General Science Force and Motion

Exercise: 9.2

Q1. What are machines?
Ans: Machines are devices which are used to reduce the human effort and make the work easier.

Q2. Name three objects that you exert force on, while doing school work.
Ans: Pencil, Eraser, Sharpener.

Q3. Name these.
Ans:
1. Straight slanted surface: Inclined plane.         2. A rod that pivots at a fixed point pulley.
3. An inclined plane wrapped in spiral screw. 4. Double inclined plane Wedge.
5. Machine consisting of a grooved wheel that holds a rope wheel and axle.

Q4. Complete the following concept map.

Exercise : 9.4 Explain how atmospheric helps you drink throw a straw?
Ans: When we take a sip through straw, we are actually putting air out of straw, the greater air pressure outside the straw pushes the liquid into the straw, so it rises up into mouth.

Additional Q/A

Q1. What is a lever? How does it work?
Lever:
A lever is a rigid rod or bar straight or curved which moves on a fixed point. The fixed point is called the fulcrum, or the pivot. A push or a pull is the force put on the one end of the lever arm. This is called the effort. This force is trying to overcome the weight of the object. This weight is called the load. In many tools and machines, levers work together in pairs and the fulcrum is often at the point where the levers are fixed together.

Q2. How many kinds of lever are there? Explain them with the help of diagram.
Ans: There are three kinds of lever. We use in our daily life. Each kind depends on the relative positions of the effort, load and fulcrum.

First kind of lever:
The first kind of lever has its fulcrum between the load and effort Example: crow bar, claw hammer, and a pair of scissors are the examples of first kind of lever.

Second kind of lever:
The second kind of lever has its load between the fulcrum and the effort.
Example: wheel barrow, bottle opener and door are the examples of second kind lever.

Third kind of lever:
In the third kind of lever, the effort lies between the load and the fulcrum. Example: Human arm, broom, tweezer, and knife are the examples of third kind of lever.

Q3. Define pulley.
Ans: Pulley:
The pulley helps us to lift heavy things straight up. A pulley is a kind of wheel with groove over which we can put a rope. The groove prevents the rope from slipping out. Craines use pulley system to lift heavy loads.

Q4. Write uses of atmospheric pressure in our daily life.
Ans: 1. Motor car tyres, bicycles tyre and tyres of other wheeled vehicles are kept hard due to air                pressure.
2. The straw used for drinking also work because of air pressure.
3. When dropper is placed in a solution then solution rises up due to air pressure.
4. A syringe also works by air pressure.

Q5. What is a screw?
Ans: A screw is an inclined plane that is wrapped in a spiral. The spiral shape groove is called a thread. A spiral stair case is like a giant screw.

Q6. Define inclined plane.
Ans: Inclined plane or ramp is another kind of simple machine. A ramp is a slope with one end higher than the other. It is used for moving heavy objects up and down.

Fill in the blanks:

1. There are six types of simple machine.
2. The simplest kind of machine is the lever.
3. A wedge has double inclined plane that moves.
4. A wheel on the end of an  axle make a simple machine.
5. The spiral shaped groove is called a thread.
6. A syringe works by air pressure.

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General Science Element, Compound & Mixture

EXERCISE 7.1:

Q1. Define Matter
Ans: Matter is any thing that has mass and occupies space.

Q2. Complete the following concept map.

Q3. How are compound different from elements?
Ans: In elements all the atoms are identical while in compounds basic unit is a molecule. Which is composed of two or more different type of atoms.

EXERCISE 7.2:
1 Ans: No, Hydrogen and oxygen are elements, and elements are the simplest substances.
2 Ans: (a) True    (b) False   (c) True
3.

Elements	Compounds
Sodium+Chlorine	Table salt (NaCl)
Carbon+Oxygen	Carbondioxide (CO2)
Carbon+Hydrogen+Oxygen	Sugar(C12 H22O11)
Sodium+Hydrogent Oxygen+Carbon	Baking Soda (NaHCO3)

4. A mixture possesses the properties of the substances which make up the mixture, For example air is a mixture of many gases such as oxygen, nitrogen, carbondioxide and others, We can change the amount of things in the mixture for example in mixed fruits and nuts we can put more fruits and less nuts.
EXERCISE 7.3:
1.Name these
(a) Element  (b)Mixture   (c) Sublimation  (d) Distillation
2. (a) Crystallization       (b) Sublimation     (c) Distillation  (d)  Decantation   (e) Filtration
(f) Decantation

Additional Questions/Answer

Q1. What is an element?
Ans: Element: An element is a substance, which can not be broken down into two or more parts. Elements are made up of atoms. Carbon, Nitrogen, Sulphur and Iron are some examples of elements.

Q2. What is compound?
Ans: Compound: Compound is a substance that is formed when the atoms of two or more elements combine chemically. A compound contains different kinds of atoms.
For example: A molecule of water (H2O) is made when two hydrogen atoms are combined with one oxygen atom
Hydrogen (Gas)+Oxygen (Gas) à Water (liquid)

Q3. Define mixture.
Ans: Mixture: Mixture is a substance which is made up of two or more substances which are not combined chemically. The substances in a mixture can be solids, Liquids and gases. Example: Air is a mixture of oxygen, nitrogen, carbondioxide and other gases.

Q4. Differentiate between mixture and compound.

Mixture	Compound
1.        Mixture is made up of two or more substances that are not chemically combined, for example air.	Compounds are made up of two or more elements that are chemically combined, for example water.
2.        A mixture possesses the properties of its components.	A compound has properties that are different from its components.
3.        A mixture can be separated into its components by physical methods.	A compound can be broken down into its components by chemical methods only.
4. Components of a mixture are not mixed in a fixed quantity.	Components of a compound are mixed in a fixed quantity.

Q5. How many physical methods are used for separating mixture?
Ans: Some common physical methods for separating mixtures are.
a) Decantation   2) Distillation   3) Crystallization   4) Sublimation
Decantation:
It is a process of removing a liquid from a mixture by pouring it, while leaving the remaining constituents in the container. For example when we cook rice, we simply let the water in the rice decantdown, leaving rice behind.

Distillation:
It is a process of purifying a liquid. When we boil sea water, it turns into steam leaving behind the solid constituents. We can get drinking water from sea water by this method. It is called distilled water.
Crystallization:
The process of cooling a hot saturated solution to obtain solid crystals is called crystallization.
Sublimation:
Some substance undergo a change of state from solid to gas or gas to solid. The conversion of a solid to gas (or vapours) without passing through a liquid phase is called sublimation.
E.g: Phenyl balls sublimate in open air resolve boldness.

Q6. Fill in the blanks.
1). The common states of matter are solid, liquid and gas.
2). Matter is composed of simplest building blocks called atoms.
3). Hydrogen is the simplest element.
4) The most abundant element on the earth is oxygen.
5) The smallest particle of a compound is called molecule.
6) Mercury is a metallic element, which occurs in nature in liquid form.

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