Why is crucible reheated?

The crucible may be placed right side up, as in the left photo, or on its side, as in the right photo. Heating it on its side is preferred because the overall strain on the ceramic material at the high temperatures used is somewhat less. When transferring a crucible to the dessicator tongs must be used.

Why the compound should not be heated to the point that it melts?

If you keep making the molecules bigger, at some point, the melting temperature would be higher than the decomposition temperature. If you heat such compounds, they decompose before they can melt.

Why are the crucible and lid cooled in a desiccator?

Function. Heated samples and beakers, or weighing dish, are cooled in a desiccator to prevent the sample or beaker from gathering moisture as it cools. The interior of the desiccator is dry due to the desiccant at the bottom and because it is sealed to keep outside, moist air from getting inside.

Why is the crucible covered during cooling?

You cover the crucible during cooling to avoid impurities from the air to combine with your compound. The air has many impurities such as oxygen gas, carbon dioxide gas, dust, smoke, etc. Determining molecular formula needs precision.

How does mixing compounds affect melting point?

When two different pure chemicals with exactly the same melting point are mixed, the resulting melting point is depressed. That mixtures have depressed melting points, even when both components have comparable melting points when each is pure, provides a useful laboratory technique.

Why is it best to cool the crucible and lid and sample in a desiccator rather than on the laboratory bench?

Why is it best to cool the crucible and lid in a desiccator rather than on the laboratory bench. The crucible does not visibly show its temperature, so we must use the clay triangle to avoid burning the work bench. Also, the crucible can pick up contaminants from the work bench.

Why do you heat a crucible at the beginning of the experiment?

The empty crucible is heated to remove moisture and ensure that the crucible is completely dry as any water present may affect the reading. To drive off any moisture or any volatile impurities from the surface of the crucible.

Why is a lid placed on the crucible while the sample cools after being heated?

Keep the crucible lid on your product after heating to avoiding adding water molecules back into the sample or container. Keep the lid partially over the sample when heating and close the lid when heating is stopped. Allow the crucible about 5 minutes to cool, then it can be weighed.

What affects the melting point of ionic compounds?

The factors which affect the melting point of an ionic compound are: The charge on the ions. Size of the ions.

How does intermolecular forces affect melting point?

The stronger the intermolecular forces are, the more energy is required, so the higher the melting point is. Many intermolecular forces depend on how strongly atoms in the molecule attract electrons — or their electronegativity. Hydrogen bonds are among the strongest intermolecular forces.