CHAPTER 5-Water and Solution.pdf

Science Module Form 2- Chapter 5

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Physical Characteristics of Water

An odorless, colorless, and tasteless liquid at room temperature

Expands upon freezing

Density = _____________

Poor electrical conductor

Physical Characteristics

Boiling point = ___________

Poor thermal conductor

Freezing point = _________

Raise the boiling point of water

Effects of impurities on water

Lower the freezing point of water

Raise the density of water



Exercise 5.1


1. Diagram 1 shows the apparatus set-up to study the effect of impurities in distilled water. A spatula of fine table salt is added into apparatus B.

Diagram 1 (a) From Diagram 1, determine the temperature recorded by (i) Thermometer A when the distilled water is boiling. ________________________________________________________ (ii) Thermometer B when the mixture of distilled water and fine table salt is boiling. ________________________________________________________

(b) If two spatulas of fine table salt are added to apparatus B, predict the boiling point recorded by thermometer B by ticking ( ) in one of the boxes provided below.

100C 102C 105C

(c) From the experimental result, define distilled water operationally. ___________________________________________________________

(d) Why is distilled water called pure water? ___________________________________________________________




(e) If a spatula of fine table salt is added into distilled water, predict the freezing point recorded by thermometer B by ticking ( ) in one of boxes provided below. -2C 0C 2C

2. Figure 2 shows an experiment to determine the freezing point of water.

(a) Define the freezing point of water. ___________________________________________________________

(b) Plot a graph of temperature (C) against time (minutes).

(c) If you add some salt into the distilled water at the beginning of experiment, what will happen to the freezing point of distilled water? ___________________________________________________________




3. The changes in the state of water is shown in the diagram.

(a) Name the processes labeled as L, M and N in the above diagram. L M N : ____________________________________________________ : ____________________________________________________ : ____________________________________________________

(b) What happens to the process L if mineral salts are dissolved in the water? ___________________________________________________________

(c) What happens to the process N if mineral salts are dissolved in the water? ___________________________________________________________

(d) The figure shows the same chemical substance undergoing the following process. Solid Z Gas

Name the process Z. ___________________________________________________________




Composition of Water

WATER

is a COMPOUND

H2O

2 hydrogen atoms

1 oxygen atom

1 water molecule

Water can be broken down to its elements through electrolysis. ELECTROLYSIS - A method to break down a compound by passing an electric current throughits liquid or solution

Electrolysis of water (a) Water is added with a little dilute sulphuric acid to make it conduct electricity better. (b) Test the gas that is collected by the (i) Cathode ( hydrogen) : Lighted splinter -: pop sound is produced. My Blog : http://jomscorescience.blogspot Email [email protected] (ii) Anode (oxygen) : Glowing wooden splinter - the splinter ignited. (c) The ratio of hydrogen to oxygen in water compound is 2 :1


Exercise 5.2

1. Diagram 1 shows the electrolysis of water.

(a) Water was electrolysed to determine its composition. The apparatus above was set-up. A chemical was added to a beaker of water and two types of gases were collected at the end of experiment. Fill in the spaces above to complete the electrolysis diagram.

2. Diagram 2 shows the apparatus set-up of an experiment to study the electrolysis of water.

Diagram 2My Blog : http://jomscorescience.blogspot Email : [email protected]


(a) Based on Diagram 2, state the ratio of the gases released. ___________________________________________________________ (b) Identify gas X and gas Y. (i) Gas X (ii) Gas Y : _______________________________________________ : _______________________________________________

(c) Diagram 3 shows the readings of gas X and Y in the measuring cylinders.

Diagram 3 Based on Diagram 3, record the readings in Table 1. Time taken ( minutes) Volume of gas X (cm3) Volume of gas Y (cm3) 0 5 10 15

(d) State the variables involved in this experiment. (i) Manipulated variable : ____________________________________ (ii) Responding variable : ____________________________________ (iii) Fixed variable : ____________________________________




3. Diagram 4 shows the apparatus set-up used to study electrolysis.

Diagram 4 The switched is turned on and the electric current is allowed to flow for 20 minutes. (a) On Diagram 4, mark X for the positive electrode. (b) What are the gases collected at the positive and negative electrodes? (i) Positive electrode (ii) Negative electrode : ____________________________________ : ____________________________________

(c) State the ratio of the volume of gas collected at the positive electrode to the volume of gas at the negative electrode. ___________________________________________________________

4. Diagram 5 shows an experiment related to water.



(a) What gas will be collected in (i) Cylinder A (ii) Cylinder B : __________________________________________ : __________________________________________

(b) What will happen if a lighted splinter is inserted into (i) Cylinder A (ii) Cylinder B : __________________________________________ : __________________________________________

(c) If the volume of gas in cylinder A is 20 cm3, what will be the volume of gas in cylinder B? ___________________________________________________________

(d) What is the conclusion that you could make about this experiment? ___________________________________________________________ ___________________________________________________________

(e) Briefly define the following terms. (i) Electrolysis of water : ___________________________________________________________ (ii) Anode : _______________________________________________

(f) Draw a molecule of water by labeling its atoms.




5. Diagram 6 shows the set-up of an experiment to determine the composition of water.

Diagram 6 (a) No bubbles of gases were seen in test tubes P and Q when the electric current is switched on. Explain why. ___________________________________________________________ (b) What should be added to the water to help overcome to the problem described in (a) ___________________________________________________________ (c) Name the gas collected at test tubes P and Q. (i) P : ____________________________________________________ (ii) Q : ____________________________________________________ (d) How can the gas released in the test tubes P and Q be identified? (i) P : ____________________________________________________ (ii) Q : ____________________________________________________ (e) What is the ratio of the gas collected? Ratio of gas collected P : Q = __________________ (f) Name the process used in the diagram. ___________________________________________________________




6. Diagram 7 shows the apparatus set-up used to study electrolysis.

Diagram 7 (a) What is the name of the process shown above? ___________________________________________________________ (b) When the switch is turned on, there is no current flow. (i) Why? ((give a reason) ________________________________________________________ (ii) State how this problem could be solved. ________________________________________________________

(c) ( After 20 minutes ) (i) What is collected in test tube A? ________________________________________________________ (ii) Name the product collected in test tube B and explain a test to determine this gas. ________________________________________________________ ________________________________________________________

(d) what is the ratio of the volume of gas collected in test tube A to the volume of gas collected in test tube B? ___________________________________________________________




7. Diagram 8 shows the electrolysis of water.

Diagram 8 (a) Why is pure water added with a few drops of dilute sulphuric acid? ___________________________________________________________

(b) The gas collected in test tube K relighted a glowing splinter whereas the gas collected in test tube L explodes with a pop sound when tested with a lighted splinter. (i) Test tube K (ii) Test tube L : __________________________________________ : __________________________________________

(c) Complete Table 1 Time (min) Volume of gas in test tube K (cm3) Volume of gas in test tube L (cm3) 0 0 0 1 2 2 4 3 6

(d) Based on Table 1, what can be said about the composition of water? ___________________________________________________________




8.

Diagram 9 (a) The above experiment is carried out to study the electrolysis of water. Complete the observations in the following table. Procedure (i) Switch on the circuit (ii) Test gas X with a burning wooden splinter (iii) Test gas Y with a glowing wooden splinter Observation

(b) Identify ; (i) Gas X (ii) Gas Y : _______________________________________________ : _______________________________________________

(c) From the above experiment, it is concluded that one molecule of water is made up of __________________ and __________________.



Evaporation of Water


Definition

The process by which a liquid changes into its vapour.

4 Factors affecting the rate of evaporation

Surface Area

Movement of Air

Temperature

Humidity

Similarities and differences between evaporation and boiling

Evaporation Both involve the change of state from liquid to gas. Both processes absorb heat

Boiling

Occurs at the liquids surface Occurs at all temperatures below the liquids boiling point A slow process

Occurs throughout the liquid Occurs at the liquids boiling point A fast process




Exercise 5.3 1. The experiment below is carried out to study the relationship between the surface area and the rate of evaporation.

(a) State the variable that (i) is fixed (ii) is manipulated (iii) responds : __________________________________________ : __________________________________________ : __________________________________________

(b) What is your observation? ___________________________________________________________ ___________________________________________________________

(c) What is the inference of the experiment? ___________________________________________________________

(d) State your conclusion. ___________________________________________________________ ___________________________________________________________

2. Diagram 1 shows three identical handkerchiefs. All the handkerchiefs are put under the Sun for five hours.



(a) Arrange the handkerchiefs in the sequence from the one that will dry fastest to the one that will dry slowest. ___________________________________________________________

(b) State three factors that influence tha rate of evaporation other than surface area. (i) (ii) (iii) ___________________________________________________ ___________________________________________________ ___________________________________________________

3. Diagram 2 shows two containers, J and K, both containing 300ml of water. The water in both containers is allowed to evaporate.

Diagram 2 (a) The water in which container will evaporate faster than the other? ___________________________________________________________

(b) Explain your answer in (a) ___________________________________________________________

(c) Suggest two ways to increase the rate of evaporation of water in both containers. (i) ________________________________________________________ (ii) ________________________________________________________




4. Diagram 3 shows an experimental set-up to study how the surface area of water affects the rate of evaporation.

Diagram 3 (a) State the observation for this experiment. ___________________________________________________________ (b) What inference can be made based on Diagram 3? ___________________________________________________________ (c) State your hypothesis based on your answer in (a). ___________________________________________________________

(d) The experiment was observed for nine days. Table 1 shows the data obtained. Container Beaker Petri dish Day 1 150 150 Volume of water left (cm3) Day 3 Day 6 147 130 140 100

Day 9 122 83

(e) State the variables involved in this experiment. (i) Manipulated variable (ii) Responding variable (iii) Fixed variable : ____________________________________ : ____________________________________ : ____________________________________

(f) Suggest a relationship between the volume of water left with the surface area of the containers. ___________________________________________________________




5. Diagram 4 shows the set-up of an experiment to study the effect of humidity on the rate of evaporation.

Diagram 4 (a) Name the following variables in the experiment. (i) Manipulated variable (ii) Responding variable (iii) Constant variable : ____________________________________ : ____________________________________ : ____________________________________

(b) What is the purpose of placing fused calcium chloride in bell jar Q? ___________________________________________________________ (c) In which bell jar does the filter paper dry faster? Explain your answer. ___________________________________________________________ ___________________________________________________________ (d) What inference can be made based on your answer in (c)? ___________________________________________________________ (e) What conclusion can you make from this experiment? ___________________________________________________________ (f) What are the other factors that also affect the rate of evaporation? (i) ________________________________________________________ (ii) ________________________________________________________ (iii) ________________________________________________________ (g) Suggest two applications of evaporation in our daily life. (i) ________________________________________________________ (ii) ________________________________________________________




6. Diagram 5 is related to the evaporation of water.

Diagram 5 (a) Name the following variables in the experiment. (i) Manipulated variable (ii) Responding variable (iii) Constant variable : ____________________________________ : ____________________________________ : ____________________________________

(b) State the observation for this experiment. ___________________________________________________________ (c) State your hypothesis based on your answer in (a). ___________________________________________________________ (d) What conclusion can you make from this experiment? ___________________________________________________________ (e) Define evaporation ___________________________________________________________ (f) What are the other factors that also affect the rate of evaporation? (i) ________________________________________________________ (ii) ________________________________________________________ (iii) ________________________________________________________



Solution and Science Module Form 2- Chapter 5 Solubility

A solute is the substance that dissolves.

A solvent is the substance that the solute dissolves in.

A solution is produced when a substance dissolved in another substance.

SolutionAll these solutions have a clear appearance

Dilute solutionContains a little dissolved solute

Concentrated solutionContains a lot of dissolved solute

Saturated solutionContains the maximum amount of dissolved solute Cannot dissolve any more solute

Can dissolve a lot more solute

Can dissolve a little bit more solute

The solubility of a solute is the maximum amount of solute in grams that will dissolve in 100 g of solvent at a given temperature.

Factors affecting solubilitya. The nature of the solvent b. The nature of the solute c. The temperature of the solvent

Rate of Factors affecting the rate of My Blog : http://jomscorescience.blogspot Size stirring dissolving Email : [email protected] of solute Temperature


Exercise 5.4




Acids and Alkali

Properties of Acids

Properties of Alkali

A chemical compound that contains hydrogen. Tastes sour Corrosive pH value is less than 7 Change blue litmus paper to red Examples organic acids: - tartaric acid - acetic acid - citric acid Examples inorganic acids: - hydrochloric acid - sulphuric acid - nitric acid gives out carbon dioxide when it reacts with carbonates

An oxide or hydroxide that is soluble in water. Tastes bitter Corrosive pH value is more than 7 Change red litmus paper to blue Common laboratory alkalis: - Sodium hydroxide - Potassium hydroxide Examples inorganic acids: - hydrochloric acid - sulphuric acid - nitric acid






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CHAPTER 5-Water and Solution.pdf