8.5E Chemical Reactions

Evidence of a chemical reaction includes anything that shows -

• a new substance has been formed

• a solid has dissolved in a liquid.

• an interaction between two gases.

• a change in the state of matter.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A clear liquid from a flask is poured into another clear liquid in a beaker. Which of the following results of this procedure would indicate a new substance was formed?

• The level of the substance in the beaker is higher after the other liquid is added.

• A yellow solid forms and then settles to the bottom of the beaker.

• Small white crystals are left behind in the flask that held the first liquid.

• The mass of the combined liquids is greater than either original liquid.

In air, phosphorous, a white solid, spontaneously reacts to produce a pale, green light. Why might the green light be evidence of a chemical reaction?

• Green is a color associated with reactions.

• Phosphorous is a solid at room temperature.

• The reaction will not occur in a closed container.

• It indicates a change in temperature.

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

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

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

• 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.

Tags

NGSS.MS-PS1-2

Four students performed four different investigations by combining different substances. Their results are shown in the table provided. In which experiment are new substances being formed?

• Experiment 1

• Experiment 2

• Experiment 3

• Experiment 4

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A chemical reaction is represented in the equation provided.

3H2+3Cl2 (ARROW) ?HCl

What number needs to go in front of the HCl to balance the equation?

• 2

• 3

• 5

• 6