Formation of a Substance Quiz

The image shows what happens when cold medicine tablets are

placed in room-temperature water. What evidence would indicate that a new substance is produced?

• The tablets dissolve in water

• The water becomes cloudy

• The water level increases slightly

• Bubbles are given off

A student measures out 100 mL of two different clear liquids and

then pours one into the other. The mixture, which has a volume of

200 mL, turns bright red, then begins to become quite cold. In

this process, the first evidence that a new substance had formed

was observed when the –

• student measured the liquids

• volume was seen to be 200 mL.

• color changed to bright red

• temperature of the mixture decreased.

Four mixtures are made by combining two clear liquids and

observations are made. Which results indicate that a new

substance has formed?

• Mixture 1: The combined liquids have a greater mass than

  either of the starting liquids.

• Mixture 2: The liquids, when mixed, produce a white solid

  which settles to the bottom.

• Mixture 3: The mixture of the two liquids takes the shape of

  the container they are in.

• Mixture 4: The denser of the two liquids lies below the other

  less dense liquid.

Which of the following observations is the best indicator that a new

substance has been formed?

• A solid has become a liquid.

• A substance has changed color.

• A solid has dissolved in a liquid

• The volume of a substance increased.

The table records the observations that result from four different

combinations. Which combination of substances shows evidence that a new

substance was formed?

• Baking Soda and Vinegar

• Sodium Chloride and water

• Oil and Water

• Iron fillings and sand

Students combine several chemicals and record the observations

in their science notebooks. A list of the observed results is given

here.

•Production of a gas (bubbles)

•Phase change (solid to liquid)

•A precipitate forms

•Change in shape

•Crystals dissolving

•Heat produced

How many of the observations are evidence that a new substance

was formed?

• 3

• 4

• 5

• 6

Bubbles and fizzing can be seen instantly when baking soda is

mixed with vinegar. The bubbles are evidence of which of the

following?

• A gas is formed when baking soda and vinegar are mixed

• Baking soda dissolves in vinegar when they are mixed

• Vinegar turns into alcohol when it is mixed with baking soda

• A precipitate is formed when baking soda and vinegar are

  mixed

A granular substance is added to a liquid. Which of the following

would provide evidence to suggest a chemical change has taken

place?

• The liquid gives off heat.

• The granules dissolve completely.

• The volume of the liquid increases

• The granules seem to get smaller

When two substances are mixed, they might form a new substance.

Which of the following would indicate that a new substance has been

formed?

• The temperature of the mixture decreases

• The volume of the mixture increases

• The mass of the mixture increases.

• One of the substances dissolves.

A student mixes two clear liquids together. After a few minutes, a

white powder can be seen settling on the bottom of the test tube.

Which of the following is a conclusion that the student can draw

based on these observations? The two clear liquids –

• have combined to produce a new substance.

• were pure substances before they were mixed

• are toxic and should be handled with extreme caution

• have been stored too long and are no longer good.