When substances change into new substances, the process must involve: a physical change a chemical change heat being produced heat being absorbed

Answer is a chemical change.

As a result of a chemical reaction, a substance is changed into new substances which involves a chemical change.

During a chemical reaction, atoms of a molecule within a substance are rearranged into different combinations by combining with the atoms of another substance to form new substances.

An example of a chemical change is the composition of sodium chloride (salt) where the atoms of sodium and chlorine combine and rearrange themselves to form salt.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.