Chemical Reactions

Question 1

What evidence is observed when a chemical reaction has taken place?

Answer 1

Temperature Colour Shape Size Odour

Question 2

Difference between products and reactants

Answer 2

Product-produced substance Reactants- reacting substance Example: sodium hydroxide+hydrochloric acid —> water+sodium chloride (NaOH+HCL—>H2O+NaCL) REACTANTS on the LEFT PRODUCTS on the RIGHT

Question 3

Chemical reaction definition

Answer 3

Two or more substances react to produce a new chemical substance

Question 4

Difference between a spontaneous and non spontaneous chemical reaction?

Answer 4

Spontaneous- they begin immediately after the two reactants are brought together. Eg) vinegar and baking soda Non spontaneous- they require a kick start in the form of energy, usually heat or light. Eg) magnesium and oxygen

Question 5

Difference between a chemical change and a physical change

Answer 5

Chemical change- (chemical reaction) one or more new substances are produced The bonds between atoms are broken and new bonds are formed eg) burning paper, baking cake Physical change- produced no new substances there is merely a change of state, shape or size No bonds between atoms are broken Eg) melting ice, boiling water, blowing up a balloon, stretching rubber band

Question 6

States of matter

Answer 6

S-solid (fixed shape and volume, strongly bonded, can’t be compressed) L-liquid (takes containers shape, weakly bonded, can’t be compressed) G-gas (no fixed shape, fills the container, easily compressed) Aq- aqueous solution (when a solute(solid particle)is dissolved in water)

Question 7

Word equation and chemical equation for photosynthesis

Answer 7

Photosynthesis is a exothermic reaction Word equation- carbon dioxide+water—>glucose+oxygen Chemical equation- 6CO2(g)+6H2O(l)—>C6H12O6(aq)+6O2(g)

Question 8

Word equation and chemical equation for respiration

Answer 8

Respiration is a exothermic reaction Word equation- glucose+oxygen—>water+energy Chemical equation- C6H12O6(aq)+6O2(g)—>6CO2(g)+6H2O(l)

Question 9

Law of conservation of mass

Answer 9

Matter cannot be created or destroyed, it is simply transfer from one form to another There are no atoms gained or lost, they are just rearranged Total mass of reactants= total mass of products

Question 10

Definition of acids

Answer 10

Acids- corrosive substances Sour taste pH of 0-7 (less than 7) Donate hydrogen ions (H+) (protons) Example of acids- hydrochloric acid, vinegar, lemons, soda, coffee, milk

Question 11

Definition of bases

Answer 11

Bitter taste Slippery or soapy Alkalis pH of 7-14 (more than 7) Accept hydrogen ions (H+) (protons) Examples of bases- dishwashing liquid, oven spray, cloudy ammonia, caustic soda, bicarbonate of soda, toothpaste

Question 12

Common acids sheet

Answer 12

Ascorbic acid- vitamin C Lactic acid- causes muscle soreness Hydrochloric acid- stomach acid Sulphuric acid- common lab, found in car batteries Acetic acid- vinegar Formic acid- ant stings Citric acids- citrus fruits

Question 13

Alkaline solution

Answer 13

Alkaline solution is a substance that is basic, and can be dissolved in water

Question 14

Indicator colour changes for bases

Answer 14

Bases litmus paper=blue Phenolphthalein= pink Methyl orange= orange/yellow

Question 15

Indicator colour changes for acids

Answer 15

Acids Litmus paper=red Phenolphthalein= colourless Methyl orange= red

Question 16

Indicator definition and examples

Answer 16

An indicator is a substance which tells us whether a acid or base is present on the basis of colour change. Examples of indicators- red cabbage indicator, natural indicators include: blue litmus paper, red litmus paper, universal indicator. synthetic indicators include: phenolphthalein, methyl orange

Question 17

Neutralisation definition

Answer 17

Acids and bases react quantitatively with each other. Getting the solution to the pH of 7 (neutral) Acid and base react to produce salt and water Acid+base(reactants)—> salt+water(products) Sodium hydroxide+Hydrochloric acid—>sodium chloride+water

Question 18

Neutralisation word equation formulas

Answer 18

Examples 1. SODIUM hydroxide+HydroCHLORIC acid—>SODIUM CHLORIDE+water 2. SODIUM hydroxide+NITRIC acid—>SODIUM NITRATE+water 3.SODIUM hydroxide+SULPHURIC acid—> SODIUM SULPHATE+water Rule: first word of the first reactant plus first word of the second reactant=first word+first word+water

Question 19

What is pH measuring, understand pH scale

Answer 19

To know how acidic or basic a substance is by using numbers or the pH scale 0-14 0-3 strong acidic 4-6 weak acidic 7 neutral 8-11 weak basic 11-14 strong basic

Question 20

Universal indicator

Answer 20

It can determine not just whether something is an acid or base but also acidic and how basic the substance is. Universal indicator changes colour at pH’s ranging from 0-14

Question 21

Red cabbage indicator

Answer 21

pH scale ranges from 0-12 0-2 red 2-4 purple/pink 4-6 violet 7 blue 8-10 blue/green 10-12 green/yellow

Question 22

EXOthermic reactions

Answer 22

Give off heat Feel warm Stored as energy then released as heat Less energy stored Chemical energy—> heat energy Eg) sunlight, condensation, making ice cubes, candle flame

Question 23

ENDOthermic reaction

Answer 23

Take in heat Feel cool Small amount of heat stored Absorbs energy More energy stored Heat energy—> chemical energy Eg) cooking an egg, evaporation, melting ice cubes

Question 24

Redox reactions

Answer 24

Oxidation reaction and reduction reaction, involve a transfer of electrons Burning fuels is a type of redox reaction called combustion

Question 25

Difference between Complete and incomplete combustion

Answer 25

Complete combustion- carbon DIOXIDE is produced Incomplete combustion- carbon MONOXIDE OR CARBON is produced Fuel+oxygen—> water+carbon dioxide (complete) Fuel+oxygen—> water+carbon monoxide (incomplete) Fuel+oxygen—> water+carbon (soot) (incomplete)

Question 26

Combustion

Answer 26

Involve 2 reactants Involve a fuel and a oxygen Produce water and another product Either carbon dioxide, carbon monoxide or just carbon