Does a physical change ever alter the appearance of a substance

A disease-resistant variety of a sexually reproducing crop was planted on a field with an existing nonresistant variety. After a few years, pests severely attacked the plants. The older, nonresistant plants died.

How does the density of air affect its movement in a convection cell?

Malik formed a hypothesis that an increase in atmospheric oxygen levels by 10% would cause red-legged grasshoppers to grow larger than normal. Suppose that Malik performs an experiment to test his hypothesis.

Enter the atomic symbols for an isotope with four protons and five neutrons

What mass of CCl4 is formed by the reaction of 5.14 g of methane with an excess of chlorine?

How should scientist respond when new evidence that challenges current is presented?

Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular temperature. Determine the equilibrium pressure of H2. D2 (g) + H2 (g) ⇌ 2 HD (g) Kp = 1.80 P (D2) eq = 1.1 * 10-3 atm P (HD) eq = 2.7 * 10-3 atm

Find δe for the change in state of 1.0 molh2o (l) at 79 ∘c to h2o (g) at 116 ∘c. the heat capacity of h2o (l) = 75.3 j/molk, heat capacity of h2o (g) = 25.0 j/molk, and the heat of vaporization of h2o is 40.7*103j/mol at 100 ∘c.

Balloon A started with a volume of 1.76 L. The temperature of the room the balloon was in was 295 K. The balloon was heated to a temperature of 253.15 K. What is the new volume?

The standard internal energy change for a reaction can be symbolized as ΔU°rxn or ΔE°rxn. For the following reaction equations, calculate the energy change of the reaction at 25 °C and 1.00 bar. Sn (s) + Cl2 (g) - - - > SnCl4 (l) + H (KJmol) - 511.3.