Evidences of Chemical and Physical Changes

What are the evidences of a chemical change?

• Change in volume

• Change in texture

• Formation of a precipitate, change in color, release of gas, and absorption or release of heat

• Change in state of matter

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NGSS.MS-PS1-2

How can you identify a physical change?

• By observing changes in the state, shape, or form of a substance without altering its chemical composition.

• By observing changes in the color of a substance

• By observing changes in the taste of a substance

• By observing changes in the smell of a substance

Provide an example of a chemical change.

• Burning of wood

• Mixing salt and water

• Melting ice

• Cutting paper

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

What are the signs of a chemical change?

• Change in texture

• Change in temperature

• Change in state

• Formation of a precipitate, change in color, release of gas, and absorption or release of energy.

Tags

NGSS.MS-PS1-2

Explain the concept of rusting in terms of physical and chemical changes.

• Rusting is a reversible process with no permanent change to the iron

• Rusting involves both physical changes, such as the appearance of rust, and chemical changes, as iron reacts with oxygen and water to form iron oxide.

• Rusting is a result of iron reacting with carbon dioxide instead of oxygen and water

• Rusting is only a physical change with no chemical reactions involved

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

What happens to the particles during a physical change?

• The particles lose mass during a physical change.

• The particles become radioactive during a physical change.

• The particles change into a different element during a physical change.

• The particles do not change their identity or composition during a physical change.

A student mixes two clear liquids together. After a few minutes, a white powdery solid 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-

• were pure substances before they were mixed

• are toxic and should be handled with extreme caution

• have gone through a chemical change in which a new substance called a precipitate was produced

• have been stored too long and are no longer good

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NGSS.MS-PS1-2

A student added white crystals to a clear liquid. The crystals dissolved in the liquid. After a few seconds, the liquid became quite warm and then turned bright red in color. Indications that a chemical change was taking place could be observed when –

• the white crystals were added to the clear liquid.

• the crystals dissolved in the liquid leaving only the liquid visible

• There are no indications of chemical change

• the temperature of the liquid increased and an unexpected color change occurred.

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NGSS.MS-PS1-2

A copper penny turning greenish after a few years is an example of ...

• Chemical Change

• Physical Change

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NGSS.MS-PS1-2

The Best Friend's Club uses "invisible ink" to write notes to each other. The invisible ink is actually lemon juice that is clear when it dries on paper, but turns brown when a club member holds a burning candle under the paper. Once it is heated, it is never invisible again.

What type of change is occurring when the paper is heated?

• Chemical Change

• Physical Change

• Elemental Change

• Temperature Change

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NGSS.MS-PS1-2

NGSS.MS-PS1-4