Experiments With Water

What this topic is about
In the chapter "Experiments with Water", the section "Introduction and Observations" helps students notice and describe what water does in different situations. Simple experiments (pouring, dissolving, soaking, heating, cooling) show the basic properties of water: it is transparent, takes the shape of its container, flows, wets materials, can dissolve some substances, and can change between liquid, vapour and ice.

How to carry out observations

• Do one small experiment at a time: pour water into different containers, put salt or sand in water, drop objects to see if they sink or float, leave a bowl of water in sun and watch what happens.
• Look carefully and write down exactly what you see: the water level, whether something mixes or not, whether the object sinks, how long it takes for water to dry up.
• Use a simple table to record: experiment, materials, what you observed, and your conclusion.

Key observations students usually make

• Shape and volume: Water takes the shape of the container it is poured into but the amount (volume) stays the same.
• Flow: Water can flow from a higher place to a lower place and it pours easily.
• Transparency: Water is clear—you can see objects through it.
• Wetting and absorption: Some materials (cloth, paper, sponge) get wet or soak up water; others (plastic, metal) do not absorb it.
• Dissolving: Some solids like sugar and salt dissolve in water and disappear while others like sand do not dissolve and settle at the bottom.
• Floating and sinking: Light or hollow objects (an empty plastic bottle, a small wooden piece) often float; heavy or dense objects (stone) sink.
• Change of state: In heat water can evaporate (becomes vapour) and when cooled it can become ice; vapour can turn back to tiny water drops (condensation).

Making simple conclusions
From these observations students learn how to describe water’s behaviour in daily life and why it is important to record experimental steps and results carefully. Encourage drawing what you see and comparing results from two or more similar experiments (for example, how fast water of the same amount evaporates from a wide bowl and from a narrow glass).

Safety and neatness
Always do experiments with an adult’s help when heating or when using glass containers. Clean up spills to avoid slipping.

What is a solution? A solution is a homogeneous mixture of two or more substances. It has a solute (the substance that gets dissolved) and a solvent (the substance that does the dissolving). In everyday life, water is the most common solvent.

Key words

• Solute: the material being dissolved (for example sugar or salt).
• Solvent: the liquid that dissolves the solute (for example water).
• Soluble: a substance that can dissolve in a given solvent (sugar is soluble in water).
• Insoluble: a substance that does not dissolve (sand is insoluble in water).
• Saturated solution: a solution that cannot dissolve any more solute at that temperature—extra solute stays undissolved.
• Unsaturated solution: a solution that can still dissolve more solute at that temperature.
• Supersaturated solution: a special unstable solution that contains more solute than the normal saturation point (usually made by heating and then carefully cooling).

Simple experiments and what they show

• Add sugar spoon by spoon to a glass of water and stir. At first the sugar disappears (it dissolves). When extra sugar starts to settle at the bottom and no more disappears, the solution has become saturated.
• Heat the saturated sugar solution and you will be able to dissolve more sugar. This shows that temperature often affects how much solute water can hold.

Factors that affect solubility

• Temperature: For most solids in water (like sugar), solubility increases as temperature rises. For some solids and gases the effect can be different.
• Stirring or shaking: speeds up how fast a solute dissolves by bringing fresh solvent into contact with the solute.
• Particle size: smaller particles dissolve faster because they have more surface area.
• Nature of substances: some pairs mix well (water and sugar), some do not (water and oil).

Why this matters

Understanding solubility helps explain cooking (making tea, dissolving sugar), cleaning (detergents help mix grease and water), medicine (how medicines dissolve in the body), and environmental topics like how salt dissolves in sea water.

What is mixing? Mixing means joining two or more substances so they spread evenly. When two liquids mix completely to form a single uniform liquid, they are called miscible. If they do not mix and instead form separate layers, they are called immiscible.

Simple experiments (Class 5 level)

• Take a glass of water and add a spoonful of sugar. Stir — the sugar disappears and the water becomes sweet. Sugar and water are miscible (sugar dissolves).
• Take another glass of water and pour some cooking oil on it. Shake and then let it stand. The oil separates and floats on water. Oil and water are immiscible.

Why do some liquids mix and others don’t?

• Polarity (simple idea): Water molecules are polar (they attract each other strongly). Some liquids like alcohol or vinegar are similar to water and mix with it. Oil molecules are non‑polar and do not mix with polar water — "like mixes with like".
• Density: If two liquids do not mix, the one with lower density floats on the one with higher density. For example, many oils have density around 0.9 g/cm³ while water has density about 1.0 g/cm³, so oil floats on water.
• Emulsions and emulsifiers: Some mixtures (like milk or mayonnaise) look mixed because they contain an emulsifier (a substance that helps oil droplets stay spread in water). Without an emulsifier, oil and water separate.

Everyday importance: Knowing which liquids mix helps in cooking (salad dressing), cleaning (detergents help mix oil with water), and safety (oil or gasoline spills on water behave differently and can pollute).

How to observe and record: Use a clear glass, add equal amounts of two liquids, shake, and note immediately and after a few minutes. Draw or photograph the layers and note which liquid is on top and whether they form one layer or two.

Suspension: A suspension is a mixture in which small solid particles are spread throughout a liquid but are not dissolved. The particles are large enough to scatter light and, if left undisturbed, they settle down under the action of gravity. Example: muddy water after stirring soil into water.

Sedimentation: Sedimentation (or settling) is the process by which the solid particles in a suspension fall to the bottom to form a layer called sediment. Sedimentation happens because the solid particles are heavier (or denser) than the liquid and gravity pulls them down. Factors that affect sedimentation include particle size, particle density, fluid density, viscosity, and temperature.

Decantation: Decantation is a simple method to separate the clear liquid from the settled solid. After sedimentation, the liquid (called the supernatant) is carefully poured off so that the sediment remains in the container. Decantation is often used when filtration is not practical or when particles are large and settle quickly.

Typical classroom experiment: Shake a bottle of muddy water (suspension). Let it stand undisturbed. Observe the particles forming a layer at the bottom (sedimentation). Slowly pour the clear water into another container (decantation). This demonstrates all three processes.

Important notes:

• Sedimentation takes time; smaller particles take longer to settle.
• Decantation must be done slowly to avoid re-suspending the sediment.
• Some mixtures (very fine particles or colloids) do not settle quickly and need filtration, centrifuging, or chemical treatment.

What they are: Sieving and filtration are simple methods to separate solid particles from solids or liquids using holes or pores. Both are physical separation techniques that do not change what the substances are; they only separate them.

Sieving: Sieving uses a device with relatively large holes (a sieve or mesh) to separate big particles from smaller ones. When a mixture of different-sized solids (or solids in liquid) is shaken or passed over the sieve, particles bigger than the holes remain on top and smaller particles pass through.

Filtration: Filtration uses a material with very small pores (filter paper, cloth, sand, charcoal) to separate finer particles from liquids or gases. The liquid (filtrate) passes through the filter while the fine solid particles are trapped.

How they work (simple view):

• Both depend on the relative size of particles and the size of holes or pores. If particle size > hole size → particle is retained. If particle size < hole size → particle passes through.
• Sieving is used for large or coarse separations; filtration is used for finer separations (e.g., muddy water).
• In practice, we often sieve first (remove pebbles, leaves) and then filter (remove fine mud and microbes) to get cleaner water.

Common materials used: Sieve (metal/plastic mesh), colander, cloth, filter paper, sand, gravel, charcoal, sponges, commercial membrane filters.

Simple classroom experiment idea: Mix sand, gravel and water. Pour the mixture through a sieve to remove gravel. Then pour the liquid+fine sand through layers of cloth or sand+charcoal inside a funnel to see clearer water come out. Observe what each step removes and how long it takes.

Evaporation is the process by which water (or any liquid) changes into water vapour (a gas) at temperatures below boiling. Evaporation happens because some molecules in the liquid move faster and escape from the surface into the air. It is a cooling process and depends on factors such as temperature, surface area, air movement (wind) and humidity.

Key points about evaporation:

• If temperature increases, evaporation becomes faster.
• If the surface area of the water is larger, more water can evaporate at the same time.
• If the air is dry (low humidity) or moving, evaporation is faster.
• Evaporation can happen at room temperature and does not need boiling.

Crystallization is the process by which dissolved solid particles (solute) come out of a solution and form solid crystals when the solution becomes too concentrated or conditions change (for example when water evaporates or the temperature falls). When water evaporates from a solution, the solute becomes more concentrated; once its concentration exceeds the solubility limit, crystals begin to form.

Key points about crystallization:

• Crystals form when a solution becomes supersaturated or when conditions favour the solute coming out of solution.
• The shape and size of crystals depend on the substance, how quickly crystallization happens, and the cleanliness of the solution.
• Common crystals from everyday life include salt, sugar, and alum crystals.

Simple experiment idea (classroom/home): Dissolve salt or sugar in warm water until no more dissolves (a saturated solution). Leave the solution in an open dish in a warm, dry place. As water evaporates, the solution becomes concentrated and crystals will start to appear on the dish or on a string placed in the solution.

What are floating and sinking?

When an object is placed in water it either stays on the surface (floats) or goes down to the bottom (sinks). Whether an object floats or sinks depends on how heavy it is compared to the amount of water it pushes away (displaces) and on the shape of the object.

Key idea — Buoyant force: Water pushes upward on the object. This upward push is called the buoyant force. If the buoyant force is equal to or larger than the object's weight, the object floats. If the object's weight is greater than the buoyant force, the object sinks.

Why shape matters: Two objects made of the same material can behave differently because of shape. For example, a small solid piece of iron (like a nail) sinks, but a large hollow iron boat floats. This happens because the boat pushes away (displaces) a large volume of water, increasing the buoyant force so that it can balance the boat's weight.

Role of density: Density (how much mass is packed into a given volume) explains floating and sinking simply. If the average density of an object is less than the density of water, it floats. If it is more, it sinks. The average density of a hollow object (like a boat) includes the air inside it, so its average density can be less than water even if the material is denser than water.

Simple experiments you can do:

• Drop a piece of wood, a stone, and a metal spoon into water and watch: wood floats, stone and spoon sink.
• Make a paper or foil boat and put small weights (coins) inside until it sinks — you will see how displacement and shape change floating.
• Put an egg in plain water (it may sink) and then in salt water (it will float). Adding salt increases water's density, increasing buoyant force.

Summary: Floating and sinking are caused by the balance between weight (downward) and buoyant force (upward). Density and shape decide the outcome. Simple experiments (boats, eggs in salt water) show these principles clearly.

Absorption is when a material soaks up a liquid into its tiny holes or spaces (pores). For example, when you drop water on a sponge, the water goes inside the sponge. The amount of liquid a material soaks up depends on how porous it is, how big the pores are, and the liquid's properties.

Wicking is a special kind of absorption where liquid moves along thin spaces or fibers without needing gravity or outside pushing. This happens because of two forces: adhesion (liquid sticking to the solid surface) and cohesion (liquid molecules sticking to each other). In thin tubes or between fibers, these forces pull the liquid along — this is also called capillary action.

Key factors that affect absorption and wicking:

• Porosity and pore size: More pores and bigger pore volume usually mean higher absorption, but very small pores can pull liquid up higher (stronger capillary action).
• Surface tension and wetting: Liquids that wet a surface (small contact angle) spread and wick better. Surface tension helps pull liquid into thin spaces.
• Material type and fiber arrangement: Cotton, paper, and some fabrics wick well; waxed or waterproof surfaces do not.

Simple classroom experiments: place strips of paper or cloth with one end in colored water and watch how the color moves up — the distance and speed show wicking. Place different materials in the same water and compare how much each soaks up in the same time to study absorption.

What it means
Cleaning and making water usable means removing visible dirt, smells and harmful germs so the water is safe for drinking, cooking and washing. There are two main goals: (1) remove suspended solids (sand, clay, leaves) and (2) remove or kill germs (bacteria, viruses).

Simple methods

• Sieving/Straining – Pass water through a sieve or piece of cloth to remove large particles such as leaves, insects and stones.
• Settling (Sedimentation) and Decantation – Leave muddy water undisturbed. Heavy dirt settles at the bottom. Pour the clearer water from the top into another container.
• Filtration (Sand–Gravel–Charcoal) – Water is passed through layers of gravel, sand and charcoal. Sand removes fine particles and charcoal helps remove smell and some dissolved impurities. This is a common household and school experiment.
• Boiling – Heating water until it boils kills most disease-causing germs. After boiling, let water cool and store it covered.
• Solar Disinfection (SODIS) – Clear plastic bottles filled with water are kept in bright sunlight for several hours. UV rays and heat reduce germs.
• Chemical Disinfection (simple explanation) – Small amounts of chlorine (or bleaching powder solutions) are used by water suppliers to kill germs. This is done carefully and in the right amounts.

Combined home method (safe and simple)
1. Let very muddy water stand until it clears at the top (settling). 2. Pour the top water through a clean cloth or a sand–gravel–charcoal filter (filtration). 3. Boil the filtered water for at least 1–3 minutes (depending on altitude) to kill germs. 4. Cool and store in a clean, covered container to avoid recontamination.

Why these steps work
Settling and sieving remove visible particles. Filtration captures smaller particles and some contaminants. Boiling or disinfecting kills invisible germs that cause sickness.

Safety and storage
Always use clean containers and utensils, cover stored water, and do not touch the inside of the container or the mouth of the water vessel with dirty hands.

Why water is important

Water is a basic need of all living things. People, animals and plants need water to drink, cook, bathe, grow food and carry out many daily activities. Water is also needed by industries, for electricity generation and to keep ecosystems (rivers, lakes, wetlands) healthy.

Limited supply and the water cycle

Although the Earth has a lot of water, most of it is salty (in oceans) and cannot be used. Only a small part is fresh and easily available. The water on Earth keeps moving in the water cycle — evaporation, condensation (clouds) and precipitation (rain). Groundwater and surface water are part of this cycle, so protecting and saving water helps keep the cycle balanced.

Why we must conserve water

• Fresh water is limited: only a small fraction of Earth's water is fresh and usable.
• Growing population and farming needs increase demand for water.
• Pollution can make water unsafe for drinking and for wildlife.
• Conserving water saves energy (less pumping and treatment) and money.

Ways to conserve water (practical steps)

• Fix leaks in taps, pipes and toilets — a dripping tap wastes many litres over time.
• Use buckets or a mug to wash dishes and vegetables instead of running water.
• Take shorter showers and turn off the tap while brushing teeth.
• Collect rainwater in barrels or drums for gardening and cleaning (rainwater harvesting).
• Reuse greywater (washed water from sinks or baths) for watering plants after simple filtering.
• Use water-efficient methods in farming, e.g. drip irrigation and mulching to reduce evaporation.
• Plant trees and maintain green areas to help ground water recharge and reduce runoff.
• Prevent pollution: don’t throw plastics, chemicals or waste into rivers and drains.

Role of students and schools

Students can check for leaks, measure daily water use at home, run awareness campaigns, set up a small rainwater collection system, and use water-saving taps and practices in the school. Small actions by many people make a big difference.

What happens if we don’t conserve water?

• Water shortages for drinking, crops and animals.
• Lower crop yields and higher food prices.
• Health problems from lack of safe water and sanitation.
• Loss of plants and animals that depend on freshwater habitats.