Table of Contents
Sub-Strand: 2.2 MATERIALS
Identify and differentiate between mixtures and compounds
What is a Mixture?
A mixture is made when two or more things are combined, but they do not form a new substance. The things in a mixture can be separated easily.
Examples of mixtures:
- Sugar and water
- Sand and salt
- Oil and water
What is a Compound?
A compound is formed when two or more things mix together and form a new substance. The new substance cannot be separated easily.
Examples of compounds:
- Water (H₂O) – made of hydrogen and oxygen
- Salt (NaCl) – made of sodium and chlorine
Differences Between Mixtures and Compound
Mixture
- Can often see the different substances
- Can be separated by physical methods like filtration or evaporation
- Each substance keeps it original
properties
Compounds
- Substances look like one new thing.
- Can not be separated easily
- The properties change.
Properties of Mixtures and Compounds.
Properties of Mixtures:
Substances in a mixture do not change chemically.
Mixtures can be solid, liquid, or gas.
The ratio in a mixture is not fixed.
Eg: You can add more ^sugar to water or less
Properties of Compounds:
A compound has a fixed composition.
(Example: Water always has 2 hydrogen and 1 oxygen atoms.)
Properties of a compound are different from the substances that form.
Compound can only be broken down using chemical reactions.
How to Separate Mixtures?
We can use different methods to separate mixtures, depending on what is mixed.
- Filtration – Used to separate solid from liquid (Example: Sand and water).
- Evaporation – Used to separate dissolved substances (Example: Salt from seawater).
- Distillation – Used to separate liquids with different boiling points (Example: Water and alcohol).
- Floatation – Used to separate substances that float (Example: Sawdust and water).
- Spinning (Centrifugation) – used to separate things of different weights. Example: removing cream from milk. Separate red blood cells from plasma
- Sieving– separates big and small particles. Example: lumps from flour. Sand from stones
Safety in Science
- Always wear safety glasses when working with chemicals.
- Do not taste or smell unknown substances.
- Handle glass equipment carefully.
- Wash your hands after experiments.
Questions
- Which method is used to separate cream from milk?
a) Sieving
b) Spinning
c) Filtration
d) Evaporation
(Answer: b) Spinning
- What is used to separate sand from stones?
a) Spinning
b) Distillation
c) Sieving
d) Filtration
(Answer: c) Sieving - Which of these is NOT an example of spinning?
a) Drying clothes in a washing machine
b) Separating blood parts
c) Removing stones from rice
d) Removing cream from milk
(Answer: c) Removing stones from rice
Fill in the Blanks
- ________ is used to separate big and small particles. (Answer: Sieving)
- Spinning helps separate substances of different ________. (Answer: weights/densities)
- In hospitals, blood is separated using ________. (Answer: spinning/centrifugation)
- ________ helps in removing lumps from flour. (Answer: Sieving)
True or False
- Sieving is used to remove cream from milk. (False)
- Washing machines use spinning to remove water from clothes. (True)
- Sieving can be used to separate blood parts. (False)
- Sand and stones can be separated using sieving. (True)
Short Answer Questions
- aWhat is the purpose of spinning in separating mixtures?
(Answer: Spinning separates substances of different weights, pushing heavier ones to the bottom and lighter ones to the top.) - Give two examples of where sieving is used.
(Answer: Removing lumps from flour, separating sand from stones.) - How does a washing machine use spinning?
(Answer: It spins fast to remove water from clothes.) - Why do hospitals use spinning in blood tests?
(Answer: To separate plasma from red blood cells.)
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