C1 8.5E, 7.5B, 7.6A, 6.6B Chemical Reactions, Flow of Energy,

Which of these observations is an indication that a chemical reaction has occurred?

• Steam forms above boiling water.

• A solid forms when a clear solution is frozen.

• A solid forms when two clear solutions are mixed.

• Sugar crystals form on the sides of a boiling pot of sugar water.

Tags

NGSS.MS-PS1-2

Which statement describes an action that most likely resulted in a chemical reaction?

• A pan of water was heated on a stove, and steam formed.

• A liquid was mixed with another liquid, and a precipitate formed.

• A liquid was sprayed into the air, and a sweet odor was smelled.

• A child blew through a wand filled with soap, and bubbles were produced.

Tags

NGSS.MS-PS1-2

Students performed a lab investigation on chemical reactions. The students put on goggles and plastic gloves and then followed these steps: 1. Pour 150 milliliters of vinegar into a beaker. 2. Place a thermometer in the vinegar and record measurements. 3. Add a piece of steel wool to the beaker. 4. Observe and record thermometer measurements. 5. Remove the steel wool from the beaker. 6. Use tweezers to pull strands of the steel wool apart and observe changes. Which observation would indicate that a chemical reaction occurred?

• The vinegar took the shape of the container in step 1.

• The steel wool sank into the vinegar in step 3.

• The temperature of the vinegar increased during step 4.

• The steel wool changed shape during step 6.

Tags

NGSS.MS-PS1-2

Some students in a chemistry lab conducted an investigation in which they added four different solid substances to separate beakers of water. They stirred the mixtures for one minute and then recorded their observations in the table below. Which substance most likely caused a new substance to be formed when mixed with water?

• Substance 1

• Substance 2

• Substance 3

• Substance 4

Tags

NGSS.MS-PS1-2

During an investigation, a student combined the two clear, colorless solutions shown below. The student observed that the temperature changed from 25°C to 23°C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?

• One of the original compounds came out of solution.

• The solutions reacted chemically.

• Some of the water froze into ice crystals.

• Rapid evaporation of water occurred, leaving a solid.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS1-5

For an investigation a student poured a blue solution of CuSO4 into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes. The student inferred that a chemical reaction occurred. What evidence supports this inference?

• A dark solid formed on the zinc metal.

• The zinc metal remained silver-colored and shiny.

• The CuSO4 solution turned blue when the zinc metal was added.

• None of these

Tags

NGSS.MS-PS1-2

The diagram shows a chemical reaction. Which of the following most likely describes the reaction in the diagram?

• The heat created a chemical reaction between the iron and sulfur, creating a compound of iron sulfide with new chemical properties.

• The heat created a physical reaction between the iron and sulfur, creating a mixture with new physical properties.

• The heat evaporated the iron and sulfur, creating a precipitate with new chemical properties.

• The heat melted the iron and sulfur, creating a solution with new physical properties.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS1-5

Unknown elements W and X interacted to form a new substance. This indicates that W and X must have experienced a —

• temperature change.

• chemical change.

• physical change.

• phase change.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Why is the formation of rust, iron oxide, considered a chemical change?

• Rust has different properties than oxygen or iron.

• Rust has the same chemical composition as iron.

• Rust has a higher combustion rate than oxygen.

• Rust has a lower density than oxygen or iron.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

An energy pyramid is shown. Which sentence best describes how energy flows through this pyramid?

• Energy is transferred down each level of the energy pyramid.

• The energy lost at each level is consumed by organisms in the top level.

• Energy is transferred from organisms in one level to those in the level above.

• The organisms at the bottom level provide energy directly to organisms in all the other levels.

Tags

NGSS.MS-LS2-3