Q1- What happens when surface of material is rubbed with sand paper?
Q2 Which solid sample substances are insoluble in water?
A. Sugar
B. Chalk powder
C. Salt
D. Sand
E. Iron
Q3 - Can we look through the oil spread paper towards the lighted bulb ? If not Why?
Q4 On what basis the object are grouped or sorted? Name two.
Q5 Why the appearance of some metals is dull before rubbing them?
Q1- What impurities are present when you buy rice , wheat and pulses from the market?
Q2 - When do you use Handpicking as a method of separation of mixture ?
Q3 - Mention different process involved in obtaining pure salt from sea water.
Q4 - Draw the flowchart describing separation of the components of a mixture containing mixture of sand and common salt .
Q.1 - Why does ring of iron blade heated before fixing it into handle of a tool ?
Q2 On lighting the candle its length decreases . How can this be reversed ?
Q3 What changes occur in a matchstick used for lighting ? What type of change is it ?
Answers
Answer:
(1)We all know that the sand paper has a rough surface which is due to the embedded sand particles. These particles when observed under microscope have sharp and irregular surface. So when we scrape the metal sheet with these papers they create scratches on the surface of the metal sheet.
(2) Sand
Substances that do not dissolve in water are called insoluble. Sand and flour are examples of insoluble substances.
(3) ______
(4) Grouping of things with similar properties is called classification. We can classify different things based on whether they are living or non living, metals or non-metals. It is also possible to classify objects based on their size, solubility in water etc.
(5) Some metals like iron, copper ,aluminium often lose their shine and appear dull due to the action of air and moisture on their surface. We should look for lustre only on the freshly cut surface of such metals or after rubbing their surface with a sand paper.
(1) Impurities present in rice are small stone and husk , in wheat soil particles and in pulses stone particles, colouring materials and inf erior quality other pulses are mixed.
(2) In order to use any substance we need to separate harmful or non-useful substances that may be present in a mixture. For example: (1) We used to separate slightly larger sized impurities like the pieces of dirt, stone, and husk from wheat, rice or pulses by handpicking method.
(3) You can boil or evaporate the water and the salt will be left behind as a solid. If you want to collect the water, you can use distillation. This works because salt has a much higher boiling point than water. One way to separate salt and water at home is to boil the salt water in a pot with a lid.
(4) ________
(1) Ring of iron blade heated before fixing it into handle of a tool because on heating ring becomes slightly larger in size, therefore it expand and handle fits easily into it.
(2) On lightening the candle its length decreases. How can this be reversed? Ans: If we take some wax in a pan and heat it, this change can be reversed.
(3) Breaking a match in two pieces is an example of a physical change. Lighting a match and letting is burn is an example of a chemical change. Chemical reactions cause chemical changes. In a chemical reaction two or more substances, called the reactants, form different substances called products.
Explanation:
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