Matter & Its Properties
How are physical properties and chemical properties different?
Physical = can be observed without changing the substance; Chemical = describe how a substance reacts or changes into something new.
What are the three subatomic particles, and what are their charges?
Proton (+), Neutron (0), Electron (−)
What does each horizontal row in the periodic table represent?
A period (number of electron shells).
What does a chemical formula show?
The elements in a compound and the ratio of their atoms.
Write the formula for density.
D = m ÷ V
What type of property is “reacts with oxygen to form rust”?
Chemical Property
What is the atomic number and what does it tell you?
It’s the number of protons in the atom.
What are the vertical columns in the periodic table called, and what do they show?
Families (groups); elements with similar properties/valence electrons.
What does the subscript “2” in H₂O mean?
There are 2 atoms of hydrogen in each molecule.
If an object has a mass of 15 g and a volume of 3 mL, what is its density?
5 g/mL
Give an example of a physical change and explain why it’s physical.
Example: melting ice; no new substance formed.
Which part of the atom has the least mass?
Electron
Which family contains very stable, non-reactive gases?
Noble gases
How many atoms are in one molecule of Al₂(SO₄)₃?
2 Al, 3 S, 12 O → 17 total atoms.
When calculating density, which unit is used for volume: mL or g?
mL (for liquids and small solids; cm³ also acceptable).
Name three clues that a chemical change has happened.
Colour change, gas produced, heat/light released, precipitate formed, irreversible change.
How does an atom become negatively charged?
It gains electrons.
What trend do you notice in reactivity as you go down the alkali metals?
Reactivity increases.
How many atoms of each element are in the following compound, and how many atoms total: 2Al₂(SO₄)₃
Al = 4, S = 6, O = 24, Total = 34
If the density of a metal is 7.8 g/mL and you have 50 g of it, what is its volume?
50g ÷ 7.8g/mL ≈ 6.4 mL
A student says that dissolving sugar in water is a chemical change because the sugar “disappears.” Explain why they’re wrong.
It’s a physical change — the sugar’s particles are still present, just dissolved. No new substance is formed, and it can be reversed by evaporating the water.
If an atom has 17 protons and 18 neutrons, what is its mass number and element?
Mass number = 35; element = chlorine (Cl).
An unknown element is shiny, conducts electricity, and tends to lose electrons. Is it a metal or a non-metal?
It’s a metal.
Why do ionic compounds form between metals and non-metals?
Metals lose electrons; non-metals gain them → oppositely charged ions attract.
A student finds that a metal cube is 2 cm on each side and has a mass of 64 g. What is its density?
V = 8 cm³, D = 64g ÷ 8cm³ = 8 g/cm³