Chemical reactions and equations

Which of the following is a chemical reaction?

• Water freezes.
• Sugar dissolves in water.
• Salt and pepper are mixed in a dish.
• Iron rusts.

Tags

NGSS.MS-PS1-2

When two substances were combined, bubbles were produced and the temperature dropped.  This most likely means that:

• a chemical reaction took place
• the two substances had low boiling points
• one substance dissolved in the other
• the two substances are non-reactive

Tags

NGSS.MS-PS1-2

Before a chemical reaction, the total mass of two reactants is measured to be 40 grams.  After the reaction, what should be the total mass of the products?

• 0 grams
• 20 grams
• 40 grams
• 80 grams

Tags

NGSS.MS-PS1-5

Copper chloride and aluminum react to produce aluminum chloride and copper.  Which of the following is the correctly balanced chemical equation for this reaction?

• CuCl₂ + Al -> AlCl₃ + Cu
• 3CuCl₂ + Al -> AlCl₃ + 2Cu
• 3CuCl₂ + 2Al -> 2AlCl₃ + 3Cu
• CuCl₂ + 3Al -> AlCl₃ + 2Cu

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Which observation would most likely indicate that an exothermic reaction has occurred?

• a color change
• the production of gas bubbles
• an increase in temperature
• a decrease in temperature

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

The first part of a balanced chemical equation is shown:  H₂SO₄ + 2NaOH → ________.  In order for this equation to be balanced, how many hydrogen (H) atoms must be present in the products?

• 2
• 3
• 4
• 5

Tags

NGSS.MS-PS1-5

Suppose two substances were combined together in a beaker. You know that a chemical reaction occurred if:

• new substances were created.
• one substance dissolved in the other.
• one substance melted in the other.
•  the two substances remained separate.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

All of the following are indicators of a chemical reaction except one.  Which one is NOT an indicator that a chemical reaction has taken place?

• he production of heat or light
• a color change
• the production of gas bubbles
• the dissolving of one substance in another

Tags

NGSS.MS-PS1-2

 The idea that matter is neither created nor destroyed in chemical reactions is known as the:

•  The idea that matter is neither created nor destroyed in chemical reactions is known as the:
• law of conservation of energy.
•  law of conservation of mass.
• second law of thermodynamics.

Tags

NGSS.MS-PS1-5

A teacher writes the equation representing the chemical reaction between hydrochloric acid and sodium on the board.HCl + Na → NaCl + H₂The teacher states that the equation has not been balanced. Which of these correctly shows the products of this reaction after the equation has been balanced?

• Na₂Cl + H₂
•  2NaCl + H₂
• NaCl + 2H₂
•  2NaCl + 2H₂

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2