Reactions 23

A substance that is formed as the result of a chemical reaction is a __________________

• Product

• Reactant

• Starters

• Enders

Which one shows that a chemical reaction has occurred?

• dissolving

• melting

• formation of a gas

• bending

the starting materials in a chemical reaction

• Products
• Reactants
• Starters
• Enders

• Mg and O
• MgO
• Mg and MgO
• O and MgO

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes
• Oxygen is present
• A new substance is produced
• Coal is made up of more than one element

A teacher is demonstrating physical and chemical changes to her class. Which action should she use to demonstrate a chemical change?

• cutting a piece of paper
• folding a piece of paper
• tearing a piece of paper
• burning a piece of paper

In a chemical reaction, the number of atoms in the reactants and the products...

• Must be the same

• Must be different

You have 2 chemicals, CHEMICAL A and CHEMICAL B. They are both liquids. When you combine them you notice some crystals starting to form within them. Did a chemical reaction occur?

• Yes

• No

In a chemical reaction, the number of atoms in the reactants and the products...

• Must be the same

• Must be different

Which of these is NOT a sign of a chemical reaction?

• A phase change

• Formation of a precipitate

• A color change

• A temperature change