Science form 2

• The sun is the largest object in our solar system
• The Dead Sea, located at the border of Jordan, is the saltiest sea in the world.
• The Dead Sea is completely surrounded by land, causing the water flowing from the Jordan River into the sea to evaporate quickly, increasing its saltiness.
• The unusual high salt content of the water in the Dead Sea causes it to be so dense that it results in natural buoyancy, allowing us to easily float in the Dead Sea.
• Water is a basic need of all life on Earth and no life would survive without water.
• More than 70% of the Earth’s surface is covered by water.
• Pure water is colourless, odourless and tasteless and exists as liquid at room temperature.
• Water has a high surface tension due to cohesive force between water molecules at the surface.
• The changes in the water molecules that undergo evaporation can be seen in Figure 5.7.
• Humidity affects the rate of evaporation of water, with higher humidity leading to lower rates of evaporation.
• The movement of air affects the rate of evaporation of water, with faster movement leading to higher rates of evaporation.
• Evaporation of water is the process that changes water to water vapour and occurs at any temperature.
• Experiment 5.1 aims to study the factors affecting the rate of evaporation of water.
• The exposed surface area of water affects the rate of evaporation of water, with a larger exposed surface area leading to higher rates of evaporation.
• The surrounding temperature affects the rate of evaporation of water, with higher temperatures leading to higher rates of evaporation.
• Capillary action in plants is a phenomenon where water is drawn up from the roots to the leaves due to cohesive force between water molecules and adhesive force between water molecules and the cell walls of xylem.
• Absorption and release of heat to the surroundings result in the change of the state of water.
• Water is a compound made up of oxygen and hydrogen that combine chemically.
• The rate of solubility of a substance is affected by several factors.
• Stir the mixture until even and observe the appearance of the mixture formed.
• A medicine in the form of suspension must be shaken before using to ensure the active substances in it are equally dispersed throughout the liquid.
• Solubility is the maximum amount of the solute that can dissolve in 100 ml of solvent at a specific temperature.
• Carry out Experiment 5.2 to determine these factors.
• The smaller the size of solute, the higher the rate of solubility.
• Let the mixture stand for 10 minutes and filter its content.
• The higher the rate of stirring, the higher the rate of solubility.
• Repeat steps 1 to 5 by replacing copper(II) sulphate crystals with chalk powder and record your observations.
• Observe if there is any residue left on the filter paper.
• Measure and pour 100 ml of water into a beaker and add one spatula of copper(II) sulphate crystals.
• Use a torchlight to direct a beam of light towards the beaker and observe whether the light can pass through the mixture.
• The higher the temperature of solvent, the higher the rate of solubility.
• The composition of elements in a water molecule can be determined through electrolysis.
• K in the water purification system stands for Coagulation.
• Vicki carried out an activity to study several water purification methods using cloudy river water as her study sample.
• Sample B, which is Boiled, would still contain suspended particles.
• K, L, M and N are the stages involved in the water purification system.
• M in the water purification system stands for Sedimentation.
• The process in stage K of the water purification system, Coagulation, is done by adding Alum.
• Sample A, which is Filtered, would become clear.
• N in the water purification system stands for Filtration.