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Topic:Physical and chemical change
Answers
Answer:
1. A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density.
2.The five conditions of chemical change: color chage, formation of a precipitate, formation of a gas, odor change, temperature change.
3. burning of paper changes to black ask
4.When acidic substances (including water) come in contact with metals, such as iron and/or steel, rust begins to form. Rust is the result of corroding steel after the iron (Fe) particles have been exposed to oxygen and moisture (e.g., humidity, vapor, immersion).
5. no ans sry
Answer:
THE ANSWERS are
1}
.they are temprory changes.
.they are reversible changes .
.no new substance formed.
.for example:ice changes into water.
2}The characteristics of chemical change are-
.Shape can change the substance .
.New substance is formed.
. It is not reversible change.
. It is a permanent change.
.The properties of substance are not retain.
Example- Curd from milk.
3} When few pieces of Fe are added to blue copper sulphate solution,the colour of the solution fades and turns into pale green due to the formation of ferrous sulphate.
4}Many factors speed up the rusting of iron, such as the moisture content in the environment and the pH of the surrounding area.
.Moisture: The corrosion of iron is limited to the availability of water in the environment. Exposure to rains is the most common reason for rusting.
.Acid: if the pH of the environment surrounding the metal is low, the rusting process is quickened. The rusting of iron speeds up when it is exposed to acid rains. Higher pH inhibits the corrosion of iron.
.Salt: Iron tends to rust faster in the sea, due to the presence of various salts. Saltwater contains many ions that speed up the rusting process via electrochemical reactions.
.Impurity: Pure iron tends to rust more slowly when compared to iron containing a mixture of metals.
5} When fresh fruits and vegetables are peeled or cut open, the enzyme called polyphenol oxidase (also called tyrosinase) contained in the cells is exposed to and reacts with the oxygen in the air. The reaction that occurs, which is called oxidation, is what turns the fruits and vegetables brown.
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