reaction 1: magnesium plus hydrochloric acid.

Question

a small piece of a silvery metal (magnesium) and a container of clear hydrochloric acid. Small bubbles are seen accumulating on the metal strip.
was this a chemical reaction or a physical reaction? How do you know?

Answer 1

The reaction between magnesium and hydrochloric acid is a chemical reaction. Here’s how we can know:

1. Formation of Gas: The small bubbles accumulating on the magnesium strip indicate the production of gas. In this reaction, hydrogen gas (H₂) is released when magnesium reacts with hydrochloric acid (HCl). The production of a gas is a common sign of a chemical reaction.

2. New Substances Formed: When magnesium reacts with hydrochloric acid, it forms magnesium chloride (MgCl₂) and hydrogen gas. The formation of new substances is a definitive indicator of a chemical reaction.

3. Energy Change: Chemical reactions often involve energy changes, which can be observed as heat, light, or sound. In this case, the reaction may be slightly exothermic, releasing heat.

Overall, the evidence from the gas evolution and the formation of new chemical products clearly indicates that a chemical reaction has occurred.

Answer 2

reaction 2: vinegar and baking soda.
A clear liquid ( vinegar) and a white powder (baking soda). The combination forms bubbles and foams. was this a chemical reaction or a physical reaction? how do you know?

Answer 3

The reaction between vinegar (which contains acetic acid) and baking soda (sodium bicarbonate) is a chemical reaction. Here’s how we can determine that:

1. Formation of Gas: The combination of vinegar and baking soda produces carbon dioxide gas (CO₂), which is observed as bubbles and foam. The effervescence (bubbling) is a strong indicator of a chemical reaction occurring.

2. New Substances Formed: The reaction results in the formation of new substances, including carbonic acid, which quickly decomposes into water (H₂O) and carbon dioxide gas. The creation of new products is a hallmark of a chemical reaction.

3. Energy Change: Like many chemical reactions, this reaction can also absorb heat, resulting in a cooling effect on the sides of the container. This is another indication that a chemical change is taking place.

Overall, the visible formation of gas and new substances, along with the energy changes, clearly indicates that the interaction between vinegar and baking soda is a chemical reaction.