CIE Chemistry (US-0439): Specimen Questions with Answers 216 - 219 of 240

Question number: 216

MCQ▾

Question

Ozone layer is very important for us because ________.

Choices

Choice (4) Response

a.

It allows the sun rays to enter the earth.

b.

It keeps the earth warm.

c.

The protects earth from UV rays

d.

None of the above

Answer

c.

Explanation

Ozone layer is very important for us because it protects the earth from harmful UV rays from the sun.

Question number: 217

Short Answer Question▾

Write in Short

Malonic acid is a white crystalline solid which is soluble in water. It melts at 135 °C. The structural formula of malonic acid is given below. It forms salts called malonates

Or

  1. How could you determine if a sample of malonic acid is pure?

result if pure [2 Marks]

Explanation

If malonic acid is pure then it starts melting else it will not.

Question number: 218

MCQ▾

Question

After the stone age, the first metal to be used by early man to make tools was ________.

Choices

Choice (4) Response

a.

Copper

b.

Iron

c.

Golden

d.

Silver

Answer

a.

Explanation

After the stone age, the first metal to be used by early man to make tools was copper.

Question number: 219

Short Answer Question▾

Write in Short

Substances can be classified as:

Elements can be divided into:

copper

Explanation

Copper is a chemical element with symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a reddish-orange color.