Heredity and Evolution — Science STD 10 — Question

When metal X is treated with a dilute acid Y, then a gas Z is evolved which burns readily by making a little explosion.

1. Name any two metals which can behave like metal X.
2. Name any two acids which can behave like acid Y.
3. Name the gas Z.
4. Is the gas Z lighter than or heavier than air?
5. Is the reaction between metal X and dilute acid Y, exothermic or endothermic?
6. By taking a specific example of metal X and dilute acid Y, write a balanced chemical equation for the reaction which takes place. Also indicate physical states of all the reactants and products.

1. Give an example of a metal which:

1. Is a liquid at room temperature.
2. Is kept immersed in kerosene for storing.
3. Is both malleable and ductile.
4. Is the best conductor of heat.

2. Name the process of obtaining a pure metal from an impure metal through electrolysis. Suppose you have to refine copper using this process, then explain mentioning inwith the help of a labelled diagram the process of purification, brief the materials used as (i) anode, (ii) cathode and (iii) electrolyte.

What is atmospheric refraction? Use this phenomenon to explain the following natural events.

1. Twinkling of stars.
2. Advanced sun-rise and delayed sun-set.

Draw diagrams to illustrate your answers.

Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.
i. State the nature of the lens and the reason for its use.
ii. Where should the palmist place/hold the lens so as to have a real and magnified image of an object?
iii. If the focal length of this lens is 10 cm and the lens is held at a distance of 5 cm from the palm, use lens formula to find the position and size of the image.

Why does menstruation occur? Describe the menstrual cycle in human females (or women).

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electron shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound. This ionic compound is added in a small amount to almost all vegetables and dishes during cooking. Oxides of elements A and B are basic in nature while those of elements E and F are acidic. The oxide of element D is, however, almost neutral. Based on the above information, answer the following questions:

1. To which group or period of the periodic table do these elements belong?
2. What would be the nature of compound formed by a combination of elements B and F?
3. Which two of these elements could definitely be metals?
4. Which one of the eight elements is most likely to be found in gaseous state at room temperature?
5. If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write the formula of the compound formed by the combination of C and G.

Suppose you have three concave mirrors A, B and C of focal lengths 10cm, 15cm and 20cm. For each concave mirror, you perform the experiment of image formation for three values of object distance of 10cm, 20cm and 30cm. Giving reason answer the following:

1. For the three object distances, identify the mirror/ mirrors which will form an image of magnification - 1.
2. Out of the three mirrors identify the mirror which would be preferred to be used for shaving purposes/ makeup.
3. For the mirror B draw, ray diagram for image formation for object distances 10cm and 20cm.

There are two similar glands P which are located on top of two similar organs Q in the human body. P are often called the emergency glands and they secrete a hormone R into the blood stream. R is secreted in large amounts when a person is frightened. It brings about temporary changes in the body which allow a lot of substance S from the liver to go into the blood to provide a lot of energy in a very short time. This helps a person to fight back or run away from the frightening situation.
What are P, Q, R and S?

The liquid connective tissue A circulates in our body continuously without stopping. This tissue contains a pigment B which imparts it a colour C. The tissue A consists of four components D, E, F and G. The component D fights infection and protects us from diseases. The component E helps in the clotting of tissue A if a person gets a cut. The component F is a liquid which consists mainly of water with many substances dissolved in it and component G carries oxygen from the lungs to all the parts of the body.

1. What is (i) tissue A, (ii) pigment B and (iii) colour C?
2. Name (i) D, (ii) E, (iii) F and (iv) G.
3. Name one substance (other than oxygen) which is transported by tissue A in the human body.
4. Which two components of tissue A are the cells without nucleus?
5. Name any two organisms (animals) which do not have liquid like A in their body.