Chemical Reactions

Chemical Reactions

by Ashley Ramsell

​In a Chemical Reactions

• ​The atoms or ions of one or more substances, called reactants, are rearranged, resulting in products.

• ​Ex. iron, water, and oxygen react to form hydrated iron oxide, or rust.

• ​Matter is neither created or destroyed during a chemical reaction.

• ​The mass of the products always equals the mass of the reactants.

• ​This principle is known as the law of conservation of mass.

​Chemical Equations.

Multiple Choice

What is the proportion for the formula for water?

$$2H_2O$$  

• 2:1

• 1:1

• 1:2

• 2:2

Multiple Choice

What is the proportions for the formula for Salt?

NaCl

• 1:2

• 2:1

• 1:1

• 2:3

​Energy in Reactions

• ​Energy is involved in all chemical reactions.

• ​There are 2 types of energy.

• ​Endothermic: a reaction in which the reactants absorb energy from their surroundings. Like cooking eggs.

• ​Exothermic: a reaction in which energy is given off with the products, usually in the form of heat or light. Like burning firewood.

• ​There is also activation energy, which is the amount of energy needed to get a reaction going.

Multiple Choice

Which of the following formulas represents the reaction in which copper (Cu) and oxygen gas $$\left(O_2\right)$$  combine to form copper oxide (CuO)?

• A.

• B.

• C.

• D.

Multiple Choice

Which of the following procedures would provide evidence for the law of conservation?

• A. Weigh the reactants, conduct the reaction in an open container, and weigh the products.

• B. Weigh the reactants, conduct the reaction in a sealed container, and weigh the products.

• C. Measure the volumes of the reactants, conduct the reaction in a sealed container, and measure the volume of the products.

• D. Write the chemical formulas for the reaction and balance it.

Multiple Choice

Juanita would like to cook a scrambled egg on her gas stove. When she first turns on the stove's burner, the electronic ignition produces a spark that sets the gas burning. As the gas burns, its heats the frying pan. As the egg cooks, it absorbs the heat energy from the pan and solidifies.

Which form of energy is needed for each step pf Juanita's cooking process?

• A. Igniting the gas requires endothermic energy, the gas burning releases activation energy, and the egg solidifying requires exothermic energy.

• B. Igniting the gas requires activation energy, the gas burning releases endothermic energy, and the egg solidifying requires exothermic energy.

• C. Igniting the gas requires activation energy, the gas burning releases exothermic energy, and the egg solidifying requires endothermic energy.

• D. Igniting the gas requires endothermic energy, the gas burning releases exothermic energy, and the egg solidifying requires activation energy.