Tijuan mixed a solid and a liquid together in a beaker. He determined that a chemical change occurred. If his conclusion is correct, which substances could he have been observing and why?

The production of bubbles indicates that a new substance formed

Explanation:

A chemical change is characterized by the following:

i) A new substance is formed

ii) It is not easily reversible

iii) Heat is evolved

When Vinegar and baking soda are mixed, a gas is evolved. The evolution of a gas indicates that a new substance has been formed, hence a chemical change has taken place.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.