Select the correct answer. Which statement is true of a chemical change? A. It involves changes in the molecular structure. B. It involves changes in phase but not changes in the molecular structure. C. It involves dissolving one substance into another. D. It involves a change in the state, or phase, of a substance. E. It involves the process of separating two or more dissolved substances.

4. a 20-kg child is tossed up into the air by her parent. the child is 2 meters off the ground traveling 5 m/s. circle one: ke / gpe / both show your work for finding the values of each type of energy the object has:

Imagine if during the cathode ray experiment, the size of the particles of the ray was the same as the size of the atom forming the cathode. which other model or scientific observation would have also been supported? 1. this would support dalton's postulates that proposed the atoms are indivisible because no small particles are involved. 2. this would support bohr's prediction about electrons moving in orbits having specific energy. 3. this would support bohr's prediction about electrons being randomly scattered around the nucleus in the atom. 4. this would support dalton's postulates that proposed that atoms combine in fixed whole number ratios to form compounds.

Why must humans find substitutes for many minerals found on earth? (a) form at an extremely slow rate (b) controlled by other countries (c) too deep in the earth to collect