Chemical Changes
What happens during a chemical change that makes it different from a physical change?
A new substance is formed with different properties.
What makes a physical change different from a chemical one?
In a physical change, the substance keeps its identity and no new substance is formed.
What is fermentation, and what does it produce?
A chemical process by which sugars are converted into alcohol or gas by microbes.
What is oxidation and where do we see it in everyday life?
It’s when a substance reacts with oxygen
Why is burning wood considered a chemical change
Because it produces ash, gases, and heat—new substances are formed.
Why is melting ice a physical change?
Because water stays chemically the same—it only changes its state from solid to liquid.
Give one example of food or drink made through fermentation.
Yogurt, bread, or beer.
What is the main difference between oxidation and combustion?
Combustion is fast and gives off heat and light, oxidation can be slow like rusting.
How can you tell that a chemical reaction has taken place?
Color change, gas production, temperature change.
Name two physical changes you can observe in daily life.
Tearing paper and freezing juice.
Why is fermentation considered a chemical change?
Because new substances like alcohol or gas are produced.
Why do apples turn brown after being cut?
Because of oxidation when their enzymes react with oxygen.
Explain why rusting is a chemical change.
Iron reacts with oxygen and moisture to form a new substance: rust.
Can a physical change be reversed? Give an example.
Yes. For example, freezing and melting water can be reversed.
What organism is usually responsible for fermentation in bread-making?
Yeast.
Explain the role of oxygen in a combustion reaction.
Oxygen helps fuel burn by reacting with it to release energy.
Give an example of a chemical change that happens in the kitchen.
Cooking an egg
Why is dissolving sugar in water considered a physical change?
Because the sugar retains its identity and can be recovered.
ow does fermentation help in preserving food?
It creates acidic or alcoholic environments that inhibit harmful microbes.
What elements are needed for something to burn?
oxygen, fuel and heat (energy)