7.1 Chemical reactions

Which of the following is considered a sign of a chemical reaction?

(Choose more than one answer)

• See huge flames or tiny sparks.

• Notice a sweet smell or a foul stink.

• Feel the chemicals getting hotter … or colder.

• Hear a loud bang or gentle fizzing

• No correct answer.

What is formed in a chemical reaction?

• Inhibitors

• Reactants

• Products

• Catalysts

In chemical reactions, new substances are formed what do we call them?

• Inhibitors

• Reactants

• Products

• Catalysts

The substances that react in a chemical reaction are called.............................

• inhibitors

• reactants

• products

• catalysts

Any reaction in which a substance reacts quickly with oxygen, and gives out heat and light.

• Combustion reaction.

• Neutralization reaction.

• Decomposition reaction.

• Perception reaction.

Heating magnesium in a crucible results in an increase in the mass of the product, why?

• Magnesium has joined with hydroxide from the water vapour.

• Magnesium has joined with oxygen from the air to produce a solid substance.

• Magnesium has joined with helium from the air to produce a solid substance.

• Magnesium has joined with oxygen from the air which is a gaseous substance.

What are the signs of a chemical reaction?

(Choose the best answer)

• See huge flames … or tiny sparks.

• Notice a sweet smell … or a foul stink.

• Feel the chemicals getting hotter … or colder.

• Hear a loud bang … or gentle fizzing.

• All choices are correct.

By the end of the chemical reaction, what you see probably looks ......................................... what you started with.

• as same as

• very different from

Magnesium + Oxygen ----> Magnesium oxide

In the reaction above, magnesium reacted with oxygen from the air to produce .............................. ash of magnesium oxide.

• black

• green

• red

• white

What is the result of heating magnesium in an open crucible?

• Change in color

• Increase in mass

• Decrease in mass

• No change in mass