|
GUESS
PAPER SUMMATIVE ASSESSMENT –I (2012) Class
– IX (Chemistry
|
|
Section
A
|
|
1.What is
dry ice ? What happens when the pressure under which it is stored is
decreased to
|
|
1 atmosphere ?
|
|
2.Why is glass or chinaware packed with straw ?
|
|
3.Name the processes by which CO2 and H2O
move into and out of the cell ?
|
|
4.List in tabular form any two differences between
homogeneous and heterogeneous mixtures.
|
|
5. (a) Define evaporation. (b)
Explain how the following factors affect the rate of evaporation of a liquid:
|
|
(i) temperature of the liquid. (ii) area of the
exposed surface.
|
|
(iii) moisture in the surrounding air. (iv) Increase in wind speed.
|
|
6.(i) Name the process or the separation technique
you would follow to separate : (a) Dyes in black ink (b) Butter from cream
(c) Ammonium chloride and common salt (d) Iron filings and sand (ii) State
the principle used in separation by centrifugation.
|
|
7. Based on the following characteristics
distinguish in tabular form the behavior of true solution, suspension and
colloidal solution. (a) appearance (b) visibility (c) filterability (d)
Tyndall effect (e) particle size OR
|
|
(a) What is distillation ? List the two conditions
essential for using this as a method of separation of components of a
mixture. (b) Draw a labelled diagram of the apparatus used to separate a
mixture of two miscible liquids.
|
|
8..Compare in tabular form , the properties of
Solids, Liquids and Gases with respect to : (i) Shape (ii) Volume (iii)
Compressibility (iv) Diffusion (v) Fluidity or Rigidity
|
|
OR ,
|
|
Account for the following : (a) For any physical
state of a substance, the temperature remains constant during its change of
state. (b) Water kept in an earthen pot becomes cool in summer. (c) We are
able to sip hot tea from a saucer rather than from a cup.
|
|
Section
B
|
|
09.If common salt is added to the unsaturated
solution of water and common salt it will
|
|
(a) become a colloid (b) become a suspension (c)
start showing Tyndall effect (d) remain a true solution
|
|
10.A student was asked to mix the white of an egg
with water and stir well. The student observed that
|
|
(a) a transparent solution is formed. (b) a translucent mixture is formed.
|
|
(c) egg white settles down at the bottom. (d) egg white floats on the surface.
|
|
11.The reaction of iron and sulphur to form iron
sulphide takes place at :
|
|
(a) at high temperature (b) in the
presence of a catalyst
|
|
(c) at
moderate temperature (d) in the presence
of an acid
|
|
12.Which of the following compounds when dissolved
in water gives coloured solution ?
|
|
(a) barium chloride (b) sugar solution (c) sodium
chloride (d) copper sulphate
|
|
13.For determining the accurate melting point of
ice we should prefer
|
|
(a) ice made from distilled water (b) ice made from tap water
|
|
(c) crushed dry ice mixed with salt (d) a mixture of ice and salt
|
|
14.Mohan used a thermometer having 20 divisions
between 30degC mark and 40degC mark. While determining
boiling point of water using this thermometer he observed that the level of
mercury becomes constant just 3 division below the 100o C mark.
Mohan should record in his note book
|
|
(a)
Least count=0.5degC, B.P.=97degC (b) L.C.=0.5degC, B.P.=98.5degC
|
|
(c)
L.C.=1degC, B.P.=98.5degC (d) L.C.=1degC ,
B.P.=97degC
|
|
15.Ramu
was asked to separate a mixture of common salt and ammonium chloride.
Sublimation is used to separate ammonium chloride because :
|
|
(a)
ammonium chloride sublimes
|
|
(b)
ammonium chloride changes directly from solid to gaseous state on heating
|
|
(c)
mixture contain a sublimable volatile component and a non Sublimable impurity
(salt)
|
|
(d) all
the above
|
|
16.Which
is the correct colour sequence of iron filings, sulphur and iron sulphide ?
|
|
(a) Greyish
black, yellow, black (b)
Black, yellow, brown
|
|
(c)
Brown, yellow, black (d) Black , yellow,
greyish black
|
|
17.The
colour of magnesium after rubbing with sand paper is
|
|
(a)
Silvery white (b) Grey (c) Black (d) Brown
|
|
18.Common
salt and sand can be separated by :
|
|
(a)
Filtration (b) Crystallisation (c) Sedimentation and Decantation
|
|
(d)
First dissolving in water, then by filtration and followed by
crystallisation.
|
|
19.A
student put five raisins each in two beakers A and B. Beaker A contained 20
mL of distilled water and beaker B has 20 mL of saturated sugar solution.
After some time the student would observe that :
|
|
(a) raisins in beaker A were more swollen
than those in beaker B.
|
|
(b)
raisins in beaker B were more swollen than those in beaker A.
|
|
(c)
raisins in both beakers A and B were equally swollen.
|
|
(d)
raisins in beaker A did not swell up at all.
|
|
20.In
the preparation of temporary mount of onion peel which of the following is
not used :
|
|
(a)
water (b) glycerine (c) safranin (d) alcohol
|
|
21.Arun,
Deepa, Uma and Priya were asked to select a plant material which would not
give blue black colour with iodine solution. Who did not select the right
material ?
|
|
(a)
Arun selected maize grains. (b) Deepa selected wheat grains.
|
|
(c) Uma
selected ground nut seeds. (d)
Priya selected potato.
|
|
22.Deepak
washed a few grains of tur dal in water. The water became yellow. He then
added a few drops of HCl to the same test tube, the water turned pink
in colour. From the above test Deepak concluded that tur dal contains. (a)
proteins (b) starch (c) turmeric (d) metanil yellow HCl
|
|
23.A
student recorded the mass of dry raisins as 2.5g and the mass of raisins
after soaking in water as 4 g . While performing the above experiment. The
percentage of water absorbed by raisin is :
|
|
(a) 20%
(b) 30% (c) 60% (d) 40%
|
|
24.The mixture of sand and water when filtered
gives.
|
|
(a) pale brown solution (b) brown
solution
|
|
(c) transparent solution (d) grey
solution
|
|
25. When a mixture of sulphur powder and iron
filings is heated.
|
|
(a) iron filings starts melting (b) sulphur sublimates leaving iron
filling behind
|
|
(c) ferrous sulphide is formed. (d) sulphur melts
|
Showing posts with label 9th Chemisty Term -I. Show all posts
Showing posts with label 9th Chemisty Term -I. Show all posts
Thursday, September 20, 2012
GUESS PAPER SUMMATIVE ASSESSMENT –I (2011) SCIENCE- Class – IX (Chemistry)
Sunday, April 29, 2012
IX Matter in Our Surroundings Assignment
1. A substance has a definite volume but no definite shape. State whether this substance is a solid, liquid or a gas.
2. Why do solids not diffuse into one another?
3. What is matter? How is it classified?
4. How will you show that air has maximum compressibility?
5) Matter has ___________.
| 1. no mass but occupies space 2. mass but occupies no space 3. mass and occupies space 4.no mass and occupies no space |
6. Among solids, liquids and gases which one has the maximum movement of molecules, the maximum inter molecular attraction and the minimum space between molecules.
7. List two properties that liquids have in common with gases.
8. What happens when a liquid is heated?
9. Why does water boil at a lower temperature at higher altitudes?
Define latent heat of fusion and vapourization?
10. A solid that sublimes on heating is _________.
1. sodium chloride 2. copper sulphate 3. lead sulphate 4. ammonium chloride
11. Why does a desert cooler cool on a hot dry day?
12. What is difference between evaporation and boiling?
13. A sponge can be pressed easily; still it is called a solid. Why?
14. Why water vapour does have more energy than water at same temperature?
15. In gases, particles vibrate _________.
| 1. about their mean position 2. about a vertical axis 3. about a horizontal axis 4.in any direction |
Saturday, September 24, 2011
Science Sample Paper – 2012 Class – IX (Chemistry)
Section -A
1. Particles of matter are continuously moving, so they possess ____________________.
2. The melting point of ice is __________________.
3. 293 K = ____________° C.
4. The concentration of a solution is the amount of _______________ present in a given volume of solution.
5. _______________ is the only metal which is liquid at room temp.
6. ________________ mixtures have uniform composition.
7. S.I. unit of latent heat of melting is ______________.
8. Rate of evaporation __________________ when surface area of liquid is increased.
9. Particles of matter have ______________ between them.
10. Soil and minerals are not ____________substances.
11. __________ number of elements occur in nature.
12. _________________ is a non-metal which is liquid at room temperature.
13.The states of matter can be changed by changing –
1. Particles of matter are continuously moving, so they possess ____________________.
2. The melting point of ice is __________________.
3. 293 K = ____________° C.
4. The concentration of a solution is the amount of _______________ present in a given volume of solution.
5. _______________ is the only metal which is liquid at room temp.
6. ________________ mixtures have uniform composition.
7. S.I. unit of latent heat of melting is ______________.
8. Rate of evaporation __________________ when surface area of liquid is increased.
9. Particles of matter have ______________ between them.
10. Soil and minerals are not ____________substances.
11. __________ number of elements occur in nature.
12. _________________ is a non-metal which is liquid at room temperature.
13.The states of matter can be changed by changing –
a. Temperature b. pressure c. both (a) and (b) d. none of these.
14. The rate of evaporation does not depend on –
a. Temperature b. humidity c. pressure d. speed of wind.
15. Which of the following is accompanied by cooling –
a. Vaporization b. evaporation c. condensation d. none of these.
Section -B14. The rate of evaporation does not depend on –
a. Temperature b. humidity c. pressure d. speed of wind.
15. Which of the following is accompanied by cooling –
a. Vaporization b. evaporation c. condensation d. none of these.
Sunday, September 11, 2011
Sample Paper – 2012 Class – IX Subject – Science (Chemistry)
2. A sponge can be pressed easily, still it is called a solid. Why?
3. Differentiate solids liquids and gases on the basis of (a) diffusion , (b) density.
4. Solids are denser as compared to liquids , still ice floats on water. Explain.
5. Define Latent heat of fusion.
6. Why does water vapour has more energy than water at same temperature?
7. How can gases be liquefied?
8. List four factors which affect the rate of evaporation.
9. Name and define the fourth and fifth state of matter.
10. Why does a desert cooler cool better on a hot, dry day?
11. Why does temperature remain constant during the boiling of water even though heat is supplied continuously?
12. What is the chemical name of Dry Ice? Why is it called dry ice?
13. What are alloys? Is it a mixture or a compound? Give reasons.
14. List four reasons to support that water is a compound and not a mixture.
15. Distinguish between homogeneous and heterogeneous mixture. Classify the following mixtures as homogeneous or heterogeneous-
i) Tincture of iodine
ii) Smoke
iii) Brass
iv) Sugar solution
16. Distinguish between true solution, suspension and colloid on the basis of stability, filterability and type of mixture.
17. How will you prepare a 10% solution of glucose in water?
18. Identify the physical and chemical changes from the following:-
i) Burning of magnesium in air
ii) Tarnishing of silver spoon
iii) Sublimation of iodine
iv) Electrolysis of water
19. State one similarity and one difference between evaporation and boiling.
Fill in the blanks:-
1. Particles of matter are continuously moving, so they possess ____________________.
2. The melting point of ice is __________________.
3. 293 K = ____________° C.
4. The concentration of a solution is the amount of _______________ present in a given volume of solution.
5. _______________ is the only metal which is liquid at room temp.
6. ________________ mixtures have uniform composition.
7. S.I. unit of latent heat of melting is ______________.
8. Rate of evaporation __________________ when surface area of liquid is increased.
9. Particles of matter have ______________ between them.
10. Soil and minerals are not ____________substances.
11. __________ number of elements occur in nature.
12. _________________ is a non-metal which is liquid at room temperature.
Wednesday, September 7, 2011
CBSE 10th Chemistry Chapter 1, Chemical Reactions and E...
Class 10, CBSE Science Practical Skills
1: What is the colour and formula of Sodium Sulphate?
(a) Colourless Na2SO4 (b) White Na2SO4 (c) Colourless NaSO4 (d) White Na(SO4)2
2: During respiration, glucose and oxygen combines in the cells of our body when energy is released.
What is the best way to describe the reaction that takes place during the process of respiration? .
Wednesday, August 31, 2011
Monday, August 15, 2011
Chemistry Class 9th:Is matter around us pure solved questions
| Q.1: Which separation techniques will apply for the separation of the following? (a) Sodium chloride from its solution in water. (b) Ammonium Chloride from a mixture containing Sodium Chloride and Ammonium Chloride. (c) Small pieces of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e) Butter from curd. (f) Oil from water. (g) Tea leaves from tea. (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in water. | ||||||
| Ans: (a) Crystallization or Evaporation. (b) Sublimation. (c) Centrifugation or Sedimentation. (d) Chromatography. (e) Centrifugation. (f) Separating funnel. (g) Hand-picking. (h) Magnetic separation. (i) Winnowing. (j) Centrifugation. | ||||||
| Q.2: Write the steps you would use for making tea. Use the words - solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue. | ||||||
| Ans: Take the solvent, water, in a kettle. Heat it. When the solvent boils, add the solute, milk. Milk and water forms a solution. Then pour some tea leaves over a sieve. Pour slowly hot solution of milk over tea leaves. Colour of tea leaves goes into solution as filtrate. The remaining tea leaves being insoluble remains as residue. Add requisite sugar which dissolves and the tea is ready. | ||||||
| Q.3: Explain the following giving examples: (a) Saturated solution, (b) Pure substance, (c) Colloid, (e) Suspension. | ||||||
| Ans: (a) Saturated Solution - a solution in which no more of the solid (solute) can be dissolved at a given temperature is called a saturated solution. Suppose 50 gm of a solute is the maximum amount that can be dissolved in 100 gm water at 298 K. Then 150 gm of solution so obtained is the saturated solution at 298 K. (b) Pure Substance - A pure substance consists of a single of matter or particles and can not be separated into other kind of matter by any physical process. Pure substances always have the same colour, taste and texture at a given temperature and pressure. For example, pure water is always colorless, odorless and tasteless and boils at 373 K at normal atmospheric pressure. (c) Colloid - Colloids are heterogeneous mixtures the particle size is too small to be seen with a naked eye, but it is big enough to scatter light. The particles are called the dispersed phase and the medium in which they are distributed is called the dispersion medium. Colloids are useful in industry and daily life. | ||||||
| A colloid has the following characteristics: | ||||||
| (1) It is a heterogeneous mixture. (2) The size of particles of a colloid lies between 1 - 100 nm and can not be seen by naked eyes. (3) The particles of colloid can scatter a beam of light passing through it and make the path visible. (4) The particles of colloid can not be separated from the mixture by filtration. The process of separation of colloidal particles is known as ‘centrifugation’. (5) They do not settle down when left undisturbed. In other words colloids are quite stable e.g. smoke, milk, fog, cloud etc. | ||||||
| (d) Suspension – | ||||||
| A ‘suspension’ is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. | ||||||
| A suspension has the following characteristics: | ||||||
| (1) It is a heterogeneous mixture. (2) The size of particles of a suspension is greater than 100 nm and is visible to naked eyes. (3) The particles of suspension can scatter a beam of light passing through it. (4) The particles of a suspension settle down when left undisturbed. (5) The particles of a suspension can be separated from its mixture by filtration. | ||||||
| Q.4: Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air, soil, vinegar, filtrated tea. | ||||||
| Ans: Homogeneous mixture - soda water, air, vinegar, filtered tea. Heterogeneous mixture - wood, soil. | ||||||
| Q.5: How would you confirm that a colourless liquid given to you is pure water? | ||||||
| Ans: Every liquid has a characteristic boiling point at 1 atmospheric pressure. If the given colourless liquid boils exactly at 373 K at 1 atmospheric pressure, then it is pure water. If the boiling point is different then the water is contaminated. | ||||||
| Q.6: Which of the following materials fall in the category of a ‘pure substance’? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Brick (h) Wood (i) Air. | ||||||
| Ans: (a), (c), (d), (e) and (f) are pure substances. | ||||||
| Q.7: Which of the following will show “Tyndall effect”? | ||||||
| (a) salt solution (b) milk (c) copper sulphate solution (d) starch solution. Ans: (b) and (d) are colloids and will show Tyndall Effect. | ||||||
| Q.8: Classify the following into elements, compounds and mixtures. (a) sodium (b) soil (c) sugar solution (d) silver (e) calcium carbonate (f) tin (g) silicon (h) coal (i) air (j) soap (k) methane (l) carbon dioxide (m) blood | ||||||
| Ans: Elements - sodium, silver, tin, silicon. Compounds - calcium carbonate, methane, carbon dioxide. Mixtures - soil, sugar solution, coal, air, soap, blood. | ||||||
| Q. 9. In the formation of sodium chloride from its constituent elements, do the properties of its elements change? Explain. | ||||||
| Ans: Sodium is a very reactive metal that reacts exothermically with water. If we were to ingest a pinch of sodium, it would burn our intestines. Chlorine is a greenish yellow gas with a characteristic irritating odour and pungent taste. When sodium and chlorine combine to form sodium chloride, the properties of the elements are totally changed. Sodium chloride is a white substance totally safe to be ingested and is used to add flavour to our food. | ||||||
| Q. 10. Briefly describe how to separate, i) Sulphur from a mixture of sulphur and sand. ii) Black CuO from a mixture of CuO and ZnO. | ||||||
| Answer: i) Add a solvent to the mixture of sulphur and sand. Sulphur dissolves in carbon disulphide while sand does not. When filtered, the residue is sand. The filtrate is kept open, carbon disulphide evaporates and the sulphur crystals form. ii) Add a solvent to the mixture of CuO and ZnO that dissolves only one component e.g. sodium hydroxide. When sodium hydroxide is added to the mixture, ZnO dissolves. Filter to obtain the residue of CuO. | ||||||
|
Thursday, July 7, 2011
IX Is matter around us pure:Related terms and Definitions
Humidity:
The term Humidity is usually taken in daily language to refer to relative humidity. Relative humidity is defined as the amount of water vapor in a sample of air compared to the maximum amount of water vapor the air can hold at any specific temperature. Humidity may also be expressed as Absolute humidity and specific humidity. Relative humidity is an important metric used in forecasting weather. Humidity indicates the likelihood of precipitation, dew, or fog. High humidity makes people feel hotter outside in the summer because it reduces the effectiveness of sweating to cool the body by preventing the evaporation of perspiration from the skin. This effect is calculated in a heat index table. Warm water vapor has more thermal energy than cool water vapor and therefore more of it evaporates into warm air than into cold air.
Mixture:
The term Humidity is usually taken in daily language to refer to relative humidity. Relative humidity is defined as the amount of water vapor in a sample of air compared to the maximum amount of water vapor the air can hold at any specific temperature. Humidity may also be expressed as Absolute humidity and specific humidity. Relative humidity is an important metric used in forecasting weather. Humidity indicates the likelihood of precipitation, dew, or fog. High humidity makes people feel hotter outside in the summer because it reduces the effectiveness of sweating to cool the body by preventing the evaporation of perspiration from the skin. This effect is calculated in a heat index table. Warm water vapor has more thermal energy than cool water vapor and therefore more of it evaporates into warm air than into cold air.
Mixture:
A mixture is a substance made by combining two or more different materials with no chemical reaction occurring. The objects do not bond together in a mixture. A mixture can usually be separated back into its original components. Some examples of mixtures are: fruit salad, ocean water and soil. Mixtures are the product of a mechanical blending or mixing of chemical substances like elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup.
Solution:
a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. A common example is a solid, such as salt or sugar, dissolved in water, a liquid. Gases may dissolve in liquids, for example, carbon dioxide or oxygen in water. Liquids may dissolve in other liquids. Gases can combine with other gases to form mixtures, rather than solutions.
Solvent:
solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. Most other commonly-used solvents are organic (carbon-containing) chemicals. These are called organic solvents. Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, leaving the dissolved substance behind. Solvents should therefore not react chemically with the dissolved compounds — they must be inert. Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water. Solvents are usually clear and colorless liquids and many have a characteristic odor. The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximal amount of compound that is soluble in a certain volume of solvent at a specified temperature.
Homogeneous mixture:
Homogeneous mixtures are mixtures that have definite, consistent composition and properties. Particles are uniformly spread. For example, any amount of a given mixture has the same composition and properties. Examples are solutions and some alloys (but not all). A homogeneous mixture is a uniform mixture consisting of only one phase. Examples are gasoline and margarine.
a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. A common example is a solid, such as salt or sugar, dissolved in water, a liquid. Gases may dissolve in liquids, for example, carbon dioxide or oxygen in water. Liquids may dissolve in other liquids. Gases can combine with other gases to form mixtures, rather than solutions.
Solvent:
solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. Most other commonly-used solvents are organic (carbon-containing) chemicals. These are called organic solvents. Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, leaving the dissolved substance behind. Solvents should therefore not react chemically with the dissolved compounds — they must be inert. Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water. Solvents are usually clear and colorless liquids and many have a characteristic odor. The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximal amount of compound that is soluble in a certain volume of solvent at a specified temperature.
Homogeneous mixture:
Homogeneous mixtures are mixtures that have definite, consistent composition and properties. Particles are uniformly spread. For example, any amount of a given mixture has the same composition and properties. Examples are solutions and some alloys (but not all). A homogeneous mixture is a uniform mixture consisting of only one phase. Examples are gasoline and margarine.
Heterogeneous mixture:
Heterogeneous mixtures are mixtures with inconsistent, non-uniform composition. The parts of a heterogeneous composition can be mechanically separated from each other. Examples include salad, trail mix and granite.
Heterogeneous mixtures are mixtures with inconsistent, non-uniform composition. The parts of a heterogeneous composition can be mechanically separated from each other. Examples include salad, trail mix and granite.
Colloid:
MATER IN OUR SURONDING DEFINATIONS
Matter:
matter is commonly defined as the substance of which physical objects are composed, not counting the contribution of various energy or force-fields, which are not usually considered to be matter per se (though they may contribute to the mass of objects). Matter constitutes much of the observable universe, although again, light is not ordinarily considered matter. Unfortunately, for scientific purposes, "matter" is somewhat loosely defined. It can also be defined as a physical substance that has mass and volume.
Volume:
The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space.
Mass:
Mass is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how much matter there is in an object". Mass is a central concept of classical mechanics and related subjects, and there are several definitions of mass within the framework of relativistic kinematics (see mass in special relativity and mass in General Relativity). In the theory of relativity, the quantity invariant mass, which in concept is close to the classical idea of mass, does not vary between single observers in different reference frames
Diffusion:
In the second sense of diffusion is the spontaneous net movement of particles from an area of high concentration to an area of low concentration through a semi-permeable membrane. For example, diffusing molecules will move randomly between areas of high and low concentration but because there are more molecules in the high concentration region, more molecules will leave the high concentration region than the low concentration one. Therefore, there will be a net movement of molecules from high to low concentration. Initially, a concentration gradient leaves a smooth decrease in concentration from high to low which will form between the two regions. As time progresses, the gradient will grow increasingly shallow until the concentrations are equalized.
Force:
force is what causes a mass to accelerate. It may be experienced as a lift, a push, or a pull. The acceleration of the body is proportional to the vector sum of all forces acting on it (known as net force or resultant force). In an extended body, force may also cause rotation, deformation, or an increase in pressure for the body. Rotational effects are determined by the torques, while deformation and pressure are determined by the stresses that the forces create.
Pressure:
Pressure is the force per unit area applied on a surface in a direction perpendicular to that surface.
Density:
density is mass (m) per unit volume (V) — the ratio of the amount of matter in an object compared to its volume. A small, heavy object, such as a rock or a lump of lead, is denser than a larger object of the same mass, such as a piece of cork or foam.
Kinetic energy: The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. Negative work of the same magnitude would be required to return the body to a state of rest from that velocity.
Speed:
speed is a quantity that measures the ratio of an evolution to time. Example: speed of sedimentation, speed of economic growth, speed of chemical reaction etc.
Melting point:
The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. Although the phrase would suggest a specific temperature and is commonly and incorrectly used as such in most textbooks and literature, most crystalline compounds actually melt over a range of a few degrees or less. At the melting point the solid and liquid phase exist in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point.
Atmospheric pressure:
matter is commonly defined as the substance of which physical objects are composed, not counting the contribution of various energy or force-fields, which are not usually considered to be matter per se (though they may contribute to the mass of objects). Matter constitutes much of the observable universe, although again, light is not ordinarily considered matter. Unfortunately, for scientific purposes, "matter" is somewhat loosely defined. It can also be defined as a physical substance that has mass and volume.
Volume:
The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space.
Mass:
Mass is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how much matter there is in an object". Mass is a central concept of classical mechanics and related subjects, and there are several definitions of mass within the framework of relativistic kinematics (see mass in special relativity and mass in General Relativity). In the theory of relativity, the quantity invariant mass, which in concept is close to the classical idea of mass, does not vary between single observers in different reference frames
Diffusion:
In the second sense of diffusion is the spontaneous net movement of particles from an area of high concentration to an area of low concentration through a semi-permeable membrane. For example, diffusing molecules will move randomly between areas of high and low concentration but because there are more molecules in the high concentration region, more molecules will leave the high concentration region than the low concentration one. Therefore, there will be a net movement of molecules from high to low concentration. Initially, a concentration gradient leaves a smooth decrease in concentration from high to low which will form between the two regions. As time progresses, the gradient will grow increasingly shallow until the concentrations are equalized.
Force:
force is what causes a mass to accelerate. It may be experienced as a lift, a push, or a pull. The acceleration of the body is proportional to the vector sum of all forces acting on it (known as net force or resultant force). In an extended body, force may also cause rotation, deformation, or an increase in pressure for the body. Rotational effects are determined by the torques, while deformation and pressure are determined by the stresses that the forces create.
Pressure:
Pressure is the force per unit area applied on a surface in a direction perpendicular to that surface.
Density:
density is mass (m) per unit volume (V) — the ratio of the amount of matter in an object compared to its volume. A small, heavy object, such as a rock or a lump of lead, is denser than a larger object of the same mass, such as a piece of cork or foam.
Kinetic energy: The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. Negative work of the same magnitude would be required to return the body to a state of rest from that velocity.
Speed:
speed is a quantity that measures the ratio of an evolution to time. Example: speed of sedimentation, speed of economic growth, speed of chemical reaction etc.
Melting point:
The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. Although the phrase would suggest a specific temperature and is commonly and incorrectly used as such in most textbooks and literature, most crystalline compounds actually melt over a range of a few degrees or less. At the melting point the solid and liquid phase exist in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point.
Atmospheric pressure:
Atmospheric pressure is the pressure at any point in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location. Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation. A column of air 1 square inch in cross section, measured from sea level to the top of the atmosphere, would weigh approximately 14.7 lbf. A 1 m² (11 sq ft) column of air would weigh about 100 kilonewtons (equivalent to a mass of 10.2 tonnes at the surface).
Latent heat:
Latent heat:
Latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i.e. solid, liquid, or gas), - also called a phase transition.
Vaporisation:
Vaporisation:
Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously become gaseous (e.g. water vapor). It is the opposite of condensation. Generally, evaporation can be seen by the gradual disappearance of a liquid, when exposed to a significant volume of gas.
elect Categories
elect Categories
Subscribe to:
Posts (Atom)
