Purity and Formulations

What a pure substance?

something that only contains 1 type of compound or element e.g water, sodium chloride

Why is it important if a substance is pure or impure?

• only pure substances melt and boil at specifc temperatures

• impure substances melt and boil over a range of temps

What will happen if you have impurities in a sample?

• lower melting point

• increased boiling point

What are formualtions?

• mixtures that have been prepared using a specific formula

• so there are precise amounts of diff components

• have a particular function

What are the uses of formulations?

• fuels

• cleaning agents

• paint

• medicine

• alloys

• fertilisers

• food and drink

What is chromotography used for?

to seperate different substances in a mixture so we can seperate them

What is paper chromotogrpahy used for?

to seperate different dyes in an ink

What are the steps to paper chromotography?

1. use a pencil to draw a line near the bottom of the filter paper called the baseline

2. add a spot of ink onto the pencil line

3. fill a shallow amount of solvent in a beaker e.g water#

4. place filter paper into solvent but make sure the pencil line and spot of ink doesn’t get submerged

5. place a lid to stop solvent from evaporating

6. wait for solvent to seep up the paper

7. the dyes that make up the ink are dissolved and move up with the solvent

8. once the solvent reached the top, take it out and leave the paper to dry

What are the patterns that are seen during paper chromotography?

• each dye will travel up paper at different rates and end up seperating out

• which tells us each substance is different

• if any chemicals aren’t soluble, they won’t dissolve and stay on the baseline

What is the mobile phase?

substances that the moleucles can move in e.g solvent

What is the stationary phase?

molecules that can’t move e.g paper

What is the equation for the Rf value?

substance distance/ solvent distance

What is the positive test of chlorine?

• damp litmus paper in test tube

• bleached litmus paper

What is the positive test of oxygen?

• glowing splint into test tube

• splint relights

What is the positive test of hydrogen?

• burning splint into test tube

• squeaky pop

What is the positive test of carbon dioxide?

• bubble limewater

• limewater goes cloudy