Track quiz
Here are the seven rules first. Use them if a question feels hard.
| Idea | The rule |
|---|---|
| Same all through, or not | A mixture is homogeneous when it is the same all through. It is heterogeneous when its parts are not the same everywhere. |
| Solution, colloid, suspension | A solution has the smallest pieces and a suspension has the largest. A colloid lies in between. Size decides what the tests show. |
| Light through a mixture | Light scatters off the pieces in a colloid or a suspension. A true solution hardly scatters light. This scattering is the Tyndall effect. |
| How strong is a solution | Concentration tells how much solute is in the whole solution. Mass by mass percentage is solute mass ÷ solution mass × 100. |
| Picking a method | Each method works on a property in which the parts differ. If the parts do not differ in it, the method fails. |
| Getting back what dissolved | For most solids, a hot saturated solution holds less when it cools. The extra solute comes out as crystals. |
| More than two parts | Each part needs its own step. The step uses a property that sets the part apart. Do each step only while its property still works. A later step must not undo an earlier one. |
Vinegar is acetic acid spread through water. What kind of mixture is it?
A liquid has pieces 500 nm wide. They do not settle. Filter paper does not catch them. What is it?
A light beam crosses starch in water and leaves a bright path. What does this show?
15 g of sugar is dissolved in 60 g of water. What is the mass by mass percentage?
Camphor is mixed with dry sand. Which method separates them?
Take 100 g of water. Potassium nitrate holds about 170 g at 80 °C. It holds about 64 g at 40 °C. How much comes out on cooling?
A bowl holds chalk powder, salt and camphor. Which step comes first?
Salt is dissolved in water. You want the pure water back. Which method works?
Which of these is a suspension?
A colloid is poured through filter paper. Its pieces are far smaller than the holes. What happens?
This is Chapter 5 of your Class 9 book, Exploration. It is called Exploring Mixtures and their Separation. Read it this week.
Next is How Forces Affect Motion. There, the question changes. It is no longer what is in a thing. It is what makes a thing move.