Is the distilled water acidic/basic/neut | Class 7 Science Chapter Acids, Bases and Salts, Acids, Bases and Salts NCERT Solutions

Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food

Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down                                               Across
(D) 1 : Thorough washing           (A) 1 : Keeps warm
      2 : Animal fibre                            2 : Its leaves are eaten by silkworms
      3 : Long thread like structure      3 : Hatches from egg of moth

Here is a crossword puzzle: Good luck!

Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human body

Down
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water

Sketch the cross section of soil and label the various layers.

Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO₂?

Solve the following crossword puzzle with the clues given:

Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.

Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.

Sketch the reproductive parts of a flower.

Describe how crystals of copper sulphate are prepared.

Why does an athlete breathe faster and deeper than usual after finishing the race?

Write one similarity and one difference between the nutrition in amoeba and human beings.

Explain how painting of an iron gate prevents it from rusting.

Name two chemicals used to disinfect water.

Explain, with examples, why we find animals of certain kind living in particular climatic conditions.

Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.
(b) The chemical name of baking soda is _________.
(c) Two methods by which rusting of iron can be prevented are _________ and _________.
(d) Changes in which only _________ properties of a substance change re called physical changes.
(e) Changes in which new substances are formed are called _________ changes.

Explain the function of bar screens in a wastewater treatment plant.

Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator.

Which of these statements are correct?
(i) All four   (ii) a and d   (iii) b and c   (iv) only d

Why do we get instant energy from glucose?

Which of the following does not yield wool?
(i) Yak     (ii) Camel     (iii) Goat     (iv) Woolly dog

Draw the circuit diagram to represent the circuit shown in Fig.14.21.

Tick (✓) mark the correct answer in each of the following:

(a) Fat is completely digested in the
     (i) stomach (ii) mouth (iii) small intestine (iv) large intestine

(b) Water from the undigested food is absorbed mainly in the
     (i) stomach (ii) foodpipe (iii) small intestine (iv) large intestine