FORENSIC SCIENCE Testing substances

Solubility of a compound

Test your knowledge

Testing pH pH measures how acid or alkaline a solution is This can be measured using an indicator Universal indicator (solution or paper) gives a range of colours that can indicate an exact pH Litmus paper is an indicator that turns red in the presence of acids, and blue in the presence of alkalis

‘Official’ flame test results

Testing for metal ions

In ionic bonding… …there are strong forces of attraction between oppositely charged ions, so ionic compounds have high melting and boiling temperatures In covalent bonding… …there are weak intermolecular forces of attraction so covalent compounds have low melting and boiling temperatures Properties of compounds s____ o______ i___ w___ i__________ h__ l__ a______ Covalent compounds share electrons Ionic compounds are positively and negatively charged

1.What colour precipitate would you see if you added sodium hydroxide to the following…? Lead (Pb 2+ ) Calcium (Ca 2+) Copper (Cu 2+ ) Iron II (Fe 2+ ) Iron III (Fe 3+ ) 3. What would you use to measure pH (acidity?) 4. Which has the highest melting temperature, ionic or covalent compounds? 5. How could we test how soluble something is? Quick Quiz 2. What colour is the flame test for… Lithium (Li+) Sodium (Na+) Potassium (K+) Barium (Ba2+) Calcium (Ca2+) Copper (Cu2+)

1.What colour precipitate would you see if you added sodium hydroxide to the following…? Lead (Pb 2+ ) WHITE Calcium (Ca 2+ ) WHITE Copper (Cu 2+ ) BLUE Iron II (Fe 2+ ) GREEN Iron III (Fe 3+ ) RED-BROWN 3. What would you use to measure pH (acidity?) LITMUS PAPER OR UNIVERSAL INDICATOR 4. Which has the highest melting temperature, ionic or covalent compounds? IONIC 5. How could we test how soluble something is? SEE HOW MUCH DISSOLVES IN WATER (OR ANOTHER SOLVENT) Quick Quiz 2. What colour is the flame test for… Lithium (Li+) RED Sodium (Na+) YELLOW-ORANGE Potassium (K+) LILAC Barium (Ba2+) APPLE GREEN Calcium (Ca2+) BRICK RED Copper (Cu2+) GREEN-BLUE