Physical and Chemical Changes

Is decorating a skate board a physical or chemical change? Tell me why.

someone baked bread in the oven

• physical

• chemical

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS1-5

A teacher places Iron filings that are mixed with sand in a bowl. The teacher asks a group of students to plan and figure out a way to separate the materials. Which of the following is the most effective way to separate the mixture to demonstrate that a physical change has occurred?

• Add water to the bowl. The sand will dissolve in water, and the iron filings will be left.

• Place the contents of the bowl into a funnel made of filter paper, and use water to separate the sand from the iron filings.

• Pour the contents of the bowl into a pot with boiling water. The sand will rise, leaving the iron filings at the bottom of the pot.

• Use a magnet to attract the iron filings so that they can be separated from the sand.

A chart of investigations made are shown. Which of the investigations demonstrate an example of a physical change?

• All of the situations are examples of physical changes because all of the investigations exhibit changes to the physical properties.

• Investigation1 A gray iron bar is heated until it glows red. Investigation 2 A nail is placed in water and a red-orange rust forms. Investigation 3 A few drops of red food coloring are used to turn water red.

• None of the situations are examples of physical changes because they all involve a color change.

• Situation 2 is a physical change because rust forming is a natural process. Situations 1 and 3 are physical changes because no new substances are formed.

Two students made a chart to show observations they made on a cup of water. Which explanation BEST describes the outcome of their observations?

• Both students added heat from the water, which caused the water to change its state.

• Both students removed heat from the water, which caused the water to change its state.

• 1. Student 1 removed heat from the water, which caused the water to change from a liquid to a solid. Student 2 added heat to the water, which caused the water to change from a liquid to a gas.

• Student 1 added heat to the water, which caused the water to change from a liquid to a solid. Student 2 removed heat from the water, which caused the water to change from a liquid to a gas.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Three students at Winterville Elementary were given an assignment by their science teacher to plan and carry out experiments where chemical changes would occur. Below, you can see each student's plan and the results he or she recorded.

• 1. Student A was the only one to create an experiment where a color change occurred.  This shows evidence of a chemical change.

• Student A, Student B, and Student C all created experiments where chemical changes occurred.  Student A observed a color change, Student B saw bubbles, and Student C was able to dissolve salt.

• Student B and Student C created experiments were chemical changes occurred.  Student A just dyed her water.  Student B and Student C both changed their substances to prove that they had chemical changes.  Student B created a gas while Student C got rid of the salt.

• Student B was the only one to create an experiment with evidence of a chemical change.  She created a new substance, a gas.

Tags

NGSS.MS-PS1-2

A student is investigating evidence of chemical changes when making pancakes. The student claims that a chemical change occurred during the investigation. Which argument BEST supports the student’s claim?

• 1. The ingredients that combined to make batter provided evidence of a chemical change because you cannot separate the original ingredients. 

• The butter that was placed on the griddle provided evidence of a chemical change because there was gas emitted when the butter changed states.

• The batter added to the griddle provided evidence of a chemical change since the batter instantly changed its physical properties.

• The batter beginning to bubble and turn a golden color provided evidence of a chemical change since there was gas and odor production from the heat.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Students investigate the best plan to separate the following mixture. 15 grams of table salt and 15 grams of sand are mixed together. Which of the four students explains effective methods to separate the mixtures and draws appropriate conclusions about the physical change?

• Student A: "I noticed that the table salt dissolved in the water. There is no way to reverse this action. The sand did not dissolve in water. I can separate the sand from the water by using my hands."

• Student B: "The table salt dissolved in the water, and the sand did not. However, the table salt is still there. To prove this, I can use filter paper to separate the sand from the saltwater solution. Then, I can boil the water to evaporate it so that only salt is left in the bottom of the glass beaker."

• Student C: "When the salt and sand were added to the water, a color change occurred. The water became cloudy. There is no way to reverse this action. We cannot remove the salt or sand from the water."

• Student D: My observations show that the table salt dissolved in water. Once something dissolves, you can no longer see it, so the salt is gone. The sand can be separated from the water. I can pour the sand and water mixture into a flat pan and place it outside in the sun. The water will evaporate leaving only the sand.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A student is asked to plan a demonstration to show a physical change with a piece of paper. Which of the following investigations could the student use to accurately represent the type of change?

• The student can fold the paper in half to show how the paper changed its chemical properties.

• The student can cut the paper into tiny pieces to show how the paper changed its physical properties.

• The student can put water on the paper to show how the paper can change its state of matter from a solid to a liquid.

• The student can burn the paper to show how the paper can also resemble ash and smoke to show a change in state.

Students were asked to choose from the list of materials below to create a plan and carry out an experiment where a chemical change will occur.

• Mixing 100mL of water and red food coloring would show a chemical change. I know this because a color change is evidence of a chemical change and the clear water turned red.

• Mixing 20 grams of salt into 100mL of water would show a chemical change. I know this because if you stir the salt enough, the salt will disappear, which creates a new substance.

• Mixing 20 grams of baking soda, 20 grams of salt, and red food coloring would show a chemical change. I know this because the materials would be difficult to separate.

• Mixing 20 grams of baking soda and 50 mL of vinegar would show a chemical change. I know this because when the materials combine, they will begin to bubble, which shows evidence of gas emitted. 

Tags

NGSS.MS-PS1-2