What is the PURE SUBSTANCE & MIXTURE.
A pure substance is a type of matter which exists in its most basic or
purest form and cannot be broken down further.
Each pure substance has its own set of unique chemical and physical
properties which helps us in identifying it.
Carbon dioxide
Chemical formula CO2
Stucture of substance
Single molecules
Molar mass
44.01 g·mol−1
Appearance
Colorless gas
Density
1.977 kg/m3 (gas at 1 atm and
0 °C)
Melting point
−56.6 °C
Solubility in water
1.45 g/L
Majority of Minerals are mixtures. They have a basis of any substance and
a certain amount of impurities.
Black Agate.
Basis:
Silicon dioxide SiO2
Impuirities:
Fe2O3, Al2O3, MgO, CaO, H2O
Stucture of substance
Appearance
Atomic Network
Matte solid stone
Types of mixtures
Heterogeneous mixture – The components of a heterogeneous mixture do
not have a uniform composition and can be viewed separately without
losing their identity.
Homogeneous mixture – The components of a homogeneous mixture have
a uniform composition, and cannot be seen separately.
How do we differentiate between pure substances and mixtures?
A Pure Substance is matter which cannot be separated into its basic
components by using a physical or a chemical process. The physical and
chemical properties of pure substances are non-changing, if it is on its own
without disturbing.
A Mixture is made up of a combination of two or more substances that are
not united using a chemical reaction. The physical and chemical properties
of mixtures vary.
Pure substances vs. Mixtures
For the following: On the first blank write if the example is a pure substance or mixture. If it is a pure
substance, then on the second blank write if the example is an element or compound. If it is a mixture, then
on the second blank, write if the example is a heterogeneous mixture or homogeneous mixture.
1. _____ ____________
Hydrogen
20. _____ ____________
Soda
2. _____ ____________
Hydrogen gas
21. _____ ____________
Italian salad
3. _____ ____________
Copper
4. _____ ____________
Brass
22. _____ ____________
Caesar salad
5. _____ ____________
Iron
23. _____ ____________
Air
6. _____ ____________
Steel
24. _____ ____________
Oxygen
7. _____ ____________
24 karat gold
25. _____ ____________
Oxygen gas
8. _____ ____________
18 karat gold
9. _____ ____________
14 karat gold
10. _____ ____________
Kool aid
11. _____ ____________
Raisin bran
12. _____ ____________
Trail mix
13. _____ ____________
Glucose
(C6H12O6)
14. _____ ____________
Milk
15. _____ ____________
Chocolate milk
16. _____ ____________
Chocolate chip
cookie
17. _____ ____________
Water
18. _____ ____________
Salt water
19. _____ ____________
Sugar water
dressing
26. _____ T/F
Pure substances are either heterogeneous or homogeneous mixtures.
27. _____ T/F
Substances composed of two or more elements combined chemically in a fixed
proportion by mass are called compounds.
Complete the diagram below with the following terms: matter, pure substance, mixture, element,
compound, homogeneous mixture & alloys, heterogeneous mixture.
1.
2.
3.
4.
5.
6.
7.
Methods of Separating Heterogenic Mixtures.
Separation techniques are physical methods.
1.
Sieving.
Can separate large particles from small particles.
Sieving is a traditional and a very easy method of separation since it doesn’t require
much of your skills.
But it cannot separate two substances in a mixture which have the same size. For
example, it cannot separate a mixture of chalk powder from flour.
2. Magnet (magnetic attraction).
Use to separate magnetic materials: iron, steel, nickel (Ni), cobalt (Co) from nonmagnetic ones in a mixture.
 Ferromagnets – Fe (iron) and it’s alloys (steel), Ni, Co - strong properties;
 Paramagnets – Al (aluminum), Mg (magnium), Pt (platinum) - small
properties;
 Diamagnets – Au (gold), Zn (zinc), Cu (copper) - don’t attracted.
3. Decantation
4. Filtration
Can separate solid that are insoluble from a liquid.
Sand gathers in the filter paper, water passes through and collect in a
beaker.
Methods of Separating Homogenic Mixtures.
1. Distillation - to separate and collect a liquid from a solution of a
soluble solid.
2. Fractional Distillation is a method of separating mixtures based on
differences in their volatilities in a boiling liquid mixture.
3. Evaporation - This method is suitable to separate a soluble solid
from a liquid. If the solution is heated, the liquid evaporates
leaving the solid behind.
4. Chromatography is a method of separating out materials from a
mixture. Ink is a mixture of several dyes and therefore we can
separate those colors from one another using chromatography.
Exercises.
1. Separating Chalk From Water.
Is this a heterogeneous/ homogeneous mixture?
That Physical property is used for separating?
2. Separating Sand and Iron Filings
Is this a heterogeneous/ homogeneous mixture?
That Physical property is used for separating?
3. Obtaining Potassium Permanganate (KMnO4) From IT’S Solution.
Is this a heterogeneous/ homogeneous mixture?
That Physical property is used for separating?
4. Separating of water and oil.
Is this a heterogeneous/ homogeneous mixture?
That Physical property is used for separating?
HOME TASK.
1) Compare physical properties or a sand and salt. Write the table:
Physical
Sand
Salt
Mixture
Property
State
Color
Solubility
Smell
Taste
 Which difference in properties can be used to separate the
mixture?
2) Prepare the mixture of water, sand and salt (NaCl). What kind of
mixture it is (homogenic/heterogenic)?
3) Think and choose suitable separation methods and separate the
components. You can not to collect water, but do it for sand and
salt separately. Write down the steps.