Science TEKS 8.6B & 8.6E

What is the significance of coefficients in a chemical equation?

• Coefficients indicate the number of molecules or moles of a substance involved in the reaction.

• Coefficients represent the temperature at which the reaction occurs.

• Coefficients are used to balance the charges in a chemical equation.

• Coefficients determine the color of the substances involved in the reaction.

What is the balanced equation for the reaction of iron and oxygen to form iron(III) oxide?

• 3 Fe + 2 O₂ → Fe₂O₃

• 4 Fe + 3 O₂ → 2 Fe₂O₃

• 2 Fe + 3 O₂ → Fe₂O₃

• Fe + O₂ → FeO

Why is it important to balance chemical equations?

• To ensure that the law of conservation of energy is upheld.

• To ensure that the law of conservation of mass is upheld.

• To make the equations easier to read.

• To increase the speed of the reaction.

What is the molecular formula for water?

• H₂O

• CO₂

• NaCl

• C₆H₁₂O₆

What does it mean for a chemical equation to be balanced?

• The number of atoms of each element is the same on both sides of the equation.

• The total mass of the reactants is greater than the total mass of the products.

• The number of molecules of reactants is equal to the number of molecules of products.

• The reaction occurs at a constant temperature.

What happens to mass during a chemical reaction?

• Mass is destroyed; the total mass of reactants is less than the total mass of products.

• Mass is created; the total mass of reactants is greater than the total mass of products.

• Mass is conserved; the total mass of reactants equals the total mass of products.

• Mass can change depending on the temperature of the reaction.

What is an example of a chemical reaction?

• The reaction between baking soda and vinegar that produces carbon dioxide gas.

• Mixing salt and water to create a saline solution.

• Heating ice to melt it into water.

• Combining iron and sulfur to form iron sulfide without heat.

In the equation 2 HgO → Hg₂ + O₂, is it balanced?

• Yes, it is balanced because the number of atoms of each element is the same on both sides.

• No, because the number of atoms of each element is not the same on both sides.

• Yes, because it follows the law of conservation of mass.

• No, because there are too many oxygen atoms on the right side.

What is the difference between a physical change and a chemical change?

• A physical change alters the form of a substance, while a chemical change alters its chemical composition.

• A physical change involves a change in temperature, while a chemical change does not.

• A physical change is reversible, while a chemical change is always irreversible.

• A physical change affects the mass of a substance, while a chemical change does not.

How many hydrogen atoms are in 2H₂O?

• 2 hydrogen atoms

• 3 hydrogen atoms

• 4 hydrogen atoms

• 6 hydrogen atoms