Chemical Reactions

A student placed 2 grams of baking soda in a balloon and 100 mL of vinegar in an Erlenmeyer flask. The mass of all materials was 180.34 grams prior to the investigation. After stretching the opening of the balloon across the neck of the flask, the student raised it to dump the baking soda into the flask. He immediately observed foaming bubbles in the flask, and the balloon began to expand. The student found the mass of all materials was still 180.34 grams after the investigation. The student concluded that —

• only a physical change was occurring

• the baking soda and vinegar were products of a chemical reaction

• the gas was oxygen

• mass was conserved in a closed system because the gas could not escape the balloon

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

H₂ + O₂ → H₂O₂

16g 2g 18g

The chemical equation above demonstrates that ―

• matter cannot be created or destroyed by a chemical reaction

• the reactants are the same substances as the products

• the number of molecules in the reactants is equal to the number of molecules in the products

• the atoms on the reactants side are changed into different atoms on the products side

Tags

NGSS.MS-PS1-5

How can a student determine that a chemical reaction demonstrates the law of conservation of mass?

• Students can compare the products and reactants to determine if the same molecules are present before and after the reaction.

• Students can compare the mass of the products and reactants to determine if the mass is the same before and after the reaction.

• Students can compare the products and reactants to determine if the same number of molecules are present before and after the reaction.

• Students can compare the products and reactants to determine if the same elements are present before and after the reaction.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The formula below represents the most common carbohydrate known as glucose. It is classified as a monosaccharide. Glucose is synthesized by chlorophyll in plants as they use carbon dioxide from the air and sunlight as an energy source during the process of photosynthesis. C₆H₁₂O₆ Which information can be determined from the chemical formula?

• The structural arrangement of the atoms in a glucose molecule

• The color of a glucose molecule

• The size of a glucose molecule

• The number of atoms of each element in a glucose molecule

Tags

NGSS.MS-PS1-1

I Subscripts are used to identify substances.

II Coefficients are used to identify substances.

IIIChemical formulas are used to identify substances.

IV The elements and the number of atoms of each element present in a chemical formula are used to identify substances.

Which of the above statements is true?

• I and II

• III and IV

• I and III

• II and III

Tags

NGSS.MS-PS1-1

A student placed 2 grams of baking soda in a balloon and 100 mL of vinegar in an Erlenmeyer flask. After stretching the opening of the balloon across the neck of the flask, the student raised it to dump the baking soda into the flask. He immediately observed foaming bubbles in the flask, and the balloon began to expand. The student concluded that —

• only a physical change was occurring

• the baking soda and vinegar were products of a chemical reaction

• the gas was oxygen

• the bubbles indicated a chemical change was occurring

Tags

NGSS.MS-PS1-2

A scientist performed an investigation in which different solid substances were added to four different beakers containing the same amount of water. After stirring the combined substances for two minutes, the scientist recorded the observations in the table below. The results of which of the investigations indicates that the substances least likely reacted chemically?

• 1

• 2

• 3

• 4

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

02During an investigation, a student combined two substances as shown below. The student observed a decrease in temperature when the substances were combined. A milky substance formed and sank to the bottom of the flask. What is the most likely reason for these results?

• The decrease in temperature produced ice crystals.

• A solid appeared after the liquid evaporated.

• The combined substances chemically reacted.

• A portion of the substances dissolved.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS1-5

During an investigation, students dropped a tarnished penny into a solution of acetic acid and sodium chloride. Tiny bubbles formed around the penny, and the penny was less tarnished after two minutes of soaking in the acetic acid and sodium chloride solution. The student inferred that a chemical reaction occurred. What evidence supports the student’s inference?

• The penny experienced a color change, and a gas was produced.

• The penny experienced a color change, and a precipitate was formed.

• The penny experienced a color change and is in a new state of matter.

• The penny experienced a color change and produced light.

Tags

NGSS.MS-PS1-2

Students in a science lab conducted an investigation. Students recorded the following observations. Which of the substances produced a chemical change?

• Substances 1 and 2

• Substances 1 and 3

• Substances 1 and 4

• Substances 2 and 3

Tags

NGSS.MS-PS1-2