Complete the text with the phrases in the box.

Salt water is denser 1 than tap water. If water is dense, 2 objects can float more easily in it. We know fresh eggs usually sink, 3 so if you put an egg into the glass, it sinks through the tap water.
But when the egg 4 comes to the water with salt in it, it stops. It stops 5 because the water is dense and 6 if the water is dense, the egg can float in it.

?Lesson 3: What do you know about water

1. Read the e-mail. Tick true (T) or false (F).

Hi Reema,
We did two experiments in yesterday’s science class. Fresh eggs sink and old eggs float because they have air in them.
When eggs get older, they take in air and go bad. They produce gas and they float.
We can tell if they are bad without breaking them.
Nina.

1. Nina is writing about her science class. T
2. If eggs are fresh, they float. F
3. If eggs are fresh, they have a bad smell. F
4. You have to break an egg to know if it is bad. F

2. Listen, number, say and write. Track 55

a) An egg sinks if you put it into tap water. But what happens if you add salt to the water?

A. 4

B. 6

C. 2

D. 5

E. 1

F. 3

c) Complete the text with the phrases in the box.

Salt water is denser 1 than tap water. If water is dense, 2 objects can float more easily in it. We know fresh eggs usually sink, 3 so if you put an egg into the glass, it sinks through the tap water.
But when the egg 4 comes to the water with salt in it, it stops. It stops 5 because the water is dense and 6 if the water is dense, the egg can float in it.

3. Ask and answer.

2. heat / water / 100 degrees / boil.

What happens if you heat water to 100 degrees?

If you heat water to 100 degrees, the water boils.

3. mix /oil /water /oil /float/on/ water.

What happens if you mix oil and water?

If you mix oil and water, the oil floats on the water.

4. some kinds / metal / get / wet / turn brown.

What happens if some kinds of metal get wet?

If some kinds of metal get wet, they turn brown.

5. heat / water / at a height / 2000m / boil / at / 90 degrees.

What happens if you heat water at a height of 2000m?

If you heat water at a height of 2000m, the water boils at 90 degrees.

6. freeze / seawater / change / ice / at 4 degrees under zero.

What happens if you freeze seawater?

If you freeze seawater, it changes to ice at 4 degrees under zero.

4. Look at the picture. Write six safety rules in your notebook.

2- If you ride a bike, always wear a helmet.

3- Never use a mobile phone when you cross the street.

4- Always wear a seat belt when you travel by car.

5- When you cross the road, always look right then left then right.

6- If there are traffic lights, always use them to cross the road.