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The following table shows the first ionisation energies for the elements of period 1 and 2.

img_1.png

a) What is the meaning of the term first ionisation energy?

 

b) Identify the pattern of first ionisation energies in a period.

 

c) Which TWO elements exert the strongest attractive forces on their electrons? Use the data in the table to give a reason for your answer.

 

d) Draw Aufbau diagrams for the TWO elements you listed in the previous question and explain why these elements are so stable.

 

e) It is safer to use helium gas than hydrogen gas in balloons. Which property of helium makes it a safer option?

 

f) ’Group 1 elements readily form positive ions’. Is this statement correct? Explain your answer by referring to the table.

16 March 2018 · siyabonga · 0 marks · 0 mins

In each of the following, say whether the chemical substance is made up of single atoms, singles molecules or giant molecules.

 

a) Ammonia gas (`N H_3`)

 

b) Zinc metal (Zn)

 

c) Graphite (C)

 

d) Nitric acid (`H N O_3`)

 

e) Neon gas (Ne)

16 March 2018 · siyabonga · 0 marks · 0 mins

Factorise:

 

(a) `2l+2w`

 

(b) `12x+32y`

 

(c) `6x^2+2x+10x^3`

 

(d) `2x y^2+x y^2z+3x y`

 

(e) `-2a b^2-4a^2b`

09 November 2015 · P Botha · 0 marks · 0 mins

The question below has reference material. View the reference material and all the questions based on it.

1.   Calculate the mean number of followers per celebrity. Round your answer the the nearest thousand.                                                                                                                  (3)

2.    Determine the median number of followers. Round your answer the the nearest whole

number.                                                                                                                     (3)

3.    Oprah Winfrey lies at the first quartile. This means that  (select the correct option):

tweet.png

(a)  25% of the celebrities have less followers than her.


(b)  75% of the celebrities have less followers than her.        (1)

02 January 2015 · Brenda Joao · 7 marks · 5 mins

The question below has reference material. View the reference material and all the questions based on it.

1.      Calculate the total number of Facebook users (A) in South Africa at the end of March

2011.                                                                                                                          (2)

2.      How many male users (B) were there in June 2011?                                                  (2)

3.      Facebook had 3 778 580 users at the end of June 2011.  The number of users

has increased to 4 036 460 at the end of July 2011. Calculate the percentage

increase in users. Round your answer to one decimal place.                                      (4)

4.      Express the number of male users in May 2011 as a percentage of the number

of female users in May 2011.        (2)

5.      Many Facebook users are becoming disenchanted with the network and feel that

their privacy is violated. As a result they have deregistered as Facebook users.

This phenomenon can also be detected among South African users. During which

month did the number of users decrease?                                                                  (1)

02 January 2015 · Brenda Joao · 11 marks · 10 mins

a) Draw a magnetic field diagram to show the force of repulsion between two bar magnets.                                                                                       (4)

b)  Describe the magnetic field directly between the two magnets.  (1)

26 September 2013 · pardeeplal · 5 marks · 5 mins

In the circuit below, one lamp breaks, causing all the other lamps to go out.  Which lamp breaks?

circuit.png

 

A.

A

 

B.

B

 

C.

C

 

D.

D

08 June 2013 · JOHNSON BADZA · 2 marks · 1 mins

EFGH is a parallelogram with vertices E(-1;2), F(-2;-1) and G(2;0). Find the co-ordinates of H by using the fact that the diagonals of a parallelogram bisect each other.

23 April 2013 · Johan Linde · 0 marks · 0 mins

Distinguish between the three business environments.

02 April 2013 · Carder Tregonning · 6 marks · 3 mins

Factorise completely:

  1. `3x^2+17x-6`
  2. `7x^2-6x-1`
  3. `8x^2-6x+1`
  4. `6x^2-15x-9`
26 June 2012 · Nicola du Toit · 0 marks · 0 mins