Cambridge Secondary (7-9). Stage 8. Science. Learner's Book - Unit 5: Materials and cycles on Earth

These three cups have been filled with water.
Would you expect these three cups to have:
a exactly the same mass
b masses that were nearly the same
c masses that were very different?
Discuss this with a partner. Give reasons for your choice.

Which sub-atomic particle has a positive electrical charge?

Which sub-atomic particle has the smallest mass?

Which sub-atomic particles make up the nucleus of an atom?

The size of the negative charge of an electron is exactly the same as the size of the positive charge on a proton. What is the overall charge of the helium atom shown in the diagram?

How are the individual atoms held together?

Explain how Thompson’s model of the atom is different from the one scientists use today.

Who discovered the electron? When did they discover it?

Who proved that the neutron existed? When did they do this?

What two things did Rutherford discover about the structure of the atom?

How is Rutherford’s model different from the model scientists use today?

An atomic timeline
In a group of three, make a time line of the discoveries that have led to the model of the atom we use today. Do some research on the three scientists J. J. Thompson, Ernest Rutherford and James Chadwick. Find out where and when they worked and some personal details; add this to your time line.

Answer the three questions on your own and then check with a partner. Be ready to share your answers with the class.

What does it mean if a substance is pure?

Answer the three questions on your own and then check with a partner. Be ready to share your answers with the class.

Which of these items are pure substances?
sodium chloride; oxygen; sea water; gold; orange juice; copper oxide; silver nitrate; soil; black ink; potassium.

Answer the three questions on your own and then check with a partner. Be ready to share your answers with the class.

Of the items in question 2, which are elements, mixtures and compounds?
sodium chloride; oxygen; sea water; gold; orange juice; copper oxide; silver nitrate; soil; black ink; potassium.

What percentage of 9 carat gold is gold?

What percentage of silver is in silver marked 900?

Which element mixed with carbon in diamonds makes them blue?

Which elements may cause a diamond to be green?

If you take 1000 g of seawater, about 35 g (or 3.5%) of it is made up of salts.



Draw up a table to show the percentage of salts found in seawater.