PS.8.1.4 - Physical and Chemical Changes

Zinc and Hydrochloric Acid

In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place.

After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable.

Which statement BEST interprets the temperature change that occurred in the experiment?

• All reactions that include zinc discs release heat.

• All reactions that include hydrochloric acid release heat.

• When the substances were combined, the physical change released heat.

• When the substances were combined, the chemical reaction released heat.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Zinc and Hydrochloric Acid

In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place.

After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable.

Which statement BEST explains why the gas in the balloon was flammable but the reactants were not?

• Atoms were created when the reaction took place, which resulted in the appearance of a flame.

• Atoms were destroyed when the reaction took place, which resulted in the appearance of a flame.

• Atoms are not destroyed during chemical reactions.

• The atoms of the reactants were rearranged into a new substance with new physical properties.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Zinc and Hydrochloric Acid

In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place.

After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable.

Did a chemical reaction take place? Explain why or why not.

• No, because neither the reactants nor the liquid product were flammable

• No, because the mass in the flask appears to change when the reaction takes place

• Yes, because the reactants were not flammable, but the gaseous product was flammable

• Yes, because the mass in the flask appears to be the same both before and after the reaction took place

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Zinc and Hydrochloric Acid

In the experiment, the teacher drops discs of zinc (Zn) into a flask of liquid hydrochloric acid (HCl). The students record that the mass of the substances before the reaction occurs is 262 grams. They also record the temperature of the substances and the fact that both zinc and hydrochloric acid are not flammable. Before the reaction begins, the zinc is placed into a balloon attached to the top of a flask containing the hydrochloric acid. This seals the flask before the reaction takes place. To initiate the reaction, the zinc is dropped into the hydrochloric acid. As soon as the substances combine, bubbles begin to form and the balloon expands. The picture shows the zinc as it is dropped into the flask, and the reaction as it is taking place.

After the reaction takes place, the temperature of the flask is recorded. The students note that the temperature of the flask is higher than before the reaction took place. The teacher then removes the balloon from the flask and carefully ignites the balloon in front of the class. The students record that the substance in the balloon was flammable.

Select the TWO observations that can be used as evidence to support that a chemical change took place.

• Bubbles form when the reactants are mixed.

• The mass of substances increase during the experiment.

• The balloon begins to expand after the reactants are mixed.

• The mass of the substances before the experiment is 262 grams.

• Bubbles are present in the hydrochloric acid before the experiment.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The students in Ms. Ramirez's science class are classifying different types of reactions. They have divided the reactions into two columns, as shown below.

Why are the reactions listed in Column B classified as physical reactions?

• They produced new substances with different properties.

• The changes do not affect the materials' characteristics/identity

• They released heat during the reactions.

• The reactions are irreversible.

Tags

NGSS.MS-PS1-2

The students in Ms. Ramirez's science class are classifying different types of reactions. They have divided the reactions into two columns, as shown below.

Why are the reactions listed in Column A classified as chemical reactions?

• The changes do not affect the materials' characteristics/identity

• The changes to the materials can be easily reversed.

• They created a new substance with different properties.

• They changed the shape of the materials.

Tags

NGSS.MS-PS1-2

Making Elephant Toothpaste

Mario is performing a science experiment to make a substance called "elephant toothpaste". The substance is given this name because it looks like a huge squeeze of toothpaste as it forms. The toothpaste looks much too large to be used by people, but is perfect for an elephant! The materials and procedure Mario will use are shown below.

Materials:

·       an empty plastic soda bottle (about 16 oz)

·       1/2 cup of liquid hydrogen peroxide (3% concentration)

·       1 package of yeast

·       1/4 cup of warm water

·       dish soap

·       a cup

·       food coloring

Procedure

1. Place a few drops of food coloring into the soda bottle with the hydrogen peroxide.

2. Add a squirt of dish soap and swirl the soda bottle to mix.

3. In the cup, mix the warm water and yeast and stir for a few seconds to combine.

4. Pour the yeast mixture into the soda bottle with the hydrogen peroxide.

5. Record observations as you watch the bottle.

The table below shows some of the observations that Mario makes while the elephant toothpaste is forming.

After the experiment, Mario noticed that the plastic bottle felt warm when touched.

If Mario repeats this experiment, what data will BEST provide further proof that a chemical change has occurred?

• The temperature should be taken at the start of the reaction and at the end of the reaction to see if a change in temperature has occurred.

• The mass of the yeast should be taken to determine if the warmth of the bottle is coming from a loss in mass because of the yeast.

• The temperature of the foam should only be taken at the end of the experiment to determine if the warmth of the bottle is coming from the foam.

• The mass of the foam should be taken to determine if the warmth of the bottle is coming from a loss in mass because of the foam.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

John and Gina completed an investigation on physical and chemical change. During the investigation, they added substances together and recorded their observations. They summarized their data in the table.

Using their data, which combination of substances resulted in a physical change?

• vinegar and baking soda

• sodium chloride and water

• calcium chloride and water

• sodium chloride and silver nitrate

Tags

NGSS.MS-PS1-2

Liam explores the decomposition of water. He attaches a battery to the ends of two pencils sharpened at both ends, and places the other ends of the pencils in a beaker of water. His set up is shown below.

Liam notices that bubbles form under the water at each pencil tip. What type of change is happening?

• no change

• a nuclear change

• a chemical change

• a physical change

Tags

NGSS.MS-PS1-2

The diagram shows a test tube of copper (II) sulfate solution before and after the addition of iron shavings during an experiment.

The experiment shows a...

• physical reaction, because it involved a compound.

• physical reaction, because the solution changed color.

• chemical reaction, because the solution changed color unexpectedly.

• chemical reaction, because it involved a mixture.

Tags

NGSS.MS-PS1-2