Question

1. scientists at nasa are studying the potential for growing plants on mars. they conducted an experiment to observe how a martian soil simulant interacts with water. they measured the mass of 100g of dry soil simulant, then added 20g of water and measured the mass again immediately after mixing and after 24 hours.

time | mass (g)
0 hours (dry soil) | 100
0 hours (after adding water) | 120
24 hours | 119
what conclusion can the scientists draw about mass conservation in this system? explain your reasoning using the data provided.

1. students are investigating the thermal decomposition of copper carbonate. they set up the following experiment:

they place 20 grams of green copper carbonate powder in a test tube. they heat the test tube and observe the formation of a black solid (copper oxide) and the release of a colorless gas.
image of two test tubes with burners
the chemical equation for the reaction they’re studying is:
cuco₃ (s) → cuo (s) + co₂ (g)
part a: based on your observations, describe the cause-and-effect relationship between heating the copper carbonate and the changes you see in the test tube.

Explanation:

Question 10

1. First, analyze the initial mass: The mass of dry soil is 100g, and 20g of water is added. So the expected total mass if mass is conserved (assuming no loss) should be \(100 + 20=120\)g, which matches the mass immediately after adding water (120g).
2. Then, look at the mass after 24 hours: The mass is 119g, which is 1g less than 120g. This suggests that in an open system (since the experiment likely isn't in a sealed container), some water might have evaporated (changed from liquid to gas and escaped the system), but mass conservation still holds in a closed system. In this case, the initial mixing shows that when the system is considered (soil + water, before evaporation), mass is conserved (100 + 20 = 120). After 24 hours, the decrease is due to water leaving the system, not a violation of mass conservation. So mass is conserved within the system when no matter is allowed to escape; the change here is due to water escaping (evaporation) from the open system.

Heating copper carbonate (\(CuCO_3\)) provides the energy (heat) needed to break the chemical bonds in \(CuCO_3\). This causes a chemical reaction (thermal decomposition) where the green solid \(CuCO_3\) breaks down into a black solid (copper oxide, \(CuO\)) and a colorless gas (carbon dioxide, \(CO_2\)). So the cause is heating (supplying activation energy for decomposition), and the effects are the color change of the solid (green to black) and the release of a gas.

Answer:

The scientists can conclude that mass conservation holds in the system when no matter escapes. Initially, the mass of dry soil (100g) plus added water (20g) equals the mass immediately after mixing (120g), showing conservation. After 24 hours, the mass is 119g, likely because water evaporated (escaped the system as gas), but this is a loss from the open system, not a violation of mass conservation (which applies to closed systems where matter can't enter/exit).

Question 11 - Part A