How can you spot a chemical change?

Unit Standards 5.P.2B.1 Obtain and communicate information to describe what happens to the properties of substances when two or more substances are mixed together. 5.P.2B.2 Analyze and interpret data to support claims when two substances are mixed the total amount (mass) of the substance does not change. 5.P.2B.3 Develop models using observations to describe mixtures, including solutions, based on their characteristics.

How can you spot a chemical change? Chemical changes produce new substances. These substances have different properties than the previous ones.

How can you spot a chemical change? Often you can see, hear, or smell the formation of new substances as a chemical changes occurs.

How can you spot a chemical change? Chemical changes form layers on metals, and often dull their color. Rust, for example, is reddish, while iron form which it forms is shiny.

How can you spot a chemical change? In fact, whenever metals corrode it is due to a chemical change.

How can you spot a chemical change? Tarnish- When corrosion of metal causes a color change.

How can you spot a chemical change? The Statue of Liberty is coated with a thin layer of copper, which turns a blue-green with age due to chemical reactions between metal and water. This process is known as patination and occurs with most copper when it's placed outside The true color of the Statue of Liberty before patination was a shiny reddish brown color. The photo to the left shows the statue and what it looked after patination occured.

How can you spot a chemical change? When you place an antacid tablet in water, a chemical reaction occurs and bubbles start to form. The appearance of bubbles is another signal that a chemical change has occurred.

How can you spot a chemical change? Precipitate- a solid formed from the chemical reaction of two solutions.

How can you spot a chemical change? When a sink isn’t cleaned, it may develop a sticky white layer. This “soap scum” is a precipitate formed from solutions of soap and water.

How can you spot a chemical change? Some chemical changes involve the release of light and heat. A burning candle, for example, produces a hot flame.

How can you spot a chemical change? The heat and light come from the combination of atoms in the candle and in the wick with oxygen from the air.

What are chemical changes? The total mass of the reactants equals the total mass of the products in a reaction. Thus, one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.