Chemical reactions conservation of mass 2023

Which of the following is a sign that a chemical reaction has occurred?

• change in shape

• bubbling

• melting

• dissolving

What characteristic defines ALL chemical changes?

• There is a change of state. (like liquid to solid)

• Electricity is produced.

• A new material is formed.

• Bubbles are produced.

Which of the following is an example that includes evidence of a chemical reaction?

• A sample of zinc is placed in water and it settles to the bottom

• Sugar that is burned gives off an odor and turns brown and then black.

• A tomato is placed into a blender and chopped up into smaller pieces.

• A solid block of ice is heated and it completely melts into a liquid.

Copper sulfate (liquid) solution and ammonium hydroxide(liquid) solution are mixed and a flaky substance forms. This represents....

• formation of a precipitate

• gas production

• release of energy

• a change in color

A strip of magnesium mixes with hydrochloric acid and the test tube warms up. This represents....

• a change of color

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  gas production

• formation of a precipitate

• change in energy

The diagram models a.....

• physical change in matter

• chemical change in matter

The diagram shows a model of molecules at the start. Three diagrams show this matter changing chemically and one shows it changing physically. Identify the diagram that shows a physical change in matter.

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Suppose a reaction were to happen in an open container in a lab. During the reaction, the scientist observes the chemicals bubble and produce a gas. During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g. Explain what happened.  

• His chemical reaction went against the law of conservation of mass

• The product destroyed mass during the reaction

• The gas that was produced was not able to be weighed since the container was open

• The reactants created matter during the reaction

How much does a 5 gram Hershey's kiss weigh after it is melted in the microwave?

• 5 grams

• more than 5 grams

• less than 5 grams

Which picture below would correctly demonstrate the Law of Conservation of Matter if this picture is the reactants?

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