Question

part 1 answer the following multiple - choice questions. write your answers on your answer sheet

1. which statement best represents evidence of a chemical reaction?

a) condensation on a glass
b) water boiling
c) lighting a match
d) lemonade freezing

1. a reaction that gives off light is known as an ____________ reaction.

a) exothermic
b) endothermic
c) endergonic
d) exergonic

1. a change in ________ means that a chemical reaction has occurred.

a) the energy and mass
b) the kinds of atoms involved
c) the properties and identity of the reacting substances
d) the energy and kinds of atoms of the reacting substances

1. if there are 5 grams of product produced by a chemical reaction, how many grams of reactant were consumed?

a) 0 grams
b) 1 gram
c) 5 grams
d) 10 grams

1. chefs often marinate meat in liquid before cooking to soften it and add extra flavor. a chef places a whole steak and 16 oz. of marinade in a bowl, and then marinates the mixture overnight in the refrigerator. many changes would speed up this marinating process. which change would slow it down?

Explanation:

1. For question 1:

• Condensation (A), water boiling (B), and lemonade freezing (D) are physical changes (changes in state). Lighting a match (C) involves a chemical reaction (combustion).

1. For question 2:

• An exothermic reaction releases energy (can be in the form of light). Endothermic reactions absorb energy. Endergonic and exergonic are more related to free - energy changes in biochemical contexts.

1. For question 3:

• A chemical reaction involves a change in the properties and identity of the reacting substances. The law of conservation of mass and atoms (so mass and kinds of atoms are conserved, not changed as in options A, B, D).

1. For question 4:

• According to the law of conservation of mass in a chemical reaction (assuming no gas loss etc., and a simple reaction), the mass of reactants consumed is equal to the mass of products formed.

Answer:

1. C. Lighting a match
2. A. exothermic
3. C. the properties and identity of the reacting substances
4. C. 5 grams