Science: Acids & Alkalis

Question 1

what are natural indicators

Answer 1

some substances in nature that show different colors when they come in contact with acidic or alkaline solutions

Question 2

give 3 examples of natural indicators

Answer 2

hibiscus pedal
grape skin
red cabbage leaf

Question 3

how do natural indicators identify between acids and alkalis

Answer 3

extract of natural indicators have pigments. the pigments react to acidic or alkaline solutions.

Question 4

how does hydrangea react to acids and alkalis

Answer 4

when grown in acidic soil: flower is blue

when grown in alkaline soil: flower is pink

Question 5

what are the effects of red litmus under - water, acid and alkalis

Answer 5

distilled water; turns red
acid: turns red
alkalis: turns blue

Question 6

what are the effects of blue litmus under - water, acid and alkalis

Answer 6

distilled water; no change
acid: turns red
alkalis: no change

Question 7

what are the limitations of litmus papers

Answer 7

cannot test how alkali or how acidic a solution is

Question 7

what is the purpose of the universal indicator

Answer 7

to measure the pH of substances

Question 7

how do we use the universal indicator

Answer 7

1) add a few drops of the universal indicator to a substance

2) match the color developed to the pH color chart

Question 8

what are the purposes of the pH values

Answer 8

to indicate the relative acidity or alkalinity

Question 8

what is the pH range ( 0 - ? )

Answer 8

0 - 12

Question 8

which one is acid and which one is alkali:

1) pH 0
2) pH 12

Answer 8

pH 0: acidic
pH 12: alkali

Question 9

what is the neutral pH value

Answer 9

pH 7

Question 10

give 4 household products that are acidic

Answer 10

orange juice
lemon juice
coffee
milk

Question 11

give 5 household items that are alkali

Answer 11

egg white
baking soda solution
bleach
oven cleaner
drain cleaner

Question 11

what is a pH meter

Answer 11

an electronic instrument used to measure the pH of solutions

Question 12

what is a data logger

Answer 12

a data logger is connected to a pH sensor. it measures the pH of a solution and can even record the change in pH over a period of time

Question 12

how do we use the pH meter

Answer 12

after calibration,

put the probe of the meter into a solution. the pH of the solution will be displayed on the screen of the pH meter

Question 13

name all advantages of pH meter

Answer 13

more precise

more accurate

can measure pH pf solutions of all colors

Question 13

name all advantages of universal indicator

Answer 13

less solution needed

convenient ( no calibration needed )

Question 14

name all disadvantages of universal indicator

Answer 14

cannot measure pH of dark solutions

less precise

less accurate

Question 15

name all disadvantages of pH meter

Answer 15

calibration needed

more solution needed

Question 15

why do gardeners use a soil pH meter to measure the soil pH

Answer 15

they can adjust the soil pH using certain chemicals if the pH is not suitable for their plants

Question 15

how accurate is a pH meter

Answer 15

it is accurate to 1 or 2 decimal places

Question 16

why shouldn't we come into contact with some acidic or alkaline substances

Answer 16

because they are irritant or even corrosive, they can burn our skin and eyes

Question 17

what neutralizes excess acid in the stomach

Answer 17

antacid

Question 18

what is the ratio of acid and alkaline neutralization ( volume )

Answer 18

1:1

Question 19

what does the residue of the heated neutralized solution look like

Answer 19

small white solids, they look like tablesalt

Question 20

what has evaporated among the residue of the heated neutralized solution

Answer 20

water

Question 20

what is the solution for the reaction of table salt

Answer 20

sodium hydroxide + hydrochloric acid = sodium choloride + water

Question 20

how does tooth decay happen?

Answer 20

the bacteria in our mouths turn the sugars in food into acids which damages the surface of our teeth. thus, causing tooth decay.

Question 21

in neutralization, will the product be heavier than the reactants? how so?

Answer 21

although new **substances** will be formed, the **mass** is still **conserved** conserved: remains the same ( keyword )

Question 22

how does stomach ache happen

Answer 22

our stomachs create acids to digest food. however, too much acid may irritate the stomach wall and cause a stomach ache

Question 22

how does toothpaste help with tooth decay

Answer 22

toothpaste is alkaline. it neutralizes the acids thereby helping tooth decay.

Question 23

what helps with stomach aches? how so?

Answer 23

antacid. it is alkaline, it neutralizes the acids in the stomach, thereby relieving pain.

Question 23

what help to regulate soil pH for agriculture? how so?

Answer 23

lime. it is alkaline. crops don't grow well in acidic soil. therefore, farmers usually add lime to acidic soil, neutralizing the acids.

Question 24

what treats wasp stings? how so?

Answer 24

vinegar. **wasp stings are alkaline** while vinegar is acidic, it neutralizes the sting.

Question 24

what treats ant and bee stings? how so?

Answer 24

baking soda. this is because **ant and bee stings are acidic** and baking soda is alkaline. it neutralizes the acids

Question 24

how do we treat chemical waste before discharging it into the ocean?

Answer 24

chemical waste may contain acids or alkalis. it will **harm aquatic life** if directly discharged. to reduce pollution we can **neutralize** the waste before discharging

Question 25

what is the reaction of zinc in acids

Answer 25

1) gas bubbles given off 2) test for hydrogen: burns with a pop sound 3) hydrogen is produced 4) becomes smaller in size

Question 26

what is the reaction of magnesium in acids

Answer 26

1) gas bubbles given off 2) test for hydrogen: burns with a pop sound 3) hydrogen is produced 4) becomes smaller in size

Question 27

what is the reaction of iron in acids

Answer 27

1) gas bubbles given off 2) test for hydrogen: burns with a pop sound 3) hydrogen is produced 4) becomes smaller in size

Question 28

what is the reaction of copper in acids

Answer 28

1) gas bubbles are not given off 2) test for hydrogen: no sound produced 3) hydrogen is not produced 4) no change in size

Question 29

how do you test the reactions of metal with acids ( give experiment steps )

Answer 29

1) fill test tube with **1/5** dilute hydrochloric acid 2) rub metal with sandpaper to rid **dirt and oxide** 3) cover the mouth of the test tube loosely with an inverted stopper

Question 30

how do we draw conclusions from the reactions of metals with acids experiment

Answer 30

1) observe if bubbles are given off 2) slight movements mean that gas is produced 9 ( remove the stopper **immediately** and put a glowing splint near the mouth to test for **hydrogen**

Question 31

what happens to the metals when they **corrode**

Answer 31

the metals decrease in size

Question 32

what is the **equation** of reactions between acids and metals

Answer 32

metal + acid = hydrogen + salt