Answer the following questions :
1. What is matter? What is it made up of?
2. Explain molecular movement in all three states of matter.
3. Explain solubility of substances in water.
4. What do you understand by evaporation and condensation?
5. Differentiate between expansion and contraction.
6. Differentiate between physical change and chemical change.
FOR THE CURIOUS MIND
Bubbles appear when you open a bottle of soda but not when you
water. Why?
Answers
Answer:
Explanation:
Ans: 1
Matter is made up of atoms. All of the atoms known to humans are listed in the periodic table of elements.
Perhaps a better question is "what is matter?" Matter is anything that has mass and volume. Because matter has mass and volume, a property of all matter is density. If you take the matter's mass and divide it by the volume, you get the matter's density. Density is one of several physical properties of matter. Another physical property of matter is solubility. Malleability and ductility are two more. Malleability is matter's ability to be pounded into thin sheets. Ductility is how well the matter can be pulled into wires. Still another physical property of matter is thermal conductivity. That property refers to how well the matter conducts heat and temperature changes.
Matter also has chemical properties. Those will describe matter's ability to change into something else with new and different physical properties. Two common chemical properties of matter are flammability and reactivity.
Ans: 2
Solids behave as if the molecules are attached by little springs, thus they vibrate about fixed positions, amplitude and frequency being governed by temperature and mass, respectively.
Gases have zero intermolecular attraction, so behave like billiard balls, moving in a straight line in all directions at all different speeds, average speed being governed by temperature, unless they (very rarely) interact with each other or (frequently) interact with their container walls.
Liquids are a combination of the two - their densities suggesting they behave more like sloppy solids than viscous gases.
Ans: 3
SOLUBILITY is understood as a maximum amount of solute that dissolves in a solvent at so called equilibrium. In chemistry an equilibrium is a state where reactants and products reach a balance - no more solute can be dissolved in the solvent in the set conditions (temperature, pressure). Such a solution is called a saturated solution.
To put it in simple words: If you take one litre of water and you start dissolving table salt in it (chemical formula of salt is NaCl) and:
temperature of water is 25oC
pressure is 1 ATM (Atmosphere - standard pressure in the open air on Earth)
you should be able to dissolve exactly 357.00 grams and not a gram more. The rest of the salt will stay on the bottom as residue and will not dissolve. Solubility of salt in water is therefore 357.00g/L. When this amount of salt is dissolved the solution reaches its equilibrium. Every chemical substance which dissolves in water has a fixed solubility. If it does not dissolve - its solubility is zero. Many of these solubilities have been measured and special charts are produced displaying solubility of many substances at once.
Ans: 4
Evaporation and condensation are changes of state:
evaporation involves a liquid changing to a gas
condensation involves a gas changing to a liquid.
Evaporation is the reason why damp clothes dry on a washing line.
Condensation is the reason why windows become foggy on a cold day.
The term Evaporation and Condensation are both steps in water cycle.
Without these two terms water cycle would not continue..
Factors affecting the rate of condensation and evaporation
The rate of condensation increases if the temperature of the gas is decreased.
On the other hand, the rate of evaporation increases if the temperature of the liquid is increased.
Evaporation
The particles in a liquid have different energies. Some will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have a lower average kinetic energy than before, so the liquid cools down as evaporation happens. This is why sweating cools you down. The sweat absorbs energy from your skin so that it can continue to evaporate.
Condensation
The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. They come close together and bonds form between them. Energy is released when this happens. This is why steam touching your skin can cause scalds: not only is the steam hot, but energy is released into your skin as the steam condenses.
Ans: 5
expansion and contraction...
let's take an example of a ball, precisely an exercise ball like the smiley one.
So, when you squeeze it,it contracts and when you release, it expands.
This is also similar to your lungs, you breathe in, your lungs contract and when you breathe out your lungs expand.
or
Substances expand (increase in size) when they get warmer, and they contract (decrease in size) when they get cooler. This property can be useful. For example:
Thermometers work because the liquid inside them expands and rises up the tube when it gets hotter.
Metal parts can be fitted together without welding, using shrink fitting. The slideshow shows how this works:
Ans: 6
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