Grade Six Science

Hello Boys and Girls,

Have you had a good week? Did you do any quizzes or any other form of evaluation? How well did you do?

Last week we looked at the different states or forms of matter. Do you remember? Did you do the exercises from last week? This week we will find out about water and what it can do when things are mixed with it.

Let’s find out !

Do you help in the kitchen? Do you make cold drinks or hot beverages? Think about how you actually did it. What materials did you collect? What did you actually do?

We’re going to do some work in the kitchen now. Get a glass of water, some sugar, salt, a teaspoonful of cooking oil and a spoon.

Now, stir about one teaspoonful of sugar into the glass of water. Observe. Taste the mixture. What have you found? Document your observations.

Do the same with the salt and the oil.

Did you find the sugar as well as the salt mixed in with the water? When this happens we say that the sugar or salt dissolved in the water. The sugar and the salt are called solutes. The water in which each was dissolved is called the solvent. The salt (or sugar) and the water mixed together is called the solution.

Many solids, liquids and gases can dissolve in water. When you dissolve a solid (or liquid or gas), it doesn’t disappear- it’s still there.

When you tasted the water in which the sugar was dissolved, didn’t you taste the sugar and the water at the same time?

Materials that dissolve in water are

water soluble.

Classify the items in this list as soluble or insoluble: sugar, nails, buttons, salt, sand, oil, milk, instant coffee. (Do add to this list.)

Name at least two solutes. Which solutes is referred to as the universal solute? Is there a limit to how much of the solute can dissolve? Let’s find out. Pour just a bit of water into a glass (about ¼ of the glass). Now stir in a teaspoon of sugar. What happens? Stir in another teaspoonful, and another, and another. What happens?

Stirring helps to further dissolve solutes, however there comes a time when n more of the solute will dissolve. When that happens we say that that solution is saturated.

How can we get more of the solute to dissolve? You can discuss this with someone else. Did you come up with: * Add more water? * Heat the water?

Yes, both of those responses are correct. It has not been raining much lately, but let’s look at Rain and the Water Cycle. Water is constantly evaporating from the Earth’s surface: from rivers, seas, lakes, pools and so on. This is caused by the sun’s heat. This water that evaporates rises into the air as water vapour. High up into the air it cools, turning into droplets in clouds. This turning from vapour into droplets is called condensation. When the clouds get too heavy they burst, and the water fall to the Earth as rain. Water gets into rivers, lakes, pools, seas and so on. Evaporation takes place, the vapour condenses into clouds, when heavy, the clouds burst and fall as rain...and this goes on over and over and over again. This process is called the Water Cycle. Look at the picture below. It will further help you to understand.

You can make a collage to show how the Water Cycle works. You need different types and pieces of material- cloth, paper, cardboard, cotton wool etc.

Have fun with this and explain the water cycle to your parents, classmates and other friends.

Does water have other forms? Let’s look at the states in which water exists. Water exists as solid, liquid and gas. These are the three states of matter we discussed some time ago. The form or state that water takes depends on the temperature.

Solid

When solid, water is ice. It expands on freezing. (At what temperature does it freeze?) Did you know that ice can float? Observe a cube of ice in a glass. What is its position in the glass?

Liquid

Ice is changed water, a liquid, upon cooling. It has a surface like a very thin skin. Have you ever seen insects walking on water? Water can be in the shape of droplets. Do remember that water takes the shape of the container in which it is. The molecules in water are not as tightly packed as they are in its solid form. That’s why it is so easily poured.

Gas The Water Cycle

Water can be changed by heating it. What is it called then? Yes, it is called vapour which is a gas. Have you ever seen steam? Did I ‘catch’ you? No, we cannot see steam. Steam is invisible. What we see coming out of the kettle is really ‘condensed steam’. Please note that steam is dangerous. It can burn you badly.

Some questions for you

1. What happens to sugar when you add it to a cup of tea?

2. What is a solution?

3. What can you do to make a concentrated solution weaker? 4. What happens when you add oil to water?

5. When you melt chocolate you are changing a solid to a ............... 6. What happens to a liquid when you freeze it?

Next week we’ll have a short practice test. Some topics to revise are:

Solar System * Animals * Plants * Systems of the body * Air *Energy *Matter *Water

* Characteristics of living things * Simple machines

Until next week, goodbye, Boys and Girls!