Students’ Learning Outcomes
· Explain how one state of matter (solid, liquid & gas) dissolves in other.
Information for Teachers
· Common salt and sugar when added in water disappear to give mixtures. This is called dissolving a solid into liquid.
· Similarly a gas (CO
2) can also dissolve in liquid water, like soda water/cold drink.
· The materials that dissolve in water are called soluble materials. The materials that don’t dissolve in water are called insoluble materials. Glucose and salt are soluble materials.
Material / Resources
Water, sugar, glass, spoon, common salt, chalk powder, soil, glucose, lemon juice and vinegar, textbook
Worm up activity
· Half fill the glass with water and add a spoon full of sugar in it. Stir it with a spoon.
· Ask the students: What happens to the sugar? Where is it gone? Can you see it? Explain them that it has dissolved in water.
· Ask students to taste the liquid. How does the liquid taste?
· Name the mixture obtained in the above activity?
(Students’ response: Solution)
· Which two states of matter make the solution formed in this activity?
(Students’ response: Solid and Liquid)
· Divide the students in groups and give each group the following substances and ask them to add one by one in water (Common salt, Chalk powder, Glucose, Sand)
· Ask the students to tick the names of the solid things which dissolve / disappear in water like the way sugar dissolves. (Common salt, Glucose)
· What about the rest of the substances?
· Explain them that when substances are mixed in water some of them mix up with water and disappear we say that they have dissolved. Others don’t dissolve. The materials that dissolve in water are called soluble materials. The materials that don’t dissolve in water are called insoluble materials. Glucose and salt are soluble materials.
v What comes out of water in the form of bubbles?
(Students’ response: CO2, a gas)
v How does soda water taste?
(Students’ response: It tastes sour)
v Soda water is a mixture of which states of matter?
(Students’ response: liquid, gas, sugar which is a solid)
Point out that soda water is a mixture of all three states of matter.
· Divide students in small groups. Give the material and instruct them to:
· Take water in one glass and lemon juice in another glass.
· Mix the two liquids.
· Ask the students to answer following questions:
(Students’ response: They dissolve in each other)
v What is the name of the mixture you get after mixing the above two liquids?
(Students’ response: Solution)
Sum up / Conclusion
· There are certain things which disappear when added in water. We say that these things dissolve in water.
· Soda water is an example of such a solution in which a solid (common sugar) and a gas (carbon dioxide) are dissolved in water (liquid)
· A liquid can also dissolve in another liquid. Inform them that next time we will study how insoluble materials are separated from water.
Ask students to:
v Name any two liquids which mix with water like the way lemon juice mixes with water.
(Students’ response: a) Honey b) Vinegar)
v Name any two liquids which don’t mix with water and form separate layers.
(Students’ response: a) Kerosene oil b) Cooking oil)
v Animals like fishes can’t live without oxygen. From where do they get oxygen in water?
(Students’ response: Some oxygen from air is dissolved in water. Fishes breathe using the oxygen dissolved in water)
v Write the following things on board and as which of these can dissolve in water and which can’t? They can conduct experiments to find the answer.
v Honey, Kerosene oil, petrol, vinegar, marble chips (stones), urea fertilizer, sand.
(Students’ response: Things which don’t mix with water are: Kerosene oil, petrol, marble chips and things which mix in water are: Honey, Vinegar and urea fertilizer)
· Write these questions on the board and ask them to note down on their note books.
v What is air? Is it a mixture?
(Students’ response: Air is a mixture of nitrogen, oxygen, carbon dioxide and water vapors)
v Sea water is a solution of which states of matter?