ECA Review

Which of the following reactions correctly shows the combustion of methane?

• A. CH₄ + 2O₂ → CO₂ + 2H₂O

• B. 2CH₄ + 2O₂ → 2CO₂ + 2H₂O

• C. CH₄ + CO₂ → O₂ + H₂O

• D. CH₄ + 2CO₂ → 2O₂ + 2H₂O

What is the complete balanced equation for the following reaction? Na + Cl₂ → NaCl

• Na + Cl₂ → NaCl

• 2Na + Cl₂ → 2NaCl

• Na + Cl → NaCl

• 2Na + Cl₂ → NaCl₂

The subatomic particle with a negative charge is the

• proton

• neutron

• electron

• ion

The table shows the number of each of the three subatomic particles for four atoms. Which atoms represent the same element?

• 1 and 3

• 2, 3, and 4

• 1 and 2

• 2 and 4

Which of the following statements regarding nuclear reactions is true?

• Breaking an atom apart into two smaller atoms is called fusion.

• Combining two smaller atoms into a larger atom is called fission.

• During nuclear reactions, mass is not conserved but energy is.

• During nuclear reactions energy and mass are conserved, with mass being converted to energy and vice versa.

Charlie is frying an egg in a pan located over a gas burner. He develops a model to determine the energy produced by the flame in the gas burner by calculating the energy absorbed by the egg. Which assumption will Charlie need to make in order for his model to be considered a closed system?

• Heat flows from the egg to the surroundings.

• Heat flows from the pan to the surroundings.

• No heat is lost from the flame or the egg to the surroundings.

• The egg receives heat from the flame and the surroundings.

The image shows energy flow from coal, to a coal-fired power plant, to a power tower, and finally to a radio. Which sequence correctly summarizes the chain of energy conversions during the overall process?

• electrical energy → chemical potential energy → thermal energy → sound energy

• chemical potential energy → thermal energy → electrical energy → sound energy

• thermal energy → sound energy → electrical energy → chemical potential energy

• chemical potential energy → sound energy → thermal energy → electrical energy

How do endothermic reactions impact the overall kinetic energy of the molecules? Select all that apply.

• Energy is absorbed during an endothermic reaction.

• Energy is released during an endothermic reaction.

• An endothermic reaction increases the overall kinetic energy of the molecules.

• An endothermic reaction reduces the overall kinetic energy of the molecules.

Choose the words to complete the sentences. As wood burns, it undergoes a _________ change. The _________ produced by this change are forms of energy.

• chemical, carbon dioxide and water

• physical, heat and light

• physical, ash and smoke

• physical, carbon dioxide and water

• chemical, heat and light

Wood is made mostly of cellulose and has a chemical formula of C6H10O5. The chemical equation for this combustion reaction is: C6H10O5(s) + 6O2(g) → 6CO2(g) + 5H2O(g) + energy What type of reaction occurred?

• Exothermic

• Endothermic

• Neutralization

• Non-energetic