1. How do endothermic and exothermic reactions differ?

a. Endothermic reactions release energy and are spontaneous.
b. Exothermic reactions release energy and are spontaneous.
c. Endothermic reactions give off heat and light.
d. Photosynthesis is exothermic.

MY CHOICE: B

2. Which is NOT a description of activation energy?

a. The energy absorbed by the reactants.
b. The energy needed to get an endothermic reaction to proceed.
c. The "push" to start a chemical reaction.
d. The energy transfer between the products and reactants.

MY CHOICE: D

3. An animal's stomach contains enzymes that break down food into smaller molecules that the animal's cells can use. Enzymes perform this function by:

a. participating in chemical reactions
b. increasing the temperature
c. changing the ionic concentration
d. lowering the pH

MY CHOICE: A

4. Milk you buy at the store has been “Pasteurized.” This means the milk was warmed up to around 150 F/65 C to kill harmful bacteria. This process probably works because:

a. it speeds up the metabolism of the bacteria and this increases their death rate
b. it causes the bacteria’s carbohydrates to under go hydrolysis, thus killing the bacteria
c. the bacteria’s enzymes will denature at the high temperature, thus killing the bacteria
d. it causes the bacteria to build many polymers, which kills the bacteria

MY CHOICE: C

5. In a test tube, a student used the enzyme catalase to break down some H2O2 (Hydrogen Peroxide). After the reaction, she discovered another bottle of H2O2 that needed to be broken down also. Will she be able to use the enzyme again?

a. No, because enzymes get broken down when they do chemical reactions
b. Yes, because enzymes are carbohydrates and does not break them down
c. No, because the enzymes denature after doing chemical reactions
d. Yes, because enzymes are not used up by the reactions they help speed up

MY CHOICE: D

I really need someone to check this for me...I would greatly appreciate any help.

1. How do endothermic and exothermic reactions differ?

To determine the difference between endothermic and exothermic reactions, we need to understand their definitions.

An endothermic reaction is a chemical reaction that absorbs or takes in energy from its surroundings. This means that the products of the reaction have more energy than the reactants. In other words, heat is being absorbed during the reaction.

On the other hand, an exothermic reaction is a chemical reaction that releases energy to its surroundings. This means that the products of the reaction have less energy than the reactants. In other words, heat is being released during the reaction.

Based on this understanding, we can eliminate option A, as endothermic reactions do not release energy. We can also eliminate option C, as endothermic reactions do not give off heat and light. Option D is incorrect because photosynthesis is actually an endothermic process, not exothermic.

Therefore, the correct answer is option B: Exothermic reactions release energy and are spontaneous.

2. Which is NOT a description of activation energy?

To understand activation energy, we need to know its definition. Activation energy is the minimum amount of energy required for a chemical reaction to occur. It acts as a barrier that reactants must overcome in order to proceed with the reaction.

Let's evaluate the options:

Option A states that activation energy is the energy absorbed by the reactants. This is incorrect because activation energy is the energy required for the reaction to start, not the energy absorbed by the reactants.

Option B correctly describes activation energy as the energy needed to get an endothermic reaction to proceed.

Option C states that activation energy is the "push" to start a chemical reaction. This is a valid description of activation energy.

Option D states that activation energy is the energy transfer between the products and reactants. This is incorrect because activation energy is not the energy transfer between the products and reactants but rather the minimum energy required for the reaction to occur.

Therefore, the correct answer is option D: The energy transfer between the products and reactants is not a description of activation energy.

3. An animal's stomach contains enzymes that break down food into smaller molecules that the animal's cells can use. Enzymes perform this function by:

To determine how enzymes break down food in an animal's stomach, we need to understand the function of enzymes. Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.

Let's evaluate the options:

Option A states that enzymes participate in chemical reactions. This is correct because enzymes facilitate the chemical reactions by lowering the activation energy required for the reaction to occur.

Option B states that enzymes increase the temperature. This is incorrect because enzymes themselves do not increase the temperature but rather decrease the activation energy, allowing the reaction to occur at lower temperatures.

Option C states that enzymes change the ionic concentration. This is incorrect because enzymes do not directly change the ionic concentration but rather interact with specific substrates to catalyze reactions.

Option D states that enzymes lower the pH. This is incorrect because enzymes do not directly lower the pH but rather function optimally at specific pH ranges.

Therefore, the correct answer is option A: Enzymes perform their function by participating in chemical reactions.

4. Milk you buy at the store has been "Pasteurized." This means the milk was warmed up to around 150 F/65 C to kill harmful bacteria. This process probably works because:

To understand why pasteurization kills harmful bacteria in milk, we need to consider the process and its effects on bacteria.

Let's evaluate the options:

Option A states that pasteurization speeds up the metabolism of bacteria and increases their death rate. This is incorrect because pasteurization actually works by denaturing the enzymes of the bacteria, not by speeding up their metabolism.

Option B states that pasteurization causes the bacteria's carbohydrates to undergo hydrolysis, thus killing the bacteria. This is incorrect because pasteurization does not directly cause carbohydrates to undergo hydrolysis.

Option C states that the bacteria's enzymes will denature at the high temperature, thus killing the bacteria. This is correct because pasteurization heats the milk to a temperature that denatures the enzymes of the bacteria, rendering them inactive and incapable of harmful actions.

Option D states that pasteurization causes the bacteria to build many polymers, which kills the bacteria. This is incorrect because pasteurization does not cause bacteria to build polymers.

Therefore, the correct answer is option C: The bacteria's enzymes will denature at the high temperature, thus killing the bacteria.

5. In a test tube, a student used the enzyme catalase to break down some H2O2 (Hydrogen Peroxide). After the reaction, she discovered another bottle of H2O2 that needed to be broken down also. Will she be able to use the enzyme again?

To determine if the student can reuse the enzyme catalase, we need to understand the nature of enzymes and their involvement in reactions.

Enzymes are catalysts that speed up chemical reactions without being consumed or permanently changed in the process.

Let's evaluate the options:

Option A states that enzymes get broken down when they do chemical reactions. This is not true; enzymes are not typically broken down in the chemical reactions they catalyze.

Option B states that enzymes are carbohydrates and do not break down. This is incorrect because enzymes are not carbohydrates but rather proteins or RNA molecules.

Option C states that enzymes denature after doing chemical reactions. This is incorrect because while certain conditions, such as high temperature or extreme pH, can denature enzymes, it does not occur after every reaction.

Option D states that enzymes are not used up by the reactions they help speed up. This is correct because enzymes remain unaffected by the reactions they catalyze and can be reused.

Therefore, the correct answer is option D: Yes, the student will be able to use the enzyme catalase again as enzymes are not used up by the reactions they help speed up.