Pure Substances & Mixtures
An element like oxygen (O₂) is an example of a ____________.
Pure substance
Which state has a definite shape and volume?
Solid
The atomic number tells us the number of ________.
Protons
Shiny, malleable, and good conductors describe ________.
Metals
What is the smallest unit of matter?
Atom
Salt water is a ____________, because it can be separated physically.
Mixture
Which state has particles that move freely and spread apart?
Gas
What do we call a horizontal row on the periodic table?
Period
Dull and brittle elements are usually ________.
Nonmetals
An element has 8 protons, 8 neutrons, and 8 electrons. Which element is it?
Oxygen
Which is a compound?
a) Gold (Au)
b) Salt (NaCl)
c) Oxygen gas (O2)
Salt (NaCl)
Which state of matter makes up stars and lightning?
Plasma
What do we call a vertical column on the periodic table?
Group/Family
Give two real world examples of metalloids.
Silicon in computer chips and boron in sports equipment
Which subatomic particle has a negative charge?
Electron
Why is water considered a pure substance, even though it’s made of two elements?
It has a fixed composition (H₂O).
Draw particle spacing for a solid, liquid, and gas.
Solid = packed; Liquid = close/sliding; Gas = spread out
What’s one pattern you notice when moving across a period?
Properties change gradually from metals → nonmetals.
What do we call elements along the stair-step line that share properties of both metals and nonmetals?
Metalloids
Which two particles are found in the nucleus?
Protons and neutrons
Compare a pure substance and a mixture in one sentence.
Pure substance = fixed composition; mixture = physical combination.
What happens to particles in a liquid when heat is added?
They speed up and vaporize (turn into gas)
Why do elements in the same column of the periodic table have similar properties?
They have the same number of electrons in their outer shell. These are called valence electrons.
What property makes metals good for wiring in homes?
They are good conductors of electricity
True or False: H20 and H2 are both compounds.
False.