Atoms & Elements
What is the tiny particle that makes up all matter and cannot be seen without a microscope?
atom
What do you call two or more atoms joined together?
A molecule
Is melting an ice cube a physical change or a chemical change?
Physical change
What are the three common states of matter?
Solid, liquid, gas
What is the name of the change from solid to liquid?
What are the three main parts of an atom called?
Protons, neutrons, electrons
Is oxygen gas (O2) a molecule, a compound, or both? Explain briefly.
Molecule — O2 is two oxygen atoms bonded (not a compound because it has only one element)
When a piece of paper burns and turns to ash and smoke, is that a physical change or a chemical change?
Chemical change
Which state of matter has a definite shape and a definite volume?
solid
What is the name of the change from gas to liquid?
Condensation
Which part of an atom has a positive charge and is found in the nucleus?
proton
What is a compound? Give one simple example.
A substance made of two or more different elements chemically bonded (example: water, NaCl)
Name two signs that a chemical change has occurred.
Color change, temperature change, gas production (bubbling), formation of a precipitate, light or odor change
Which state of matter takes the shape of its container and can flow, but has a definite volume?
Liquid
If you cool water vapor, what change of state will occur? Give the correct term.
Condensation (gas to liquid)
True or False — All atoms of the same element have the same number of protons.
False
How is a molecule different from an element?
A molecule is two or more atoms bonded together; an element is a substance made of only one kind of atom
Explain why dissolving sugar in water is a physical change, not a chemical change.
The sugar dissolves but its molecules remain sugar; no new substance is formed and it can be recovered by evaporating the water
Describe how particles are arranged and how they move in a solid versus a gas
Solids: particles tightly packed and vibrate in place; gases: particles far apart and move freely
Explain what happens to the particles of a substance when it freezes.
Particles slow down and move into fixed positions, forming a regular pattern (crystalline) and the substance becomes solid.
Explain why atoms are considered the basic building blocks of matter.
Atoms are the smallest units of matter that keep the properties of an element and combine to form all substances.
Describe (in words) how water is made from hydrogen and oxygen atoms. (Explain how many of each atom are in one water molecule.)
Water is H2O: two hydrogen atoms bonded to one oxygen atom
What are the two types of mixtures and what are their definitions?
Homogenous mixture - evenly blended together
Heterogenous mixture - not equally blended together
Explain why plasma is different from the other three states of matter (solid, liquid, gas) and give one example where plasma is found.
Plasma is ionized gas with free electrons and ions, often found in stars, lightning, and neon sign
Describe how energy (heat) is involved when a substance melts and when it condenses.
Melting requires adding heat (energy absorbed) so particles move faster and break fixed positions; condensation releases heat (energy is released) as particles slow and come closer together.