Atoms & Particles
The tiny particles that make up all matter
What is Atoms?
Give one example of a physical property you can observe without changing the substance.
Example: color, shape, texture, hardness, melting point, boiling point, magnetism, density.
What are the three common phases (states) of matter taught in 5th grade?
Solid, liquid, gas.
What do we call the energy that can cause ice to melt when it warms up?
Heat (thermal energy)
What does it mean to say "matter is conserved" during changes?
It means the amount (mass) of matter stays the same before and after physical or chemical changes.
True or False: Atoms can be seen with your eyes without any tools.
False. (Atoms are too small to see with the naked eye.)
If you mix sand and water, do the original substances change their physical properties? Explain briefly.
No; mixing sand and water is a physical mixture — the sand retains its physical properties.
Which phase has a definite volume but no definite shape?
Liquid
True or False: Adding heat can change a liquid to a gas.
True
If you heat a sealed container of water and it changes from liquid to gas inside the container, does the total mass change? Explain in one sentence.
No — the total mass stays the same in a sealed container because matter is conserved
Name two things that would be considered atoms or made of atoms.
Examples: oxygen atom, carbon atom, or objects made of atoms (rock, water)
Which physical property would you test to tell salt from sugar without tasting them?
Solubility test in water (salt dissolves well; sugar dissolves too but can be distinguished by taste in non-classroom answer) or observe crystal shape under magnifying glass.
What happens to particles when a solid melts into a liquid? (One or two sentences.)
Particles gain energy and move more freely so they can slide past each other, making the solid become a liquid.
Explain how removing heat causes water vapor to become liquid (use the word "energy").
Removing energy (cooling) lowers particle motion so gas particles come together to form a liquid.
Name two measurements or observations scientists can use to identify materials (5th-grade level)
Mass, volume, color, density, melting point, boiling point, magnetism.
Explain in one sentence why a solid holds its shape, referring to particles.
Particles in a solid are packed tightly and stay in fixed positions, so the solid keeps its shape.
Describe how you could separate a mixture of iron filings and sand. (Name the method and one sentence explaining it.)
Use a magnet to remove iron filings from sand because iron is magnetic and sand is not.
Give one real-world example of vaporization (not boiling) and name the phase change.
Evaporation from a puddle or wet clothes drying — liquid to gas (vaporization).
A pot of water boils on the stove. Where does the added energy go — raising temperature or changing phase — once the temperature stops rising? Explain briefly.
The added energy goes into changing the phase (breaking intermolecular attractions) rather than raising temperature once boiling temperature is reached
You mix two clear solutions and nothing visible changes. What test could show whether a new substance formed? (Name one simple investigation.)
Measure mass before and after reaction (mass stays same if no gas escapes); or test for new properties like pH or color change and confirm mass change.
What is the difference between a molecule and an atom?
An atom is a single particle; a molecule is two or more atoms bonded together.
Explain why dissolving sugar in water is considered a physical change, not a chemical change.
When sugar dissolves, the sugar molecules spread through the water but the sugar's identity remains the same — no new substance formed.
Describe what happens at the particle level during condensation
Gas particles lose energy, slow down, come closer together, and form liquid droplets.
Describe how sunlight can cause a puddle to disappear, naming the phase change and role of energy.
Sunlight supplies thermal energy that causes liquid water to gain energy and change into water vapor (evaporation).
Design a quick classroom investigation (3 steps) to show that mixing certain substances does not change the total mass (include measurement step).
Example investigation:
Measure mass of beaker + substance A and beaker + substance B separately.
Mix A and B in a sealed container on a balance; record mass.
Show final mass equals initial total mass (within measurement error), demonstrating conservation of matter.