Answer Key
Guided Reading 6.1
Observing Chemical Change Guided Reading and Study Use Target Reading Skills Sample questions and
answers: Question What are physical properties of matter? Answer Physical properties are
characteristics that can be observed without changing one substance into another. Question What is the
evidence for chemical reactions? Answer The evidence for chemical reactions is the formation of new
substances and changes in energy.
1. Matter is anything that has mass and takes up space.
2. chemistry
3. a. Physical b. Only by changing one substance into another
4. False
5. a, b, d
6. chemical reaction, or chemical change
7. They break and form new bonds, producing new substances.
8. Formation of new substances and changes in energy
9. The change in color is an indication of a change in properties, and a change in properties is a sign that
a chemical reaction occurred.
10. precipitate
11. It might indicate a chemical reaction, because the bubbles are gas, and the presence of a gas
indicates a new substance may have been formed.
12. True
13. A change in temperature reflects a change in energy.
14. False
15. a. Energy is absorbed b. Exothermic
6.2
Describing Chemical Reactions Guided Reading and Study Use Target Reading Skills a. A chemical
equation is a short, easy way to show a chemical reaction. b. A substance you have at the beginning of a
reaction is a reactant. c. A new substance produced in a reaction is a product. d. Conservation of mass
means that during a chemical reaction, matter is not created or destroyed. e. In an open system, matter
can enter from or escape to the surroundings. f. In a closed system, matter is not allowed to enter or
leave. g. A coefficient is a number in a chemical equation telling you how many atoms or molecules of a
reactant or product take part in the reaction. h. Synthesis means combining two or more elements or
compounds to make a more complex substance. i. Decomposition means breaking down compounds
into simpler products. j. Replacement is the process in which one element replaces another in a
compound or two elements in different compounds trade places.
1. A short, easy way to show a chemical reaction
2. True
3. By its chemical formula, CO2
4. reactants
5. products
6. Yields
7. a. Reactant b. Reactant c. Product
8. b, d
9. True
10. The total mass of the reactants is the same as the total mass of the products.
11. During a chemical reaction, matter is not created or destroyed.
12. Matter can enter from or escape to the surroundings.
13. Sample answer: a sealed plastic bag
14. When it accurately represents the conservation of mass by showing the same number of each type
of atom on both sides of the equation
15. There are two atoms of oxygen on each side.
16. d
17. coefficient
18. It tells you how many atoms or molecules of each reactant or product take part in the reaction.
19. There are two oxygen atoms in the reactants, but only one oxygen atom in the product.
20. 2 H2 + O2 → 2 H2O
21. Synthesis, decomposition, and replacement reactions
22. Synthesis
23. a. Synthesis b. Compounds are broken down into simpler products c. Replacement
24. a. Decomposition b. Synthesis c. Replacement
6.3
Controlling Chemical Reactions Guided Reading and Study Use Target Reading Skills a. Increase in
surface area b. Increase in temperature c. Increase in concentration d. Use of a catalyst
1. activation energy
2. True
3. The activation energy can be a spark.
4. Exothermic reaction
5. Endothermic reaction
6. For the reaction to start, a tiny amount of activation energy is needed. Once a few molecules react,
the rest will quickly follow because the first few reactions provide activation energy for more molecules
to react.
7. The energy of the products is greater than the energy of the reactants.
8. Endothermic
9. The peak of the curve
10. Surface area, temperature, concentration, use of a catalyst, or use of an inhibitor
11. Increasing the surface area allows more particles of a substance to react, and this increases the rate
of the reaction.
12. Reaction rates are faster at higher temperatures.
13. a, c
14. concentration
15. Increasing the concentration of the reactants supplies more particles to react.
16. True
17. A catalyst is a material that increases the rate of a reaction by lowering the activation energy.
18. False
19. enzyme
20. Many chemical reactions necessary for life happen at temperatures that would kill living things.
Enzymes are necessary to allow these reactions to occur at body temperature.
21. An inhibitor is a material used to decrease the rate of a reaction.
22. Most inhibitors work by preventing reactants from coming together.
6.4
Fire and Fire Safety Guided Reading and Study Use Target Reading Skills Sample answers: What You
Know
1. A fire needs fuel to burn.
2. A fire needs oxygen to burn
3. All homes should have smoke detectors.
What You Learned 1. Fire is the result of a combustion reaction.
2. The most deadly fires start with cigarettes.
3. Baking soda can be used to put out small fires.
1. Combustion is a rapid reaction between oxygen and a substance called a fuel.
2. fuel
3. Fuel, oxygen, and heat
4. a
5. True
6. Water covers the fuel, which keeps the fuel from coming into contact with oxygen. The evaporation of
water also uses up heat, which cools the fire.
7. Small heaters, cooking, faulty wiring
8. baking soda
9. a,c,d