Question

hmh science dimensions biology, unit 2, lesson 1, pages 79 - 84

1. think about the last food you ate. how do you know the chemical bonds in your food were broken?
2. analyze the chemical reaction in figure 13 on page 79. what are the inputs and outputs of the reaction?
3. what is activation energy?
4. how do endothermic and exothermic reactions differ in terms of energy?
5. according to the graph on page 82, how does a catalyst increase the rate of a chemical reaction?

Explanation:

1. When you ate the food, you gained energy. The breakdown of chemical - bonds in food during digestion releases energy, which your body can use for various functions like movement, thinking, etc.
2. Without seeing Figure 13, in a general chemical reaction, inputs are reactants and outputs are products. Reactants are substances that start the reaction and products are substances formed as a result of the reaction.
3. Activation energy is the minimum amount of energy that reactant particles must have in order to undergo a chemical reaction. It is like an energy "hill" that must be overcome for the reaction to proceed.
4. Endothermic reactions absorb energy from the surroundings (usually in the form of heat), causing the temperature of the surroundings to decrease. Exothermic reactions release energy to the surroundings (usually as heat), causing the temperature of the surroundings to increase.
5. A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. This allows more reactant particles to have enough energy to react, thus speeding up the reaction.

Answer:

1. You gained energy from the food, indicating bond - breakage.
2. Inputs are reactants; outputs are products.
3. Minimum energy for reaction start.
4. Endothermic: absorb energy; Exothermic: release energy.
5. Provides lower - activation - energy pathway.