Final answer:
The pure substance from the list provided is sugar, which is a compound with a uniform composition and consistent properties across any sample.
Step-by-step explanation:
The question is asking to choose the pure substance from a list. Pure substances have a constant composition and exhibit the same physical and chemical properties throughout any sample.
Among the options provided - sugar water, iced tea, a casserole, and sugar - the pure substance is sugar, also known as sucrose.
Sucrose is a compound, which means it is made up of more than one type of element chemically bonded together, and it has a uniform composition (42.1% carbon, 6.5% hydrogen, and 51.4% oxygen by mass) and consistent properties.
Other options like sugar water and iced tea are homogeneous mixtures (solutions), and a casserole would be a heterogeneous mixture.
The difference lies in the consistency of composition throughout the sample, where mixtures exhibit a variability not found in pure substances.
A pure substance from the list provided would be sugar. Sugar is a compound composed of carbon, hydrogen, and oxygen atoms, and it has a constant composition and properties regardless of its source.
It is not a mixture like sugar water or iced tea, and it is not a casserole, which is a combination of different ingredients.