Conservation of Mass in Reactions

Miss Jack explains the law of conservation of mass, stating that mass cannot be created or destroyed, only transformed. She uses a cake-baking analogy and chemical equations to illustrate how the mass of reactants equals the mass of products. The video emphasizes balancing equations and understanding mass conservation in chemical reactions.

What does the law of conservation of mass state?

• Mass is always decreasing.

• Mass can be created and destroyed.

• Mass can only be transformed, not created or destroyed.

• Mass is always increasing.

In the cake example, if you start with 1 gram of eggs, 1 gram of oil, and 5 grams of cake mix, what is the mass of the final cake?

• 5 grams

• 8 grams

• 6 grams

• 7 grams

What are reactants in a chemical reaction?

• The substances that disappear in a reaction.

• The substances you start with in a reaction.

• The substances that are not involved in a reaction.

• The final products of a reaction.

In the equation 2 H2 + O2 -> 2 H2O, if you start with 10 grams of H2 and 4 grams of O2, what is the mass of the water produced?

• 10 grams

• 12 grams

• 14 grams

• 16 grams

In the equation CaCO3 -> CaO + CO2, if you have 23 grams of CaCO3 and 16 grams of CaO, what is the mass of CO2 produced?

• 7 grams

• 39 grams

• 23 grams

• 16 grams

What is the missing mass in the equation C + 2 H2 -> CH4, if you have 6 grams of carbon and 19 grams of CH4?

• 11 grams

• 17 grams

• 13 grams

• 15 grams

Why is it important to balance chemical equations?

• To decrease the mass of reactants.

• To ensure the reaction is fast.

• To make sure the mass is conserved.

• To increase the mass of products.

What does the arrow in a chemical equation represent?

• The transformation from reactants to products.

• The start of the reaction.

• The end of the reaction.

• The destruction of mass.

In a balanced chemical equation, what should the mass of the reactants equal?

• The mass of the reactants is irrelevant.

• Half the mass of the products.

• Twice the mass of the products.

• The mass of the products.

What is the key concept of the law of conservation of mass?

• Mass can be lost in a reaction.

• Mass is always conserved in a reaction.

• Mass can be created in a reaction.

• Mass is irrelevant in a reaction.