Physics, Chemistry and Biology: Post your doubts here!

[Awesome12]

hi
if in chemistry we r being asked to test for pure water , so here do they mean physical or chemical test

Its really easy. Just tell the melting point and boiling point of water. If the thermometer shows a reading of 0 and 100 degrees celcius respectively, it is pure, otherwise it is impure, as impurities cause the melting point to decrease and boiling point to increase

 

[princess sofia]

Its really easy. Just tell the melting point and boiling point of water. If the thermometer shows a reading of 0 and 100 degrees celcius respectively, it is pure, otherwise it is impure, as impurities cause the melting point to decrease and boiling point to increase

bt hw do we knw if they r askng chemical or physical propeties

 

[Lola_sweet]

bt hw do we knw if they r askng chemical or physical propeties

If they ask specifically for a chemical test then only answer with the chemical test. But if they ask just a test for water, give either physical or chemical!

 

[princess sofia]

If they ask specifically for a chemical test then only answer with the chemical test. But if they ask just a test for water, give either physical or chemical!

k thnx

 

[Allah's Slave]

Does anybody have the topics for igcse English second lang. May/June 2014 speaking test?

 

[Rio...]

Thanks!

 

[exploded diper]

how to draw the best fit lines for graphs ......

 

[Rio...]

how to draw the best fit lines for graphs ......

with pencil!!!

 

[Rio...]

how to draw the best fit lines for graphs ......

chose the points and the line should be passing through most of the points

 

[exploded diper]

with pencil!!!

oh thank god u said that....i was gonna use a glitter pen......

 

[Rio...]

oh thank god u just that....i was gonna use a glitter pen......

HHAHAHA lol

 

[Lola_sweet]

what is a time-delay circuit? can someone please explain.

 

[exploded diper]

chose the points and the line should be passing through most of the points

but does it have to be like this that the points missed on top n bottom of the line are equal in number

 

[Rio...]

but does it have to be like this that the points missed on top n bottom of the line are equal in number

No the points missed should be equal on the left and right of the line

 

[Rio...]

what is a time-delay circuit? can someone please explain.

Time delay circuits
As it takes a finite time for a capacitor to charge or discharge, they can be used in time delay circuits. A circuit such as shown below can be used as a prt of burglar alarm or temperature sensor.

 

[Rio...]

but does it have to be like this that the points missed on top n bottom of the line are equal in number

Lines of best fit
The 'line of best fit' is a line that goes roughly through the middle of all the scatter points on a graph. The closer the points are to the line of best fit the stronger we can say the correlation is.

Look at the diagrams below:

The line of best fit is drawn so that the points are evenly distributed on either side of the line. There are various methods for drawing this 'precisely', but you will only be expected to draw the line 'by eye'.

You may be asked to comment on the nature of the correlation. This means you will be expected to say whether there is positive, negative or no correlation. Using terms such as 'strong', 'moderate' or 'weak' will give a clearer indication of the strength of the connection.

When drawing the line of best fit, use a transparent ruler so you can see how the line fits between all the points before you draw

 

[exploded diper]

Lines of best fit
The 'line of best fit' is a line that goes roughly through the middle of all the scatter points on a graph. The closer the points are to the line of best fit the stronger we can say the correlation is.

Look at the diagrams below:

The line of best fit is drawn so that the points are evenly distributed on either side of the line. There are various methods for drawing this 'precisely', but you will only be expected to draw the line 'by eye'.

You may be asked to comment on the nature of the correlation. This means you will be expected to say whether there is positive, negative or no correlation. Using terms such as 'strong', 'moderate' or 'weak' will give a clearer indication of the strength of the connection.

When drawing the line of best fit, use a transparent ruler so you can see how the line fits between all the points before you draw

thx bro

 

[Lola_sweet]

Time delay circuits
As it takes a finite time for a capacitor to charge or discharge, they can be used in time delay circuits. A circuit such as shown below can be used as a prt of burglar alarm or temperature sensor.

thnk u for this! but wht happens once the capacitor starts to discharge.

 

[Awesome12]

thnk u for this! but wht happens once the capacitor starts to discharge.

The amount of current flowing in the circuit increases and the voltage in the circuit decreases

 

[exploded diper]

The amount of current flowing in the circuit increases and the voltage in the circuit decreases

can u explain thoroughly how this circuit works