Investigate and analyze the effect of different factors on the rate of a physical and chemical change (e.g., temperature, surface area, pressure, catalysts). Explain how chemical changes produce substances with different chemical properties and the same total mass. Describe the products of radioactive decay in terms of the conservation of matter and energy (e.g., a radioactive nucleus decays into a new nucleus and emits particles and rays). Recognize and explain that the rate of radioactive decay of a substance is constant, not affected by any factors (e.g., the half-life of a radioactive substance is constant over a long time and a wide range of conditions found on Earth).