Chemical reactions

For an investigation, a student poured a blue solution of copper (ii) sulphate [CuSO₄] into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes.

The student inferred that a chemical reaction occurred. What evidence (or sign) supports this inference?

• A dark solid formed on the zinc metal.

• The zinc metal remained silver-colored and shiny

• The copper (ii) sulphate [CuSO₄] solution turned blue when the zinc metal was added.

• None of these

The reactants are on the left side of the chemical equation.

• True
• False

A scientist performed four investigations using eight different liquids. In each investigation, the scientist combined two of the liquids under a fume hood and recorded observations in the table below.In which investigation is it least likely that the liquids reacted chemically?

• 1
• 2
• 3
• 4

Which of these is NOT a sign that a chemical reaction has occurred?

• A loss of transparency

• An unexpected color change

• A temperature change

• The formation of a precipitate

The picture shows a copper penny turning greenish after a few years. Which of the signs shows that a chemical reaction has occurred?

• the smell changed

• formation of precipitate

• there is fizzing on the surface

• change in shape

What is a chemical reaction?

• It is a reaction of chemicals.

• The process by which protons or neutrons are removed from the nucleus of an atom.

• It is mixing substances and heating them up.

• When the atoms of the reactants rearrange themselves and join together in a different way. A new substance is always formed.

Tick the pair of signs that correctly indicate a chemical reaction has occurred.

• Color change

  Temperature change

• A strong scent is emitted

  Substance dissolves

• Precipitate is formed

  Bubbles form

• The liquid level rises

  Gentle fizzing

Identify the reactant(s) and product(s) of the reaction.

• All three are reactants and none are products.

• Hydrogen and water are the reactants, and oxygen is the product.

• Water and oxygen are the reactants, and hydrogen is the product.

• Hydrogen and oxygen are the reactants, and water is the product.

Which of the following is NOT a sign that a chemical reaction has occurred?

• produces light/heat

• production of a gas

• formation of a precipitate

• melting

Tags

NGSS.MS-PS1-2

The substances that react in a chemical reaction

• reactants

• products

• balanced equation

• catalyst