Particle Model of Matter
What is everything that has mass and takes up space called?
Matter
Distilled water contains only water particles. Is it a pure substance or a mixture?
Pure substance
What is another name for a homogeneous mixture?
A solution
What type of change occurs when ice melts?
A physical change
Is colour a qualitative or quantitative property?
Qualitative
According to the particle model, what is all matter made of?
Extremely tiny particles
What are the two main types of pure substances?
Elements and compounds
In which type of mixture are particles not uniformly distributed?
A heterogeneous mixture
What is the key question used to determine whether a chemical change occurred?
Did a new substance form?
Is boiling temperature a qualitative or quantitative property?
Quantitative
What happens to the average speed of particles when temperature increases?
The particles move faster.
Air contains nitrogen, oxygen, carbon dioxide, and other gases. Is it a pure substance or a mixture?
Mixture
What type of mechanical mixture contains particles that settle out over time?
A suspension
What happens to a substance’s chemical composition during a physical change?
It remains the same.
What is a precipitate?
An insoluble solid that forms when solutions are mixed.
In which state of matter are particles close together but able to move past one another?
Liquid
Classify each substance as a pure substance or mixture: oxygen, salt water, copper, and soil.
Pure substances: oxygen and copper. Mixtures: salt water and soil.
What is an emulsion?
A mixture in which one liquid is dispersed throughout another liquid that it normally does not mix with.
Why is burning paper considered a chemical change?
New substances with different properties, such as smoke (CO2) and a black solid, are formed.
Name three possible clues that a chemical change has occurred.
Any three: temperature change, colour change, gas bubbles, formation of a precipitate, starting material being used up, formation of a material with new properties, or difficulty reversing the change.
Explain why scientists use a particle model to study matter.
Particles are too small and move too quickly to observe directly, so the model helps scientists visualize and explain their behaviour.
Two clear samples look identical. Sample A contains one kind of particle, while Sample B contains several kinds of particles distributed evenly. Classify each sample.
Sample A is a pure substance. Sample B is a homogeneous mixture.
Mayonnaise contains liquids that normally do not mix but remain combined with the help of another substance. What type of mixture is mayonnaise, and what helps it remain mixed?
It is an emulsion, and an emulsifier helps it remain mixed.
Boiling water produces bubbles that appear to be a gas. Why is boiling still considered a physical change?
The gas is water vapour, so no new substance is formed.
Why does observing a colour change or gas bubbles not automatically prove that a chemical change occurred?
These clues can also occur during physical changes. A chemical change is only confirmed when evidence shows that a new substance formed.