Posted by Moira on Thursday, September 11, 2008 at 2:46pm.
The original post was a day or so ago and I don't remember all of the question. Have you identified the two white powders? If so, post that information and I can respond.
Well I know the first two answers. 2a) was sublimination- turning directly from a solid to a gas and I worked out that 2b) was zinc oxide- it turned yellow on heating and white on cooling.
Changing a solid to a gas by sublimation is a physical change because it was the same material before and after; i.e., the composition has not changed. I also think the ZnO is a physical change since the composition did not change. (Some oxides decompose on heating to give the metal + oxygen but I don't think ZnO is one of those).
Related Questions
Read Y9 chemistry (then anwer this) - 2a) Someone finds teo bottles without ...
Chemistry - Experiment 10: Which Fuels provide the most heat? There are many ...
chemistry - describe how you would produce pure samples of iron and sulphur ...
chemistry - Which best describes the physical change of an aluminum soda can ...
physics - Cause and Effect Make a graphic organizer like the one on page 301 of ...
chemistry - Posted a question earlier but it was the wrong question. If anyone ...
chemitry--- physical & chemical change--- - describe a physical change that...
Physics - I'm understanding most of this physics, but here is one last ...
science - I need a little assistance. Can you help? The question which seems to ...
Chemistry - Record the amount of heat needed to change phases for water-ice to ...
For Further Reading
