Page 13 - Nilam_Publication_module_Chemistry_Form.pdf

Chemistry Form 4 • MODULE

3 The melting point of acetamide can be determined by heating solid acetamide until it melts as shown in the diagram
below. The temperature of acetemide is recorded every three minutes when it is left to cool down at room temperature.
Takat lebur asetamida boleh ditentukan dengan memanaskan pepejal asetamida sehingga lebur seperti dalam rajah di bawah. Suhu asetamida
dicatatkan setiap tiga minit semasa disejukkan pada suhu bilik.

Thermometer / Termometer
Boiling tube / Tabung didih
Water / Air
Acetamide / Asetamida

(a) What is the purpose of using water bath in the experiment?
Apakah tujuan menggunakan kukus air dalam eksperimen ini?
To ensure even heating of acetemide. Acetamide is easily combustible.
(b) State the name of another substance which its melting point can also be determined by using water bath as shown
in the above diagram.
Namakan satu bahan lain yang mana takat leburnya boleh ditentukan dengan menggunakan kukus air seperti rajah di atas.
Naphthalene

(c) Sodium nitrate has a melting point of 310°C. Can the melting point of sodium nitrate be determined by using the
water bath as shown in the diagram? Explain your answer.
Natrium nitrat mempunyai takat lebur 310°C. Bolehkah takat lebur natrium nitrat ditentukan dengan menggunakan kukus air seperti
yang ditunjukkan dalam rajah di atas? Jelaskan jawapan anda.
No, because the melting point of water is 100°C which is less than the melting point of sodium nitrate.

(d) Why do we need to stir the acetemide in the boiling tube in above experiment?
Mengapakah asetamida dalam tabung didih itu perlu dikacau sepanjang eksperimen?
To make sure the heat is distributed evenly

(e) The graph of temperature against time for the cooling of liquid acetamide is shown below.
Rajah di bawah menunjukkan graf suhu melawan masa untuk penyejukan cecair asetamida.
Temperature / Suhu/°C

T
3
Q R
T
2
T
1 Time / Masa/s
(i) What is the freezing point of acetamide?
Apakah takat beku asetamida?
T 2 °C
(ii) The temperature between Q and R is constant. Explain.
Suhu antara titik Q dan R adalah tetap. Jelaskan.
The heat lost to the surrounding is balanced by the heat released when the liquid particles

rearrange themselves to become solid.
(f) Acetemide exists as molecules. State the name of another compound that is made up of molecules.
Asetamida wujud sebagai molekul. Namakan sebatian lain yang terdiri daripada molekul.
Water/naphthalene
(g) What is the melting point of acetamide?
Apakah takat lebur asetamida?
T 2 °C

11
Nilam Publication Sdn. Bhd.

01-Chem F4 (3p).indd 11 12/9/2011 5:59:30 PM