1. The Law of Conservation of Matter is a fundamental principle in chemistry. Which statement accurately summarizes this law?
- A. The mass of reactants must equal the mass of products.
- B. The volume of reactants is always conserved in a reaction.
- C. Energy is neither created nor destroyed, only transformed.
- D. In any reaction, a visible solid product must be formed.
2. A student dissolves an effervescent tablet in an open beaker of water. They measure the mass before and after the bubbling stops and find the final mass is lower. Why does this observation NOT violate the Law of Conservation of Matter?
- A. The law does not apply to reactions that occur in water.
- B. Some of the tablet's mass was converted into heat energy.
- C. A gas was produced and escaped from the container, carrying mass with it.
- D. The water dissolved the tablet, which is a physical process that inherently reduces the total mass of the system.
3. A scientist performs a reaction in a sealed, rigid container and observes that the total mass inside has not changed, but a liquid has disappeared and the pressure inside has increased. What is the most logical deduction?
- A. The liquid was destroyed during the reaction.
- B. The container must have developed a leak that let extra air in.
- C. The liquid evaporated or reacted to form a gas.
- D. The reaction failed to follow the known laws of chemistry.
4. If 12 grams of carbon react completely with 32 grams of oxygen, how many grams of carbon dioxide (CO2) will be produced, assuming it is the only product?
- A. 20 grams
- B. 32 grams
- C. 44 grams
- D. It is impossible to determine without seeing the reaction.
5. When sodium bicarbonate (baking soda) reacts with acetic acid (vinegar), bubbles of carbon dioxide gas are produced. If you perform this reaction in an open bowl placed on a digital scale, what will happen to the mass reading on the scale as the reaction proceeds?
- A. It will increase as new matter is created.
- B. It will decrease as the CO2 gas escapes.
- C. It will stay exactly the same.
- D. It will first increase, then decrease rapidly.
6. What fundamental principle explains why scientists would search for the 'missing' nitrogen and hydrogen atoms from the fertilizer after it reacts to form rust?
- A. The theory of general relativity
- B. The law of conservation of mass
- C. The principle of buoyant force
- D. The law of thermodynamics
7. A student claims that in the reaction forming rust, the nitrogen and hydrogen atoms from the fertilizer simply 'disappeared.' Why is this statement scientifically incorrect?
- A. Atoms can change into other types of atoms.
- B. Atoms are rearranged to form new substances.
- C. Atoms are too small to be tracked in a reaction.
- D. Atoms can be converted into pure energy.
8. To properly test the law of conservation of mass during the rust investigation, what would be the most critical change to the experimental setup?
- A. Use a more precise scale.
- B. Conduct the reaction in a sealed container.
- C. Increase the amount of fertilizer.
- D. Heat the reactants to speed up the reaction.
9. In an experiment, a fertilizer containing nitrogen (N) and hydrogen (H) reacts with iron (Fe). The only visible product is rust (iron oxide). Why does this observation suggest an incomplete analysis of the reaction?
- A. The nitrogen and hydrogen atoms must have been destroyed during the chemical process.
- B. Iron is more reactive than nitrogen and hydrogen, so they were not involved in the reaction.
- C. The nitrogen and hydrogen atoms from the fertilizer must have combined to form other, unobserved products.
- D. The rust must have been contaminated with other substances before the experiment began.
10. A student burns a piece of wood that weighs 500 grams. After burning, the remaining ash weighs only 20 grams. The student concludes that 480 grams of matter were destroyed. Why is this conclusion incorrect?
- A. The 480 grams of matter were converted into energy, such as heat and light.
- B. The ash is much denser than wood, which accounts for the difference in mass.
- C. The 480 grams of matter were converted into invisible gaseous products, like carbon dioxide and water vapor.
- D. The initial measurement of the wood's mass must have been flawed.