G7 Ch5 Purity

What is winnowing?

• A method used to separate the components of a mixture which are in different sizes

• The practice of separating undesirable solid substances and impurities from useful solids by hand.

• A method used to separate lighter components of a mixture from the heavier ones by wind or by blowing air.

• process of separating components of mixtures by using a magnet to attract magnetic substances

which process do we use to get salt from sea water?

• decantation

• evaporation

• condensation

• centrifugation

The process of settling down of particles of a solid in a liquid is __________

• Sublimation

• Sedimentation

• Filtration

• Decantation

While preparing chapatis, Ilakkiya found that the flour to be used was mixed with wheat grains.
Which out of the following is the most suitable method to separate the grains from the flour?

• Threshing

• Sieving

• Handpicking

• Filtration

Sawdust is not soluble in water. If, accidentally some particles of sawdust drop into a glass of water. How would you separate them from water?

• decanting

• filtering

• sieving

• distillation

Which one describes purity or pure element?

• it has two or more different types of atom

• it has one and the same type of atoms all throughout

• it is made up of sub-atomic particles

• it is a matter and has the different subatomic particles

If a diamond has 1000 parts, it is said to be pure diamond. If the diamond is mixed with parts of other atoms, what is the concentration of a diamond if it has at least 800 parts?

• 50%

• 70%

• 60%

• 80%

About 35 g of salts in 1000 g of seawater. What mass of magnesium chloride would you expect to find in the 1000 g seawater sample?

• 5.11 g

• 3.99 g

• 1.09 g

• 23.8 g

Answer explanation

mass of magnesium chloride = 14.6% of 35 g = (14.6 x 35)/100 = 5.11 g

What is the correct equation to calculate purity if the mass of the pure product is 10 g and the mass of the impure product is 40 g?

• Purity = 40 / 10 x 100

• Purity = 10 / 40 x 100

• Purity = 10 + 40 x 100

• Purity = 40 - 10 x 100

What is the purity of distilled water?

• 100%

• 80%

• 50%

• 10%