Classification of
Matter
Matter can be classified into two main categories: pure
substances and mixtures.
1. Pure Substances
A. Elements: Consist of only one type of atom.
Examples include oxygen (O₂), gold (Au), and
iron (Fe).
B.Compounds
Compounds are pure substances formed when
two or more elements chemically combine in a
fixed ratio.
Properties: Compounds have unique chemical and
physical properties different from their constituent
elements.
Examples: Water (H₂O), Sodium chloride (NaCl), and
Carbon dioxide (CO₂).
Separation: Compounds can only be separated into
their elements by chemical reactions.
2. Mixtures
Definition: Mixtures are combinations of two or more
substances that are physically mixed but not
chemically bonded.
Properties: The substances in a mixture retain their
individual properties.
Separation: Mixtures can be separated by physical
methods like filtration, distillation, or magnetic
separation.
Types of Mixtures:
1. Homogeneous Mixtures:
They are mixtures that have a uniform
composition throughout.
Examples: Saltwater, air, and vinegar.
Characteristics: Different components of
the homogeneous mixtures are not visibly
distinguishable.
2. Heterogeneous Mixtures:
They are Mixtures that do not have a
uniform composition.
Examples:- sand and iron filings, and oil
and water. salad
Characteristics: The different components
are visibly distinguishable.
Separation Methods:
Filtration: is the process used to separate
solid particles from liquids or gases.
Distillation: Used to separate
components based on differences in
boiling points.
Magnetic Separation: Used to separate
magnetic materials from non-magnetic
ones.
Decantation: Used to separate liquid
from solids by pouring off the liquid.
Centrifugation: Used to separate
components based on their densities by
spinning them at high speed.
elements
pure
compound
matter
hetrogenuous
mixture
homogenuous
Practice Questions
1. What type of mixture has a uniform composition
throughout?
A) Heterogeneous mixture
B) Homogeneous mixture
C) Colloidal mixture
D) Suspension
2. Which of the following is an example of a
heterogeneous mixture?
A) Saltwater
B) Air
C) oil and water
D) Sugar solution
3. What term describes a mixture where the different
components can be seen and easily separated?
A) Heterogeneous mixture
B) Colloid
C) Suspension
D) Homogeneous mixture
4. Which of the following is NOT a characteristic of a
mixture?
A) Components maintain their properties
B) Precise chemical formula
C) Components can be separated by physical means
D) Variability in composition
5. Which of the following represents a compound?
A) Oxygen gas (O2)
B) Table salt (NaCl)
C) Iron (Fe)
D) Elemental carbon (C)
6. Which technique is commonly used to separate
a mixture of solids based on particle size?
A) Distillation
B) Filtration
C) Chromatography
D) Evaporation
7. If you mix oil and water, what type of mixture
do you create?
A) Homogeneous mixture
B) Colloid
C) Heterogeneous mixture
D) Solution
8. Which of the following is a method to separate
the components of a mixture based on their
boiling points?
A) Filtration
B) Magnetism
C) Distillation
D) Decantation
9. What method is commonly used to separate an
insoluble solid from a liquid?
A) Distillation
B) Filtration
C) Chromatography
D) Evaporation
10. Which separation technique relies on
differences in boiling points?
A) Centrifugation
B) Distillation
C) Magnetic separation
D) Sieving
11. What method separates mixtures based on
the size of particles?
A) Evaporation
B) Chromatography
C) Filtration
D) Sieving
12. Ifyou want to separate a solid that sublimates
from a mixture, which method would you use?
A) Decantation
B) Sublimation
C) Filtration
D) Evaporation
13. Which method uses centrifugal force for
separation?
A) Filtration
B) Decantation
C) Magnetic separation
D) Centrifugation
14.In which method would you use a filter paper?
A) Filtration
B) Distillation
C) Evaporation
D) Centrifugation
15. How can you separate water from salt after
dissolving salt in water?
A) Chromatography
B) Filtration
C) Distillation
D) Decantation
16. Which method is best for separating
magnetic materials from a mixture?
A) Chromatography
B) Evaporation
C) Magnetic separation
D) Filtration
More on Solutions… •
Solutions can be- solid, liquid, or gas
Example liquid Solution – salt water
Gas Solution – air
Solid Solution – bronze, brass
Acids and Bases
Acids and bases are two important categories of substances in
chemistry.
Acids:
Acids are substances that taste sour (like lemon juice or
vinegar).
They turn blue litmus paper red.
Acids are proton donors, meaning they release hydrogen ions
(H⁺) when dissolved in water.
Common examples include
hydrochloric acid (HCl),
sulfuric acid (H₂SO₄), and
citric acid (found in citrus fruits).
Properties of Acids:
Conduct electricity when dissolved in water (electrolytes).
React with metals to produce hydrogen gas.
React with bases to form salt and water in a neutralization
reaction.
Bases:
Bases taste bitter and feel slippery (like soap).
They turn red litmus paper blue.
Bases are proton acceptors, meaning they can accept
hydrogen ions (H⁺).
Common examples include sodium hydroxide (NaOH) and
magnesium hydroxide (found in antacids).
Properties of Bases:
Also conduct electricity when dissolved in water.
React with acids to form salt and water.
Can feel caustic or damaging to skin if concentrated.
pH Scale:
The pH scale measures how acidic or alkaline a solution is.
The scale ranges from 0 to 14.
a pH of 7 is neutral.
a pH less than 7 is acidic, and
a pH greater than 7 is basic.
1. The pH scale measures how acidic or basic a solution is,
ranging from 0 to 14.
o A pH of 7 is neutral (like pure water).
o A pH less than 7 indicates an acidic solution.
o A pH greater than 7 indicates a basic solution.
2. What is the pH value of a neutral solution at 25°C?
a) 0
b) 7
c) 14
d) 10
3. Which of the following solutions is considered acidic?
a) Lemon juice
b) Baking soda
c) Pure water
d) Ammonia
4. What color does litmus paper turn in a basic solution?
a) Red
b) Blue
c) Green
d) Yellow
5. What ion is responsible for the acidic properties of a
solution?
a) Hydroxide ion (OH⁻)
b) Hydronium ion (H₃O⁺)
c) Sodium ion (Na⁺)
d) Chloride ion (Cl⁻)
6. In terms of their pH values, which of the following
solutions is the most acidic?
a) pH 3
b) pH 5
c) pH 7
d) pH 1
7. Which of the following compounds is not considered a
strong acid?
a) Hydrochloric acid (HCl)
b) Sulfuric acid (H₂SO₄)
c) Acetic acid (CH₃COOH)
d) Nitric acid (HNO₃)
8. If a solution has a high concentration of hydroxide ions
(OH⁻), what can be said about its properties?
a) It is acidic.
b) It is neutral.
c) It is basic.
d) It is volatile.
9. What happens to the pH of a solution if an acid is added
to a neutral solution?
a) The pH increases.
b) The pH decreases.
c) The pH remains the same.
d) The pH becomes 14.
Structure of Matter
Structure of Matter
1.Atoms:
Basic Building Blocks: All matter is composed of
atoms.
Subatomic Particles: Atoms consist of protons,
neutrons, and electrons.
Protons:
Positively charged particles found in the
nucleus.
Determines the identity of the element
Neutrons: Neutral particles also located in
the nucleus.
Electrons: Negatively charged particles
orbiting the nucleus in energy levels or
shells.
Ele
ctro
n
Pro Negati
vely
ton charge
Positiv
ely
charged
ne
ucl
eu
s
Neutral atoms have equal number of
electron & proton(neutral )
neu
tro
n
no
charge
2.Atomic Number and Mass Number:
Atomic Number: The number of protons in an atom’s
nucleus, which determines the element.
The atomic number is also the number of electrons that
surround the nucleus of a neutral atom.
Atomic number (Z) = Number of protons= number of electrons
For neutral element number of electrons & protons are equal.
Mass Number: The total number of protons and
neutrons in the nucleus.
Mass number (A) is the sum of the number of protons
and the number of neutrons in the nucleus of an atom.
Except for the most common form of hydrogen, which has
one proton and no neutrons, all atomic nuclei contain both
protons and neutrons.
Mass number (A) = Number of protons + Number of neutrons.
= Atomic number + Number of neutrons.
The mass and atomic numbers of a given atom
are often specified using the notation:
X <----
Atomic number
A -------Symbol of element
Z <----Mass number
6
Example: 12 C , mass number = 12,
atomic number = 6, and
C is the symbol of carbon.
Determination of the electrons, protons and
neutrons
Proton is equal to the atomic number of atoms.
Number of protons = atomic number (Z)
Number of electrons = atomic number (Z) = number of protons
The number of neutrons in an atom is equal to
the difference between the mass number and
the atomic number or proton number.
6
3.Isotopes:
Atoms of the same element with different
numbers of neutrons, resulting in different mass
numbers
They have the same number of electron &
protons
e.g., Carbon-12 and Carbon-14
4.Electron Configuration:
The arrangement of electrons in an atom’s
energy levels, which influences the chemical
properties and reactivity of the element.
5.Valence Electrons:
Electrons in the outermost energy level, crucial
for chemical bonding and determining an
element’s reactivity.
Questions
1. What is the basic unit of matter?
a) Molecule
b) Atom
c) Ion
d) Compound
2. Which part of the atom carries a positive
charge?
a) Electron
b) Neutron
c) Proton
d) Nucleus
3. What is the charge of an electron?
a) Positive
b) Neutral
c) Negative
d) Dependent on the atom
4. Where are the protons and neutrons located in
an atom?
a) In the electron cloud
b) In the nucleus
c) In the outer shells
d) Floating freely
5. What is the atomic number of an element?
a) The number of neutrons
b) The total number of protons and neutrons
c) The number of electrons
d) The number of protons in the nucleus
6. Which of the following is a type of
isotope?
a) Ions
b) Atoms with different numbers of electrons
c) Atoms of the same element with different numbers of
neutrons
d) Different elements with the same mass
7. What determines the chemical properties of an
element?
a) The number of neutrons
b) The electron configuration
c) The number of protons
d) The size of the atom
8. What is the maximum number of electrons that
can occupy the first shell of an atom?
a) 2
b) 8
c) 18
d) 32
9. Which subatomic particle has
the least mass?
a) Proton
b) Neutron
c) Electron
d) They have the same mass
Acids and Bases
Acids and bases are two important categories of
substances in chemistry.
Acids:
Acids are substances that taste sour (like lemon juice
or vinegar).
They turn blue litmus paper red.
Acids are proton donors, meaning they release
hydrogen ions (H⁺) when dissolved in water.
Common examples include
hydrochloric acid (HCl),
sulfuric acid (H₂SO₄), and
citric acid (found in citrus fruits).
Properties of Acids:
Conduct electricity when dissolved in water
(electrolytes).
React with metals to produce hydrogen gas.
React with bases to form salt and water in a
neutralization reaction.
Bases:
Bases taste bitter and feel slippery (like soap).
They turn red litmus paper blue.
Bases are proton acceptors, meaning they can
accept hydrogen ions (H⁺).
Common examples include sodium hydroxide
(NaOH) and magnesium hydroxide (found in
antacids).
Properties of Bases:
Also conduct electricity when dissolved in water.
React with acids to form salt and water.
Can feel caustic or damaging to skin if concentrated.
pH Scale:
10. The pH scale measures how acidic or basic a solution is, ranging from 0 to
14.
o A pH of 7 is neutral (like pure water).
o A pH less than 7 indicates an acidic solution.
o A pH greater than 7 indicates a basic solution.
11. What is the pH value of a neutral solution at 25°C?
a) 0
b) 7
c) 14
d) 10
12. Which of the following solutions is considered acidic?
a) Lemon juice
b) Baking soda
c) Pure water
d) Ammonia
13. What color does litmus paper turn in a basic solution?
a) Red
b) Blue
c) Green
d) Yellow
14. What ion is responsible for the acidic properties of a solution?
a) Hydroxide ion (OH⁻)
b) Hydronium ion (H₃O⁺)
c) Sodium ion (Na⁺)
d) Chloride ion (Cl⁻)
15. In terms of their pH values, which of the following solutions is the
most acidic?
a) pH 3
b) pH 5
c) pH 7
d) pH 1
16. Which of the following compounds is not considered a strong acid?
a) Hydrochloric acid (HCl)
b) Sulfuric acid (H₂SO₄)
c) Acetic acid (CH₃COOH)
d) Nitric acid (HNO₃)
17. If a solution has a high concentration of hydroxide ions (OH⁻), what
can be said about its properties?
a) It is acidic.
b) It is neutral.
c) It is basic.
d) It is volatile.
18. What happens to the pH of a solution if an acid is added to a neutral
solution?
a) The pH increases.
b) The pH decreases.
c) The pH remains the same.
d) The pH becomes 14.
The law of conservation of mass states that in a
closed system, the total mass remains constant
during chemical and physical changes.
Formulated by Antoine Lavoisier in the 18th century, it
implies that mass cannot be created or destroyed—
only transformed.
Examples:
1. Burning of Wood: When wood burns, it combines
with oxygen to form ash, water vapor, and gases. The
total mass of the wood and oxygen before burning
equals the mass of the ashes and gases produced.
Wood + Oxygen ash + vapor + gases
2. Dissolving Sugar in Water: When sugar dissolves in
water, the total mass of the sugar and water before
mixing equals the mass of the sugar-water solution
afterward.
Sugar(500g) + water(1000g) sugar
solution(1500g)
3. Chemical Reaction in a Sealed Bag: If baking soda
and vinegar are mixed in a sealed bag, the mass
before mixing equals the mass after the reaction, even
though new substances (carbon dioxide gas, water, and
sodium acetate) are formed.
Baking soda + vinegar Carbondioxide + water +
Sodium
QUESTION
1. What does the law of conservation of mass
state?
a) Mass can be created or destroyed
b) The mass of reactants equals the mass of products
c) Mass can only be converted to energy
d) Mass varies with temperature
2. Who is credited with the formulation of the law
of conservation of mass?
a) Albert Einstein
b) Antoine Lavoisier
c) John Dalton
d) Dmitri Mendeleev
3. In a chemical reaction, if 10 grams of reactants
produce 9 grams of products, what happens to
the extra mass?
a) It is lost to the environment
b) It is converted to energy
c) There is an experimental error
d) It combines with the products
4. Which of the following processes illustrates the
law of conservation of mass?
a) Burning wood
b) Dissolving salt in water
c) Melting ice
d) All of the above
5. In an isolated system, if a 5 kg block of ice
melts, what will be the mass of the water
formed?
a) Less than 5 kg
b) More than 5 kg
c) 5 kg
d) Dependent on environmental factors
6. Which of the following chemical reactions
demonstrates the conservation of mass?
a) 2H₂ + O₂ → 2H₂O
b) H₂ + O₂ → H₂O
c) 4Fe + 3O₂ → 2Fe₂O₃
d) All of the above
7. An experiment measures the mass of a closed container before and
after a reaction occurs inside it. If the mass before is 200 grams and
after is 200 grams, what conclusion can be drawn?
a) The reaction did not occur
b) Mass was lost during the reaction
c) The law of conservation of mass is upheld
d) The container gained mass
8. Why is the law of conservation of mass important
in chemical reactions?
a) It helps predict the amount of reactants needed
b) It allows for the calculations of chemical yields
c) It ensures accurate measurements in experiments
d) All of the above
Answers
1. b) The mass of reactants equals the mass of products
2. b) Antoine Lavoisier
3. c) There is an experimental error
4. d) All of the above
5. c) 5 kg
6. c) 400 grams
7. d) All of the above
8. b) 18 grams
9. c) The law of conservation of mass is upheld
10.d) All of the above
1. Which law states that energy cannot be created or destroyed, only
transformed?
a) Law of Conservation of Mass
b) Law of Conservation of Energy
c) Law of Conservation of Charge
d) Law of Conservation of Momentum.
2. In a chemical reaction, if 10 grams of reactants produce 10 grams of
products, which law is being observed?
a) Law of Conservation of Matter
b) Law of Conservation of Energy
c) Law of Conservation of Charge
d) Law of Conservation of Mass
3. When two objects collide in a perfectly elastic collision, which quantity is
conserved?
a) Mass only
b) Kinetic energy and momentum
c) Temperature only
d) Volume only
4. In a closed system, if energy is transformed from one form to another, the
total energy of that system will:
a) Increase
b) Decrease
c) Remain constant
d) Become unpredictable
5. Which of the following statements is true regarding the Law of
Conservation of Charge?
a) Charge can be created and destroyed.
b) The total electric charge in a closed system remains constant.
c) Charge can flow freely without any loss.
d) Charge can exist in two forms: positive and negative.
6. In thermodynamics, which law states that energy always flows from a
higher temperature to a lower temperature?
a) First Law of Thermodynamics
b) Second Law of Thermodynamics
c) Third Law of Thermodynamics
d) Law of Conservation of Energy
7. During a combustion reaction, if 5 grams of gasoline is burned and
produces carbon dioxide and water, the total mass of the products will be:
a) Greater than 5 grams
b) Less than 5 grams
c) Exactly 5 grams
d) Cannot be determined
8. Which of the following scenarios illustrates the Law of Conservation of
Energy?
a) A ball rolling down a hill converts potential energy into kinetic energy.
b) Water freezing into ice loses mass.
c) A battery storing electrical energy is only used in one circuit.
d) An explosion converts mass directly into light.
Answers:
1. b) Law of Conservation of Energy
2. c) Conservation of Momentum
3. b) The total mass of substances in a closed system remains constant.
4. d) Law of Conservation of Mass
5. b) Kinetic energy and momentum
6. c) Remain constant
7. b) The total electric charge in a closed system remains constant.
8. b) Second Law of Thermodynamics
9. c) Exactly 5 grams
10. a) A ball rolling down a hill converts potential energy into kinetic ene
