Evidence of a chemical reaction is anything that shows

• a new substance has formed

• a solid dissolved in a liquid

• interaction between 2 gases

• a change in the state of matter

One of the signs of a chemical reaction taking place is:

• Bubbles are produced

• Reactants are not combining

• Products are not forming

• Color is not changing

Which of the following describes a precipitate?

• a liquid forms when a block of metal is heated

• a solid forms when one liquid is poured into another

• a gas forms when a solid is placed in a liquid

• bubbles form when an acid is poured on a rock

Which is NOT an indication of a chemical change?

• temperature change

• formation of a precipitate

• shape change

• production of light

You know you a chemical reaction has occurred if

• there is a precipitate.

• there is a color change.

• there is a temperature change.

• All of these answers are evidence.

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

• A solid block of ice is heated and it 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.

A student places a piece of a potato into a container of hydrogen peroxide. One observation the student makes is that bubbles form around the potato. The presence of bubbles might indicate the formation of a new substance because bubbles -

• could show that a gas is forming.

• always rise to the top of a liquid.

• are almost always perfectly spherical.

• usually burst after a few minutes.

Jonathan places a pot of water on a stove. As the water boils, how does the state of the water change?

• from gas to liquid

• from liquid to gas

• from liquid to solid

• from solid to liquid

Matter changes state when...

• energy is added or removed

• energy is added

• energy is removed

• there is no energy

What state of matter is present at 50° C for water?

• solid

• liquid

• gas

• plasma