The dough is no longer flexible, but much more rigid. Maybe the cheese has melted. You certainly want the pizza to be cooked, not half-raw. How can a scientist tell if a chemical reaction is taking place? There are four visual clues that indicate that a chemical reaction is likely occurring:. A change in color occurs during the reaction. A gas is produced during the reaction. A solid product called a precipitate is produced in the reaction.
A transfer of energy occurs as a result of the reaction. Mercury II oxide is a red solid. The red color of the mercury oxide reactant becomes the silver color of mercury. Metals with dilute acid. We can use a gas syringe to measure the reaction of metals with dilute acid. When zinc reacts with hydrochloric acid it produces zinc chloride and hydrogen gas.
We can measure the rate of the reaction by measuring how fast the reaction produces hydrogen. Magnesium is a more reactive metal than copper. When a strip of magnesium metal is placed in an aqueous solution of copper II nitrate, it replaces the copper.
The products of the reaction are aqueous magnesium nitrate and solid copper metal. This subcategory of single-replacement reactions is called a metal replacement reaction because it is a metal that is being replaced copper. Many metals react easily with acids and when they do so, one of the products of the reaction is hydrogen gas.
Zinc reacts with hydrochloric acid to produce aqueous zinc chloride and hydrogen figure below. In a hydrogen replacement reaction, the hydrogen in the acid is replaced by an active metal. Some metals are so reactive that they are capable of replacing the hydrogen in water.
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