Unit test 2

7. Elements combine in many ways to form compounds. Which of the following is a compound? Correct Answer A) water B) oxygen C) nitrogen D) carbon

The answer is A. Water is a compound consisting of two parts hydrogen to one part oxygen.

The atoms in a molecule are held together by: A) gravitational attraction B) chemical bonds C) frictional forces D) physical bonds

The answer is B. The atoms in a molecule are held together by chemical bonds.

2. All of the following are classified as compounds except A) CO2. B) H2O. C) HCl. D) Pb2. .

The answer is D. Lead 2 is not a compound; it is a molecule of lead. Compounds consist of two or more atoms of different elements chemically combined together.

Compounds and mixtures are both made of two or more substances. However, there is a definite difference between the two types of substances. Identify that difference. Correct Answer A) Substances in compounds are chemically combined. B) Mixtures are liquids and compounds are solids. C) Mixtures are more difficult to separate into parts. D) Compounds are made from elements which are easily separated by physical means such as filtering.

The correct answer is A. Compounds are made of substances that are chemically combined, and, therefore, cannot be separated by ordinary means such as filtering. An example of a compound is table salt which is made of the elements sodium (Na) and chlorine (Cl). The substances that make up a mixture are not chemically combined and, therefore, can easily be separated by physical means. An example of a mixture is a salad because the different items in the salad can easily be separated.

1. Which of the following is not an example of a diatomic molecule? A) I2 B) SO2 C) Cl2 D) H2

The correct answer is B SO2 has more than one type of element. Diatomic molecules consist of one element. View Recommendations

13. A diatomic molecule is made from __________. A) any atom B) more than one kind of atom C) two atoms from the same element D) unstable atoms

The correct answer is C. A diatomic molecule consists of two atoms of the same element, such as O2, H2, or N2.

4. Identify the difference between elements and compounds. A) Elements contain more than one kind of atom, while compounds contain only one kind of atom. B) Elements can be separated by physical means while compounds cannot. Correct Answer C) Elements contain only one kind of atom, while compounds contain more than one kind of atom. D) Elements are acids while compounds are bases.

The correct answer is C. Compounds are substances that contain two or more kinds of atoms. Elements are substances that contain only one kind of atom.

1. Which of the following is NOT TRUE about the dangers of releasing raw sewage and excess fertilizers into surface waters such as a pond? A) The pollutants provide extra food and cause animal populations to grow quickly. B) The pollutants can build up in the tissues of fish and harm those who eat them. C) Fish and other organisms die from a lack of food and oxygen. D) The pollutants contain large amounts of nitrogen which causes algae to grow quickly.

a

13. Chemicals are used as preservatives, additives, and artificial coloring in food products. What is one risk of chemical use in food products? A) health problems B) air pollution C) crop death D) soil damage

a

15. What is a chemical change? A chemical change is when ______. A) substances with different properties form a new substance B) substances with different properties keep their same properties C) a mixture occurs between two or more substances D) a solid dissolves into a liquid

a

2. A woman wants to get rid of insects in her home. Which of these would be the most effective alternative to chemical pesticides? A) closing up cracks and holes around doors and windows B) raising the temperature in the house C) spraying perfumes or scented oils along the floor D) leaving food around the outside of the house

a

3. Identify what the products are in a chemical reaction. A) the substances that result from the reaction B) the substances that change as the result of the reaction C) the substances that change as a result of and from the reaction D) neither the changing nor resulting substances

a

6. Which example best describes a synthetic material? A) A human-made material that is a combination of natural materials. B) A material that is found in nature. C) A material that has no useful properties. D) A human-made material that can be recycled without damaging the environment.

a

7. Explain what is meant by a balanced chemical equation. A) The equation has the same number of each particular atom on each side. B) The equation has the same number of each particular molecule on each side. C) The equation has the same total number of atoms on each side. D) The equation has the same total number of molecules on each side.

a

9. In a chemical equation, the arrow is analogous to a(n) _______ sign in a mathematical equation. A) equal B) plus C) division D) multiplication

a

The following chemical equation represents a reaction involving propane (C3H8): C3H8 + 5O2 → 3CO2 + 4H2O + thermal energy Is this reaction exothermic or endothermic, and why? A) The reaction is exothermic because it releases energy. B) The reaction is exothermic because it absorbs energy. C) The reaction is endothermic because it releases energy. D) The reaction is endothermic because it absorbs energy.

a

10. Which describes a benefit of chemical use? A) Chemicals used in medicine may have side effects. B) Chemicals used in cleaning products kill infectious bacteria. C) Chemicals used in agriculture to help crops grow accumulate in soil and water. D) Chemicals used as preservatives may have an affect on the immune system of some people.

b

3. Chemicals are used to make the medicine aspirin. What is the main benefit of this medicine? A) It fights cancer. B) It relieves pain. C) It strengthens bones. D) It improves vision.

b

4. What is one benefit of using chemical pesticides on food plants? A) The soil around the crops becomes richer. B) Insects cannot eat or lay eggs on the crops. C) The crops absorb more nutrients. D) The food that is produced lasts longer without spoiling.

b

6. Catalysts are atoms or molecules that A) increase the amount of energy released in a chemical reaction B) change the rate of chemical reactions C) increase the amount of product produced in a chemical reaction D) decrease the amount of product produced in a chemical reaction

b

9. Read each of the examples below. Then answer the question. * Rain hits the road and washes oil and other chemicals into the ground. * Pesticides and fertilizers are washed into the ground. * Industrial waste is released directly into a pond. The above examples list some ways that humans create which kind of hazard? A) air pollution B) water pollution C) erosion D) greenhouse effect

b

3. At least how many different types of elements are required to form a compound? A) 1 B) 2 C) 3 D) 4

b; 2

10. A/An _________ forms when two or more different elements form a chemical bond when their opposite charges from charged atoms (ions) attract. A) covalent compound B) elemental compound C) ionic compound D) binary compound

c

2. The idea that matter is neither created nor destroyed in chemical reactions is known as the: A) law of conservation of chemicals. B) law of conservation of energy. C) law of conservation of mass. D) second law of thermodynamics.

c

6. What is a molecule? A) an atom B) two or more parts of an atom bonded together C) two or more atoms chemically bonded together D) two or more atoms fused together by nuclear fusion

c

9. Which of the statements about compounds is true? A) Compounds are chemical substances. B) Compounds form between two or more elements. C) both A and B D) neither A nor B

c

14. How does an exothermic reaction compare with an endothermic reaction? A) Both changes absorb energy as reactants become products. B) Both changes release energy as reactants become products. C) An exothermic reaction absorbs energy, and an endothermic reaction releases energy. D) An endothermic reaction absorbs energy, and an exothermic reaction releases energy.

d

5. How is organic farming different from traditional farming? A) Organic farming causes more pollution. B) Organic farming does not use machines. C) Organic farming uses more land. D) Organic farming does not use chemical pesticides

d

Study this.

how to do a chemical equation.