- (a) Filtration
- (b) Sedimentation
- (c) Decantation
- (d) Centrifugation
Answer:
(d) Centrifugation
- (a) Common salt
- (b) Juice
- (c) Carbon dioxide
- (d) Pure silver
Answer:
(b) Juice
- (a) Heterogeneous mixture
- (b) Compound
- (c) Homogeneous mixture
- (d) Suspension
Answer:
(c) Homogeneous mixture
- (a) Separating funnel
- (b) Filter paper
- (c) Centrifuge machine
- (d) Sieve
Answer:
(a) Separating funnel
- (a) Pure substance
- (b) Mixture
- (c) Colloid
- (d) Suspension
Answer:
(a) Pure substance
If false, correct the statement.
Answer: True
Answer: False
Correct Statement:
A compound can be broken into simpler substances by chemical methods.
Answer: False
Correct Statement:
Liquid-solid colloids are called gels.
Answer: True
Answer: False
Correct Statement:
Aspirin is a compound because its elements are chemically combined in fixed ratio.
| A | B |
|---|---|
| Element | Pure substance |
| Compound | Made up of molecules |
| Colloid | Intermediate mixture |
| Suspension | Settles down on standing |
| Mixture | Impure substance |
Correction made:
Original matching “Compound – made up of atoms” was scientifically inaccurate. Compounds are made up of molecules or ions.
- A homogeneous mixture has no visible boundary between components.
- A substance that sublimes is camphor or dry ice.
- Alcohol is separated from water by fractional distillation.
- Petroleum refining uses fractional distillation.
- Chromatography is based on differences in solubility and adsorption.
| Absorption | Adsorption |
|---|---|
| Substance enters bulk of another substance | Substance accumulates only on surface |
| Entire material involved | Surface phenomenon |
| Example: sponge absorbing water | Example: charcoal adsorbing gases |
Answer:
Direct conversion of solid into vapour without becoming liquid is called sublimation.
Examples:
- Camphor
- Naphthalene
- Dry ice
Answer:
Dettol forms an emulsion in water.
Oil particles disperse in water causing scattering of light, making mixture appear cloudy or turbid.
(i) Miscible liquids
- Distillation apparatus
- Fractionating column
(ii) Immiscible liquids
- Separating funnel
| Mixture | Components |
|---|---|
| Ice cream | Milk, cream, sugar |
| Lemonade | Lemon juice, sugar, water |
| Air | Nitrogen, oxygen, gases |
| Soil | Sand, clay, minerals |
Given:
- Ice
- Milk
- Iron
- Hydrochloric acid
- Mercury
- Brick
- Water
Pure Substances:
- Ice
- Iron
- Mercury
- Water
Correction made:
Hydrochloric acid solution and brick are not pure substances.
Answer:
Oxygen is an element.
It contains only one kind of atom.
Answer:
22-carat gold is an alloy.
Hence it is an impure substance (mixture).
Answer:
Step 1:
Use magnet to remove iron filings.
Step 2:
Heat remaining mixture.
Naphthalene sublimes and gets separated.
Step 3:
Sawdust remains behind.
| Homogeneous Mixture | Heterogeneous Mixture |
|---|---|
| Uniform composition | Non-uniform composition |
| Single phase | Multiple phases |
| Components not visible | Components visible |
| Example: salt solution | Example: sand in water |
| Elements | Compounds |
|---|---|
| Made of one type of atom | Made of different atoms |
| Cannot be broken chemically | Can be broken chemically |
| Smallest particle is atom | Smallest particle is molecule |
| Example: Copper, Oxygen | Example: Water, CO₂ |
Correction made:
Gold symbol corrected from Ag to Au.
# Brownian Movement
Random zig-zag movement of colloidal particles.
Cause:
Unequal collision by molecules of medium.
# Tyndall Effect
Scattering of light by colloidal particles.
Observation:
Path of light becomes visible in colloid.
Example:
Sunlight entering dusty room.
Step 1:
Take mixture in separating funnel.
Step 2:
Allow layers to settle.
- Oil forms top layer
- Salt solution forms bottom layer
Step 3:
Open tap to collect salt solution.
Step 4:
Evaporate water to obtain salt.
Air and Brass
Air:
Mixture of gases.
Brass:
Alloy of copper and zinc.
Hence brass is a mixture.
Iron and Sulphur
Without Heating
Iron and sulphur remain mixture.
On Heating
Chemical reaction occurs:
Iron sulphide formed.
Correction made:
Original text incorrectly mentioned “iron sulphate”.
Mixture or Compound
| Substance | Type |
|---|---|
| Sand + water | Mixture |
| Sand + iron filings | Mixture |
| Concrete | Mixture |
| Water + oil | Mixture |
| Salad | Mixture |
| Water | Compound |
| Carbon dioxide | Compound |
| Cement | Mixture |
| Alcohol | Compound |
Sugar, Starch and Wheat Flour in Water
Observation:
- Sugar dissolves completely.
- Wheat flour settles after some time.
Conclusion:
Some substances form solutions while others form suspensions.
# Test Yourself
Answer:
Milk scatters all colours of visible light equally due to suspended fat particles, making it appear white.
Answer:
Water absorbs longer wavelengths (red, orange) more strongly and scatters shorter blue wavelengths.
Answer:
Earth’s atmosphere scatters shorter wavelengths like blue and violet.
Remaining light reaching eyes appears yellowish.
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