States of Matter
What are the three main states of matter?
Solid, liquid, gas
Do particles move faster or slower when heated?
Faster
What is an element?
A pure substance made of only one type of atom.
A flat line on a heating curve means…
Temperature is constant (change of state)
A student says “All molecules are compounds.” Explain why this is incorrect and give an example.
Not true — some molecules are made of only one element (ex: O₂, N₂). Compounds must contain different elements.
Which state has a definite shape and volume?
Solid
Which state has particles tightly packed and vibrating?
Solid
What is a molecule?
Two or more atoms chemically bonded together.
A rising line means…
Temperature is increasing
You have salt crystals sitting in salt water. Name every type of matter present and why.
Compound in a lattice (salt crystals = NaCl lattice) and mixture (salt dissolved in water).
Which state has no fixed shape but has a definite volume?
Liquid
Which state has particles far apart and moving freely?
Gas
A student mixes iron filings and sulfur with a spoon. No heat or catalysts are added. Is it a mixture or a compound?
It is a mixture — they are not chemically bonded and can be separated with a magnet.
A falling line means…
Temperature is decreasing
Hydrogen and oxygen are pumped into a tank together. No reaction happens. What type of matter is inside the tank? Then a spark is added and water forms. BEFORE and AFTER classification.
Before: Mixture (H₂ + O₂)
After: Compound (H₂O molecules)
Gas to solid without becoming a liquid first is called…
Deposition
What happens to particle motion when energy is removed?
They slow down
Identify whether the following is a compound or element.
Helium in a balloon
During melting, temperature stays the same because energy is used to…
Break particle bonds / change state
Two clear liquids are mixed. You see bubbles form, temperature rises, and a new white solid sinks to the bottom. What type of change happened, and what type of matter (element or compound or mixture) did you make?
Chemical change → formed a compound (new substance, solid precipitate, temperature change, gas bubbles)
Dry ice creating fog is…
Sublimation
A balloon filled with air is left outside on a hot day. What happens to the particle motion, collisions, and the size of the balloon, and why?
Particles gain energy and move faster → they collide with the inside of the balloon more often and with more force → pressure increases → the balloon expands (and might pop if stretched too far).
Are diamonds and graphite elements or compounds? Why?
Elements - both are made of carbon.
What happens at boiling point on a graph?
Temperature remains constant until fully gas
A sealed container holds pure oxygen gas (O₂).
The gas is cooled until it becomes a liquid.
Question:
Did the substance change from a molecule to something else (like a mixture or compound) when it changed state?
Explain why or why not using particle ideas.
No — it stayed a molecule (O₂).
The state of matter changed (gas → liquid),
but the particles did not change.
Same molecule (O₂)
Same atoms (two oxygen atoms bonded)
Same substance
Only particle spacing and energy changed
A state change does not change identity — only how close and energetic the particles are.