Chemical Reactions

What is meant by a chemical reaction?

• A chemical reaction occurs when substances are heated together without altering their structure.

• A chemical reaction is the process of mixing two liquids without any change.

• A chemical reaction is a method of measuring the weight of substances before and after a process.

• A chemical reaction is a process where substances (reactants) are transformed into different substances (products) through the rearrangement of atoms.

Which of the following is a characteristic of a chemical reaction?

• Formation of new substances

• Absence of color change

• No change in energy

• Rearrangement of existing substances

What indicates that a chemical reaction has occurred?

• Indicators of a chemical reaction include color change, temperature change, gas production, precipitate formation, and odor change.

• Formation of a solid without a reaction

• No change in color

• Increase in mass

Which of the following is an example of combustion?

• Burning wood in a fireplace

• Boiling water in a kettle

• Rusting of iron

• Photosynthesis in plants

What is the role of reactants in a chemical reaction?

• Reactants are the final products of a chemical reaction.

• Reactants are the starting materials that undergo change in a chemical reaction.

• Reactants are substances that do not change during a reaction.

• Reactants are the energy sources required for a chemical reaction.

How can you identify a chemical change?

• Check the pH level of the solution.

• Measure the temperature change during the reaction.

• Look for signs like color change, gas production, or precipitate formation.

• Look for the boiling point of the substance.

What happens to the energy during a chemical reaction?

• Energy is destroyed in a chemical reaction.

• Energy is only released and not transformed.

• Energy is created during a reaction.

• Energy is conserved; it is transformed but not created or destroyed.

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

• Physical changes result in new substances, while chemical changes do not.

• Physical changes involve a change in temperature, while chemical changes do not.

• Chemical changes can be reversed easily, while physical changes cannot.

• Physical changes do not change the substance's chemical identity, while chemical changes do.

What is produced in a chemical reaction?

• Reagents

• Products

• Solvents

• Catalysts

Why is balancing chemical equations important?

• It ensures the conservation of mass and accurate representation of chemical reactions.

• It is necessary for cooking recipes.

• It helps in predicting the weather.

• It allows for faster chemical reactions.