Chemical Reactions and Mixtures CFU

Abigail is conducting an experiment in her kitchen. She notices that when she mixes two clear liquids together, the mixture suddenly changes color. Which of the following is a sign that a chemical reaction has occurred?

• The substance changes shape.

• The substance changes color.

• The substance is mixed with water.

• The substance is broken into smaller pieces.

Answer explanation

The change in color indicates a chemical reaction has occurred, as it shows that new substances are formed. The other options do not necessarily indicate a chemical change.

Tags

NGSS.MS-PS1-2

Match each property with the type of change it is most likely to indicate when mixing two clear liquids and observing a reaction.

• Often changes if a chemical reaction occurs

• Volume

• May change slightly due to gas formation, but often stays similar

• Shape

• Usually remains the same in a chemical reaction

• Color

• Usually does not change in a chemical reaction

• Mass

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Grace is making a salad by mixing lettuce, tomatoes, and cucumbers, while Hannah is baking a cake using flour, sugar, and eggs that react together. What is the main difference between what Grace and Hannah are making?

• Mixtures are always liquids, while compounds are solids.

• Mixtures can be separated by physical means, while compounds cannot.

• Compounds are made of only one element, while mixtures are not.

• Mixtures have a fixed composition, while compounds do not.

Answer explanation

The main difference is that Grace's salad is a mixture, which can be separated by physical means, while Hannah's cake involves a chemical reaction, forming a compound that cannot be separated by physical methods.

Match each process with what happens to the material when it is added to water or exposed to certain conditions.

• Iron left in moist air

• It burns like wood

• Sugar stirred into water

• It bakes like a cake

• Cake mixture in an oven

• It dissolves in the water

• Wood in fire

• It rusts like iron

Grace is helping her teacher with a science experiment. She mixes vinegar and baking soda in a beaker. What evidence would indicate a chemical reaction has taken place?

• The mixture becomes cold.

• The mixture bubbles and produces gas.

• The mixture turns blue.

• The mixture becomes thicker.

Answer explanation

The correct evidence of a chemical reaction is when the mixture bubbles and produces gas, indicating a release of carbon dioxide from the reaction between vinegar and baking soda.

Tags

NGSS.MS-PS1-2

Henry can demonstrate that the components of the mixture of iron filings and sand retain their identity by (a)   .

• By observing a change in temperatur

• By separating the components using

• By observing a color change

• By measuring the mass of the mixtur

Answer explanation

Henry can demonstrate that the components retain their identity by separating the components using physical methods, such as filtration or magnetism, which shows that iron filings and sand can be distinguished and remain unchanged.

Tags

NGSS.MS-PS1-2

Mason wants to show that a chemical reaction creates new substances with new properties. He mixes vinegar and baking soda in a beaker. What would be a key step in Mason's experiment?

• Measure the mass of the reactants and products.

• Observe the color of the reactants.

• Mix the reactants and wait for 5 minutes.

• Record the temperature of the reactants.

Answer explanation

Measuring the mass of the reactants and products is crucial to demonstrate that a chemical reaction occurs, as it shows the conservation of mass and indicates the formation of new substances with different properties.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

James is curious if mixing salt and water is a chemical reaction. How would you help James investigate this claim?

• Check if the mixture changes color.

• Evaporate the water to see if salt remains.

• Measure the temperature change of the mixture.

• Observe if gas is produced.

Answer explanation

To determine if mixing salt and water is a chemical reaction, evaporating the water will show if salt remains. If salt is left behind, it indicates a physical change, not a chemical reaction.

Tags

NGSS.MS-PS1-2

Avery is conducting an experiment to learn about different properties of materials. She observes that one material can dissolve in water, another can conduct electricity, a third reacts with acid, and a fourth can be cut into pieces. Which of these observations best describes a chemical property?

• The ability to dissolve in water

• The ability to conduct electricity

• The ability to react with acid

• The ability to be cut into pieces

Answer explanation

The ability to react with acid is a chemical property because it involves a change in the substance's chemical composition. The other observations describe physical properties, which do not alter the material's chemical identity.

Lily accidentally mixed some sand and iron filings while playing in the garden. The best method she should use to separate them is (a)   .

• Use a filter

• Use a magnet

• Add water and stir

• Heat the mixture

Answer explanation

The best method to separate sand and iron filings is to use a magnet. Iron filings are magnetic and will be attracted to the magnet, allowing them to be easily separated from the non-magnetic sand.