Homogenous mixtures have a uniform composition throughout e.g. salt water and sugar water, tincture alcohol [iodine+alcohol]. Solid solutions like alloys [brass = zinc + copper] and gaseous solutions like air are possible too.
Heterogeneous
mixtures have non uniform composition and physically
distinct parts. e.g.: salt and iron fillings, salt and
sulfur.
Suspensions are solutions in which solutes don’t dissolve in the solvents but remain in suspension. e.g.: chalk powder in water.
Colloids: these are heterogeneous mixtures but the solutes are small in size they can’t be visible to naked eye and so the mixture appears homogenous. Colloids can scatter beam of light passing through it i.e. tydall effect. Also the particles of a colloid don’t settle if left undisturbed. e.g.: milk
Components of a colloid are:
Dispersed phase
[solute-like] and Dispersing medium [solvent like].
These can be separated by Centrifugation.
| Dispersed Phase | Dispersing Medium | Type | Example |
| Liquid | Gas | Aerosol | Fog, clouds, mist |
| Solid | Gas | Aerosol | Smoke, automobile exaust |
| Gas | Liquid | Foam | Shaving cream |
| Liquid | Liquid | Emulsion | Milk, face cream |
| Solid | Liquid | Sol | Milk of magnesia, mud |
| Gas | Solid | Foam | Foam, rubber, sponge, pumice |
| Liquid | Solid | Gel | Jelly, cheese, butter |
| Solid |
Solid |
Solid Sol |
Coloured gemstone, milky glass |
Table 1: Examples of colloids
Ref: N.C.E.R.T. Textbook Class VIChromatography is the process of separating of solutes that dissolve in the same solvent. It’s also used for separating colors in dye, pigments from natural colors and drugs from blood.
Separation of two miscible liquids that have sufficient difference in their boiling points can be done by distillation. If difference is less than 25k then fractional distillation is done.
Q. Consider the following pairs:
Commonly used material vs. Unwanted or controversial chemicals found in them
1. Lipstick: Lead
2. Soft drinks: Brominated vegetable oils
3. Chinese fast food: Monosodium glutamate
Which of the pairs given above is/are correctly matched? (UPSC CSAT 2017)
1 only
2 and 3 only
1 and 3 only
1, 2 and 3
Ans . D
Q. Consider the following statements:
1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue.
2. Sexual transmission of Zika virus disease is possible.
Which of the statements given above is/are correct? (UPSC CSAT 2017)
1 only
2 only
Both 1 and 2
Neither 1 nor 2
Ans . C
Dengue, Zika and chikungunya are spread through a common vector, the Aedes aegypti mosquito. Although Zika virus is primarily transmitted through mosquitoes, it can also be sexually transmitted as well.
Q. The terms Event Horizon, Singularity, ‘String Theory and Standard Model are sometimes seen in the news in the context of (UPSC CSAT 2017)
Observation and understanding of the Universe
Study of the solar and the lunar eclipses
Placing satellites in the orbit of the Earth
Origin and evolution of living organisms on the Earth
Ans . A
Q. What is the purpose of ‘evolved Laser Interferometer Space Antenna (eLISA)’ project? (UPSC CSAT 2017)
To detect neutrinos
To detect gravitational waves
To detect the effectiveness of missile defence system
To study the effect of solar flares on our communication systems
Ans . B
Q. In India, it is legally mandatory for which of the following to report on cyber security incidents?
1. Service providers
2. Data centres
3. Body corporate
Select the correct answer using the code given below: (UPSC CSAT 2017)
1 only
1 and 2 only
3 only
1, 2 and 3
Ans . D
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