In a beaker, sugar is dissolved in water, and then the water is heated and evaporates. the sugar is recovered, and heat is again applied. vapor is released, and the material in the beaker changes from white to black. what must you know to determine if a chemical change occurred? a) the boiling point of water b) the boiling point of sugar c) the identity of the black substance d) temperature at which sugar evaporates

The characteristics of two different types of reactions are shown below: reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of an element. which statement is true about the atoms of the elements that participate in the two reactions? their identity changes in both reaction a and reaction b. their identity changes in reaction a but not in reaction b. their identity changes in reaction b but not in reaction a. their identity remains the same in both reaction a and reaction b.

Which of the following is true about the products formed during photosynthesis? (5 points) select one: a. they have the same mass as the mass of reactants. b. they are the same set of compounds as the reactants. c. they have more mass than the mass of reactants. d. they are chemically the same as the reactants.

Acompound has the molecular formula c3h8. which class of organic compounds does it belong to?