture

PROBLEM 1-8 solution solution compound

PROBLEM 1-9 heterogeneous mixture solution compound

PROBLEM 1-12 Place a glass of water outside. It will freeze if the temperature is below 0 °C.

PROBLEM 1-14 physical property chemical property physical property physical property

PROBLEM 1-15 chemical property physical property chemical property physical property

PROBLEM 1-16 melting or fusion boiling or evaporation sublimation freezing condensation deposition