Matter&Changes
What is the particle theory of matter?
This theory says all matter is made up of tiny particles that are always moving.
🔹 A solution is made by dissolving sugar in water. Which is the solvent?
water
What is density
is the amount of mass per unit volume
What are the 3 subatomic particles in an atom
Protons,Neutrons, Electrons
What type of bond is formed between a metal and a non-metal?
an ionic bond?
What is deposition? give one example of it in the real world
when a gas turns directly into a solid?
A real-world example of deposition is frost forming on a window
🔹 What’s the difference between a saturated and an unsaturated solution?
A saturated solution cannot dissolve more solute; an unsaturated one can.
what should the density of an object be in order for it to float on water and for it to sink?
For it to float the density should be less than 1.0 g/cm3
For it to sink it should be more than 1.0 g/cm3
🔹 How many valence electrons does oxygen have?
6
Name the compound: CO₂ and
N2O3
CO2 = Carbon dioxide
N2O3 = Dinitrogen trioxide
Identify this change: Ice melting into water. Is it chemical or physical? and why?
Physical change because it can be reversed back to its original state
🔹 Identify each as a pure substance or mixture: gold ring, salt water, air, copper wire.
Gold: pure substance salt water:mixture air:mixture copper wire:pure substance
List 3 physical properties of a metal spoon
lustre
good conductor
Is a solid
🔹 Draw a Bohr-Rutherford diagram for a neutral fluorine atom (Atomic number: 9).
2 electrons in first shell, 7 in second
19-9= 10
9 protons 10 neutrons
Which family on the periodic table is very reactive and which group are they found in and give one example of them
Alkali Metals, They are found on group 1. Example: Luthium
Give 2 example of a chemical change and explain how you know it's chemical
When you burn a paper and a car rusting
Its A chemical change because a new substance is being formed and it is not reversible
what is the difference between a homogeneous mixture and a heterogeneous mixture and give one example of each
Heterogeneous Mixture:
you can see the different parts
ex salad
Homogeneous Mixture
You cannot see the different parts
ex juice
A rock has a mass of 250 g and a volume of 50 cm³. What is its density
Density = M/V
250/50 = 5g/cm3
🔹 What is an isotope? Give 3 example.
Atoms of the same element with different numbers of neutrons examples
Carbon-12 and Carbon-14
Hydrogen-1, Hydrogen-2 and Hydrogen-3
Oxygen-16 and Oxygen-18
🔹 Explain the difference between ionic and covalent compounds, using an example for each.
Ionic: Transfer of electrons (e.g., NaCl). Covalent: Sharing of electrons (e.g., H₂O).
If you leave a sealed container of water in the freezer and later open it to find the container cracked and filled with ice, explain how the particle theory and phase changes help you understand what happened. Also, is this a physical or chemical change? Why?
When water is placed in the freezer, it undergoes a phase change from a liquid to a solid — this is called freezing. According to the particle theory of matter, as water cools, its particles lose energy and move more slowly. When it freezes, the particles arrange themselves into a fixed, organized structure (ice) that actually takes up more space than liquid water. This expansion can put pressure on the walls of the container.
This is a physical change, not a chemical one, because:
No new substance is created
why is air considered a mixture and what are 3 of the components that make up air
Air is considered a mixture because it is made up of several different gases
Nitrogen,Oxygen,Carbon dioxide
A block of wood has dimensions 25 cm x 15 cm x 50 cm and a density of 0.4 g/cm3. What is the mass of the wood?
l = 25 cm, w = 15 cm, h = 50 cm
V = l x w x h
V = 25 cm x 15 cm x 50 cm
V = 18750 cm3
M = D x V
M = 0.4g/cm3 x 18750 cm3
M = 8 x 103g
Why do elements in the same group (column) of the periodic table often react in similar ways? Use valence electrons to explain your answer.
Since chemical reactivity depends on how easily an atom can gain, lose, or share electrons, elements with the same number of valence electrons will tend to form the same types of bonds and react in similar ways.
Example:
Group 1 elements like lithium (Li), sodium (Na), and potassium (K) all have 1 valence electron
Why are noble gases (Group 18) much less reactive than alkali metals (Group 1), even though both are in the same periodic table? Explain using their electron arrangements.
Noble gases have full outer energy levels, which makes them very stable. They don't need to gain or lose electrons, so they rarely react with other elements.
Alkali metals, on the other hand, have only 1 valence electron. They are very unstable and want to lose that one electron to become more stable, which makes them very reactive