Chemical Reactions + Physical & Chemical Properties

Which observations are evidence that a chemical reaction is taking place?

Answer explanation

• The formation of a precipitate, The release of heat (bottom of beaker feels warm to the touch) or light, The formation of bubbles/gas, & Color, odor, or sound change

Tags

NGSS.MS-PS1-2

When vinegar and baking soda are combined, bubbles begin to form. Explain how the formation of bubbles is evidence of a chemical reaction.

Answer explanation

The formation of bubbles is evidence of a chemical reaction because bubbles indicate the formation of a gas as a new product.

Tags

NGSS.MS-PS1-2

Four students performed four different investigations by combining different substances. Their results are shown in the table below. In which experiment did a chemical reaction take place, and how do you know?

Answer explanation

I know a chemical reaction took place in Experiment 1, because bubbles were produced, which indicates a new substance was formed.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Why are chemical equations written?

Answer explanation

to describe a chemical reaction - They show the reactants and products of the reaction

Tags

NGSS.HS-PS1-7

If the products have the same chemical properties as the reactants, has a chemical process occurred? Explain.

Answer explanation

No. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, & these new substances have different properties from those of the reactants.

Tags

NGSS.MS-PS1-2

Hydrogen and Oxygen react to form water. At an atomic level, how do we know that a chemical reaction has occurred?

• For every Oxygen atom, two Hydrogen atoms are needed.

• Oxygen atoms are much larger than Hydrogen atoms.

• Hydrogen molecules are negative, and Oxygen positive.

• The Hydrogen and Oxygen atoms regroup into a new molecule.

Tags

NGSS.MS-PS1-2

The chart below shows the results of combining various substances. Which of the following statements is true?

• We know combining Substances C & D resulted in a  chemical reaction because of the lack of a temperature change.

• We know combining Substances A & B resulted in a chemical reaction because of the lack of a temperature change.

• We know combining Substances A & B resulted in a chemical reaction because a gas was formed.

• We know that neither combination resulted in a chemical reaction because neither one had a color change.

Tags

NGSS.MS-PS1-2

Which of the following is the best description of the results of a chemical reaction?

• The substance seems to disappear after dissolving in water.

• The reaction can be reversed to get back the original substance.

• A new substance with different properties is formed.

• The substance changes from liquid to solid at a low temperature.

Tags

NGSS.MS-PS1-2

Rust forming on a piece of iron is an example of which of the following?

• A natural process of decay as metallic ions age

• A violation of the laws of physics because new mass has been created.

• A physical change because the process can be reversed

• A chemical change because Oxygen atoms from the atmosphere bonded with the Iron atoms

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following statements is true?

• Freezing water is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

• Melting ice is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

• Cutting paper is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

• Burning paper is an example of a chemical reaction because a new substance is formed and the process cannot be undone.

Tags

NGSS.MS-PS1-2