11) Chemical Changes

Which of the following is a sign that a chemical reaction has occurred?

• change in shape
• melting
• formation of a gas
• dissolving

Is melting butter for popcorn a chemical or physical change?

• chemical
• physical

Which of the following is NOT an example of a physical change?

• crumpled paper
• pencil sharpening
• shrunken clothing
• rust

Which of these is a result of a chemical change?

• A mixture
• A solution
• A new substance
• Melting or freezing

Which type of reaction takes place in the presence of oxygen and produces carbon dioxide and water?

• Neutralisation

• Thermal decomposition 

• combustion 
• rusting

True or false, combustion must result in the production of carbon dioxide

• True

• False

Which process does not produce carbon dioxide?

• combustion of hydrocarbons

• photosynthesis

• respiration

• acid + carbonate reaction

What is the term for when a large molecule is broken down into smaller molecules?

• neutralisation

• decomposition 
• combustion

• melting

Which metals rusts?

• Copper

• manganese

• iron

• potassium

What are the best conditions required for rusting?

• cold and dry

• cold and damp

• hot and damp

• hot and dry