CHAPTER3 Metals and Non-metals - NCERT

1 Metals and Non-metals3 CHAPTERIn Class IX you have learnt about various elements. You have seenthat elements can be classified as Metals or non- Metals on the basis oftheir of some uses of Metals and non- Metals in your daily properties did you think of while categorising elementsas Metals or non- Metals ?nHow are these properties related to the uses of these elements?Let us look at some of these properties in PHYSICAL PROPERTIESAL PROPERTIESAL PROPERTIESAL PROPERTIESAL MetalsThe easiest way to start grouping substances is by comparing theirphysical properties. Let us study this with the help of the followingactivities.

2 For performing Activities to , collect the samples offollowing Metals iron, copper, aluminium, magnesium, sodium, lead, zinc and any other metal that is easily samples of iron, copper, aluminium and magnesium. Notethe appearance of each the surface of each sample by rubbing them with sand paperand note their appearance , in their pure state, have a shining surface. This property iscalled metallic small pieces of iron, copper, aluminium, and to cut these Metals with a sharp knife and note a piece of sodium metal with a pair of : Always handle sodium metal with care.

3 Dry it bypressing between the folds of a filter it on a watch-glass and try to cut it with a do you observe?2022-23 Science38 You will find that some Metals can be beaten into thin sheets. Thisproperty is called malleability. Did you know that gold and silver are themost malleable Metals ?Activity pieces of iron, zinc , lead and any one metal on a block of iron and strike it four or fivetimes with a hammer. What do you observe?nRepeat with other the change in the shape of these will find that Metals are generally hard. The hardness variesfrom metal to the Metals whose wires you have seen in daily ability of Metals to be drawn into thin wires is called is the most ductile metal .

4 You will be surprised to know that a wireof about 2 km length can be drawn from one gram of is because of their malleability and ductility that Metals can begiven different shapes according to our you name some Metals that are used for making cooking vessels?Do you know why these Metals are used for making vessels? Let us dothe following Activity to find out the an aluminium or copperwire. Clamp this wire on astand, as shown in Fig. a pin to the free end of thewire using the wire with a spirit lamp,candle or a burner near theplace where it is do you observe after sometime?

5 NNote your observations. Doesthe metal wire melt?The above activity shows that Metals are good conductors of heatand have high melting points. The best conductors of heat are silver andcopper. Lead and mercury are comparatively poor conductors of Metals also conduct electricity? Let us find are goodconductors of and Non-metals39 You must have seen that the wires that carry currentin your homes have a coating of polyvinylchloride (PVC)or a rubber-like material. Why are electric wires coatedwith such substances?What happens when Metals strike a hard surface? Do they producea sound?

6 The Metals that produce a sound on striking a hard surfaceare said to be sonorous. Can you now say why school bells are made ofmetals? Non-metalsIn the previous Class you have learnt that there are very few non-metalsas compared to Metals . Some of the examples of non- Metals are carbon,sulphur, iodine, oxygen, hydrogen, etc. The non- Metals are either solidsor gases except bromine which is a non- Metals also have physical properties similar to that of Metals ?Let us find up an electric circuit as shown in Fig. the metal to be tested in the circuitbetween terminals A and B as the bulb glow?

7 What does this indicate?Figure are goodconductors of samples of carbon (coal or graphite), sulphur and out the Activities to and with these non-metalsand record your your observations regarding Metals and non- Metals in Table ofHardnessMalleabilityDuctilityConductsS onoritysurfaceElectricityOn the bases of the observations recorded in Table , discuss thegeneral physical properties of Metals and non- Metals in the class. Youmust have concluded that we cannot group elements according to theirphysical properties alone, as there are many exceptions.

8 For example (i)All Metals except mercury exist as solids at room Activity , you have observed that Metals have high melting2022-23 Science40points but gallium and caesium have very low melting two Metals will melt if you keep them on your palm.(ii)Iodine is a non- metal but it is lustrous.(iii)Carbon is a non- metal that can exist in different forms. Eachform is called an allotrope. Diamond, an allotrope of carbon, isthe hardest natural substance known and has a very high meltingand boiling point. Graphite, another allotrope of carbon, is aconductor of electricity.(iv)Alkali Metals (lithium, sodium, potassium) are so soft that theycan be cut with a knife.

9 They have low densities and low can be more clearly classified as Metals and non-metalson the basis of their chemical a magnesium ribbon and some sulphur the magnesium ribbon. Collect the ashes formed and dissolvethem in the resultant solution with both red and blue litmus the product formed on burning magnesium acidic or basic?nNow burn sulphur powder. Place a test tube over the burningsulphur to collect the fumes some water to the above test tube and this solution with blue and red litmus the product formed on burning sulphur acidic or basic?

10 NCan you write equations for these reactions?QUESTIONS? an example of a metal which(i)is a liquid at room temperature.(ii)can be easily cut with a knife.(iii)is the best conductor of heat.(iv)is a poor conductor of the meanings of malleable and CHEMICAL PROPERTIES OF metal PROPERTIES OF metal PROPERTIES OF metal PROPERTIES OF metal PROPERTIES OF METALSALSALSALSALSWe will learn about the chemical properties of Metals in the followingSections to For this, collect the samples of following Metals aluminium, copper, iron, lead, magnesium, zinc and sodium.