25 T2 L12 Application of expansion and contraction.

Predict what will happen to the dented table tennis ball in the hot water. Give a reason for your answer.

Voorspel wat gaan gebeur met die ingeduikte tafeltennisbal in die warm water. Gee 'n rede vir jou antwoord.

Answer explanation

The dented ball will regain its shape because the heat of the water will make the gas inside the ball expand and push out the sides of the ball. The water will need to be hot enough.

Die ingeduikte bal sal sy vorm herwin, want die hitte van die water sal die gas binne-in die bal laat uitsit en die kante van die bal uitstoot. Die water sal warm genoeg moet wees.

Give the three example appliances where expansion and contraction are used. ​

Gee die drie voorbeeldtoestelle waar uitsetting en inkrimping gebruik word.

(a)   ​ (b)   ​ (c)  

• thermometer |  termometer
• steam iron |  stoom strykyster
• fire alarm  |  brandalarm
• table tennis ball |  tafeltennisbal
• kettle | ketel

Thermometers are a closed system. Is the liquid always mercury? If no, what other liquid is used? What precaution needs to be taken with mercury?

Termometers is 'n geslote stelsel. Is die vloeistof altyd kwik? Indien nee, watter ander vloeistof word gebruik? Watter voorsorgmaatreëls moet met kwik getref word?

Answer explanation

Mercury is NOT the only liquid.

Alcohol is often used.

If the termometer breaks do not handle the mercury with bare hands.

Kwik is NIE die enigste vloeistof nie.

Dikwels word alkohol gebruik.

As die termometer breek moenie die kwik met kaal hande hanteer nie.

The two metals used in the fire alarm are: ​

Die twee metale wat in die brandalarm gebruik word, is:

​ (a)   ​ (b)  

The fire alarm works with:

Die brandalarm werk met:

​ (c)   ​ (d)   ​

• bronze | brons
• iron | yster
• copper | coper
• steel | staal
• heat | hitte
• cooling | afkoeling
• expansion | uitbreiding
• cooling | afkoeling
• contraction | sametrekking

If there were no gaps in railway tracks, they would be damaged by...

As daar geen gapings in spoorlyne was nie, sou dit beskadig word deur...

• high temperatures and expansion.

  hoë temperature en uitsetting.

• low temperature and contraction.

  lae temperatuur en sametrekking.

• low temperature and expansion.

  lae temperatuur en uitsetting.

• high temperature and contraction.

  hoë temperatuur en sametrekking.

Predict why electricity cables hang loosely between poles.

Voorspel hoekom elektrisiteitskabels los tussen pale hang.

Answer explanation

They hang loosely so that in cold weather they do not snap due to contraction.

Hulle hang los sodat hulle in koue weer nie breek as gevolg van sametrekking nie.