Science

Energy is needed to break bonds in chemical reactions. True False

true

When a chemical equation contains the same number of atoms on both sides, the equation is balanced. True False

true

Breaking a chemical bond _____. a. creates energy that did not previously exist b. absorbs energy from the surroundings c. releases energy into the surroundings d. uses up energy that then no longer exists

b

Each substance written to the right of the arrow in a chemical equation is a ____. a. precipitate b. product c. reactant d. catalyst

b

Which of the following is certain proof a chemical reaction has occurred? a. bubbles b. change of chemical properties c. change of color d. all of the above

b

All substances _____. a. contain hydrogen b. are elements c. have a fixed arrangement of atoms d. are compounds

c

Sulfur trioxide reacts with water to make sulfuric acid. This is a _____ reaction. a. single-replacement b. decomposition c. synthesis d. double-replacement

c

reaction that absorbs energy

endothermic

reaction that releases energy

exothermic

According to the law of conservation of mass, three atoms of calcium can react to produce six atoms of calcium. True False

false

All chemical reactions occur at the same rate. True False

false

All types of chemical reactions involve(s) a substance combining with oxygen and releasing energy. True False

false

Chemical equations are balanced by changing the subscripts of the molecules. True False

false

reactant mass equals product mass

law of conservation of energy

Exothermic reactions do not require any activation energy. True False

False

A chemical reaction in which more energy is absorbed than is released is endothermic. True False

True

A change in _____ is a sign of energy being used in a chemical reaction. a. temperature b. odor c. color d. texture

a

According to the law of conservation of mass, how does the mass of the products in a chemical reaction compare to the mass of the reactants? a. The masses are always equal b. There is no relationship. c. The mass of products is sometimes greater. d. The mass of reactants is greater.

a

An exothermic reaction _____. a. releases thermal energy b. needs more energy to break the chemical bonds than is released when products form. c. absorbs thermal energy d. needs energy to be added constantly in order to continue

a

Chemical reactions ______. a. can either release more energy than they absorb or absorb more energy than they release, depending on the reaction. b. release more energy than they absorb c. absorb more energy than they release d. release and absorb exactly the same amount of energy

a

Forming a chemical bond _____. a. releases energy into the surroundings b. absorbs energy from the surroundings c. creates energy that did not previously exist d. uses up energy that then no longer exists

a

Which type of reaction requires more activation energy? a. endothermic reactions b. exothermic reactions c. They use the same amount of activation energy. d. none of the above

a

Why is the law of conservation of mass true? a. All atoms at the start of a chemical reaction are present at the end of the reaction. b. The substances at the start of a chemical reaction gather more atoms to make up for those lost in the reaction. c. All molecules at the start of a chemical reaction are present at the end of the reaction. d. All the molecules in a substance remain intact during a chemical reaction.

a

Which of the following is NOT a result of a chemical reaction? a. a solid forming from two liquids reacting b. the light given off by a firefly c. bubbles in boiling water d. copper turning green when exposed to air

c

Zinc combines with hydrochloric acid, the zinc replaces hydrogen. The chemical equation for this reaction looks like: Zn + 2HCl → ZnCl2 + H2 This is a _____ reaction a. double-replacement b. decomposition c. single-replacement d. synthesis

c

frying an egg

chemical change

A catalyst is which of the following? a. a reactant b. a product c. both a and b d. neither a nor b

d

Atoms rearrange when _____. a. chemical bonds break b. particles collide with enough energy c. neither a nor b d. both a and b

d

Endothermic reactions ______. a. can either release more energy than they absorb or absorb more energy than they release, depending on the reaction. b. release and absorb exactly the same amount of energy c. release more energy than they absorb d. absorb more energy than they release

d

If the arrangement of atoms in a substance changes, then which of the following is true? a. The chemical properties of the substance stay the same but the physical properties change. b. The physical state of the substance changes. c. The physical properties of the substance stay the same but the chemical properties change. d. A chemical reaction has occurred.

d

Metallic chlorates, when heated, results in metallic chlorides and oxygen. This is a _____ reaction. a. synthesis b. double-replacement c. single-replacement d. decomposition

d

Some baking soda and vinegar were weighed separately and the weights added together. The two substances are mixed and a chemical reaction occurred, producing carbon dioxide, sodium acetate, and water. When the three new substances are weighed and the weights totaled, which of the following will be true? a. There is no way to know, because changes in mass are random. b. The new weights will be more because there is more mass. c. The original weight will be more because there was more mass. d. The two weights will be equal, because the mass is the same.

d

Which of the following materials will burn the fastest in open air? a. a log, two feet in diameter b. Both logs and the splinters will burn at the same rate. c. two logs, each one foot in diameter d. a pile of small splinters made from a two-foot diameter log

d

Which one of the following factors would NOT speed up a chemical reaction? a. raising the temperature b. adding a catalyst c. increasing the concentration of a reactant d. making the reactant particles larger

d

Sodium fluoride and silver nitrate become sodium nitrate and silver chloride. Carbonate and hydrogen ions become water and carbon dioxide. This is a _____ reaction. a. decomposition b. single-replacement c. synthesis d. double-replacement

d-In a double-replacement reaction, the negative ions in two compounds switch places, forming two new compounds. In this type of reaction, two compounds react and form two new compounds.

ice melting

physical change

a measure of how fast a reaction occurs

rate of reaction

present before a chemical reaction

reactant

number of atoms in a chemical formula

subscript