The Material World

NAME: ______H.R: ______DATE: ______

SCI & TECH 204

The Material World SECTION 1:The Properties of Matter

NOTE-TAKING WORKSHEET

Acids and Bases (p. 183-189)

Acids and Bases: We Can’t Live Without Them (p. 183)

• Sourness (or tartness) is a property of acidic substances
• Baking powder is an example of a basic substance
• Your body produces strong acids and bases
• Your stomach secretes hydrochloric acid which helps break down dissolved food
• As food exits the stomach, they mix with strong bases secreted by the pancreas
• Bicarbonates neutralise the effects of an acid when the food is in the small intestine
• The venom produced by some insects is another example of an acidic substance
• Bites and stings are acidic and can be treated using baking soda and water
• Since baking soda is basic it neutralises the acidity of the venom
• List 2 acidic and 2 basic substances and their uses:

Measuring Acidity and Alkalinity (p. 185)

• The pH of a substance indicates whether it is very acidic or mildly acidic, very basic or somewhat basic
• The pH of rainwater is 5.6
• An indicator can be used to measure the acidity or alkalinity of a substance
• An indicator is a substance that changes colour in the presence of an acid or base
• Some flowers are natural indicators, for example hydrangea.
• List 4 other substances that change color in the presence of an acidic or basic substance.

1. lichens

2. red cabbage juice

3. tea

4. grape juice

______

Litmus Paper: A Useful Indicator (p. 186)

• Litmus paper comes in 2 colors: red and blue
• When you soak both papers in a substance one type of paper will change color
• If neither types of litmus paper change color the substance is neutral

Fill in the table below

pH: An Accurate Measurement Scale (p. 186)

• To get a more accurate pH reading we use the pH scale
• pH scale ranges from 0 to 14
• Acidicsubstances have a pHbelow 7.
• Basic substances have a pHabove 7.
• Substances with a pH of 7 are said to be neutral
• Fill in the following table

Different Degrees of Acidity (p. 187)

• Every increment on the pH scale is a factor of 10
• This means that a lemon is 10 times more acidic than an apple

Universal Indicator Paper (p. 188)

• Universal indicator paper is more practical and accurate than litmus paper
• Each degree of acidity or alkalinity has its own colour
• Universal indicator provides the specific pH of a substance

The pH Meter (p. 188)

• The pH meter is an electronic instrument that provides the pH of a substance
• It uses the conductivity of liquid substances to read the pH
• The more acidic or basic the substance, the better it conducts electrical current

Do Memory check questions #8 & 11 (p. 189) in the space below.

8.a) pH scale

9.a) An indicator is a substances that changes colour in the presence of an acid or a base.

b) Universal indicator paper is more accurate than litmus paper because, litmus paper can only tell you whether a substance is acidic, basic or neutral while universal indicator paper can tell you the specific pH of a substance.

10 a) She can conclude that the unknown solution is not basic, but that it could be either acidic or neutral.

b) She could test the solution with blue litmus paper. If it turns red, the solution is basic. If it does not change colour, the solution is neutral.

11.a) Cheese is more acidic because its pH is lower than that of sea water.

b) Sea water is more basic because its pH is above that of cheese.

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